Remarkable progress has been made in surface icephobicity in the recent years. The mainstream standpoint of the reported antiicing surfaces yet only considers the ice–substrate interface and its adjacent regions being of static nature. In reality, the local structures and the overall properties of ice–substrate interfaces evolve with time, temperature and various external stimuli. Understanding the dynamic properties of the icing interface is crucial for shedding new light on the design of new anti‐icing surfaces to meet challenges of harsh conditions including extremely low temperature and/or long working time. This article surveys the state‐of‐the‐art anti‐icing surfaces and dissects their dynamic changes of the chemical/physical states at icing interface. According to the focused critical ice–substrate contacting locations, namely the most important ice–substrate interface and the adjacent regions in the substrate and in the ice, the available anti‐icing surfaces are for the first time re‐assessed by taking the dynamic evolution into account. Subsequently, the recent works in the preparation of dynamic anti‐icing surfaces (DAIS) that consider time‐evolving properties, with their potentials in practical applications, and the challenges confronted are summarized and discussed, aiming for providing a thorough review of the promising concept of DAIS for guiding the future icephobic materials designs. Combating excessive icing through designing and deploying material surfaces has received growing interests. In this review, the practical design principles of anti‐icing surfaces through enabling dynamic changes in the chemical/physical states of the ice/substrate/ice–substrate interface with tailored functions by the three dynamic anti‐icing surfaces categories, namely, surfaces with dynamic substrates, dynamic interfaces, and dynamic ice structure are summarized. As such, enormous interests have been aroused in deploying surfaces that can control icing and mitigate its related damages. The so‐called icephobic or anti‐icing surfaces with properties like repelling incoming water droplets, delaying ice nucleation, repressing ice growth and weakening ice adhesion are designed for anti‐icing purpose. From the early lotus‐leaf inspired superhydrophobic surfaces (SHS) fabricated for repelling water droplets and delaying ice nucleation to the recent omniphobic pitcher‐plants‐inspired slippery liquid‐infused porous surfaces (SLIPS) developed for multiple anti‐icing, there are currently a colorful spectrum of anti‐icing surfaces reported in the literature showing great potentials with practical low ice adhesion strength 0.2–10 kPa  and easy achievable large‐scale ice remove capacity.Icing is one of the most common natural phenomena that greatly impact human activities. Undesired ice formation and accumulation can result in numerous safety problems to aircraft, power grid, transmission line, roadway, marine vessel, renewable energy infrastructure, and many others.7, 8 One of the key characteristics of these surfaces is that the ice–substrate contact area after ice formation is regarded as “constant.” The main focus of surface design lies on the states before ice formation but not the dynamic changes after icing. For instance, the anti‐icing performance of SHS including repelling incoming water and delaying ice nucleation has been widely discussed, with attentions only on the phenomena before ice formation. However, once ice forms on surfaces, especially in icing/deicing cycles, the anti‐icing performance of the SHS decays very fast because the surfaces asperities can be easily damaged. Another commonly used anti‐icing surface SLIPS with lubricant layer atop that enable the surfaces with excellent repellence to any immiscible materials also focus on the surface activities before icing. After ice formation on SLIPS, the lubricants can be exhausted easily due to ice removal. Generally, the static anti‐icing surfaces (SAIS) have disadvantages, for example, inapplicability at extremely low temperature, fragility to surfaces damage and surfaces degradation, and inadaptability to environmental changes.Despite the remarkable progress already made in surface icephobicity in the recent years, the anti‐icing surfaces are generally designed from a static perspective, for instance, texturing the surfaces structures, tuning the modulus of substrates, and modifying the surfaces energy without considering the evolution of properties.24 One These emerging anti‐icing surfaces can be regarded as dynamic anti‐icing surfaces (DAIS), thanks to the integrated evolving properties that can mitigate the interactions between ice and substrate even after ice formation. Extraordinarily, certain effective approaches in the traditional active deicing methodologies were featured in the design of DAIS. Unlike the direct and abrupt application of external mechanical, chemical, and electrical energy as driving force to remove ice, DAIS integrate the active strategies into the evolution of the ice–substrate contacting regions to reduce the resistance of removing ice. For instance, integrating dynamic antifreeze‐secreting capacity into superhydrophobic surfaces to introduce continuous assistance for ice removal even after ice formation. This strategy inherits the advantages of superhydrophobic surfaces in preventing ice forming and triggers evolution of properties at icing region after ice formation for easy ice removal. New anti‐icing surfaces with photothermal traps can actively melt interfacial ice, which utilize solar energy in deicing directly. Importantly, DAIS exhibit improved durability, wider temperature tolerability, and better environment adaptivity, and thus have gained increasing interests in the anti‐icing research and application fields.Very recently, we witness a shift in anti‐icing surface design principles from being of static nature, namely, from no consideration on the changes at the ice–substrate contacting areas after ice formation, to the focus on enabling dynamic changes of the chemical/physical states of the ice/substrate/ice–substrate interface for enhanced anti‐icing performances.40 TheFigure  Surfaces with dynamic properties at the ice–substrate interfaces provide the possibility of altering interface interactions for lowering ice adhesion. Surfaces with dynamic ice are able to direct ice growth, propagation, and even ice melting, which can mitigate ice accumulation and assist ice removal on the surfaces. One can see that DAIS is introduced in this review with the purpose of promoting rethinking of the design principles of new anti‐icing surfaces rather than recategorizing of the known anti‐icing materials. It should be emphasized that the traditional deicing methodologies are still actively in use despite their obvious shortcomings. Under the DAIS concept, the focus is to utilize the evolution of the ice–substrates and its adjacent region in materials design, but not to distinguish active or passive deicing. The following sections detailed the categories of DAIS surfaces.This review aims to provide a thorough survey on the newest development of DAIS. Focusing on the most relevant ice–substrate interfacial regions Figure 1a, and tFigure 44 Sur22.1Figure  Such surface lubricating is driven by the under‐skin disjoining pressure or concentration gradient. The mechanism underling self‐responsive surfaces has inspired the design of anti‐icing surfaces with embedded lubricants in the substrates.Many surfaces exhibit dynamic changes in response to their internal forces. Such self‐responsive surfaces are widely observed in natural organisms and systems. For instance, as shown in Figure 55 Suc Such droplet‐embedded gel system by phase separation of the microscale oil droplet nucleation and formation was metastable, and was able to secrete a lubricating film on the surface with a spreading factor of S = γga – (γla – γgl) > 0, where γga, γla, and γgl are the gel–air, liquid–air, and gel–liquid interfacial tensions, respectively. The surface lubricant layer was regenerable under the driving force of disjoining pressure originated from the van der Waals interactions at the gel surface. Both the thickness of the lubricant layer and the size of the embedded droplets in this substrate were controllable through polymer crosslinking strength and oil content, which offered a strategy for preparing similar substrates for improving anti‐icing performance. Icephobic surfaces following the same strategy for surface regenerable lubricant layers indeed showed ice adhesion strength below 40 kPa, with regenerated lubricating layers after 15 wiping/regenerating tests and long‐term ice adhesion strength below 70 kPa. Through a precise proportioning of polymer and oil, novel self‐lubricating organogels (SLUG) displayed extremely low ice adhesion strength of 0.4 kPa. The ice formed on the SLUG with small tilting angles could slide off at −15 °C, which demonstrated the great potential of self‐responsive substrates in anti‐icing.One notable self‐responsive substrate was developed through phase separation, as shown in Figure 56 Suc For example, alkane embedded in a polymer substrate can diffuse onto the surface driven by the concentration gradient and the internal stress of the polymer matrix, resulting in a solid alkane layer as shown in Figure  Recently, perfluoroalkane wax was verified as a good lubricant candidate for fabricating solid‐lubricant regenerable surfaces. The perfluoroalkane wax regenerating surface demonstrated low ice adhesion strength (≈20 kPa) and high environmental stability. Comparing to the liquid counterpart, solid lubricant layers are mechanically more robust in icing/deicing cycles. For both liquid and solid lubricant regenerable surfaces, the limited regenerating capacity of surfaces hinders their application. Unlike earthworm and poison dart frog that can secrete lubricant from body, the embedded lubricant in the surfaces can be used out easily. Therefore, future studies need to focus on self‐responsible surfaces with long‐term lubricant regenerating capacity.Besides small liquid oil molecules, solid lubricants were also used in self‐responsive substrates for regenerating surface lubricating layers to facilitate ice removal.61 For Such substrates showed significant improvements in mechanical durability because of the self‐healing ability of surface damages at subzero temperature to maintain their smooth topographies  icephobic substrates were prepared by optimizing polymer chain flexibility and concentration of hydrogen bonding, which can restore ≈80% of the ultimate tensile strength of the substrate after healing for 45 min at room temperature. The self‐healing substrates can be promising candidates for robust anti‐icing surfaces in practical environment if the self‐healing functionality is further improved especially at low temperature.Surface damages in practical applications are severely harmful to the icephobicity and durability of anti‐icing surfaces, since any possible interlocking between ice and surface can greatly enhance ice adhesion. Therefore, self‐responsive substrates with self‐healing functionality have been fabricated for anti‐icing purposes.71 Sucs Figure . One of 2.2 By integrating temperature sensitive components during fabrication, anti‐icing substrates can respond to temperature change in the surrounding. One of such substrates incorporated a binary liquid mixture (silicon oil and liquid paraffin) into a PDMS network, and the resulting reversibly thermosecreting organogel (RTS‐organogel) demonstrated distinct morphologies at different temperature, as shown in Figure  Specifically, the substrate was transparent at high temperature as the internal silicon oil and liquid paraffin were miscible. Upon cooling to icing temperature, the substrate secreted visible oil droplet to its surface owing to the collapse of the polymer matrix and the phase separation of the silicon oil from paraffin. Unlike the liquid layer propelled by internal force in the above‐mentioned SLUG shown in Figure  The RTS‐organogel was believed to be more durable than the SLUG, because they could reversibly absorb lubricant into the polymer matrix for replenishing the internal lubricants in storage and against evaporation/contamination.Many anti‐icing surfaces use dynamic substrates that respond to the ambient conditions of temperature, magnetic field, light, and so on.81 By  Interestingly, special temperature responsive lubricants provide a feasible solution to avoid such issue. As shown in Figure  Because the lubricant had a phase transition point from liquid to solid above water freezing point at ≈3 °C, the durability of the fabricated PTSLIPS was greatly improved. The PTSLIPS showed a low ice adhesion strength of ≈4 kPa and long‐term ice adhesion strength of 16 kPa after 30 icing/deicing cycles. Although the PTSLIPS can be fabricated using daily accessible materials like foams and common paper, its anti‐icing performance was superior than the results obtained on other conventional SLIPS used for anti‐icing. Because the phase transition point of the lubricant in the PTSLIPS was only marginally above water freezing temperature, displaced lubricants on the substrate surface in deicing can be restored in the subsequent phase transition cycle of the lubricant at slightly increased temperature, rendering self‐healing abilities and promising application potentials. Furthermore, the solid lubricant can physically prevent water from permeating into the substrate, thus suppressing mechanical interlockings during ice formation on the substrate. It is worth noting here that similar phase change materials (PCMs) were introduced into concrete for anti‐icing. During the phase transition upon cooling, the PCMs released substantial latent heat and hindered ice accumulation in walking pavements. Although the RTS‐organogel and PTSLIPS significantly increase the durability of anti‐icing surfaces, the soft polymer matrices limit their mechanical robustness. Matrices with superior mechanical and chemical resistance should be explored for further improving their durability.Liquid lubricants in anti‐icing substrates can be depleted in limited number of icing/deicing cycles due to the weak interaction between the lubricant and the base materials, which leads to poor durability.32 Int The magnetic slippery surfaces (MAGSS) were the successful representatives of this type of anti‐icing substrates, which used magnetic fluid  along with a magnetic field for controlling surface properties, as shown in Figure  The MAGSS responded to external magnetic field and generated a volumetric force to suppress water droplets from sinking into the substrate body with bulk oil, which led to small water droplet sliding off angle of 2.5°. Remarkably, the MAGSS maintained its liquid‐like phase at low temperature and were highly slippery to ice, showing extremely low ice adhesion strength (≈2 Pa) without degradation after 60 icing/deicing cycles.Magnetic field is currently not often applied in anti‐icing practice. However, utilizing magnetic field as stimuli to modulate substrates has been reported, with encouraging results illustrating the potentials in active deicing technology.80 The By integrating light‐absorbing azobenzene groups into polymer skeleton of the base materials, the so‐called UV responsive substrates (UVRS) were able to utilize UV energy for polymer chain conformation conversion. As shown in Figure 3O4 nanoparticles were infused into porous structures together in fabricating lubricant‐infused surfaces (LIS). Upon irradiation with infrared light, the LIS can absorb optical energy via Fe3O4 nanoparticles, and led to melting of the internal solid cocoa oil as lubricant for surface slippery liquid. The LIS thus possessed switchable hydrophobic/slippery functionality by turning off/on the light source. The smart responses of substrates to magnetic field, UV light and infrared light enhance icephobicity of the surfaces, however, and limit the application scopes of these surfaces at the same time. Novel environmentally responsive substrates which can function under more universal conditions are in demand.Light is another important stimulus source for triggering dynamic changes in anti‐icing substrates.88 By 2.3 Notably, an ultradurable icephobic coating was designed by introducing slide‐ring crosslinkers, namely, molecular pulleys, into PDMS base matrix  on solid surfaces, because ions can greatly impact the structure of water and suppress ice nucleation. Polyelectrolyte brushes hosting ions was employed to probe the effects of counter ions on ice adhesion  had maximum ice adhesion reduction (25–40%) comparing to the bare glass (G) at −18 °C, because of the most negative water structural entropy resulting from strong hydration. In comparison, the polyelectrolyte brushes with chaotropic counterions  did not change the ice adhesion, owing to positive water structural entropy of weak hydration. The nature of the polyelectrolyte layer also affected ice adhesion significantly. For instance, brushes with G‐SO3−Li+ decreased ice adhesion dramatically, which was not observed on samples with G‐COO−Li+. Such results suggested that kosmotropic counterions incorporated with strongly dissociating polyelectrolyte brush could facilitate ice removal. This study provided important reference for integrating counterions for related anti‐icing applications.trimethylammonium chloride)‐Cl (PMETA‐Cl) brush was synthesized on silicon wafers, which can accommodate different ions via ion exchange. Brushes with counterions of Cl−, ClO4−, PF6−, TFSI−, and PFO− were investigated, showing hydrophobicity Cl− < ClO4− < PF6− < TFSI− < PFO−. It was found in the study that ice propagation was efficiently on the highly hydrated PMETA‐Cl and PMETA‐ClO4 brushes, while much longer time were needed for ice form on brushes with counterions of PF6−, TFSI−, and PFO−. Thus, it was assumed that water molecules in the hydrophilic polymer brush (PMETA‐Cl and PMETA‐ClO4) moved toward the ice growth fronts when freezing occurred and consequently promoted ice propagation. By contrast, brushes with PF6−, TFSI−, and PFO− counterions and higher hydrophobicity could result in “water depletion regions,” which reduced the freezable water molecules and suppressed ice propagation /poly (PSS/PAH) and the PSS/poly (PSS/PDAD) coatings were fabricated by tuning the compositions of polyelectrolyte pairs during the layer‐by‐layer deposition. The PDAD had polyelectrolyte interacting more strongly with water in the outmost layer than that in the PAH. Consequently, ice propagation time on the PSS/PAH was two orders of magnitude longer than on the PSS/PDAD with same number of deposition layers. The ice propagation time can be tuned by simply change the composition of the outmost layers, but not by the number of deposition layers. Counterions and their concentration also showed positive effects on ice inhibiting performance on the PEMs. The results indicated that ice propagation was inhibited by depressing the water molecules trapped in the outmost layer of polyelectrolyte coatings. More importantly, the ice growth inhibition properties of PEMs layer in real environment was also investigated in the related studies  placed on the PEMs acting as the artificial ice nuclei, the PSS/PAH samples were still able to delay ice propagated for 2700 s, demonstrating the robustness and wide applicability of their anti‐icing performances. Suppressing ice propagation through counterions is an effective way to avoid rapid frost coverage on whole surfaces comparing to other strategies. However, the ice propagation delaying time still need to be extended for practical usage.To understand the mechanism that control the ice propagation, ice propagation behaviors on polyelectrolyte multilayer (PEM)‐coated surfaces were investigated.52 Thes Figure .[52]4.2 Such phenomenon was caused by the overpressure beneath the droplet originated from fast vaporization and the countering surface adhesion restricting the vapor flow. Because strong vaporization led to high degree of cooling on a supercooled droplet, a rapid recalescence freezing was initiated at the free surface. The latent heat released during the freezing increased the droplet temperature to the equilibrium freezing temperature (0 °C). Under the low‐pressure and low‐humidity conditions, a sudden increase in the vaporization of droplets surfaces resulted in rapid increasing in the overpressure beneath the droplet, which enabled self‐levitation of the droplet when freezing happened. Such phenomenon can be observed on various surfaces with different textures, as shown in Figure Controlling ice growth in a defined pattern on a surface can also be an effective approach to achieve icephobicity, given that ice formation is unavoidable after growth inhibition for a limited period. It was found that water droplets on superhydrophobic surfaces showed spontaneous levitation and trampoline‐like bouncing behavior in a low‐pressure environment.174 Su It was found that the key for self‐dislodging of frozen droplets lied in the freezing orientating process. Specifically, the successful self‐dislodging required free spherical surface of the droplet to be solidified first, forming an ice shell on the external surfaces while maintaining the droplet–substrate contacted region remained liquid. As the subsequent freezing phase boundary moved inward in the droplet asymmetrically, the volume of droplet expanded during the solidification process and caused mass displacement toward the unsolidified droplet–substrate interface. On nonwetting surfaces with pinned ice–liquid–vapor contact line, the displaced mass had no extra space to spread in the final state of solidification and lifted the droplet upward. This dislodging process was observed on various substrates with a wide range of wettability (from hydrophilic to superhydrophobic) and topography, as shown in Figure The freezing‐driven ice‐removal mechanism was further explored on various surfaces.54 It  By depositing silver iodide (AgI) nanoparticles as ice nucleation active sites on surfaces, ice nucleation was controlled to occur concurrently. It was found that the ice crystals on a hydrophilic surface (with water contact angle of 14.5°) possessed an along‐surface growth (ASG) mode. However, the ice on the hydrophobic surface (with water contact angle of 107.3°) exhibited an off‐surface growth (OSG) mode  between ice and its substrate, and subsequently the ice adhesion strength. In the OSG mode, the optimal Acontact was only around 10% of projected area (Aproject). By contrast, the ASG mode resulted in almost full ice contact of the surface project area (Acontact/Aproject ≈ 90%). In ice‐removal tests, the OSG ice was easily blown away by a wind breeze with velocity of 5.78 m s−1 at −3 °C, while the ASG ice remained firmly on the surface. This unique off‐surface growth mode provides alternative ways for assisting surface frost removal, but further investigation is needed for testing on the icephobicity of the surface against larger water drops.By controlling the multicrystal ice growth pattern on exposed surfaces, another important design for novel dynamic ice repellency was also developed recently.13 By 4.3 On surfaces fabricated by assembling poly(poly(ethylene glycol) methyl ether methacrylate)/PDMS (P(PEGMA)/(PDMS)) Janus particles, ice was found to grow into ice crystals/dendrites in certain regions, leaving the other regions dry and clean. The underlying mechanism of the distinct ice growth pattern on the Janus surfaces was elucidated, as depicted in Figure Because the dynamic ice growth patterns are important for anti‐icing, recent investigations further strived to program ice growth on the whole surfaces through surface chemistry/structure deign.178 On On these patterned surfaces, icing was designed to initiate from the polyelectrolyte domains and propagated atop, as shown in Figure  By contrast, ice growth at the ice‐free zone was inhibited. Thus, ice accumulated on the frozen area was accompanied by the consumption of condensed droplets and resulted in the continuous expansion of the ice‐free zones. It was showed in the experiments that the fraction of ice‐free region could be tuned by the grafting density and pattern of polyelectrolyte brushes. By using polyelectrolyte multilayer and polyelectrolyte hydrogel for patterning surfaces, ice‐free regions occupying ≈96% and ≈88% of the total surface area were achieved, respectively.The guided ice growth pattern on Janus surfaces suggested that surface chemistry design could dynamically create ice‐free zone. However, the locations of ice‐free zones on a surface were mostly random. In a recent report, ordered and large scale ice‐free zones taking up ≈96% of the entire surface area were programmed and created on surfaces with patterned polyelectrolyte.177 OnFigure  The unique feature of such surfaces was the introduction of water into microstripes on the surface. Under cooling, the water stripes on the surface froze first, serving as frozen regions. The formation of ice‐free and dry area on the surface followed the same process as discussed above, which led to as high as 90% of the total surface area as dry‐zone (or ice‐free zone). Interestingly, it was found that the growth rate of frost on the ice‐stripes was one order of magnitude lower than that on smooth solids. In short, the prefrozen ice pattern not only protected the other region from icing but also restrained ice propagation.Besides patterning in surface chemistry, microstructures can also be utilized for programming ice‐free zone on surfaces. As shown in Figure 178 Th The microtextures on the artificial leaves resulted in large scale ice‐free area without predesigned water/ice stripes, affecting both water condensation and ice formation on the surface. As water molecules in a supersaturated ambient air diffused more easily to the peaks than to the valleys, the artificial leaves accumulated more and larger droplets on top of its microtexture, where the freezing of droplets initiated at lower temperature. After ice formation on the peaks of the microtextures, the low vapor pressure led to the evaporation of droplets and created stable ice free zones in the valleys, as shown in Figure α, namely, the vertex angle, was proposed to quantitatively correlate to the percentage of ice‐free regions and the microtexture on the surface. The relationship between α and frost coverage was mapped under various ambient humidity, providing significant instructions for constructing ice‐free regions through surface design and structure fabrication. These surfaces with programmed ice‐free zone can be used to protect specific area from icing. Nevertheless, challenges like maintaining the function after surface contaminations and enabling large area of surfaces free from ice in practical application still need to be addressed.Natural surfaces can also program ice formation in winter, namely, ice accumulation on convex veins is more preferred than flat zones. Inspired by such phenomena, artificial leaves with ice‐free regions were designed recently.50 The4.4 Surfaces that can dynamically melt ice were commonly created by integrating materials with thermal effects, including electrothermal, near‐infrared photothermal, magnetothermal, and solar photothermal effects.Ice melting on anti‐icing surfaces is another important aspect of dynamic ice change for avoiding unwanted ice accumulation.181 Su Passive icephobic surfaces, such as superhydrophobic and the SLIPS surfaces, can also integrate active thermal effects for anti‐icing, as introduced in Section 3.2. By enhancing the power density on such surface, ice can be dynamically and constantly melted at the ice–substrate interface until being fully consumed. Recently, a so‐called slippery liquid infused porous electric heating coating (SEHC) was prepared, and contained MWCNTs as electrothermal generators. The SEHC also contained lubricating oil with high thermal conductivity that enabled reduction of ice adhesion strength from 1940 to ≈58 kPa. The obvious advantage of using SEHC instead of superhydrophobic surface was the high thermal conductivity of the infused lubricant, which was nearly one order of magnitude higher than that of air, and thus also enabled higher electrothermal efficiency. With power density of 0.58 W cm−2, ice on SEHC surface was melted completely while ice on superhydrophobic surface was remained . Surfaces with embedded Fe3O4 nanoparticles (0.5 wt%) into the substrate was prepared for melting surface ice. The temperature of such surfaces increased for more than 50 °C in 10 s under irradiation, owing to the excellent near‐infrared thermal response of the Fe3O4 nanoparticles. In an ice‐melting test, the ice layer on the surface can be melted with ambient temperature below −5 °C  increased 13 °C in 5 min.The Fen Figure 20a.[18 Despite the complex design, these surfaces are efficient in ice melting. For instance, superhydrophobic icephobic surfaces with photothermal effects by using cheap candle soot was newly fabricated. Because of the hierarchical structure and the black color, the candle soot has excellent photothermal conversion efficiency. As shown in Figure −2. In a frost‐melting test at −30 °C, the accumulated frost started melting after illuminating 60 s and the surface became free of ice in 720 s, demonstrating superior dynamic ice melting performances. Despite the efficient interface melting even ice melting performance, challenges are remained for the electrothermal and photothermal enhanced surfaces. First, huge thermal input is required to remove vast ice on surfaces. Second, light irradiation is difficult to reach the surface for initiating photothermal effects with heavy snow/ice coverage. Therefore, efforts that can enhance the efficiency of electrothermal/photothermal effects in harsh conditions need to be made.The dynamic ice melting surfaces described above by using electric power, near‐infrared irradiation, and magnetic field were attractive. However, these approaches were partially costly. The photothermal trap surfaces that used solar irradiation energy for ice melting were outstanding candidates and have raised great interests.189 De5Unwanted icing is one of the long‐lasting challenges accompanying mankind in the whole civilization history. It is unfortunate that the most common ways utilized today to combat unwanted icing are still the traditional deicing methodologies involving direct mechanical forces, energy‐intensive thermal treatments or costly chemical handling. Despite that the passive anti‐icing concept has been proposed for more than a decade, automatic ice removal on application scale or at any industrial technology readiness level is still unavailable. Nevertheless, there are significant successes in the anti‐icing materials related researches, especially on the superlow ice adhesion surfaces that enable natural forces for effective ice removal. Although challenges such as durability, anticontamination, functioning at extremely low temperature and harsh conditions need to be addressed, the upscale of such anti‐icing surfaces from laboratory does promise a bright future. In concluding this review, we summarize the dynamic design principles of anti‐icing surfaces through enabling dynamic changes in the chemical/physical states of the ice/substrate/ice–substrate interface with tailored functions by the three DAIS categories, namely, surfaces with dynamic substrates, dynamic interfaces, and dynamic ice.Owing to the abilities of response to stimuli, DAIS with dynamic substrates possess highly appealing potentials. This type of anti‐icing surfaces can utilize various stimuli like temperature, magnetic field, and light for enabling surfaces icephobicity, although not all external stimuli are available in harsh icing situations. For making more practical DAIS in this category, taking the advantages of the intrinsic properties of water and ice for triggering responses of the substrates is the most feasible approach, given that water and ice are always the existing component in the anti‐icing operations. It can be envisioned that novel DIAS with substrates responding sensitively to the interfacial water/ice in cold temperature can provide sensible possibilities in application.DAIS with dynamic interfaces mainly focus on the ice–substrates interaction. To enable dynamic evolution of the interface, the following two pathways are recommended. The first is to enable dynamic change at the interface states, either by generating new interlayers to replace the ice–substrate interfaces or by melting the interface from rigid solid to lubricating liquid. The second is to enable dynamic evolution of the interactions between ice and substrates. This will require better understanding on the fundamental interactions between ice and solid. New interface layers and lubricating layers no doubt have reduced ice–substrates interactions. However, the practical approach of utilizing the intrinsic properties of ice and solids for lowering ice–substrates interactions is still missing. Further investigations that can accelerate such evolutions and apply them for effectively weakening ice adhesion are required.The current DAIS with dynamic ice indicates that ice evolution after formation is not independent from surface properties. Both structures and chemical components of the surfaces can be predesigned for affecting ice propagation, growth and following evolution. It should be noted that both ice growth/propagation inhibitors and programming ice‐free zone cannot make surfaces free of ice. These methods provide alternative choices in specific situations when ice‐free surfaces in confined regions and limited time are required. Dynamic ice melting using solar illumination can be a better choice for outdoor large‐scale anti‐icing applications. However, more studies on the improvement of solar absorption efficiency of these surfaces, especially with ice/snow covering, are still highly essential before these surfaces are ready for practical applications. is relatively low‐cost with abundant materials available, the scale‐up performance still needs further exploration. Furthermore, there is currently no large‐scale demonstration of DAIS available. Extensive studies focusing on scaling up fabrication will speed up transformation of DAIS from laboratory products to practical application.The DAIS also offers alternative pathways for solving the durability problem of icephobic surfaces. Generally, anti‐icing surfaces are designed by modifying the contacts between water/ice and surfaces, for instance, using micro/nanostructured surfaces for depressing water–surface interaction and designing surfaces with low surface energy for weak ice–surface interactions. Such surfaces have poor durability owing to the degradation of the surface topography in usage, because surface nanostructures and chemicals degradation are almost unavoidable in practice. The icephobicity of SAIS commonly suffers from such irreversible decay. There is an unavoidable trade‐off in the performance of SAIS, namely, choosing hard materials for the increase the durability by sacrificing of a decrease in icephobicity or using soft materials for the increase the icephobicity by sacrificing of a decrease in durability. The DAIS pinpoints the importance of evolutions after ice formation in anti‐icing surfaces design. One promising durable icephobicity could be achieved by integrating tough materials/structures with large capacity of abrasion resistance. Such tough materials/structures can provide long‐term durability, while the dynamic components in the surface can weaken ice–substrate interactions and provide excellent icephobicity. More works focus on enabling dynamic functions into robust surfaces and on extending the life spans of dynamic components can promote practical applications of the design of durable icephobic surfaces. There is still a long way for well‐established DAIS approaching large‐scale applications. First, DAIS such as stimuli‐responsive surfaces and photothermal trap surfaces integrate expensive functional components, which significantly increase the cost of large‐scale fabrication. Although alternative methods, such as utilizing PTSLIPS,36 is Given the abundant research results on anti‐icing materials, the understanding of the icing problem also needs to be updated. Regarding ice formation on a surface, it is crucial to realize the dynamic evolution of the interaction between the ice and its substrates. For the practical usage, the surfaces that can maintain long time‐span dynamic properties and can respond to external stimuli are of promising potentials. For instance, ice adhesion on the liquid layer generators and other surfaces that secrete interfacial lubricant can constantly decrease to a negligible level with time. As such, automatic ice removal can be realized even in the outdoor environment if the functionality life‐time of such surfaces is further enhanced. Several anti‐icing surfaces have combined external energy inputs in design. It is fair to say that energy input from solar illumination is one of the most favorable and sustainable choices. Such surfaces still have relatively low power density or suffer from critical environmental limitation such as extremely low temperature, which deserves continuous research effort in the future research. Last but not least, the rational structure–property–function relationship in the current anti‐icing surfaces is still missing. It is certainly difficult to establish this relationship given that approaches to realize surface icephobicity vary greatly as well as a wide variety of materials have been selected for surface fabrication. More theoretical researches on DAIS and new approaches should be promoted, including atomistic modeling and simulation, multiscale approaches, and even machine learning. Based on the current fast evolving status of anti‐icing research, the society can hold an optimistic attitude on unwanted icing and expect practical passive dynamics anti‐icing surfaces in a very near future.The authors declare no conflict of interest.


Infra-acetabular screws enhance the fixation strength in acetabular fractures with separation of both columns. Placement without iatrogenic femoral head violation is challenging.To assess the impact of the acetabular configuration, the patients’ age and gender on safe infra-acetabulum screw insertion.n = 200 hips), the lateral center–edge angle (LCE) was measured on radiographs. Using corresponding axial CT scans the residual distance from  of the screw to  the femoral head  was determined. Statistical analysis was carried out using linear regression, multiple linear regression and normal distribution estimation.In 112 patients , the Pearson correlation between LCE and “RD_SFH” is − 0.56 . Age did not have a significant impact on the relation between LCE and “RD_SFH” . Compared to male patients, in females, the intercept is 4.62 mm  less, the slope parameter is 0.09  larger.The mean (range) LCE angle was 30° (7°–51°) and the mean (range) “RD_SFH” was 5 mm (1–14 mm). The linear regression model shows a significant linear relation between LCE and “RD_SFH” with a slope parameter of − 0.15 (The virtual possibility to place an infra-acetabular screw was given in all patients. An increasing depth of the acetabulum correlated with a decrease in residual distances. As hip joint cartilage thickness was not considered in measurements, intraoperative rule-out of screw mispositioning especially in deep acetabular sockets and females is still of utmost importance. An increasing incidence of geriatric acetabular fractures involving the anterior column according to the classification by Judet et al.  has beenLatest fixation techniques related to the management of these fractures include the use of infra-acetabular screw Figs. , 2 and sIs placement of an infra-acetabular screw without violation of the femoral head in acetabular fracture fixation independent on acetabular configuration?Is there any impact of patients’ age and gender on the feasibility to place that screw without violation of the femoral head?Is it appropriate to refer on one hip to estimate the chance for screw placement of the contralateral side within an individual without violation of the femoral head?To our knowledge, the residual distance from the lateral border of an infra-acetabular screw to the medial border of the femoral head has not been described until now. However, a negative correlation of the minimum thickness of the medial acetabular wall with the acetabular depth was reported previously . AccordiConsequently, the aim of this study was to evaluate and correlate residual distances between the lateral border of a potential infra-acetabular screw and the medial border of the bony femoral head in different acetabular socket configurations within and between patients of different age and gender.Out of an existing radiographic database at our institution from 2003 to 2015, 200 hips were selected by randomization. Hips were included if CT scans and anteroposterior radiographs of the pelvis were both available and radiographs were with correct rotation and tilt , 9. HipsThe computed tomography scans were generated by a Somatom Sensation 64 Multislice  and since 2012 by a 128-detector row CT Scanner Somatom Definition Edge  as part of the routine clinical workup. Patients were placed in the supine position on the CT table. The image resolution was 512 × 512 pixels; slice thickness was 0.6 mm–1 mm.On anteroposterior radiographs, the lateral center–edge angle (LCE angle) was measured by the angle formed by a line parallel to the longitudinal pelvic axis and a line connecting the center of the femoral head with the lateral edge of the acetabular sourcil as reported earlier , 11 and t test was performed to see, if there is a difference in mean between the left and right LCE angle. To predict the LCE angle of one hip by the “RD_SFH” of the contralateral hip within one individual, a normal distribution with mean zero was modeled and a 95% prediction interval was calculated. All analyses were performed with R Core Team .The measured differences between the LCE angle on the left side and the LCE angle on the right side are shown in a histogram in Fig. Geriatric acetabular fractures have been increasing rapidly; whereas, traditional hip fractures declined significantly within the last 20-year period , 14. TheThe literature provides evidence that an infra-acetabular screw is a sufficient modification of standard techniques independent on the used plate systems and obtainable everywhere as a low-cost opportunity to enhance fixation strength in geriatric acetabular fractures , 15. In Gras et al. described in a biomorphometric analysis that a bony corridor with a diameter of at least 5 mm for secure infra-acetabular screw placement could be determined in 93% of cases . HoweverTo our knowledge, the herein study assessed for the first time the relation between the acetabular configuration (with focus on a deep acetabulum) expressed by standard parameters (LCE angle). Others used the LCE angle previously to clarify its relationship to the thickness of the medial acetabular wall to assist orthopedic surgeons in planning total hip replacements  or to deThe results of our study show that secure placement of an infra-acetabular screw in acetabular fracture fixation is dependent on the acetabular configuration. The residual distances decrease with increasing LCE angles and vice versa. For dysplastic hips, the results are in accordance with a previous report showing a thicker medial acetabular wall . HoweverA limitation of our study and also of previous reports might be that measurements were performed using CT scans so that evaluated residual distances “femoral head-to-screw” are based on bony landmarks only. Thus, conclusions based on our measurements might be limited. Femoral head cartilage thickness was measured in cadavers previously with a median thickness of about 3 mm . AccordiStrengths of our study include: (1) the measurement of the true residual distance from the lateral border of a potential infra-acetabular screw to the medial border of the femoral head rather than dimensions of potential screw pathways, (2) not only normal and dysplastic but also deep acetabular configurations were included in the analysis, (3) the application of a commonly in use radiographic parameter (LCE angle) enhanced feasibility, (4) a side-to-side analysis was performed to clarify if measurements performed on the uninjured hip joint are appropriate to be used for reference for the fractured side and (5) measurements were performed at the level of the acetabular fovea (the isthmus of the screw corridor) tangential to the quadrilateral plate in direction of infra-acetabular screws.The virtual possibility to place an infra-acetabular screw was given in all patients in our study setup independent of the acetabular socket configuration, age or gender. The contralateral uninjured hip might be used for reference in preoperative planning. An observed variation at smaller residual distances especially within females might be of concern in clinical practice just as the limitation that hip joint cartilage thickness was not considered in our measurements using CT scans only. Therefore, individual preoperative planning and intraoperative rule-out of screw mispositioning is still of utmost importance, especially in the deep acetabulum and in females.


Tyrosinase is a multifunctional copper-containing oxidase enzyme that initiates melanin synthesis in humans. Excessive accumulation of melanin pigments or the overexpression of tyrosinase may result in skin-related disorders such as aging spots, wrinkles, melasma, freckles, lentigo, ephelides, nevus, browning and melanoma. Nature expresses itself through the plants as a source of phytochemicals with diverse biological properties. Among these bioactive compounds, flavonoids represent a huge natural class with different categories such as flavones, flavonols, isoflavones, flavan-3-ols, flavanones and chalcones that display antioxidant and tyrosinase inhibitor activities with a diversity of mechanistic approaches. In this review, we explore the role of novel or known flavonoids isolated from different plant species and their participation as tyrosinase inhibitors reported in the last five years from 2016 to 2021. We also discuss the mechanistic approaches through the different studies carried out on these compounds, including in vitro, in vivo and in silico computational research. Information was obtained from Google Scholar, PubMed, and Science Direct. We hope that the updated comprehensive data presented in this review will help researchers to develop new safe, efficacious, and effective drug or skin care products for the prevention of and/or protection against skin-aging disorders. Tyrosinase is a multifunctional copper-containing oxidase enzyme, involved in the initial steps of melanin production . MelaninExcessive production of melanin pigments resulted in different dermatological disorders such as skin aging spots, wrinkles, melasma, freckles, lentigo, ephelides, nevus and melanoma . More seAsphodelus microcarpus, Morus nigra L. Limonium tetragonum, Arctostaphylos uva-ursi, Artocarpus lowii, Artemisia aucheri, Cassia tora, Silybum marianum, Humulus lupulus, Rhodiola crenulata, Alpinia officinarum, Mangifera indica, Podocarpus falcatus, Momordica charantia, Cymbopogon citrates, Vitis vinifera and Glycyrrhiza glabra −5′-O-β-d-glucopyranoside (32) [50 = 100 ± 0.5 μM), comparable to kojic acid (6.4 ± 0.04 μM). Quercetin (33), the most abundant flavonol in green tea, apples, berries, onions, and many other fruits, vegetables and grains was proved to possess potent inhibitory activity on the monophenolase and diphenolase activities of tyrosinase. An in silico study by Fan et al. [33) the reversible and competitive inhibition of quercetin on the diphenolase activity of tyrosinase with an IC50 value of (3.08 ± 0.74) × 10−5 mol L−1. The interaction of the 3′, 4′-dihydroxy groups of quercetin (33) with copper ions at the active sites is beyond the inhibitory activity of quercetin (33), as revealed by molecular docking studies. In another study with quercetin (33) isolated from Persicaria senticosa (Polygonaceae), it was reported to inhibit tyrosinase with IC50 values of 14.31 ± 3.93 μM, which is close to the positive control  [50 = 22.71 ± 0.53 μM), comparable to BHA (IC50 = 271.70 ± 19.45 μM).A certain in vitro study was conducted on the aerial parts of ide (32) . This con et al. , demonst4.16 μM) . MoreoveO-α-arabinopyranosyl-(1→6)-β-glucopyranoside (34) inhibited the enzyme with an IC50 value of 46.94 ± 3.09, near that of kojic acid (IC50 = 45.69 ± 1.65 µM). Similarly, the methanol extract of Scrophularia lucida’s aerial parts yielded hesperidin (hesperetin-7-rutinoside) (35) (394 μg/g extract) as a major component [Atraphaxis frutescens and investigated for their inhibitory actions on mushroom tyrosinase [β-d-glucopyranosyloxy-3′,4′,5,5′-tetrahydroxy-7-methoxy-3-α-l-rhamnopyranosyloxyflavone (36) (IC50= 0.90 ±0.02 mM), 3′,4′,5,5′,8-pentahydroxy-7-methoxy-3-α-l-rhamnopyranosyloxyflavone (37) (IC50 =1.20 ± 0.03 mM) and europetin 3-O-α-l-rhamnopyranoside (38) (IC50 =1.10 ± 0.07 mM), compared to kojic acid (IC50 = 0.088 ± 0.002 mM). However, isolated flavonol aglycones did not show any inhibitory properties. Hence, the presence of 3-O-rhamnosyl moiety was suggested to participate in tyrosinase inhibition. Kishore et al. investigated the tyrosine inhibitory activity of myricetin-3-O-α-l-rhamnopyranoside (39), isolated from Myrsine africana methanol extract [50 value of 0.12 ± 0.002 mM. The molecular docking analysis supported its inhibitory activity. The chemical structures of the flavonols with anti-tyrosinase activities are presented in A molecular modeling study evaluated the anti-tyrosinase activity of nine structurally related flavonols, naturally occurring in many plants . Among tomponent . This corosinase . It was  extract . It demo40), an isoflavanoid isolated from Glycyrrhiza glabra roots, was investigated for inhibitory effects and binding mechanisms on tyrosinase [50 value of 0.43 μmol/L through a multiphase kinetic process. Further, glabridin (40) forms stable a glabridin-tyrosinase complex through the strong quenching of intrinsic tyrosinase fluorescence. The molecular docking studies confirmed non-direct binding of glabridin (40) to the tyrosinase active site. Moreover, glabridin (39) did not exert any side effects on melanin synthesis or toxicity in a zebrafish model [41) from the ethanolic extract of the aerial parts of Pueraria 1lobate (Fabaceae) [41) significantly reduced the mRNA and protein expression levels of MITF, TRP-1, and tyrosinase in α-MSH-stimulated B16F10 murine melanoma cells. It potently inhibited tyrosinase activity at a rate of 45.50% at 50 µM, compared to arbutin (12%). Additionally, it effectively reduced melanin content in a reconstructed human 3D skin model, compared to arbutin. Mechanistically, it suppressed the melanin production through modulation of Akt/GSK−3β and MEK/ERK signaling transduction pathways. About twenty-seven flavonoids were identified by Promden et al. [Dalbergia parviflora and tested for tyrosinase inhibition. Among these flavonoids, -3,8-dihydroxy-9-methoxy pterocarpan (42) was the most promising tyrosinase inhibitor by 84.60%, showing an IC50 of 16.70 ± 5.00 μM, similarly to kojic acid (IC50 = 16.80 ± 4.60 μM) at a concentration of 200 μM. Furthermore, this compound (42) effectively suppressed the melanin production by 60% at a concentration of 15 μM without any effect on the cell viability of B16-F10 melanoma cells. Recently, Qu et al. [C-glucoside) (43) (7.66 mg/g), as a major compound in the Puerariae lobatae radix. The isoflavone (43) effectively inhibited the catalytic oxidation process of the tyrosinase enzyme with an IC50 of 0.537 mg/mL in a concentration-dependent manner. In 2018, Wagle et al. [Pueraria lobata (Fabaceae) roots. Among the list of these compounds, calycosin  (44) was characterized as the only potent inhibitor one , superior to the standard, kojic acid . Kim and his team published a report about the isoflavonoids isolated from Apios americana (Fabaceae) tubers and screened them for tyrosinase inhibition [45) and 2′-hydroxygenistein-7-O-gentibioside (46) dose-dependently displayed moderate competitive tyrosinase inhibitors with IC50 values of 39.70 ± 1.5 and 50.00 ± 3.70 µg/mL, respectively, whereas the IC50 of kojic acid was equal 25.20 ± 0.80 µg/mL. The chemical structures of the isoflavones with anti-tyrosinase activities are presented in Glabridin  . This con et al.  in Dalbeu et al.  identifie et al.  describehibition . Of the Silybum marianum) is well-known to be rich in flavonolignans with antioxidant, anti-inflammatory, antiviral and antifibrotic properties [47) was demonstrated to be the most potent one for tyrosinase inhibition, with an IC50 value of 1.70 ± 0.07 µM, compared to kojic acid (IC50 = 15.30 ± 0.50 µM) [47) showed mixed type 1 inhibition of enzyme and a significant binding affinity with Ki value of 0.7 µM. A study published by Chunhakant and Chaicharoenpong reported characterization of phytochemicals from Manilkara zapota (Sapotaceae) bark [48) demonstrated the most potent tyrosinase inhibitory effect with IC50 of 55.41 ± 0.38 μM, comparable to kojic acid (IC50 = 53.43 ± 0.38 μM) and α-arbutin (IC50 = 365.93 ± 0.45 μM). Furthermore, (+)-dihydrokaempferol (48) exhibited the strongest antioxidant activity of isolated compounds through three different assays; 2,2-diphenyl-1-picrylhydrazyl , 2,2′-azino-bis , and ferric reducing antioxidant power , compared with Trolox . Fan et al. [49), a common natural flavonoid, on tyrosinase. This compound is fitted in the pocket of tyrosinase with hydrophobic interactions and hydrogen bonds, resulting in conformational changes of tyrosinase that hinder substrate binding. Consequently, it inhibited tyrosinase activity in a mixed-type manner with an IC50 value of 3.66 ± 0.14 × 10−5 mol/L, compared with kojic acid (IC50 = 4.64 ± 0.37 × 10−5 mol/L). In addition, the combination of dihydromyricetin (49) with vitamin D3 displayed a synergistic effect on the enzyme inhibition. In Turkey, a group of researchers isolated a new catechin, namely (−)-8-chlorocatechin (50), from Quercus coccifera bark [50) expressed tyrosinase inhibition with IC50 value of 4.05 ± 0.30 µg/mL, more potent even than kojic acid (IC50 = 50.75 ± 0.25 µg/mL). Molecular modeling studies revealed the good fitting properties of the compound to the catalytic site of tyrosinase via 4-chromanone moiety with its hydroxyl groups. The chemical structures of the flavan-3-ols with anti-tyrosinase activities are presented in The milk thistle (operties . Among t0.50 µM) . Based oae) bark . Among tn et al.  studied era bark . The isoMorus alba leaves resulted in the isolation of twelve flavonoids which were evaluated for anti-melanogenesis effects in B16-F10 mouse melanoma cells [51) dose-dependently inhibited melanin production via the suppression of intracellular tyrosinase activity, MITF and TRP-1. Moreover, steppogenin (51) effectively modulated CREB and p38 signaling pathways in alpha-melanocyte stimulating hormone (α-MSH)-activated B16-F10 melanoma cells, proceeding to anti-melanogenesis effects. Interestingly, the structure–activity relationship elucidated that the compound possesses a unique structure for tyrosinase inhibition, including hydroxyl groups at C-2′ and C-4′ of the B-ring, at C-5 and C-7 of the A-ring and free C-3. Eriodictyol  (52), a flavanone isolated from Eriodictyon californicum, has been investigated for anti-melanogenic effects in cultured murine melanoma cells (B16-F10) and primary human keratinocytes (PHK) [51) displayed time and concentration-dependent inhibition of tyrosinase in the tested cells. Moreover, it exerted intracellular free radical scavenging potential against hydrogen peroxide (H2O2)-induced oxidative stress at a concentration of 50 μM in B16-F10 and PHK cells. Among the flavanones isolated from the wood of Artocarpus heterophyllous, artocarpanone  (53) demonstrated the most potent inhibitory activity against the tyrosine enzyme with an IC50 of 2.00 ± 0.1 μM [51) and liquiritigenin  (54) demonstrated concentration-dependent inhibition of the enzyme with IC50 values of 7.50 ± 0.50 and 22.00 ± 2.50 μM, respectively. They demonstrated more potent inhibition compared to the positive control, kojic acid, with an IC50 of 44.60 ± 0.40 μM. Pinostrobin (55) was isolated from Egyptian Propolis among other phenolic compounds and was evaluated for its tyrosinase inhibitory activities [55) was the most potent of the isolated compounds of Propolis, demonstrating a moderate inhibitory activity (36.30%) compared with vitamin C, demonstrating 60% inhibition. It was concluded that flavonoids possessing hydroxyl groups at the A and B rings are crucial tyrosinase inhibitors via Cu2+ chelate formation. Investigating the tyrosine inhibitory activity of the isolated flavonoids of Sophora flavescens, kushenol A (56) demonstrated the most potent inhibitory activity, demonstrating an IC50 value of 1.10 ± 0.70 μM [An in depth phytochemical study of 70% ethanolic extract of ma cells . Among tes (PHK) . Steppog± 0.1 μM . Additiotivities . Pinostr 0.70 μM . MoleculLoranthus acutifolius’s aerial parts. These compounds were identified as 2′4′-dihydroxy-6′-methoxy-chalcone (57) (IC50 = 5.70 ± 0.02 μM), comparable with kojic acid (IC50 = 13.90 ± 0.34 μM). Among seventeen phenolic compounds isolated from Angelica keiskei (Umbelliferae) roots, Lee et al. [58), showed a moderate tyrosinase inhibitory property with IC50 values of 15.87 ± 1.21 μM, compared to kojic acid (IC50 = 3.80 ± 0.20 μM). Interestingly, this study used a combinatorial novel approach that includes in vitro tyrosinase inhibition assay coupled with UPLC-MS/MS to screen isolated compounds. Flavokawain A  (59) and flavokawain B  (60), naturally occurring chalcones of Kava (Piper methysticum), were investigated for their melanogenic inhibition in α-MSH-induced B16/F10 cells and zebrafish [Humulus lupulus through tyrosinase activity-guided fractionation of its methanol extract [61), xanthoumol B (dehydrocycloxanthohumol Hydrate) (62) and xanthohumol C (dehydrocycloxanthohumol) (63) demonstrated dose-dependent inhibition of the monophenolase and diphenolase activities of tyrosinase, with IC50 values ranging from from 15.40 to 22.1 μM and from 41.10 to 46.70 μM, respectively. The more potent inhibition was demonstrated with chalcones bearing an isoprenyl group at ring A. Kinetic studies using Dixon and Lineweaver–Burk plots demonstrated the competitive inhibitory activity of the isolated chalcones against tyrosinase.Ticona et al.  identifie et al.  found thebrafish . Both co extract . Among tGreyia radlkoferi and its isolated flavonoids was investigated for their tyrosinase inhibitory effects [50 value of 17.96 μg/mL. Among the isolated flavonoids, 2′,4′,6′-trihydroxydihydrochalcone (64) was characterized as the most potent tyrosinase inhibitor, with an IC50 value of 17.70 μg/mL, comparable to that of kojic acid (IC50 = 3.87 μg/mL). The investigation of the underlying mechanism of inhibition using RT-qPCR was demonstrated to be post-transcriptional. Moreover, molecular docking studies revealed the influence of interaction with Cu2+ ions at the active site on tyrosinase. The chemical structures of the chalcones with anti-tyrosinase activities are presented in The methanolic extract of  effects . The ext65), sanggenon C (66), and sanggenon M (67) with sanggenon O (68) were isolated from the petroleum ether extract of Morus nigra twigs [65) being the most potent, with IC50 values of 0.17 ± 0.01 µM, followed by sanggenon O (68) (IC50 = 1.15 ± 0.03 µM), sanggenon C (66) (IC50 = 1.17 ± 0.03 µM), then sanggenon M (67) (IC50 = 13.06 ± 0.58 µM), compared to kojic acid (IC50 = 32.62 ± 1.24 μM). Two major prenylated flavonoids, namely kuwanon O (69) and sanggenon T (70), were isolated from Morus australis root extract and evaluated for depigmenting effects in different melanocyte systems and artificial skin models [69) and sanggenon T (70), demonstrated an outstanding depigmenting effect in the artificial skin model. Dehydroglyasperin C (71), a major prenylflavonoid of Glycyrrhiza uralensis (Fabaceae), suppressed intracellular tyrosinase activity and related proteins (TYR-1 and TRP-2) at a low concentration (1 μM) in α-MSH-induced B16F1 melanoma cells [Three new isoprenylated flavonoids, namely, kuwanon J , a prenylated form of Broussonetia kazinoki Sieb bark (Moraceae), to evaluate its anti-melanogenic effect on human melanoma cells, normal human melanocytes, and zebrafish [72) potently downregulated MITF by means of the acceleration of AMPK and MAPK protein phosphorylation, which are MITF inhibitors. Moreover, it exhibited anti-melanogenic effects in an vivo model of zebrafish without developmental defects. Cycloheterophyllin (73), a prenylated flavonoid isolated from Artocarpus lowii heartwood and leaves (Moraceae), was characterized as a tyrosinase inhibitor (IC50 = 104.6 μM), compared to kojic acid (IC50 = 219.6 μM) [50 = 102.80 μM), FRAP method (4.70 mM) and ABTS (SC50 = 320.00 μM) [Another study was conducted on kazinol U , a preny19.6 μM) . Furtherophyllin , a prenyArtocarpus pithecogallus (Moraceae) twigs, morachalcone A (74) and 6-prenylapigenin (75) exhibited the most potent tyrosinase effects with IC50 values of 0.77 ± 0.01 μM and 24.29 ± 0.12 μM, respectively, compared to kojic acid (IC50 = 17.32 ± 0.24 μM) [76) and isoxanthohumol (77), from Humulus lupulus methanol extract, among other flavonoids. Both compounds demonstrated significant inhibition of tyrosinase, with IC50 values of 38.1 and 77.4 µM, respectively, for monophenolase and IC50 values of 77.2 and 157.4 µM, respectively, for diphenolase. Kinetic studies using Dixon and Lineweaver–Burk plots demonstrated mixed type inhibition by both flavanones against monophenolase. However, noncompetitive inhibition was demonstrated by both compounds against diphenolase. A study by Kim et al. [Sophora flavescents. Investigating the inhibitory effects of the isolated flavonoids, 8-prenylkaempferol (78) demonstrated potent inhibitory activity (IC50 = 2.40 ± 1.10 μM) against tyrosinase exceeding the chalcones isolated. Molecular docking simulation revealed the competitive inhibition of the prenylated flavonol via its docking to His244 residue of tyrosinase. The chemical structures of the prenylated flavonoids with anti-tyrosinase activities are presented in Upon screening analysis of nine prenylated phenolic compounds isolated from alcone A  and 6-pr0.24 μM)  isolatedm et al.  led to t79) and mesuaferrone B (80) are major bioflavonoids, isolated from the methanolic extract of Mesua ferrea L. stamens with contents of 0.35 ± 0.04% and 0.55 ± 0.06%, respectively [50 values of 10.6 and 10.3 µg/mL, respectively, compared with arbutin (IC50 = 87.20 µg/mL). Furthermore, the dimerization of flavonoid units was found to contribute effectively in potent tyrosinase inhibitory activities, comparable to the original flavonoid monomers. The chemical structures of the biflavonoids with anti-tyrosinase activities are presented in Rhusflavanone  of flavonoids and tyrosinase inhibitory activity. It is worth mentioning that the number and the position of hydroxyl groups especially at ring B drastically affect the activity of different flavonoid classes via CuDespite this extensive research, we observed that the studies addressing the safety profile the promising flavonoids are very scarce. Additionally, some studies are recommended to be extrapolated from in vitro assays to animal and clinical studies to assess the pharmacokinetics, topical permeation, bioavailability, dose issues, lifespan, anatomy and metabolic status. As the conventional whitening market products suffer from severe side effects such as dermatitis and skin cancer in long-term use, we highly recommend well-designed long-term studies in the human subjects to investigate the potential toxic effects, biochemical and molecular mechanisms of the bioactive flavonoids. Interestingly, these studies will potentially push researchers to develop a novel drug for treating skin-aging ailments using medicinal chemistry approaches to synthesize more potent derivatives and study their detailed mechanisms of action.


We assessed the spatial and seasonal variations of NPAHs and OPAHs atmospheric levels, their cancer risks and their gas-to-particle partitioning. To this end, about 250 samples of fine particulate matter (PM−3 for Σ9NPAHs and from 1.64 to 4330 pg m−3 for Σ11OPAHs, with significantly higher concentrations in winter compared to summer.The average particulate concentrations were ranging from below limit of quantification to 593 pg mIn winter, the particulate levels of NPAHs and OPAHs were higher at the traffic site compared to the urban background site in Brno while the opposite was found in Ljubljana. NPAHs and OPAHs particulate levels were influenced by the meteorological parameters and co-varied with several air pollutants. The significance of secondary formation on the occurrence of some NPAHs and OPAHs is indicated. In winter, 27–47% of samples collected at all sites were above the acceptable lifetime carcinogenic risk. The gas-particle partitioning of NPAHs and OPAHs was influenced by their physico-chemical properties, the season and the site-specific aerosol composition. Three NPAHs and five OPAHs had higher particulate mass fractions at the traffic site, suggesting they could be primarily emitted as particles from vehicle traffic and subsequently partitioning to the gas phase along air transport. This study underlines the importance of inclusion of the gas phase in addition to the particulate phase when assessing the atmospheric fate of polycyclic aromatic compounds and also when assessing the related health risk.  •NOPAH particulate levels were generally correlated with PM, OC, EC, CO, Cu and Zn.•2 but decreased with O3.In winter, NOPAH levels generally increased with NO•Significant cancer risks from the inhalation of PAHs, NPAHs and OPAHs were found.•Cancer risks might be significantly underestimated if the gas phase is not sampled. Over thInformation on the environmental fate of NOPAHs is limited by the current data available. Although the atmosphere has been the most studied environmental medium for NOPAHs, only a limited number of studies investigating NOPAH levels simultaneously at several sites impacted by different anthropogenic emissions  were perIn the framework of the ICARUS EU2020 project (‘Integrated Climate forcing and Air pollution Reduction in Urban Systems’), about 300 24-h air samples were collected in two central European cities at four sampling sites (i.e. traffic and urban background), as well as one rural site in winter and summer 2017 and were analyzed for NPAHs and OPAHs. The aim of this study is to provide novel atmospheric data on particulate NPAHs and OPAHs in Brno, Czech Republic and Ljubljana, Slovenia at each a traffic (T) and urban background (UB) sites, as well as at a rural site (in the Czech Republic). This study improves the current knowledge on the atmospheric fate of NOPAHs by assessing their seasonal and spatial variations as well as their gas-particle partitioning as a function of proximity to primary emissions. In addition, the impacts of NPAHs and OPAHs on human health via the characterization of the cancer risks due to the inhalation of these compounds were also evaluated.22.12.5 sampling head) were collected within the ICARUS air sampling campaign  and in different seasons have shown that most (i.e. >80%) of particulate NOPAHs present in the air were bound to fine particles (3 h−1 at the Brno T site and the R site) or low volume air samplers  were used. Particles were collected on Quartz Fiber Filters (QFFs) from Whatman  for the Brno T and R sites, and from Pall  for all remaining sites. The sampled volumes were 752–829 m3 for those sites equipped with a HVAS and 38–55 m3 for those with a LVAS (Table S1). Only eight of the samples collected at the R site for each season underwent chemical analysis. Along particles, gas-phase was also collected on polyurethane foam (PUF) plugs  for seven or eight days simultaneously at each of the Brno sites and at the R site in both seasons (Table S1). The limited number of gaseous samples collected at each of these sites could limit their seasonal representability due to the high variability of meteorological conditions. Prior sampling, PUF plugs were pre-cleaned for 8 h by extraction with acetone and dichloromethane (DCM) each.In this study, 24-h air samples of fine particles . The samples were loaded and eluted with 5 mL of n-hexane followed by 50 mL of DCM. The eluate volume was then reduced by a gentle stream of nitrogen in a TurboVap II  concentrator unit and transferred into a vial. PCB 121  was added as syringe standard prior analysis. The final volume was 200 μL. All the samples were analyzed by means of gas-chromatography  using a 30 m × 0.25 mm × 0.25 μm Rxi-5Sil MS column  coupled to an atmospheric pressure chemical ionization tandem mass spectrometer , GC-APCI-MS/MS. Additional details on the analytical methods used are available elsewhere , prior to be used for the analysis of PAHs and their derivatives at the RECETOX Centre. All samples  were extracted with dichloromethane (DCM) using an automatic warm Soxhlet extractor . Surrogate recovery standards  were spiked on each sample prior to extraction. The extracts were cleaned using a silica column , 1,6-dinitropyrene  and 1,8-dinitropyrene ) as well as 11 OPAHs , naphthalene-1-aldehyde (1(CHO)NAP), 9H-fluoren-9-one (9-OFLN), 9,10-anthraquinone , 1,4-anthraquinone , 9,10-phenanthroquinone , 11H-benzo-a-fluoren-11-one (BaOFLN), 11H-benzo-b-fluoren-11-one (BbOFLN), benzanthrone (BAN), benz(a)anthracene-7,12-dione  and 5,12-naphthacenequinone ) were quantified in the 298 samples collected (252 samples in the particulate phase and 46 in the gaseous phase).These compounds were selected to cover the most abundant species, possible derivatives of abundant parent PAHs, and based on available analytical standards.In total, 17 NPAHs , 2-nitronaphthalene (2-NNAP), 3-nitroacenaphthene (3-NACE), 5-nitroacenaphthene (5-NACE), 2-nitrofluorene (2-NFLN), 9-nitroanthracene (9-NANT), 9-nitrophenanthrene (9-NPHE), 3-nitrophenanthrene (3-NPHE), 2-nitrofluoranthene (2-NFLT), 3-nitrofluoranthene (3-NFLT), 1-nitropyrene (1-NPYR), 2-nitropyrene (2-NPYR), 7-nitrobenzoaanthracene (7-NBAA), 6-nitrochrysene (6-NCHR), 1,3-dinitropyrene  (Table S4).In this study, 28 field blanks (21 QFFs and 7 PUFs) and 24 solvent blanks were analyzed as per samples. The levels of individual analytes in these blanks were generally below detection limit or low otherwise (<10% of average sample mass for detected compounds), suggesting minor contamination during sampling, transport and analysis. However, in some cases, such as for the most volatile NPAHs and OPAHs in summer or winter on QFFs or for the less volatile compounds on PUFs, the blank levels were close to those observed in the samples, reflecting their gas-particle partitioning in ambient air rather than contamination during sample preparation and analysis. The average recoveries (in QFFs and PUFs) were ranging from 83 ± 26% (1-NNAP) to 111 ± 43% (2-NFLT) (Table S2). The concentrations reported in this study were blank corrected by subtracting the average of the field blanks for each season and city, separately for QFFs and PUFs, but were not corrected for recoveries. The instrumental limits of quantifications (iLOQs) were determined from individual sample chromatograms as a signal-to-noise ratio of ten. In addition to iLOQs, the reported levels were also verified against the LOQs determined from the blanks , which were generally higher than the iLOQs. The accuracy of the analytical method has been assessed by two independent manners. Firstly, one extra filter was collected in winter 2016 on the rooftop of the Brno University Campus (very close to the Brno UB site) using the HVAS and was cut onto four pieces analyzed separately. The reported levels of those individual NPAHs and OPAHs which were higher than the iLOQs were consistent among the four samples . Secondly, three pre-clean PUFs spiked with standards of all targeted analytes were analyzed and the average recoveries were ranging from 53 ± 5% (1-NNAP) to 133 ± 21% , the Slovenian Environment Agency (http://meteo.arso.gov.si) and the Municipality of Ljubljana, when available (Table S5). In addition to the targeted analytes, PAHs, PM2.5, toxic metals , elemental (black) and organic carbon, anions and cations were also determined in these samples  were obtained from air monitoring networks (https://www.ljubljana.si/sl/moja-ljubljana/varstvo-okolja/stanje-okolja/kakovost-zraka/), when available (Table S5). The Pearson correlations between the NOPAHs levels and both the meteorological parameters and the concentrations of air pollutants were assessed in order to better understand the inter-sample variability for each site and each season.For each of the sampling sites, meteorological data  were obtained from the Czech Hydrometeorological Institute (2.5a)pyrene equivalents (BaPeq) were calculated by multiplying the concentration of individual compounds (Ci) with their potency equivalent factors (PEFi) as:In this study, carcinogenic risk assessment from exposure to PAH mixtures was done using the potency equivalent factor (PEF) approach , which tBaP is the unit risk of BaP, which represents the number of people at risk of contracting cancer from inhalation of BaPeq concentration of 1 ng m−3 over a life time of 70 years and equals to 8.7 × 10−5 . The cancer risks from inhalation of the targeted substances were estimated as:7 × 10−5 .33.12PYR, 6-NBAP, 3-NACE and 5-NACE) were never detected, while four NPAHs  were rarely found , mainly at the Brno traffic site. The lack of detection of 5-NACE, which is emitted from biomass and coal combustion as well as traffic  were usually found in summer >LOQ at R, but mostly found <LOQ at the Ljubljana sites, obviously influenced by a volume up to 20 times lower of air sampled . This highlights the importance of long-range atmospheric transport of some OPAHs to the rural site. In the following, we will refer to Σ9NPAHs as the sum of 1-NNAP, 2-NNAP, 9-NANT, 3-NPHE, 2-NFLT, 3-NFLT, 1-NPYR, 2-NPYR and 7-NBAA.Unlike 11 OPAHs which were all frequently detected on the filters, only 9 out of the 18 targeted NPAHs were consistently found in the particulate phase . Indeed, five targeted NPAHs . Σ11OPAHs exhibited atmospheric levels about one order of magnitude higher than those of Σ9NPAHs, with average particulate concentrations for individual sites ranging from 915 pg m−3 to 4330 pg m−3 in winter and from 1.64 pg m−3 to 102 pg m−3 in summer (Tables S9–S10). Compared to parent PAHs (data not shown), the levels of NPAHs and OPAHs were significantly lower . In addition, in terms of mass, NOPAHs represent only a negligible fraction (i.e. 3 ppb – 1 ppm) of the ambient fine particles. Although the number of individual NOPAHs investigated by previous studies or the phase sampled is different, the levels of NOPAHs found in this study are consistent with those reported from polluted or urban air in Europe, i.e. up to a few ng m−3 and 20 ng m−3 for NPAHs and OPAHs, respectively,  , except in summer at the Brno traffic site where it contributed on average for 34%, while this compound was previously found to dominate NPAH levels at traffic sites (2BAA (8–10%) and 9,10-O2ANT (8–9%). In Brno, the UB site was dominated by BAN (46%), BbOFLN (18%) and BaOFLN (13%) while the T and R sites, which had similar profiles, were dominated by 9,10-O2ANT (30–37%), BAN (19–20%) and to a lower extent also by 9,10-O2PHE (12–19%) which was only detected in winter at these two sites.The composition profiles of particulate NOPAHs are presented as an average in burning)  and secoburning) , contribburning) . Photolaburning) . The conic sites . Concernic sites , and is 3.29NPAHs and Σ11OPAHs,  as well as for Σ11OPAHs, , or more11OPAHs, , which r11OPAHs, ). Higher11OPAHs, : (i) hig11OPAHs,  includin11OPAHs, , and eve11OPAHs, . (ii) lo9NPAHs and Σ11OPAHs, respectively, than at the UB site, which were in turn, 5.3 and 4.9 times higher than those at the rural site (Tables S12–S14). The highest ratios between the traffic and the urban background sites (i.e. T/UB) were found for individual compounds which are known to be primarily emitted from traffic . In summer, for both cities, the concentrations of NOPAHs were the highest at the traffic sites (Tables S12–13), although the levels and the number of compounds detected at all sites were rather low, limiting therefore the assessment of the spatial gradients. The differences observed between Brno and Ljubljana in the spatial distribution of NOPAHs in winter between the traffic and the urban background sites suggest differences in the extent of primary sources. Emissions from domestic heating are unlikely to be higher in Ljubljana than in Brno due to the higher winter temperatures in Ljubljana (Table S5) but also to the higher usage of wood and coal in Brno  using the samples collected simultaneously site by site. In winter, the spatial distributions of particulate NOPAHs differed between Brno and Ljubljana. In Brno, a strong traffic to rural gradient was observed, with the highest concentrations of NOPAHs at the traffic site and the lowest at the rural site . Indeed, in Brno , which a in Brno . Possibl in Brno , are mor in Brno . Moreove in Brno , particu3.32.5 but also PM10 sometimes), particularly in winter and at the traffic sites (Tables S15–S24). At the Brno UB site, which measured both PM1, PM2.5 and PM10 in winter, higher correlations were observed with the finest particles, consistent with the fact that NOPAHs are usually sorbed to submicron particles  were found in winter but generally not in summer (Tables S15–S24). Indeed, in winter, NOPAH levels increased with NO2, but decreased with O3, which is consistent with previous studies . In general, the correlations found between NOPAHs levels and the different parameters were more significant in winter compared to summer, related to the lower detection frequencies of individual NOPAHs and the low levels in summer. Concerning the meteorological parameters, in winter, the increase in wind speed and temperature lead to significant decrease in NOPAH levels at all sites where these were measured, highlighting the influence of atmospheric dispersion and temperature-dependency of primary emissions on NOPAH levels. NOPAHs concentrations generally showed significant positive correlation with particulate mass  and at the Brno traffic site for Σ11OPAHs (r = 0.73) . In addition, Pearson correlations were also assessed between individual NOPAHs (Tables S25–S31). Several NOPAHs  were generally not or poorly correlated with 1-NPYR. 1-NPYR is a compound classified as probably carcinogenic to humans (i.e. Group 2A) and a marker of primary emissions from traffic in general  correlated with 1-NPYR highlighting a possible diesel origin, as previously suggested  or the nitrate radical (night) (3 (Tables S15–S24), whose high concentrations enhance the gas-phase and heterogeneous nitration of PAHs  ratios were investigated to distinguish between primary and secondary sources or even to distinguish between diesel and petrol exhaust emissions. Significant (p < 0.05) and strong (r = 0.64–0.98) correlations were found between Σ general , but mor general  although general . The lac general , which tuggested . Moreove (night) . Given t of PAHs , we suggHs . Considering the secondary formation along atmospheric transport of NOPAHs, one may expect higher ratios in summer (enhanced photochemistry) and in aged air masses, as the PAH derivatives are expected to degrade slower than their parent compounds , and were slightly lower or above the acceptable lifetime carcinogenic risk (i.e. 1 × 10−6) in winter while in summer the risks were negligible (i.e. <4 × 10−8). In winter, 27–47% of samples collected at all sites were above the acceptable lifetime carcinogenic risk. The main contributors to ECR were BAN, 9,10-O2ANT, 2-NFLT and 1-NPYR contributing on average for 27%, 26%, 25% and 20% although large variations were observed according to the season or site considered. 6-NCHR and 1,6-N2PYR, which have the highest PEFs among all targeted compounds , contributed to 30–33% of the ECR in the few samples in which they were detected. When considering both NOPAHs and PAHs, 77–100% of all samples collected exceeded the acceptable lifetime carcinogenic risk (Table S35). This suggests significant health risk associated with the inhalation of polycyclic aromatic compounds in these two Central European cities. This is consistent with a recent study showing that 70% of the global population breathes air which exceeds the safe threshold level, with higher risks in China, India, Central and Eastern Europe  . Secondl3.62.5). NOPAH mass size distributions have been found centering in the PM2.5 size fraction at both urban and rural sites  but mainly in the gas phase in summer (Θ = 0 for R and UB and 0.09 ± 0.04 for T) while OPAHs were mainly found as gases for all sites and seasons investigated (i.e. Θ < 0.36). These values should be taken with caution as they are obviously dominated by the most abundant compounds, and do not reflect the large variations in the particulate mass fractions observed across individual NOPAHs , 7,12-O2BAA, and 5,12-O2NAC but not for the remaining compounds  which resulted in a higher average particulate mass fraction in summer (Θ = 0.17 ± 0.34) compared to winter (Θ = 0.04 ± 0.04). Similarly, 9,10-O2PHE was only found in the particulate phase in summer at the traffic site (i.e. Θ = 1) while it had an average Θ of 0.24 ± 0.25 in winter. This behavior has been previously reported for 1,4-O2NAP and was attributed to slow relaxation to equilibrium in the vicinity of the source, which could be particularly important when the emission temperature is higher than the ambient temperature  were similar. Hence, the higher particulate mass fractions found for these specific NPAHs and OPAHs at the traffic site suggest that these compounds are primarily emitted from traffic as fine particles and are subsequently partitioning to the gas phase along transport. The same trend is not necessarily found when comparing urban and the rural background site: The winter particulate mass fractions of 9,10-O2ANT, 1,4-O2ANT and 9,10-O2PHE at the rural background site were slightly higher than those at other sites. This is not inconsistent, though, as the aforementioned parameters, photolysis, particulate matter abundance and chemical composition, can vary significantly on this spatial scale.Significant spatial distributions in the gas-particle partitioning of some NOPAHs were found. Indeed, higher particulate mass fractions were observed in at least one of the seasons investigated at the traffic site compared to the urban background or rural sites for three NPAHs  and five OPAHs  (Tables S46–S47). For both NPAHs and OPAHs, the composition profile differs significantly between the total (gaseous + particulate) and the particulate phase, due to the higher contribution of the most volatile NOPAHs and significant seasonal variations . Moreover, the seasonal variations of the total mass concentration is found lower, except for few OPAHs NAP and 1,12-O2BAA) (Table S48). 5-NACE, which was found only in the gaseous phase (Table S38), differs from the other NOPAHs as it had levels significantly higher in summer compared to winter at both the traffic and the rural site . This must be related to the photochemical formation from the parent acenaphthylene or revolatilisation from surfaces, or both. In addition, at the rural site in summer, the gaseous concentrations of 5-NACE, 3-NPHE, 2-NFLT and BaOFLN were positively correlated  with the average temperature which showed an amplitude of 10 °C, which points again at secondary formation or revolatilisation from surfaces. Generally, monitoring of the particulate phase only ignores gaseous emission sources such as re-volatilisation of semivolatiles stored in surface compartments . A previous study in summer in central Europe has shown that for some light PAHs, this process was significant and controlling their ambient concentrations . However, in summer, for which data in the particulate phase were limited, when considering the total concentrations, the UB site had levels higher than those at the traffic site  for all NOPAHs, except for 1-NPYR and 5-NACE. This could suggest secondary formation along transport from the traffic site to the UB site.Concerning assessment of exposure, neglect of the gas-phase may cause significant underestimates . This is4This study provided novel information on levels of toxic organic chemicals in the atmosphere of two cities (Ljubljana and Brno) and a rural site in Central Europe, and assessed their seasonal and spatial variations as well as their gas-particle partitioning and their impact on human health via inhalation. Such type of data, so far rather limited for NOPAHs, are crucial to improve our understanding of their environmental fate, including their potential for air-surface exchange  and long-range transport.This study helped to identify the multiple parameters influencing NOPAH levels such as the proximity to primary sources, the meteorological conditions or occurrence of other atmospheric pollutants. Moreover, the significance of secondary formation of some NOPAHs, further away from primary sources has been shown. In winter, the estimated cancer risks related to the inhalation of NOPAHs were above the acceptable lifetime carcinogenic risk for 27–47% of samples collected at all sites. This study underlines the importance of inclusion of the gas phase in addition to the particulate phase when assessing the atmospheric fate of polycyclic aromatic compounds and also when assessing the related health risk. Considering that information on toxicity was available only for a limited amount of NOPAHs and that this study targeted only a limited amount of all atmospherically relevant PACs, the true cancer risks are eventually significantly higher. Efforts to characterize human health risks through inhalation of both particulate and gaseous PACs, besides other organic contaminants, need to be pursued.Céline Degrendele: Conceptualization, Investigation, Methodology, Writing – original draft. Tjaša Kanduč: Investigation, Methodology, Writing – review & editing. David Kocman: Investigation, Methodology, Writing – review & editing. Gerhard Lammel: Conceptualization, Investigation, Writing – review & editing. Adriana Cambelová: Investigation. Saul Garcia Dos Santos: Methodology, Writing – review & editing. Milena Horvat: Resources, Writing – review & editing. Petr Kukučka: Methodology, Writing – review & editing. Adéla Holubová Šmejkalová: Methodology, Writing – review & editing. Ondřej Mikeš: Methodology, Writing – review & editing. Beatriz Nuñez-Corcuera: Methodology. Petra Přibylová: Methodology, Writing – review & editing. Roman Prokeš: Methodology. Ondřej Saňka: Methodology, Writing – review & editing. Thomas Maggos: Conceptualization, Methodology, Resources, Writing – review & editing. Denis Sarigiannis: Conceptualization, Methodology, Resources. Jana Klánová: Methodology, Resources, Writing – review & editing.The authors declare that they have no conflict of interest.


The state anxiety level was evaluated before and after the intervention. There was no significant difference in the state anxiety levels after an exergame session between the single and multiplayer modes  = −0.12, defined as small). Furthermore, there was no significant difference in the state anxiety levels before and after an exergame session in single-player mode  = 0.14, defined as trivial) and multiplayer mode . In conclusion, state anxiety level after exergame beach volleyball did not differ between the single and multiplayer modes in adult men.This study compared the exergame beach volleyball’s acute effects on state anxiety level in single vs. multiplayer mode in adult men. Sixty adult men (age: 21.98 [4.58] years, body mass: 75.40 [15.70] kg, height: 1.77 [0.09] m, and body mass index: 24.19 [5.44] kg/m Anxiety is a normal reaction of the body to stress, but it can become a mental health disorder at increased levels. In the latter case, symptoms of anxiety impair the quality of life . AnxietyAccording to the World Health Organization, 264 million people worldwide had anxiety disorders in 2015, corresponding to 3.6% of the world population )  and multiplayer mode  .Both the single and multiplayer modes presented intermediate state anxiety levels before  and after  the exergame session. There was no significant difference in the change in state anxiety levels after the exergame session between the single and multiplayer modes  A. Furthe; 0.72]) B. In addp-value = 1.000, rB = 0.00 “trivial” ) (The single-player (median: 32.0 [IQR: 6.0]) and multiplayer (median: 32.5 [IQR: 5.0]) modes reported high enjoyment levels after the exergame session. However, there was no significant difference in enjoyment levels after the exergame session between the two modes  . p-value = 0.201, d = −0.33 “small” )  (There was no significant difference in RPE between single (12 ± 2) and multiplayer (11 ± 2) modes  A. There ; 0.33]) B. ® beach volleyball on state anxiety levels, enjoyment level, and exercise intensity between single and multiplayer modes in healthy adult men. Contrary to our initial hypothesis, the state anxiety levels after the exergame session did not differ between single and multiplayer modes, and the exergame sessions did not improve the state anxiety level. Moreover, there were no differences in the enjoyment levels and exercise intensity between the single and multiplayer modes. The present study evaluated the effects of the exergame Kinect Sports® performed at moderate intensity on the state anxiety level in healthy young women and found a significant reduction after the session. In addition to moderate-intensity exercise, the authors attributed the anxiolytic effect to the participants’ high enjoyment levels. In the present study, the enjoyment level was found to be high  [We found no statistical difference in the changes of state anxiety levels between the single and multiplayer modes and no statistical difference before and after a session of exergame in both the modes. Recently, da Silva et al. (2021) conducted a study to compare the acute effects of an exergame-based calisthenics session versus a traditional calisthenics session on state anxiety levels in healthy adult men . The autl score) ,19. Thusl score) ,19. A prl score) . Our fin® beach volleyball [Ensari et al. 2015) reported that a bias, which permeates many studies on anxiety, is associated with recruiting persons with average or lower levels of state anxiety. Therefore, it is not possible to further decrease anxiety levels 15 report. In the lleyball ,37,38,39lleyball ,41. Garwlleyball . Our reslleyball . As we d®  in young adults [® in Xbox 360 Kinect®. The intensity of the sessions was measured based on the HR. All the participants played the three modalities in single and multiplayer modes separated by a week’s interval. The results showed that the HR in the single-player mode was 120 ± 28 bpm (boxing), 82 ± 30 bpm (soccer), and 125 ± 21 bpm (track and field). At the same time, the HR in the multiplayer mode was 147 ± 18 bpm (boxing), 122 ± 15 bpm (soccer), and 136 ± 15 bpm (track and field). The authors found that the HR was higher during a multiplayer mode for boxing and soccer. This result indicated that playing exergame in the multiplayer mode can be more vigorous, but the effects are game-dependent [® beach volleyball practice between the single and multiplayer modes. Our findings showed no significant difference in the mean HR and RPE between the single and multiplayer modes in healthy adult men.Another aim of our study was to compare the exercise intensity between both the modes. We found no significant difference in HR and RPE between the single and multiplayer modes. We hypothesized that the multiplayer mode would elicit a higher exercise intensity. Exergames featuring a competitive element were more likely to induce a higher level of physical activity if played in a multiplayer mode rather than in a single-player mode . McGuireg adults . Ten youependent . Bonettiependent . They fo2max = ~52 mL/kg/min). This is a possible explanation that the exergame beach volleyball from Kinect Sports® did not challenge the participant’s cardiorespiratory fitness level. A well-designed exergame will take people to “Flow Zones”, where the person’s abilities are matched as per a challenge, delivering feelings of pleasure and happiness. Thus, games should adapt to the players’ skills to keep them in the flow zone. However, if the challenge exceeds the person’s abilities, “anxiety” can be experienced, whereas minor challenges in terms of complexity and fun leads to “boredom” [® beach volleyball should be prescribed with caution to healthy adult men who seek to reach the recommended level of physical exercise proposed by the American College of Sports Medicine as light exercise intensity is evoked by this exergame [In addition, previous exergame experience has been indicated as a factor that could influence exercise intensity since it minimizes the exertion and improves the movement precision . Furtherboredom” . Therefoexergame .® on enjoyment levels between the single and multiplayer modes and found that the multiplayer mode presented with more enjoyment levels than the single-player mode [® beach volleyball was found between the single and multiplayer modes.Finally, our study compared the enjoyment levels between the two modes. Participants reported high levels of enjoyment in both single and multiplayer modes, without any significant differences. One possible explanation for the high enjoyment levels found in the present study may be related to the fact that young adults are more receptive to innovative technology . Mackintyer mode . These rOur study has certain limitations. First, there was no control group characterized by quiet rest. Therefore, it is recommended that future studies include a non-exercise control group or placebo intervention. Second, due to our study design’s singularities, participants were not randomized to single or multiplayer modes. However, there were no statistical differences in participants’ characteristics between the two modes. Third, as we used questionnaires and scales, the results were dependent on the participants’ honesty. Fourth, we did not investigate any clinical population with diagnosed anxiety as a disorder, which might have affected the floor effect on decreasing state anxiety levels after both exergame modes. Sixth, due to the characteristics of the exergame used in our study, we could not control the magnitude of load and density (effort/pause ratio) in each game mode (singleplayer and multiplayer).® beach volleyball on the state anxiety levels in individuals with low cardiorespiratory fitness and/or anxiety disorders as well as participants from both sexes and different ages to better understand the impact of the exergames. Finally, we investigated only adult male individuals. Nevertheless, we believe that these limitations do not limit our conclusions. Future research investigating different exercise intensities (light vs. moderate vs. vigorous) and modes (single vs. multiplayer) would be beneficial. They would provide more information about the exergame’s effect on state anxiety. It is also necessary to investigate the impact of the exergame Kinect SportsThere was no difference in the state anxiety levels between the single and multiplayer modes. Furthermore, both of the exergame modes did not evoke an anxiolytic effect. We did not find any significant difference between the enjoyment level and exercise intensity between the single and multiplayer modes.