Climate change is anticipated to have a major impact on concrete structures through increasing rates of deterioration as well the impacts of extreme weather events. The deterioration can affect directly or indirectly climate change in addition to the variation in the carbon dioxide concentration, temperature and relative humidity. The deterioration that occurs from the very beginning of the service not only reduces the lifespan of the concretes but also demands more cement to maintain the durability. Meanwhile, the repair process of damaged parts is highly labor intensive and expensive. Thus, the self-healing of such damages is essential for the environmental safety and energy cost saving. The design and production of the self-healing as well as sustainable concretes are intensely researched within the construction industries. Based on these factors, this article provides the materials and methods required for a comprehensive assessment of self-healing concretes. Past developments, recent trends, environmental impacts, sustainability, merits and demerits of several methods for the production of self-healing concrete are discussed and analyzed. Human settlements are dependent on infrastructure systems  to mediate a wide range of human activities. . GloballThe impact of climate change on human life and ecosystems can be varied and manifest either in a direct or indirect manner. These include the increasing sea levels, intensification in the rate and/or severity of extreme weather phenomena, increase in the frequency of heat waves, and enhanced rate of precipitation. Thus, from the perspective of engineering, more and more research attention must be directed towards the effect of climate change on the structural features of the concretes. Simultaneously, risk-based techniques can effectively be employed to evaluate how the viable strategies of climate adaptation produce an economic benefit. For example, a model for improving the hurricane risk evaluation was developed by Bjarnadottir et al.  by takinThe durability of a material is typically aided by the self-repair capability, especially in challenging situations for human intervention, like constructions situated in areas with deleterious physical and chemical conditions ,13,14. AThe purpose of the present study is to review the current investigations on concrete structures based on various nanomaterials with self-repair capabilities and their implications for future uses in sustainable projects. In short, this presentation consists of three parts. First, it is argued that unlike standard concretes, self-repairing concretes are more eco-friendly and can reduce pollution levels, thereby enabling the construction industry to move towards a greater sustainability and intelligent development. The second part deals with several effective and detailed self-repair methods with comparative analysis of the advantages and disadvantages of each method. The last part involves the self-repairing systems that are proposed as viable options of concrete self-recovery mechanisms in response to corrosion, damage, and cracking.Economically, the serviceability of building materials is of great importance, especially in contemporary infrastructures and constituent parts. In the context of urban development, the most commonly employed concrete materials have to comply with the requirements of the standard codes of practice with regard to strength and durability ,18,19,20Cracks are detrimental not only in terms of facilitating corrosion, but also concerning the aesthetics because they make the porous structure in the concrete visible, expanding in size if no remedial action is taken. The hazardous chemicals can permeate concrete through the large cracks, leading to the chemical or physical deterioration of the concrete. However, it is not possible to completely prevent micro-cracks in the concrete because it is too expensive in terms of maintenance and repairs . ConsequThe formation of cracks in concrete is a major issue that must be addressed adequately. The drying-related shrinkage, thermal contraction, external or internal restraint to shortening, subgrade settlement, and overloading can all determine the formation of cracks. Although a complete avoidance of crack formation is nearly impossible, some methods are available for mitigating such issues. The main points at which cracks form are prior to and following the concrete hardening . In ordeThe settlement of concretes is the key determinant of the formation of pre-hardening cracks. It starts when the water is lost in the plastic state. Factors including the lack of adequate vibration, high slumps associated with exceedingly wet concretes or insufficient covering of the embedded items (for example steel reinforcement) or at the margin of the concrete are responsible for the settlement cracking. In addition, plastic shrinking can engender the pre-hardening cracking as well . Such crThe factors that can stimulate crack formation and post-hardening of concrete include drying-related shrinkage, thermal contraction, and subgrade settlement. The strategy of inserting regularly spaced construction joints is usually applied to avoid shrinkage and manage the crack location. For instance, the joints can be inserted in such a way as to determine the formation of the cracks in locations where they can be anticipated without difficulty. Furthermore, the number of cracks can be minimized through the introduction of horizontal steel reinforcement that can further hinder excessive crack expansion.Self-repair technology is a new innovation in the concrete industry that refers to materials having high quality and the ability to repair damage on their own without any external interference. In fact, this technology is introduced in order to satisfy the demands for reduction in expenditure related to concrete structure repair and maintenance . IntenseTo make the concrete structures more serviceable and expand their use life, crack repair is essential. A material with self-repair capabilities is referred to as an intelligent or smart material, meaning that it systematically integrates both the construct of information and physical indexes like strength and durability , affordiOne type of energy technology considered with great potential in making building structures more sustainable and energy efficient is the low carbon emission and energy-efficient building material with self-repair capabilities. Sustainable development is geared towards the careful management of human activities to ensure the future survival of humanity on this planet whilst avoiding any disruption to the ecological equilibrium . TherefoIn the human body, skin and tissues are capable of repairing themselves through replacements of damaged areas based on nutrient uptake. Similarly, the essential products that serve as nutrients in the cement-based materials with self-repair capability may enable these materials to repair the damage or deterioration . Ample r2O3–Fe2O3-tri (Aft), Al2O3–Fe2O3-mono (Afm), and calcium carbonate (CaCO3) were created in cracked concrete and Ca(OH)2 crystal air voids. The working assumption argued for the leaching out of such hydration yields and renewed crystallization in flow water via fractures. In line with this, a range of repair agents, including expansive agents, geo-materials, and chemical mixtures together with their blends were used to assess the performance of concrete in terms of its ability to repair itself [4A3S, CaSO4, and CaO. Results showed that the presence of expansive agents in the concrete beams nearly enabled the repair of an early 0.22 mm crack after more than 30 days with the detection of rehydration yield between the cracks. In contrast, for the standard concrete structures, partial repair of the cracks occurred during an identical interval of time. Hence, in comparison to the standard concrete, a higher efficiency was demonstrated by the expansive agent re-crystallization in the air voids for self-repair [In a study by Kishi et al. , it was r itself ,45,46. If-repair . Qureshif-repair  provided2 and 15.4% Al2O3 to the expansive material through a separate polymerization of the aluminate and silicate complexes [3, Na2CO3, and Li2CO3. Such composition triggered the cementitious re-crystallization and concrete particle precipitation [It was demonstrated that the geo-polymer was formed due to the addition of the geo-material with a content of 71.3% SiOomplexes . The prepitation . The conSelf-repair is made possible by the hollow fibers as illustrated in The technology of crack repair in cementitious materials is based on the same mechanism as the self-healing biological functions similar to blood coagulation ,55. It iThe buoyant process associated with self-repair has been discussed in various studies ,56,57. TAccording to Joseph , apart f3 precipitation in the concrete micro-crack zones. Several parameters were employed to describe this process, including the amount of dissolved inorganic carbon, the pH of the material, the levels of calcium ions, and nucleation site accessibility. The walls of the bacterial cells represented the nucleation sites, while the other parameters were regulated by the bacterial metabolism [2)2) into the ammonium ions (NH4+) and carbonate radicals (CO3−2). In the chemical reactions 1 mol of urea underwent intracellular hydrolyses to 1 mol of carbonate and 1 mol of ammonia following Path I. Then, carbamate was hydrolyzed spontaneously to form one extra mole of ammonia and carbonic acid via path II. These products later formed 1 mol of bi-carbonate (HCO3−) and 2 moles of ammonium (NH4+) and hydroxide (OH−1) ions (Path III and IV). Path IV and V was responsible for the enhancement of pH, drifting the bicarbonate equilibrium to form carbonate ions.Biological mechanisms for repair involving the introduction of bacteria into the concrete have been recently suggested ,61,62,63tabolism . Tittelbtabolism  used bac+2 on the cell wall surface. The reaction between Ca2+ and CO3−2 resulted in the precipitation of CaCO3 on the surface of the cell wall (Path VI and VII), thus providing active nucleation sites. The repair of surface cracks was made possible through this method of bacterial-based localized CaCO3 precipitation as illustrated in The walls of the bacterial cells had a negative charge, so cations from the surrounding environment can be accepted by the bacteria, with the deposition of CaInspired by the natural phenomena, several encapsulation materials have been made with diverse sizes, from macro- to nano-scale. At the macroscopic level, natural encapsulation in its most basic form is embodied by the bird eggs or seeds. Whereas, at the micro level natural encapsulation is embodied by an egg or seed cell ,66,67. TIn a study conducted by Nishiwaki , epoxy rThe integration of functional materials such as shape memory alloys (SMAs) or shape memory polymers, into cementitious concrete structures to promote self-repair has been advocated in a number of studies ,76,77,78Sakai et al.  studied The supplementary functionalities created by the latest material technology innovations brought the concept of “intelligent material”, which refers to the ability to effectively respond to extrinsic stimuli . This has led to the successful development and testing of advanced construction materials such as coatings for concrete with self-repair capabilities and particular durability qualities ,83. For Identification of the strategies for preventing micro-crack formation in concrete structures  has been the focus of ample research, but no definitive conclusions have been reached so far ,87,88. TOver the years, diverse organic and inorganic materials have been employed as healing agents to achieve high performance self-repairing. The protection of rebar against corrosive agents  commonly relies on epoxy coatings. Studies have also been dedicated to the creation of polymer coatings capable of activating crack repair in response to external stimuli . The heat-responsive coatings became successful and few of them can maintain their mechanical properties even after repeated heat cycles ,91. It hThe ultra-ductile fiber-reinforced cementitious composite also called the engineered cementitious composite (ECC) is a special type of concrete that was introduced at the beginning of the 1990s. The ECC was continually refined over past two decades . It is hThe notion of self-repair is feasible for the ECC due to the major property of tight crack size control of this material, as explored by two distinct empirical studies . The firThe self-repair capability of cementitious materials and the use of external chemicals as repair glue in concrete were investigated by Li et al. ,105,106.Waste matter and/or by-products were employed by Zhou et al.  for locaThrough release of the healing agents, the presence of microencapsulated modules generally promoted improvement of ECC micro-crack behavior and likelihood of crack formation. Consequently, the processes of sensing and actuation were made effective via microencapsulation. As previously mentioned, a considerable importance is attached to the ECC tight crack size as it minimizes the amount of healing agents needed to seal cracks and makes it easier for these agents to bridge cracks from both sides. In short, the self-repair capability of the ECC is greater compared to standard cements because of its higher proportion of cementitious materials and lower ratio of water to binder.In the concrete industry, the use of self-repairing materials is still a relatively recent innovation. These materials refer to the materials that contain cement and are capable of autonomous recovery from deterioration caused by various factors. Simultaneously, a considerable interest is currently being raised by the possibility of producing sustainable concrete using nanomaterials. Thus, concrete can be made more durable and sustainable by integrating self-repair and nanomaterial technologies ,109. In Qian et al.  investigT, Bacillus cohnii NCCP-666, and Bacillus sphaericus NCCP-313, were included in the concrete matrix along with the calcium lactate pentahydrate and urea as the organic nutrients. It was found that natural fibers are capable of substantial immobilization of bacterial spores. In addition, the flax fibers provided a better protection to the bacteria with improved crack-healing and regained compressive strength. The concrete composite is made of binders, fine and coarse aggregates, and short length discontinuous fibers. These fibers can significantly enhance the impact resistance, ductility, and energy absorption of concrete in addition to the higher values of splitting tensile and flexural strengths dispersed in the concrete mixture ,112. ManDiverse tests and techniques have been devised to assess the efficiency of different self-repair mechanisms. Several factors that determine the capability of crack repair include the width and age of cracks and type of curing ,117. In Self-repair is considered to restore the compressive strength in a proportion of as much as 60% and it has also been reported to improve ultrasonic pulse velocity. Consequently, taking into account the test results, the strategy of biological self-repair could be beneficial for long-term durability, prolonging the use life of concrete infrastructures. Conversely, not much attention has been paid to additional key tests, including the strength of bonding between the materials deposited in the cracks and the actual concrete, the stress–strain relationship curve, and gas permeability tests. As such, different approaches should be adopted in assessing the capability of concrete self-repair. In short, a more comprehensive understanding is required regarding the materials’ deposition capacity for binding in the cracks and their structural compatibility with the components of the concretes.Micro-tensile, bending and bulge tests were carried out to evaluate the concretes’ mechanical performance at the micro-size or smaller. Ghidelli et al.  stated tIt is established that inclusion of self-healing materials in the concrete matrix can offer several advantages/disadvantages to the mechanical properties depending on the nature of the materials and self-healing process. It was found insertion of the capsules in the concrete matrix can result in voids or holes in the concrete after releasing the contained agent. These voids in turn can negatively affect the strength performance of the concrete . The useAmple research has been conducted on self-repair technology in the last ten years and its potential for promoting an autonomous crack healing in concrete has been highlighted. This has led to the development of several self-repair mechanisms for cementitious materials. The evaluation of various products and services in terms of their effect on the environment from the moment of development until discontinuation is based on the life cycle assessment (LCA) methodology achieved standardization as ISO 14040-14044. In essence, the LCA is geared towards determining whether self-repairing concrete is more sustainable than standard concrete. Diminished deterioration rate, prolonged use life, decreased frequency and low cost of repair over the lifespan of a concrete infrastructure are among the main advantages of self-repairing concrete. These can make concrete more sustainable as reduced repair frequency translates to a decrease in the amount of material resources and energy used, decrease in the environmentally damaging emissions associated with the manufacture and transport of materials, and reduction in the traffic changes to transport infrastructure required by the repair or reconstruction work ,130,131.Van et al.  discoverSelf-healing concretes are characterized through several significant traits such as low pollution level, cheap, eco-friendly, and elevated durability performance in harsh environmental conditions. These properties make these concretes effective sustainable materials in construction industries.The internal encapsulation and hollow fiber-activated self-healing strategies are efficient for multiple-damages repair. However, these two strategies encounter some complexity in casting and have a negative impact on the mechanical properties of the proposed concretes.The inclusion of expansive agents and mineral admixtures in the concrete demonstrated superior efficiency in the self-healing process. However, it is not very effective in the presence of multiple damages.The design of the nanomaterial-based self-healing concretes with improved performances and endurance are useful for several applications, thanks to the advancement of nanoscience and nanotechnology.The environmental pollution can considerably be reduced by implementing the high strength and durable cementitious composites fabricated using diverse nanoparticles, carbon nanotubes and nanofibers.In the domain of building and construction, production of materials via the nanotechnology route is going to play a vital role in sustainable development in the near future.Use of smart materials in concrete is advantageous in terms of the improved engineering properties of the cementitious materials, especially for the generation of self-healing and sustainable concretes.This comprehensive review is believed to provide taxonomy to navigate and underscore the research progress toward smart materials based self-healing concrete technology.In recent times, the production of sustainable concretes via self-healing technology became useful in construction industries worldwide. The exponential increase in the usage of the OPC caused severe environmental damages. The immense benefits and usefulness of self-healing concrete technologies were demonstrated in terms of their sustainability, energy saving traits and environmental affability. The foremost challenges, current progress and future trends of smart technology enrooted self-healing concretes were emphasized. An all-inclusive overview of the appropriate literature on smart material-based self-healing concretes allowed us to draw the following conclusions:


The purpose of this paper was to assess the presence of researchers on two author identifier services (ORCID and ResearcherID) and to compare the results with two academic social networks (Academia.edu and ResearchGate) using the categories of discipline, career advancement, and gender in a medium sized multidisciplinary university in France (University of Caen Normandy). Metrics such as number of publications per researcher, h-indexes, and average number of citations were also assessed. Of the 1,047 researchers studied, 673 (64.3%) had at least one profile on the four sites, and the number of researchers having multiple profiles decreased as more sites were studied. Researchers with only one profile numbered 385 (36.8%), while 204 (19.5%) had two, 68 (6.5%) had three, and only 16 (1.5%) had four. ResearchGate had by far the highest number of researchers present, with 569 (54.3%), whereas presence on the other sites was about 15%. We found that, apart from Academia.edu, researchers in Sciences, Technology, and Medicine (STM) were over-represented. Overall, experienced male researchers were over-represented on the sites studied. Our results show that, because of the numerous profiles lacking publication references (particularly on ORCID) and a low presence of researchers on the four sites studied (except for ResearchGate), assessing the number of publications, h-indexes, or average number of citations per article of individuals or institutions remains challenging. Finally, our data showed that French researchers have not adopted the use of the two author identifier sites (i.e. ORCID and ResearcherID). As long as French researchers remain reticent, these sites will not be able to provide the services for which they were created: addressing the problem of author misidentification, consequently providing exhaustive access to scientific production and bibliometric indicators of individual researchers and their institutions. To assess researchers’ scientific output, several online bibliographic databases have been available (since the late 1990s), but access to nearly all of them is limited by a paywall . The sites are compartmentalized, often thematic, and incomplete by definition. Some repositories  offered, in the early 2000s, free access to full texts with open access. Nevertheless, these tools of the era lacked a fundamental feature: direct communication between those actively doing research and other researchers. These sites required intermediate operations, such as obtaining the authors’ email by searching for articles in which they were declared as the corresponding author or searching on the internet on what appeared to be an author’s personal/institutional page, then having to send an email to contact them. Another drawback of these bibliographic databases was that their content could not be controlled and corrected by adding references to researchers if necessary. In 2008, two Academic Social Networks (ASNs), ResearchGate and Academia.edu, appeared almost simultaneously, responding favorably to these expectations. They allowed researchers to communicate directly with their peers with an internal and “proprietary” mailing system, and adding their scientific publications onto their profiles  . The number of active ORCID users is 7.65 million, whereas only 1.91 million ORCID profiles mention publications. Hence, 75% of profiles do not indicate any publications. These data underline the principal drawback of ORCID. That is, some researchers create a profile on ORCID to access internet services such as submission platforms (e.g. Scholar One) but access them infrequently (e.g. whenever it is required) [The number of publications per individual found for researchers on the four sites compared to the Scopus database is presented in equired) ,33 withoequired) . One canequired) . The facConversely, the average number of publications referenced per researcher available on ResearchGate is generally higher than the number of publications on Scopus (71.1 vs 46.5). Using ResearchGate to assess the number of publications per researcher allows 91.2% of the researchers to maximize this number. On Academia.edu, there is approximately the same number of cases in which the number of publications is higher or lower than on Scopus, with many outliers, causing large discrepancies in some researchers’ statistics.Apart from ResearchGate, and to a lesser degree ResearcherID, Spearman’s rank correlation coefficient shows a poor correlation between the number of publications and those found on Scopus. Furthermore, due to numerous outliers, results presented in At an institutional level, the total number of citations for articles (number of times the article was cited) found in the profiles of the Caen University researchers was 172,689 on ResearcherID and 513,236 on ResearchGate compared to 657,319 on the Scopus database. We were not able to assess the h-index for institutions for the entire population of researchers because data on overall numbers of citations for each researcher was gathered, and data on the number of citations for each article was not collected.For individuals, as shown in Our data suggest that assessing the number of citations per article or h-indexes for individuals and institutions using ResearcherID or ResearchGate gives overall results that are quite different from those obtained using the Scopus database. This confirms previous findings which have shown that the usefulness of bibliometric indicators derived from ASNs for institutions –43 or inThe objective of the present study was to assess the presence of researchers on two AIDs (ORCID and Web of Science ResearcherID) and to compare the results with two ASNs (Academia.edu and ResearchGate) in a medium-sized multidisciplinary university in France (University of Caen Normandy). Few studies have focused on AIDs  and, to Our data show that a large majority of Caen University researchers are not currently interested in using AIDs (75.1%), and to a lesser extent ASNs (40.2%). Moreover, our results show that the two AIDs studied are not presently able to provide the services for which they were created  and cannS1 Data(XLSX)Click here for additional data file.


EA) and large electronegativity that introduces deep-level traps into epoxy resin and restrain the electron transport. In this work, the origin of traps has been investigated by the simulation method. It is revealed that the functional properties of POSS side group can tailor an extensive network of deep traps in the interfacial region with epoxy and enhance the breakdown strength of the epoxy/POSS nanocomposite.To date, breakdown voltage is an underlying risk to the epoxy-based electrical high voltage (HV) equipment. To improve the breakdown strength of epoxy resin and to explore the formation of charge traps, in this study, two types of polyhedral oligomeric silsesquioxane (POSS) fillers are doped into epoxy resin. The breakdown voltage test is performed to investigate the breakdown strength of neat epoxy and epoxy/POSS composites. Electron traps that play an important role in breakdown strength are characterized by thermally stimulated depolarized current (TSDC) measurement. A quantum chemical calculation tool identifies the source of traps. It is found that adding octa-glycidyl POSS (OG-POSS) to epoxy enhances the breakdown strength than that of neat epoxy and epoxycyclohexyl POSS (ECH-POSS) incorporated epoxy. Moreover, side groups of OG-POSS possess higher electron affinity ( With growing direct current high voltage (HVDC) applications, insulation failure has attracted much attention for epoxy-based insulating equipment to ensure power system reliability . Hence, 2O3 nanocomposites and found that the DC breakdown strength was dominated by deep trap level, which is improved by the incorporation of nanoparticles [In the interfacial region of nanocomposites, the dielectric strength is influenced by several factors, i.e., molecular chain dynamics, carrier traps, potential barrier of polymer structure against the charge transport, etc. ,6,7. In articles . S. Li earticles . The traarticles ,12,13. Harticles ,15,16. Aarticles . POSS caarticles . HoweverEA), density of states (DOS), and frontier molecular orbital of EP/POSS nanocomposites, i.e., LUMO distribution. Finally, the origin of traps and the effects of traps on breakdown performance are discussed.To investigate the charge trapping mechanism and explore the origin of traps that influences the DC breakdown strength of epoxy nanocomposites, two kinds of POSS fillers are incorporated into the epoxy matrix, and the DC breakdown strength of EP/POSS nanocomposites is studied. Trap characteristics are analyzed by thermally stimulated depolarization current curves, and molecular simulation techniques are used to calculate the electron affinity (Epoxy resin Di-glycidyl ether of bisphenol-A type (DGEBA) was used as a matrix. Methyl tetrahydro phthalic anhydride (MeTHPA) was selected as a hardener. Epoxy/POSS composites were prepared by introducing two different types of POSS, i.e., octa-glycidyl POSS (OG-POSS) and epoxycyclohexyl POSS (ECH-POSS), respectively . Both kinds of POSS features eight side groups attached to the silicon core, an accelerator (DMP-30) was used to fasten the curing process. The nomenclature of the samples is listed in 3), and IKA T25 high-speed shearing machine was used to mix the liquid for 15 min with 5200 rpm speed. Then, the liquid is degassed and de-foamed by THINKY mixing machine for 30 min. To ensure the homogenous dispersion of POSS fillers into curing agent, sonication was performed for 15 min at 50 °C using an ultrasonic device of 99W power. Then, the DGEBA (ρ = 1.03 g/cm3) and DMP-30 accelerator was blended with the liquid. The same stirring and de-foaming procedures were repeated. Steel molds were cleaned by ethanol and kept in a kiln at 60 °C for 2 h before the liquid was cast into the different shapes and sizes of molds. An anti-setting agent was applied on the surface of molds to ensure an easy detachment of backed specimens. The mixed liquid was cured for 4 h at 80 °C and then for 8 h at 120 °C. The samples were then cooled to room temperature using an annealing process to get an adequately cured sample and to avoid cracks. The samples were cleaned with ethanol and then kept at 60 °C for 12 h before the experiments were carried out. A typical stoichiometric ratio for Epoxy, MeTHPA, POSS, and DMP30 was set as 100:80:2.5:1. POSS was added with a filler loading of 2.5 wt.% as an optimal value reported in Reference [The fabrication process has been represented in eference . The cheiP is expressed in Equation (1).biE is experimental values of breakdown strength (kV/mm), α is a scale parameter that shows the cumulative failure probability of 63.2% samples in kV/mm, β is a shape parameter that reflects the variation of data. The iP of experimental data (biE) can be approximated according to the IEEE-930 standard [The DC Breakdown test was conducted using steel spherical electrodes in transformer oil at room temperature (25 °C). The diameter of spherical electrodes was 25 mm, and a computer-controlled DC voltage (HJC-100 kV) was applied with a ramp rate of 1kV/s. The sample with a thickness of 200 μm was selected for experiments. The DC breakdown data were statistically analyzed by two-parameter Weibull distribution. The cumulative probability of failure i represents the result of the ith rank, while ascending order is adopted for sorting all the values of biE. n is total breakdown attempts, which are 16 in this work. The schematic is shown in Here, I(T) as a function of linear temperature increase at rate β, expressed [The thermally stimulated depolarized current (TSDC) experiment was carried out to analyze trap characteristics of epoxy/POSS composites. Before the experiment, samples were gold-sputtered with a 30 mm diameter on both sides. Initially, the samples were polarized at 110 °C for 30 min under an applied electric field of 250 V. The sample was then abruptly cooled to 0 °C with −30 °C/min cooling rate and remained at this state for 10 min to ensure stable conditions. The applied electric field is removed, and the sample was short-circuited for a short time. The induced electrical charges remain inside the bulk. Finally, the sample temperature was increased with a ramp rate of 2 °C /min from 0 °C to 150 °C. After removing the applied electric field, the de-trapped carriers generate a depolarized current inside the bulk in the absence of an applied electric field. A Keithley 6517B  was used to measure the current xpressed  as:(3)I. Coefficient A and B are dependent on the model used for the TSDC curve, but independent of the T and H, which are in References [Here, ferences ,22.(4)BMT is the corresponding temperature of peaks and β is the heating rate in °C/min. The number of trapped charges TSCQ at the depolarization stage can be calculated by the integration of the current peak.T1 and T2 are the initial and final temperatures of the peak, respectively. From the depolarized current, trap parameters H and TSCQ were analyzed. The schematic is shown in Here, The DGEBA, MeTHPA, POSS, and DMP30 monomer molecules were constructed using Material studio software 2017  . Based oTo investigate the charge trapping sites of epoxy composites, ab-initio quantum chemical calculation using DFT method was employed using DMol3 package in Material Studio 2017. Based on the DFT calculation, the geometry optimization and energy calculations were investigated by the Perdew–Burke–Ernzerhof (PBE) function . The comWeibull plots for the breakdown strength of epoxy/POSS nanocomposites are shown in The TSDC results are shown in α peak is characterized into two peaks, i.e., deep trap peak (α1) and shallow trap peak (α2), as shown in the inset figure of the EP/ECH-POSS sample. For epoxy/POSS composites, the trap levels are higher than that of neat epoxy. EP/OG-POSS has the highest deep trap energy of 2.15 eV. EP/ECH-POSS and neat epoxy have 2.0 eV, and 1.8 eV deep traps energy, respectively. It has been illustrated that tailoring deeper trap energy lowers the probability of trapped charges to escape. The deep trap has higher retention potency to restrain the trapped charges until some external factors are applied, such as temperature in this case is applied. Additionally, the TSDC peak for EP/OG-POSS occurs at higher temperatures. It shows that incorporating OG-POSS can form a large network of traps that restrain trapped electrons from de-trapping at earlier temperatures, as it requires external energy to escape. The neat epoxy has a smaller peak and a lower trap level . The small peak of neat epoxy occurs at low temperatures, which indicates that trapped electrons escape at earlier temperatures. It means that only a low temperature is required to stimulate the trapped electrons to escape. In Qs and Qd of neat epoxy are low, which causes the amount of de-trapped charges to be lower than the other two samples. For EP/ECH-POSS, it has the highest peak with large quantities of sQ and dQ, and its trap energy and corresponding temperature of peak are higher than neat epoxy. However, the trap’s energy of EP/OG-POSS is higher than EP/ECH-POSS, and the TSDC peak occurs at higher temperatures. In this case, it is difficult for electrons to escape from deep traps in EP/OG-POSS.EF is located in the middle of the bandgap. There are many peaks in the whole energy level. On the right side of EF, the first peak (shaded) is recognized as the trapping peak, while the second peak is the bottom of the CB. Hence, a number of traps accumulate near the CB, and the gap distance between the center of the trapping peak and the CBM peak is defined as trap depth. For neat pristine epoxy resin, the trap depth is 2.05 eV. The trap depth is improved by the introduction of POSS to the epoxy matrix. For EP/ECH-POSS, the trap depth increases by 0.05 eV compared to neat epoxy resin, while it increases 0.28 eV for EP/OG-POSS. It is obvious that EP/OG-POSS has a larger trap depth.EF are regarded as the trap density. Referring to 2, which is larger than the EP/ECH-POSS and pristine sample, i.e., 31.8 A2 and 24.1 A2, respectively. The trap characteristics of EP/POSS nanocomposites calculated by TDOS are consistent with TSDC results.Shaded areas in EF. The vacuum level (VL) is at the zero energy level, and the gap distance between VL and LUMO is the electron affinity (EA), which is the released energy when the composite acquires an electron and closely associated with the trapping depth in the bulk of the matrix [EA is 1.331 eV. While for EP/ECH-POSS and EP/OG-POSS, the EA is 1.504 eV and 1.606 eV, which is 0.173 eV and 0.275 eV higher than neat epoxy.e matrix . For neaEA) increase, the DC breakdown strength increases, which indicates that the trapping mechanism strongly influences the breakdown strength. DC breakdown strength has a positive relationship with the trap level, and EA is calculated from the energy distribution diagram in EA, which eventually enhances the DC breakdown strength.A molecular structure containing a large number of electronegative atoms has higher electrostatic potential (ESP). Higher ESP positively influences the dominant features of DOS and energy level distribution . ChemicaΦ0 of electrodes and the applied field E, and the potential barrier Φ1 for electrons injection can be calculated by the Schottky effect:β1 is a coefficient of Schottky effect, which can be expressed as:e is the charge quantities of an electron (1.602 × 10−19 C), ε0 is permittivity in vacuum (8.854 × 10−12 F/m) and εr is relative permittivity.Traps play an important role in DC breakdown performance as confirmed from TSCQ improved by POSS reduce the space charge and enhance the DC breakdown strength, which is consistent with the phenomenon in trP and deP are the trapping and detrapping probabilities, tE and tN are the trap level in eV and trap density in m−3, μ0 is carrier mobility in m2·V−1·s−1, and ATEυ is the attempted escape frequency in s−1. In Equations (8) and (9), the Pde decreases with the trap level, which indicates that the trapped charges in deep trap cannot gain enough energy to detrap unless the applied field is improved, while the increase of trap density improve the Ptr and capture more charges into the trap. Hence, the increases of trap level and density suppress the charge transport process in the dielectric material, reducing the conductivity and improving the dc breakdown strength. In addition, the charge transport process in dielectric material is determined by Poole-Frenkel effect [Φ1 for charge function is the same as Equation (6), but the Φ0 is the trap level and β1 is the coefficient for the Poole-Frenkel effect:The charge migration process under high-applied field is also associated with the traps in the EP/POSS nanocomposites. For the charges, the trapping and detrapping probabilities take the form of:l effect . The potIn this case, the increase in trap level by POSS suppresses the charge transport process in dielectric and further improves the dc breakdown strength for EP/POSS nanocomposites.E is dominated by the longest free path lst, and the height of potential barrier Eth, the free volume breakdown criterion can be expressed as:thE is the trap level in this work, which indicates that the breakdown strength is improved by the increase in deep trap level.Furthermore, the dc breakdown characteristics in the epoxy nanocomposites are not only dominated by the trap characteristics. The free volume length, the potential barrier around the nanoparticles, and the scattering effects of nanoparticles are all potentially influencing factors for dielectric failure. All the changes in trap characteristics, local electrical field, and space charges may affect the dc breakdown characteristics for epoxy composites. From this work, a reliable path is provided to improve the DC breakdown strength by tailoring the traps through nano-structured POSS incorporation.Incorporation of OG-POSS and ECH-POSS nanofillers to epoxy matrix successfully increases the deep trap level and breakdown strength, the DC breakdown strength of EP/OG-POSS, and EP/ECH-POSS increases 17% and 15% compared to neat epoxy.EA).A positive relationship has been established between DC breakdown strength and trap parameters, i.e., deep trap level and electron affinity (Traps originated from the interfacial bonded region of EP/POSS. The depth of the trap level has a positive correlation with the electronegativity of atoms in the side groups of POSS. The greater the electronegativity of polymeric composite, the larger would be the trap depth.The increment in deep trap level and density suppresses the charge injection and transport process in the dielectric material, restraining the carriers from hopping over the potential barrier and further improves the DC breakdown strength.In this study, two different types of POSS were incorporated into the epoxy matrix. The influence of POSS side groups on tailoring the charge traps and their impact on breakdown strength was investigated. The trapping phenomenon in polymeric insulators was studied by the experimental results of TSDC and simulation results by TDOS and energy distribution diagram. Based on the experimental and simulation results, the main conclusions are as follows:


Poly(lactic-co-glycolic acid) nanocapsules containing amphiphilic biosurfactant sophorolipids were formulated using a dispersion-based procedure. Di-block copolymers were used to vary peripheral poly(ethylene glycol) density, and variation in the oil core was used to achieve efficient encapsulation of the sophorolipid payload. Particulate size, zeta potential, encapsulation efficiency, release and stability were characterised. A glyceryl monocaprate core composition had the lowest particulate size, maximum encapsulation efficiency and optimum shelf-life stability compared to other formulations. This core composition was used to deliver sophorolipid to both in vitro and in vivo model tumour cell lines (CT26 murine colon carcinoma) and the effect of peripheral hydrophilicity was evaluated. Formulations with 10% poly(ethylene glycol) density achieved more than 80% reduction in cancer cell viability after 72 h and enhanced cellular uptake in CT26 cells. These formulations exhibited higher tumour accumulation and a longer blood circulation profile when compared to the non-poly(ethylene glycol)-containing nanocapsules. Animals treated with sophorolipid-loaded nanocapsules showed a tumour growth inhibition of 57% when compared to controls. An assessment of tumour mass within the same study cohort showed the biggest reduction when compared control and free drug-treated cohorts. This study shows that hydrophilic poly(lactic-co-glycolic acid) nanocapsules loaded with sophorolipids can address the poor intracellular delivery associated with these biosurfactants and is a promising approach for the treatment of colon neoplasia. Natural surfactants are classified according to their chemical composition and source of origin (plant or microorganism) . SpecifiCandida floricola, Candida apicola, Candida bastistaeic and Starmerella bombicola [0 and G2 phases [Biosurfactants with a carbohydrate moiety (glycolipid) have therapeutic potential in the management of disease. Four main types are recognised. These are the (i) sophorolipids (SL), (ii) trehalolipids, (iii) mannosylerythritol lipids and (iv) rhamnolipids . The SL ombicola . SL are ombicola . Recentlombicola , 8. Actiombicola . Furtherombicola  and coloombicola . A detai2 phases .Although preliminary investigations demonstrate promise, the translational applications of SL for the treatment of disease have been hindered by a number of factors, such as high production cost, limited purification, poor aqueous solubility and an overall lack of understanding of interactions with cells . Therefo) and in in vivo murine model.A second aim of the study was to evaluate the effect of polymer hydrophilicity. Previous studies have shown that NC formulated from PEGylated PLGA polymers have improved the anticancer effects of lipophilic drugs, such as curcumin, used in the investigational treatment of colon neoplasia , 18. PEGPEG-PLGA diblock copolymers (Resomer® RGP d 5055 (5% PEG of MW 5 kDa) and Resomer® RGP d 50105 (10% PEG of MW 5 kDa)) were purchased from Boehringer Ingelheim Ltd. . PLGA with a 50:50 lactic:glycolic ratio  was purchased from Sigma-Aldrich . Sophorolipid , coumarin 6 (3-(2-Benzothiazolyl)-7-(diethylamino)coumarin, 3-(2-Benzothiazolyl)-N,N diethylumbelliferylamine), DiR , DAPI , dialysis tubing (MWCO 2000 Da), SP-Sephadex C-25 resin, castor oil, palm oil, Tween® 80, acetone and absolute ethanol (ultra-pure grades) were obtained from Sigma-Aldrich . Glyceryl monocaprate (Capmul® MCM C10) was a generous gift from ABITEC Corporation, USA. RPMI-1640 and DMEM media, trypsin/EDTA, phosphate buffered saline (PBS), fetal bovine serum (FBS) and penicillin/streptomycin were obtained from Gibco, Invitrogen, UK. Isoflurane (IsoFlo®) was purchased from Abbott Laboratories Ltd. (UK).The solubility of SL in three different oils used for NC preparation  was determined using a simple saturation method . An exce−1 to remove non-entrapped drug.SL-loaded NCs were prepared using a modified nanoprecipitation method . PolymerFluorescent SL-loaded NCs were prepared by adding either coumarin 6 100 μg) or DiR (150 μg) to the non-aqueous phase. Coumarin 6 was chosen for qualitative cellular uptake analysis, and DiR labelling was used an instrument-specific dye to provide optimum in vivo biodistribution imaging data. Process variables, such as the polymer type and composition of the oil core, were modified, as shown in Table 00 μg or Particle size, size distribution and poly dispersity index (PDI) of SL-loaded NCs were determined using dynamic light scattering at 90° . A liquid aliquot from the SL-loaded NC colloidal suspension was diluted in ultrapure water and an average of three measurements was recorded. Zeta potential  of SL-loaded NC was determined using laser Doppler electrophoresis applied to an aliquot of colloidal suspension, diluted in aqueous 0.001 M KCl to adjust for conductivity . Morphology was examined using transmission electron microscopy (TEM) (JOEL JEM 2000 EX200). A sample of NC suspension was placed on a Formvar-coated grid operating at an accelerating voltage of 80 kV. Fluorescent SL-loaded NCs were evaluated using similar methods for particle size, polydispersity index and zeta potential.Samples of SL-loaded NC suspensions were sealed in glass vials and stored in the dark under refrigeration (4 °C). Stability was evaluated every 10 days by visual inspection of physical properties  and by determination of size, PDI and zeta-potential, as described in “−1, comprising a linear gradient of acetonitrile and water over a run time of 40 min, were used [The percentage SL encapsulation efficiency (%EE) in SL-loaded NC was determined by an indirect method of analysis. The amount of non-encapsulated SL in fractions following column purification of a NC suspension was determined by HPLC . A reversed-phase column  and a mobile phase, at a flow rate of 1.0 ml minere used .A liquid sample of SL-loaded NC formulation containing a predetermined amount of SL was placed into a 10-kDa dialysis bag. The dialysis membrane was dialysed against a receiver medium of 50 ml PBS containing Tween® 80 (1% w/v) at pH 7.4. The release was studied at 37 °C at 100 rpm. At predetermined time interval points, 1.0 ml sample was taken and replaced by an equivalent amount of fresh medium, thereby maintaining sink conditions. Drug concentration was assessed by HPLC, as previously described.2 canted-neck tissue culture flasks. Cells were cultured in complete RPMI media supplemented with FBS (10% v/v), L-glutamine (2 mmol l−1), penicillin (100 U ml−1) and streptomycin (100 μg ml−1). CCD-841-CoN, normal colonic epithelium cells, were maintained in complete DMEM media supplemented with 10% fetal bovine serum. Cells were passaged every 3 days at 80% confluence. All cultures were incubated at 5% CO2 and 37 °C.CT26 murine colon carcinoma (CT26) cells were grown in 100 cmg (4 °C) for 5 min and the pellet resuspended in RPMI complete growth medium. A cell count was performed on a sample of cell suspension (10 μl) using a haemocytometer. CCD-841-CoN cells were seeded using similar conditions, with DMEM complete growth medium being used instead of RPMI medium.CT26 cells were harvested when the cells were 90% confluent. The cell suspension was centrifuged at 1500Cellular uptake of coumarin 6-tagged SL-loaded NC  was evaluated using flow cytometry and fluorescence microscopy . BrieflyCellular localisation of coumarin 6-tagged SL-loaded NC was evaluated qualitatively by fluorescence microscopy . Intracellular distribution of fluorescent NC into CT26 cells was detected using fluorescence imaging 1 day after treatment. CT26 cells were seeded into a 6-well plate, containing two fixed coverslips incubated into 2.0 ml of RPMI growth medium. Coverslips were mounted using mounting media (VectaShield) and subsequently counterstained with DAPI. Cellular localisation of labelled NC was represented by the green signals, while cells nuclei were detected in blue. The untreated CT26 cells and cells treated with free coumarin 6 were used as negative and positive controls, respectively.2. DMSO (500 μl) was added, and the absorbance at 570 nm was recorded . Results were expressed as the percentage cell viability, compared to controls. Each treatment was tested three times and the measurements were presented as an average ± SD (n = 3).CT26 murine colon cancer cells and CCD-841-CoN normal colon epithelium cells were seeded in 24-well plates and incubated with 0.5 ml of complete growth media. After 24 h, cells were treated with blank NC or three different concentrations of SL  in either the free form or the equivalent amount of SL-loaded NC (F9). Cytotoxicity was examined using a modified MTT assay [6 cells in 0.1 ml PBS subcutaneously at both lower flanks [Female Balb/c mice, weighing approximately 20 g and aged between 4 and 6 weeks, were allowed to acclimatise to laboratory conditions for 10 days before starting the experiment. Mice were fed water and standard pellet chow ad libitum for the duration of the in vivo experiment. All animal experiments were performed in compliance with the UK Home Office (1989) Code of Practice for the Housing and Care of Animals used in Scientific Procedures. A xenograft model of CT26 colon carcinoma was induced by implanting 1 × 10r flanks . A palpan = 4) were used in an organ biodistribution study. Control animals in the first group were injected with PBS. The second group was treated with F3 and the third group was treated with F9 through IV injection. The treated groups were injected intravenously with prepared DiR-labelled SL-loaded NC in PBS solution at a dose of 10 mg SL kg−1 and scanned using an in vivo imaging system  at 1-, 4- and 24-h post-injection [Three different groups (njection . All anin = 6) were used in an in vivo antitumour activity study. Once anaesthetised, subjects were injected via the tail vein with the following:(Group 1) 200 μL of saline (control group);(Group 2) 200 μL of blank NC nano-suspension;−1;(Group 3) 200 μL free SL at a dose of 10 mg kg−1.(Group 4) 200 μL of SL-loaded NC (F9) nano-suspension containing SL at a dose of 10 mg kgFour groups  and the whole tumour volume was recorded. Mice were sacrificed after the end of the experiment by cervical dislocation, and the tumour was excised and washed with saline to measure its final mass.p < 0.05 was considered statistically significant in all experiments.For all in vitro experiments, data were presented as mean ± SD. In in vivo experiment, results were presented as mean ± SEM. Significant differences between different groups were examined using one-way ANOVA followed by post hoc Tukey’s test. Polymeric SL-loaded NCs were fabricated using the nanoprecipitation method, and the impact of formulation variables, such as PEG density on the PLGA chain and the type of oil core, on the physicochemical characteristics of the SL-loaded NCs was investigated. Mean particle size, PDI, zeta potential, encapsulation efficiency, in vitro release profile and in vitro stability were determined. The aim of the work was to use this data and select an optimised formulation for further in vivo evaluation. This optimised formulation was considered to be one with the smallest diameter, best encapsulation efficiency, longest shelf-life stability and controlled therapeutic action.p < 0.01) than NC prepared from 10% PEGylated polymers of (F9) (117.5 ± 11.5 nm). A non-significant difference was observed when compared to 5% PEGylated NC (F6) (177.4 ± 14.5 nm) (p ˃ 0.05). SL-loaded NC prepared from 10% PEG-PLGA diblock copolymers (F9) were significantly smaller than NC prepared from 5% PEG-PLGA copolymer (p < 0.01), .Modification of PLGA by incorporation of PEG blocks within the polymeric structure is a common experimental variable within the formulation strategy of a nanoparticulate system. Effects on aqueous solubility of poorly soluble payloads, aggregation, stability and opsonisation are often reported , 23. How1), Fig. . Similarζ-potential of NC colloidal suspension plays an important role in maintaining in vitro stability. In vitro stability of colloidal suspension depends on the degree of electrostatic repulsion between nanoparticles. Higher negative or positive zeta potential values resulted in good in vitro stability with low tendency of particles aggregation [ζ-potential values (− 21.9 ± 2.8 mV) compared to the PEGylated PLGA NC (F6 and F9) (p < 0.001) . The lower negative ζ-potential of PEGylated NC is due to the presence of surface-decorated PEG chains which mask the free negative surface charge represented by the free anionic groups of PLGA [The regation . F3 exhi01) Fig. . Increas of PLGA , 23.p < 0.001). Encapsulation efficiency was increased from 68.8 ± 6 in PLGA to 92.18% ± 1.8% in 10% PEG-PLGA . Burst release after 24 h was 53.2% ± 8.9, 60% ± 4.2 and 50% ± 8.3 from F3, F6 and F9, respectively , being significantly lower than that in both castor oil (1.79 mg ml−1) and glyceryl monocaprate (2.21 mg ml−1). The physicochemical characteristics of different SL-loaded NC fabricated using these different oil cores are shown in Fig. p < 0.05). However, this trend was not apparent in the PLGA NC  observed for (F9) is probably a consequence of the lower viscosity of the glyceryl monocaprate compared with the palm oil and castor oil used for preparation of F8 and F7, respectively [ζ-potential of the different NC formulations (p ˃ 0.05)  Fig. .Fig. 2EfThe % encapsulation efficiency of all SL-loaded NC ranged from 56.3 ± 5.9 to 92.18% ± 1.8%. Glyceryl monocaprate-based NC exhibited the highest encapsulation efficiency values compared to other oil-based formulation, regardless the type of the polymer Fig. . This isIn vitro release profiles showed that changing the oil core influenced the initial burst release from different NC Fig. . In PLGAThe appropriate morphology of nanoparticulate drug delivery system is crucial for the successful design of therapeutic drug delivery systems. In this work, TEM was used to visualise the particulate and to evaluate aggregation or adhesion of SL-loaded NC. TEM images revealed a smooth spherical shape of (F9) homogenous size with no aggregations Fig. . The aveζ-potential immediately after purification at time zero and every 10 days over 1 month of storage at 4 °C (Table p ˃ 0.05) increase of size, PDI and zeta potential compared to freshly prepared ones. Although F6 prepared from 5% PEG-PLGA diblock copolymer showed non-significant (p ˃ 0.05) increase in size and zeta potential, it showed a significant (p ˂ 0.05) increase in PDI value after 30 days from preparation. No apparent change in colour, clarity or phase separation was observed in any of NC preparations. Herein, stability results showed that SL-loaded NCs prepared from 10% PEG-PLGA copolymer were biocompatible, stable and monodisperse nanosystem for SL encapsulation, with potential applications for drug delivery. Our results prove that nanoprecipitation technique leads to efficient stabilisation of oily core PEGylated NCs. The in vitro stability measurements showed sufficient colloidal stability for 1 month. Stability results confirmed lack of evident destabilisation phenomena associated with no degradation over time which can affect the size, PDI and zeta potential of the prepared NCs.After formulation of all SL-loaded NC, non-entrapped drug was removed by gel filtration chromatography. The purified NC formulations  were selected for further study as they showed superior physicochemical properties for each polymer type compared to other NC. These formulations were characterised for their size, PDI, °C Table . The resp < 0.001) than other NC formulations with lesser amounts of PEG in the polymer coat (F3 and F6). Interestingly, these results were in good agreement with the optimum physio-chemical properties of F9, with the lowest particle size, highest PEG content and lowest zeta potential [This study investigated the efficiency of cellular uptake of SL-loaded PLGA and PEGylated PLGA NC by CT26 colon cancer cells. The effect of polymer type on the in vitro cellular uptake results are shown in Figs. otential . These potential .Fig. 4QuGiven that SL and the other formulation components possess no fluorescent activity, it was necessary to add a fluorescent dye to determine the position of NC following exposure in the test cell lines. Images from fluorescence microscopy supported particulate uptake in CT26 cells Fig. . The SL-An assessment of the physicochemical data for all formulations used in this work allowed selection of F9 as an optimised formulation. This was based on F9 having the smallest size, highest %EE, optimum shelf-life stability and highest cellular uptake. Therefore, F9 was selected for further cell viability and organ distribution studies.50 which is the drug concentration resulting in 50% growth inhibition of colon cancer cells. Free SL showed a dose-dependent effect as cell viability decreased with increasing dose from 20 to 60 μM. Significant reduction in cell viability compared to control (p < 0.05) was observed. Treatment with SL-loaded NC (F9) reduced cell viability in a dose-dependent effect meanwhile it maintained its cytotoxic action up to 3 days after treatment due to sustained drug release. The mean IC50 value for SL-loaded NC (F9) in CT26 cells was approximately 60 μM, which was achieved within 24 h. Different doses of free SL showed a slight decrease in cell viability of CCD-841-CoN normal colon epithelial cells especially after 3 days of treatment  cytotoxic effect on normal colon epithelial cells within the concentration range used in this study. This confirms the safety profile of the designed drug delivery system compared to free drug for further in vivo applications. Interestingly, these results are different from other studies [p < 0.001).The cytotoxic action of SL-loaded NC (F9) on CT26 colon cancer cells and CCD-841-CoN normal colon epithelial cells was evaluated by MTT assay after 24, 48 and 72 h of treatment with 20, 40 and 60 μM of free SL and SL-loaded NC Fig. . Blank Nent Fig. . Twenty- studies . This miTumour accumulation and organ biodistribution of DiR-tagged SL-loaded NC (F3 and F9) were assessed in vivo in mice bearing the murine colon cancer CT26 model. Whole-body in vivo imaging was performed at 1, 4 and 24 h after injection Fig. . ImagingIn vivo imaging data from mice treated with PBS (control group) confirmed that no background fluorescence was present (data not shown). SL-loaded NC (F3) formulated from PLGA polymer showed no tumour uptake after 1, 4 and 24 h, but did confirm accumulation in the liver and spleen Fig. . Tumour p < 0.001) which confirms high tumour accumulation of F9. Fluorescence intensity quantified from the liver in animals treated with F3 was highly significant compared to animals treated with F9 (p < 0.001).The excised organs from control animals (treated with PBS) showed no fluorescence. Animal treated with F3 showed high fluorescence from both liver and spleen, but low fluorescence from the tumour masses. Excised organs from animals treated with F9 showed the highest fluorescence intensities from the tumours when compared to other organs Fig. . FluoresSize and surface properties of nanocarriers play an important role in controlling drug pharmacokinetics, biodistribution and drug resistance in some cancer cells , 33. NanA low number of studies have investigated the therapeutic potential of SL in vivo. A sepsis model has been used, which showed that SL mixtures containing both acidic and lactonic SL reduced mortality in rats with experimentally induced sepsis via cecum puncture . Recentlp ˃ 0.05) loss in body weight was detected. There were no toxicity signs after treatment with either free SL or SL-loaded NC (F9) at the drug concentration used. The dose used for this study was 10 mg SL per kg of mice weight, and 5 injections were administrated in vivo to the mice. The in vivo tumour growth inhibition study in mice bearing CT26 colon cancer after SL treatment showed no antitumour activity of blank NC and a pronounced anticancer effect of SL-loaded NC (F9) . At the end of the experiment, the average size of the tumour mass of control animals treated with saline was found to be 993.5 ± 142.5 mm3. The average tumour size of animals treated with free SL was 706.7 ± 105.3 mm3 and the percentage tumour growth inhibition (% TGI) was 28.9%. A more pronounced effect was recorded in animals treated with F9. There was a significant reduction in the volume of tumour mass at each time point starting from the 10th day till the end of the experiment when compared with control and free drug-treated group. The final average size of tumour was found to be decreased to 426.6 ± 115.4 mm3 and the % TGI was 57.09%  confirming its greater antitumour activity than free SL.All animal involved in this study appeared healthy throughout the whole experiment duration and no significant (F9) Fig. . The ave09% Fig. . It was p < 0.001) and free drug-treated mice (p < 0.01). The percentage reduction in tumour weights was 37.5% in mice treated with free SL, which is statically significant compared to control mice (p < 0.01).At the end of the in vivo experiment, all mice were sacrificed, and implanted tumours were excised and weighed Fig. . The chaThis study investigated, for the first time, the formulation and optimisation of a nanocapsule drug delivery system for SL encapsulation and in vivo administration in CT26 colon cancer. Formulation of PEG-PLGA-based polymeric NC with an oil core showed high SL loading and sub-micrometre particle size. PEGylated 10% NC (F9) showed superior physio-chemical properties compared to similar SL-loaded PLGA NC and a favourable shelf-life stability. This formulation achieved efficient cellular uptake by CT26 colon cancer cell line compared to other polymeric NC which facilitated its cytotoxic action in vitro meanwhile it was safe to normal colon cells. PEGylation makes F9 suitable for passive targeting due to a prolonged blood circulation profile by evading the immune system thus maximising its accumulation in colon tumour mass and minimising its unnecessary biodistribution to other body organs after i.v. administration. F9 was capable of inhibition of tumour growth and tumour weight in vivo while being safe to treated subjects. In conclusion, these results suggest that SL-loaded 10% PEGylated NC could be an effective anticancer therapy for colon cancer. Our future work will involve testing the anticancer activity of this novel drug delivery system against different types of tumours.


EAAC1) is a type of neuronal glutamate transporter and considered to have an additional action involving the neuronal uptake of cysteine, which acts as a crucial substrate for glutathione synthesis. Previously, our lab demonstrated that genetic deletion of EAAC1 leads to decreased neuronal glutathione synthesis, increased oxidative stress, and subsequent cognitive impairment. Therefore, we hypothesized that reduced neuronal transport of cysteine due to deletion of the EAAC1 gene might exacerbate neuronal injury and impair adult neurogenesis in the hippocampus after transient cerebral ischemia. EAAC1 gene deletion profoundly increased ischemia-induced neuronal death by decreasing the antioxidant capacity. In addition, genetic deletion of EAAC1 also decreased the overall neurogenesis processes, such as cell proliferation, differentiation, and survival, after cerebral ischemia. These studies strongly support our hypothesis that EAAC1 is crucial for the survival of newly generated neurons, as well as mature neurons, in both physiological and pathological conditions. Here, we present a comprehensive review of the role of EAAC1 in neuronal death and neurogenesis induced by ischemic stroke, focusing on its potential cellular and molecular mechanisms.Although there have been substantial advances in knowledge regarding the mechanisms of neuron death after stroke, effective therapeutic measures for stroke are still insufficient. Excitatory amino acid carrier 1 ( EAAC1), and it carries out this function by increasing the cysteine concentration in the cell. EAAC1, also known as SLC1A1 or excitatory amino acid transporter 3 (EAAT3), increases intracellular glutathione (GSH) levels by importing cysteine from the extracellular space. The process includes the expression of the gene that affects neurons -thymidine. These cells can also be marked by retrovirus-related substances that detect the M-phase of neurons, such as green fluorescent protein (GFP) or LacZ. Other substances, such as Ki67, collapsin response mediator protein 4 (CRMP4) , polysialic acid–neural cell adhesion molecule (PSA–NCAM), SOX gene families, and calretinin, are used to detect dividing neurons. Neurons that are differentiating can be detected by doublecortin (DCX), proopiomelanocortin (POMC), or neuronal nuclei (NeuN) antibodies. It has been reported that newly generated neurons in the dentate gyrus and striatum are GABAergic interneurons, with the former requiring two maturation steps and the latter needing only one ,43,45,46Although stem cells in the CNS are in comparatively low oxidative conditions compared to neurons in other organs , they ar2+ circumstances, it is clear that this imbalance impairs cellular division in the DG [Because the reperfusion state causes the unregulated elevation of the oxidation level in low-pH and high-Can the DG . Inflictn the DG . As a ren the DG ,46,51.EAAC1 as the main cysteine importer of cysteine in hippocampal regional mitosis. Our previous study showed that EAAC1 is important for the survival of newborn neurons in the adult hippocampus under physiological and ischemic conditions [EAAC1−/− mice under ischemia-free conditions compared to the age-matched WT mice. However, EAAC1−/− mice showed poor survival outcomes of newly generated neurons in both young and aged mice. In addition, EAAC1−/− mice had fewer progenitor cells and their subsequent neuroblasts 7 days after ischemia. The neuronal maturation and survival rate of newly generated cells were also decreased in EAAC1−/− mice 30 days after ischemia  is not essential for novel proliferation in the DG, which illuminates the importance of nditions . We founischemia . This clIn the sites where the pathological nucleic acid and lipids were analyzed, oxidative stress can be a problem in neurogenesis in the aspect of blocking proliferation of normal type I cells. Studies show decreased efficiency of pyruvate dehydrogenase and other types of mitochondrial dysfunction during the first 30–45 min of reperfusion, during which the number of hydroxyl radicals is at its maximum ; the memEAAC1 is one of the important neuroprotectants in the aspect of oxidative stress, manipulating factors related to EAAC1 will multiply the effect of the gene on neural death and neurogenesis. The main interference involves factors that reinforce the expression of EAAC1 in the cell membrane or lessen factors that impair the expression of EAAC1. As the expression of EAAC1 is inhibited by GTRAP3-18, inhibition of GTRAP3-18 results in an increase in EAAC1. Many studies have revealed that protein expression can be induced by adding MeβCD, altering the cellular GSH level. This may be rooted in MeβCD elevating cAMP response element (CRE)-mediated gene expression and extracellular signal-related kinase (ERK) as cholesterol is cellularly discharged, both promoting the expression of GTRAP3-18 and physically impeding EAAC1 [EAAC1 is done through the same pathway, finding that a cholesterol-rich glial culture medium increases glutamate transport means that the existence of extracellular cholesterol impedes the synthesis of GSH by changing the membrane composition of neural cells [EAAC1 are shown by the accumulation of metals such as Mn. A distinct negative correspondence between injected MnCl2 and mRNAs of the transporter, and the same variable with the amount of xCT-positive astrocytes, was detected in the striatum of the brain in neonatal mice. The phenomenon involves alteration of EAAC1 and xCT directly by the metal ion itself, altering the cysteine level in the microcellular environment and increasing oxidative stress [EAAC1.As ng EAAC1 ,55. As tal cells . Some ste stress . TherefoEAAC1′s role in producing GSH in neurons, the addition of a substance that can promote the cellular production of GSH itself will reduce cell death and increase functional neurons during the reperfusion state. Such an example is NAC. The effectiveness of NAC has been shown in many studies on the ischemia–reperfusion state to prove that defects of EAAC1 are related to neural damage and neural production at the same time because NAC provides cellular cysteine [Considering cysteine ,46. The Considering increases in mitotic factors such as basic fibroblast growth factor (bFGF) and inflammatory process inducers such as nitric oxide synthase, leukotrienes may promote a cellular deficit from ischemia . In the EAAC1 and both neuronal death and neurogenesis, it is evident that the oxidative stress from an outside stimulus is a critical factor in these phenomena. EAAC1 was proved to have more significant functions in cysteine uptake for the synthesis of GSH, which, in turn, controls the oxidative level of cells. This was more evident in ischemia models. After an ischemic event, an increased level of GSH helped lessen the number of degenerating cells. The main mechanism is the diminishing of oxidative stress from the outside stimulus and saving neurons from the crisis. For neuronal plasticity, a controlled oxidative level increased the number of cells that correctly matured, and GSH seems to support the differentiation of new cells, therefore increasing the rate of real neurogenesis and the formation of functional cell layers.Through deep insights about the relationship between EAAC1 expression in neurons would bring about the same neuroprotective effects. Achieving this result would fortify current theories indicating a linkage between EAAC1 and oxidative stress. For example, more studies should be performed on the relationship between GTRAP3-18 and cellular death or cellular regeneration. Understanding how it is linked to cytoskeletal changes during neuronal development gives insights into this aspect. Substances that are linked to fetal neural development, such as retinoic acids, need more investigation to uncover the role of oxidative stress in cellular processes that include not only correct maturation but also cellular development itself.Further studies should focus on whether a direct increase in


High-strength concrete is used to provide quality control for concrete structures, yet it has the drawback of brittleness. The inclusion of fibers improves the ductility of concrete but negatively affects the fresh properties of fiber-reinforced concrete. The effects of different fine to coarse aggregate ratios on the fresh and hardened properties of steel fiber reinforced concrete were investigated in this study. Mixtures were prepared with various fine to coarse aggregate (FA/CA) ratios incorporating 1% steel fiber content (by volume) at constant water to cement ratio. The workability, unit weight, and temperature of the concrete in the fresh state, and the mechanical properties of steel-fiber-reinforced concrete (SFRC) were investigated. The inclusion of fiber in concrete influenced the mobility of concrete in the fresh state by acting as a barrier to the movement of coarse aggregate. It was observed that the concrete with an FA/CA ratio above 0.8 showed better flowability in the fresh state, whilst an above 0.9 FA/CA ratio requires excessive superplasticizer to maintain the flowability of the mixtures. The compressive and flexural strength of SFRC increased with an increase in the FA/CA ratio by around 10% and 28%, respectively. Experimental values of compressive strength and flexural strength showed good agreement, however, modulus of elasticity demonstrated slightly higher values. The experimentally obtained measurements of the mechanical properties of SFRC conformed reasonably well with the available existing prediction equations, and further enabled establishing predictive isoresponse interactive equations within the scope of the investigation domain. The utilization of high-strength concrete (HSC) has become an integral part of modern day construction, due to its excellent behavior in both mechanical and durability related properties. However, HSC is brittle in nature compared to normal-strength concrete (NSC). Silica fume (SF) is one of the essential materials included in HSC mixtures, however, there was no significant difference between densified SF and undensified SF in the properties of fresh and hardened ultra-high performance fiber-reinforced concrete . HowevermaxD values on the mechanical properties of SFRC were investigated by Chenkui and Guofan [maxD led to improvements in all strength values. In another study, various fiber types with different groups of aggregate were used to make SFRC mixtures. The bond strength was improved in these mixtures by increasing the fine aggregate (FA)-to-coarse aggregate (CA) ratio [maxD values [Steel fibers of various shapes and sizes can be produced as specified by ACI 544.1R . The cond Guofan . It was A) ratio . Thus, tx values . For thex values  recommenx values , and 1.0x values .Coarse and fine aggregate contents affect a given dosage of fiber content in SFRC more significantly. Several researchers have introduced different mixture design approaches based on optimization of the packing density, and some of these researchers studied the effects of the contents of cement and water on the mechanical properties of SFRC ,15,21,22Ordinary Portland cement (OPC), conforming to ASTM type-I, was used for the preparation of all mixtures, and satisfies the ASTM C150 specifications . The cheGlenium 51 produced by BASF , a polycarboxylic ether-based structure superplasticizer (SP), satisfying the ASTM C494 type F specifications , was useFA with a size of 0–3 mm and CA with a nominal grain size of 10 mm, conforming to ASTM C33,  was usedHooked-ended steel fibers used in this investigation were as given in 3, a water-to-cement (w/c) ratio of 0.30, and a fiber content of 78.5 kg/m3 were used. The SP dosage was optimized for each mixture to assess its targeted workability. A series of mixtures were prepared with different FA/CA ratios of 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.10, and 1.20 to determine the optimal dosage of SP. The mixture proportions are presented in A total of sixteen SFRC mixtures with different FA/CA ratios were prepared. Eight mixtures were without fibers, and eight with fibers. The volume fractions of steel fibers, cement, and water, as well as the total aggregate content, were kept constant. In the mix design, a cement content of 500 kg/mAll aggregates were mixed in a dry state with the addition of water for absorption, followed by the addition of cement. The constituents were mixed for one minute and 70–80% of the water was added and mixed for 1 min. After that, the rest of the water along with the SP was added to the mixture, and mixing continued for 3 min, followed by a rest of 3 min. Then, lastly, mixing occurred for 2 min. Fibers were added at the end and mixed until the fibers were well dispersed in the mixture. Then, the slump was measured to evaluate the horizontal flow of FRC. The mixtures were designated as M50, M60, etc., where 50 represents an FA/CA ratio of 0.5.Casting and compacting was conducted in accordance with ASTM C31 . After tThe testing of all mixtures, with and without fibers, was performed in both fresh and hardened states. The workability, unit weight, and temperature were measured in the fresh state, whereas the compressive strength, the modulus of elasticity, and the flexural strength were investigated in the hardened state.An experimental investigation with two steps was designed. In the first step, the slump of concrete (with and without fiber), the unit weight, and the temperature were measured to investigate the influence of the addition of steel fibers in the fresh state. At the second step, the mechanical properties of the concrete were investigated. All samples were stored in a tank of lime saturated water at 20 ± 2 °C until testing. To evaluate the workability of the fresh concrete, a truncated cone apparatus, with a cone diameter of 100–200 mm and height of 300 mm, was used. This cone was centered on the base plate and, after the filling of the cone, this cone was lifted vertically upward, and the drop in the height of the concrete was measured as the slump.Ec is modulus of elasticity (psi), S2 is stress corresponding to 40% of ultimate load, S1 is stress corresponding to a longitudinal strain, ε1, of 50 millionths (psi), and ε2 is longitudinal strain (produced by stress S2).A 100 × 200 mm cylinder was used to measure the uniaxial compressive strength. A compressometer set up was used to measure the modulus of elasticity of the concrete. The modulus of elasticity was measured as per the ASTM C469  method uPrismatic samples 100 × 100 × 300 mm were tested at a loading rate of 0.2 mm/min, with third point loading using the set up shown in Based on the experimental results, quadratic interactive response surface models were developed using Minitab software . These mA responsive variable The properties of the fresh concrete measured as slump (with and without fiber content), temperature, and unit weight are presented in The measured slump was also plotted against the FA/CA ratio before and after adding steel fiber, as shown in As seen from A change in the FA/CA ratio affected the compressive strength of the concrete, as shown in The addition of fine aggregates influenced the compressive strength; however, the difference between the compressive strength of mixtures with low and higher FA/CA ratios was smaller . A higheThe measured values of modulus of elasticity are presented in Equation (6) was plotted as interactive isoresponse contours for the prediction of modulus of elasticity, as shown in P is the peak load, L is the span length of the prism, b is the width of the specimen, and d is the depth of the specimen. The variation in the flexural stress for different ratios of FA/CA is shown in The relationship between the load versus the deflection behavior of steel fiber reinforced concrete is shown in The relationship of the load versus the deflection curve of the prisms was determined using the set up shown in the experiment, as shown in The predictive relationships for the calculation of the uniaxial compressive strength and the modulus of elasticity are mentioned in different codes such as Equation (8) , EquatioThe relationships between the uniaxial compressive strength and flexural strength available in the present literature such as Equation (13) , EquatioThe generalized forms of these relationships can be seen in Equation (18). A comparison between the experimental data and the predictive curves is shown in With an increase in compressive strength, the experimental data fit between the ACI 318 [The results revealed that the curves proposed by Xu and Shi  and PeruThe modulus of elasticity values were used to establish models (using Equation (1)) using the measured values of compressive strength and flexural strength, as follows:The addition of fiber contents greatly influences the workability of SFRC, and caused a reduction in slump. The material movement was reduced due to the addition of fibers, which act as a barrier to the movement of coarse aggregate.An increase in the FA/CA ratio affects the workability of SFRC, however, it does not have negative effect on its compressive strength.FA/CA ratio above 0.8 showed better flowability in the fresh state of SFRC, however, FA/CA ratio above 0.9 needed excessive superplasticizer to maintain flowability.Higher values of FA/CA ratio increased both compressive strength and flexural strength of SFRC, up to 10% and 28%, respectively.Steel fibers transferred the load to the concrete matrix by bridging the crack by means of bond stress, and continued to take load after the first crack or fracture of plain concrete.Experimental values of compressive strength and flexural strength showed good agreement with the available existing prediction equations, however, modulus of elasticity demonstrated slightly higher values.Experimentally obtained measurements enabled the establishment of isoresponse interactive equations and contours, which have prediction capabilities within the scope of the investigation domain.FA and CA contribute up to 75% of total concrete volume, therefore, balancing the usage of FA and CA plays a vital role in determining the performance and quality of the concrete.The main conclusions of this investigation can be summarized as follows:


Doxorubicin (DOX) is widely used to treat many types of cancer; however, it is associated with chemotherapy-related complications such as cognitive dysfunction, known as chemobrain. Chemobrain affects up to 75% of cancer survivors, and there are currently no available therapeutic options. This study aims to examine whether metformin (MET) can protect against the neurotoxicity caused by DOX treatment. Forty male rats were divided into four groups (10 rats/group): control, DOX, DOX + MET, and MET. Rats treated with DOX received five doses of 4 mg/kg DOX weekly (cumulative dose: 20 mg/kg). For the DOX-MET and MET groups, MET (3 mg/mL) was dissolved in drinking water. Behavioral and glucose tests were performed one day after treatment was completed. We found DOX  caused learning and memory impairment in the Y-maze, novel object recognition, and elevated plus maze behavioral tests. MET did not rescue these DOX-induced memory impairments. Neither DOX nor MET nor MET + DOX altered glucose levels following the treatment. In summary, DOX treatment is associated with memory impairment in rats, but MET does not rescue this cognitive dysfunction. Recent advancements in chemotherapy have shown success in eradicating various types of cancer. The main mechanism underlying the action of chemotherapeutic agents is cytotoxicity. However, the toxicity associated with chemotherapy leads to several acute and chronic adverse side effects ,2,3,4,5,Preclinical and clinical studies have revealed chemotherapy is associated with impairment of cognitive function. For example, chronic use of cyclophosphamide (CYP), doxorubicin (DOX), and cisplatin were shown to severely impair hippocampus-dependent cognitive function in rodents . These cGrowing evidence has documented the beneficial effects of metformin (MET), a commonly used anti-diabetic drug, on multiple diseases other than diabetes. For instance, the long-term use of MET has been associated with anticancer effects  and exteTherefore, this study aims to investigate whether MET co-administration can protect against DOX-induced cognitive impairment using rat models.Forty male rats (200–250 g) were individually housed and maintained on a 12-h light/dark cycle with free access to food and water. Animals were observed daily, and their body weights measured every 3 days. All behavioral tests were performed during the light phase of the cycle. The ethics and protocol of this research were approved by the Research Unit at the College of Pharmacy at Qassim University. This is no informed consent required for this study.Animals were divided into four groups: DOX, MET, DOX + MET, and control groups. Rats received an intraperitoneal (i.p.) injection of 4 mg/kg DOX weekly for 5 weeks . MET was dissolved in the rats’ drinking water at a concentration of 3 mg/mL. MET was administered daily, starting the day before DOX treatment. The rats underwent behavioral tests after receiving five scheduled DOX doses.The Y-maze test measures an animal’s ability to recognize places they have already explored and their ability to explore new places . We usedWe used the novel object recognition (NOR) test to evaluate memory function . The tes2. The maze was placed 50 cm above the floor. In the training session, the rat was placed at the end of an open arm, facing the central platform, and allowed to explore the apparatus for 10 min. Three hours later, the rat was placed in the same spot as in the training session, and the transfer latency time  and total time spent in the closed arms were recorded using a video camera [The elevated plus maze (EPM) test is used to measure anxiety as well as learning and memory processes. The wooden apparatus consists of two opposing arms: the open arms (50 × 10 cm) and the closed arms (50 × 10 cm). The height of the sidewalls of the closed arms was 30 cm. The central platform between all arms measured 10 cmo camera .The blood glucose test was used to evaluate the glucose levels of rats. The tail vein was injured with a clean, sterile needle to obtain optimum-quality blood. An Accu-Chek glucometer with strips was used to test the blood glucose level based on the manufacturer’s instructions.p-value <0.05 was considered statistically significant.All results are presented as means ± standard error of the mean (SEM) and were analyzed using Graphpad Prism 5 software. The survival rate, Y-maze, NOR, EPM, and blood glucose data for each group were analyzed using one-way analysis of variance followed by Dunnett’s analysis. All the treatment group data were compared with that for the control group. A Chronic DOX treatment did not affect the survival rate of rats; however, we found a higher incidence of death among the rats that received both DOX and MET A. In totDOX-treated rats showed significantly fewer entries into the novel arm than DOX + MET-treated rats A. HoweveThe DOX, DOX + MET, and MET-alone groups were significantly different from the control group in the NOR test, suggesting DOX and/or MET potentially alter memory function in rats .The transfer latencies in the DOX-treated and MET-treated groups were significantly higher than those in the control group A. SimilaGlucose levels were assessed one day after treatment was concluded. As shown in Preclinical and clinical studies have shown that DOX can alter cognitive functions ,24. HereAlthough we hypothesized that MET could improve memory dysfunction in Alzheimer’s disease patients by enhancing insulin sensitivity and signaling , we obseDuring NOR tasks, memory was impaired in DOX-treated animals, as well as in the MET- and DOX + MET-treated groups, confirming that cognitive functions were affected. Rats spent less time exploring the novel object in the DOX, MET, and DOX + MET groups, indicating memory was impaired as a result of the treatments. In addition, in the EPM, all treatment groups had longer transfer latency times compared with the control group. However, the total time spent in the closed arms was similar to that in controls, indicating the longer transfer latency time was due to memory issues and not a result of lethargy following treatment. Together, these data suggest that DOX treatment can impair memory function that relies on the hippocampus, and MET treatment failed to alleviate these deficits.We also found a higher incidence of death among rats receiving both DOX and MET . TherefoIn conclusion, our study supports the results of previous studies that show memory loss due to DOX treatment using behavioral tests. Although MET can reduce the cytotoxic effects of several chemotherapy agents ,


Among the four immunoglobulin G (IgG) subclasses, IgG4 is the least represented in serum of a healthy human and it is considered an “odd” antibody. The IgG4 antibody has unique structural features that affect its biological function. These include the ability to undergo antigen-binding fragment (Fab)-arm exchange, to create fragment crystallizable (Fc) – Fc binding with other IgG4 and other IgG subclass antibodies, have a unique affinity profile for Fc gamma receptors (FcγRs) and no binding to complement component C1q. Altogether, these characteristics support anti-inflammatory roles of IgG4 leading to immune tolerance. Under conditions of chronic antigenic stimulation and Th2-type inflammation, both tissue and serum IgG4 levels are increased. This review seeks to highlight how in allergen immunotherapy IgG4 can confer a protective role as a “blocking” antibody and safeguard from subsequent allergen exposure, while IgG4 can confer immunomodulatory functions to support malignancy. While Th2 conditions drive polarization of macrophages to the M2a subtype, chronic antigen stimulation drives B cell class switching to IgG4 to further support phenotypical macrophage changes towards an M2b-like state. M2b-like macrophages can secrete chemokine (C-C motif) ligand 1 (CCL1) and interleukin-10 (IL-10) to support regulatory cell recruitment and to further shape a tolerogenic microenvironment. Thereby, IgG4 have a Janus-faced role, favorable in allergy but detrimental in cancer. The four human immunoglobulin (IgG) subclasses, defined IgG1, IgG2, IgG3, and IgG4 following their descending order of abundance, were discovered in the 1960s following extensive studies using specific rabbit antisera against human myeloma IgG proteins. Despite an amino acid homology of over 90%, each subclass has a unique structural and functional profile in antigen binding, immune complex formation, complement activation, effector cell activation, serum half-life, and placental transport . Fcγ. Fcγ6]. To produce antibodies that maintain the antigen specificity but have a different effector function, proliferating B cells are subjected to class switch recombination (CSR). Class switch recombination is an intrachromosomal DNA recombination between the switch (S) region located downstream the variable diversity joining segments (VDJ) region, or variable heavy (VH) region, and the S region upstream the constant heavy (CH) region. The activation-induced cytidine deaminase (AID) enzyme controls this process . In addiIgG4 is the least abundant IgG subclass in human serum with an approximately total IgG relative abundance of 4–5% . The strAn even more peculiar characteristic of IgG4 is the so-called Fab arm exchange (FAE); the exchange of two half-molecules, consisting of one heavy and one light chain (Fab arm) derived from two distinct IgG4 antibodies. Fab arm exchange enables the association of two different specificities within one IgG4 molecule, enabling a bi-specific configuration. The FAE process is facilitated by two unique features which weaken the interactions between the two Fab arms of the cognate IgG4 molecule: (1) the serine at position 228 in the core hinge region causing a cysteine–proline–serine–cysteine (CPSC) motif instead of the cysteine–proline–proline–cysteine (CPPC) sequence of the other IgG isotypes A; (2) thThese features of IgG4 result in a more flexible core hinge domain and allow two hinge isomers: one with the typical inter-heavy chain disulfide bonds  and the other with intra-heavy chain disulfide bonds  .Several studies determined that the FAE process is controlled by redox conditions and can be accomplished in vivo as well as in vitro by choosing an appropriate redox buffer. However, with a redox buffer that mimics plasma conditions, the IgG4 FAE rate was an order of magnitude lower than the actual rate of exchange calculated based on in vivo observations . The exaA direct consequence of FAE is the phenomenon of functionally monovalent but bi-specific IgG4 antibodies that are unable to crosslink identical antigens or form large ICs against a specific target, yet even prevent formation of large immune complexes by other antibodies. In the last years, different therapeutic IgG4 antibodies were designed for treating several diseases, and a S228P mutation, which renders the IgG4 core hinge more IgG1-like, was considered to abolish FAE in vitro and in vivo .Among the different unique characteristics of IgG4 there is also the Fc–Fc interactions that describe the interaction between human IgG4 and several other IgG subclasses, but not with other human Ig classes  Figure C. This FIn recent years, several studies demonstrated that there is a range of binding affinities for FcγRs by the four different IgG subclasses . The comIt is known that often repeated or prolonged exposure to the antigen fosters IgG4 responses . The Th2Naive B cells expressing IgM can directly switch to the IgG4 class . FurtherAs outlined above, IgG4 serum levels increase, mostly following repeated or chronic exposure to an antigen ,18. On o+ producing Th2 cytokines such as IL-4 and IL-13 supporting isotype switch by B lymphocytes to allergen-specific IgE and subsequent binding of IgE to its high-affinity receptor FcεRI on mast cells and basophils; (2) the effector phase characterized by a subsequent encounter with the same allergen that crosslinks the IgE–FcεRI complexes on sensitized basophils and mast cells, leading to the release of anaphylactogenic mediators (effector phase) [Type I hypersensitivity (IgE-mediated hypersensitivity) is characterized by 2 phases: (1) the sensitization phase characterized by differentiation and clonal expansion of CD4r phase) . Importar phase) . + B cells by allergens and decreased IgE production. All five mechanisms synergize to counteract the allergic inflammation and support specific immune tolerance to the specific allergen. After AIT, the levels of IgG4 in sera may rise 10–100 fold , and theOn the other hand, improvement of clinical symptoms throughout AIT, often correlates with increased production of IL-10 which is simultaneously responsible for both total and allergen-specific IgE suppression as well as IgG4 induction, the reduction of the IgE/IgG4 ratio and skewing towards a tolerogenic microenvironment. Regulatory T (Treg) cells are essential for the induction and maintenance of peripheral tolerance by preventing excessive immune responses. There are two types of human Tregs, distinguishing the naturally occurring thymus derived CD4+CD25+FOXP3+ Tregs, also called nTregs, and the inducible Treg cells (iTregs). Among the iTregs, other sub-categories: FOXP3 expressing iTregs, IL-10 secreting iTregs (Tr1), and TGF-β expressing iTregs (Th3) can be identified. Human Tr1 cells suppress T effector cells by various means: (1) they express C-C Motif Chemokine Receptor (CCR)2, CCR4, and CCR8 to inhibit the migratory capacity of T effector cells; (2) they express inhibitory receptors such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1); (3) and they secret inhibitory cytokines such as IL-10, IL-35, and TGF-β ,40. It was shown that IL-10 secreting Tregs can selectively enhance IgG4 versus IgG1 production by B cells, and that this requires cell–cell contact, later shown to be dependent on glucocorticoid-induced TNFR-related gene (GITR) and TGF-β in addition to IL-10 . This efIt should also be considered that many other cell types, including monocytes, DCs, NK cells, macrophages, and mast cells, can produce IL-10 ,45. Seve+ B cells [Numerous studies provide evidence that chronic inflammation increases the risk of cancer ,49,50. C B cells ,33,57, t B cells  and Breg B cells  in the tIn recent years, one area in the emerging field of AllergoOncology compares the characteristics of specific immune responses in allergy, AIT, and cancer immune tolerance ,60,61. LThe elevated levels of tissue and serum IgG4 have been associated with poorer prognosis in biliary tract cancers , in gastA study on human melanoma xenograft models in mice demonstrated that anti-tumor specific IgG4 antibody impaired and counteracted anti-tumor specific IgG1, and had weak anti-tumoral effector functions in vivo . SeveralIn fact, high levels of tumor non-specific IgG4 antibodies could exert their blocking functions via Fc–Fc interaction with tumor specific IgG1 antibodies linked on solid antigen, if the IgG1 heavy chains is partially dissociated . In factIn both AIT and cancer, a modified Th2 microenvironment based on IL-10 production by Tr1 and Br1 cells can lead to high levels of IgG4 expression by B cells and the establishment of immune tolerance. This is beneficial in AIT, reducing classical Th2 allergic responses, but can be detrimental in cancer. In both models, macrophages might have a key role in establishing and maintaining immune tolerance. Macrophages are the most abundant immune cells in the lung  as well+FOXP3+ Tregs from the periphery [We have reported a phenotypic and functional change of pro-allergic M2a toward an M2b-like phenotype only in the presence of IgG4 but not IgG1 isotype antibodies . Our dateriphery ,77,78. TIgG4 is the least abundant IgG subclass in human serum; nevertheless, it is unique among the IgG subclasses and presents distinct structural and functional features. The attributes of IgG4 comprise: (i) the ability to form FAE, a bi-specific antibody that is functionally monomeric; (ii) a lack of fixing complement and consequent inhibition of immune-complex formation by other isotypes; (iii) affinity for FcγRs, including the highest for inhibitory FcγRIIb; (iv) high antigen affinity that results from B cell affinity maturation during class switching. In consequence, IgG4 has a low capacity to trigger ADCP and ADCC and can antagonize IgG1 antibodies in cancer and IgE-mediated histamine release from allergic effector cells in AIT. IgG4 has also sustained immunosuppressive effects mediating a tolerogenic microenvironment by polarizing macrophages in immunoregulatory M2b-like cells, thereby presumably facilitating the recruiting of Tregs via CCL1-CCR8 interaction. Recently the CCL1-CCR8 axis was considered one of the most promising targets for tumor immunotherapy ,56. Due