An uncoated fibre is employed to compensate for bending losses that are likely to occur during movement. A linear fit to the response of the sensing system to RH demonstrates a sensitivity of 3.02 mV/% (R2 = 0.96), hysteresis ± 1.17% RH when 11 bilayers of PAH/SiO2 NPs are coated on the tip of the fibre. The performance of two different textiles (100% cotton and 100% polyester) were tested in real-time relative humidity measurement for 10 healthy volunteers. The results demonstrate the moisture wicking properties of polyester in that the relative humidity dropped more rapidly after cessation of exercise compared to cotton. The approach has the potential to be used to monitor sports performance and by clothing developers for characterising different garment designs.An optical fibre sensor for monitoring relative humidity (RH) changes during exercise is demonstrated. The humidity sensor comprises a tip coating of poly  (PAH)/silica nanoparticles (SiO Humidity, the amount of water vapour in the air, is an important indicator relating to human comfort and performance during work and sport. Tsutsumi et al. reported that low indoor humidity level has positive effects on human wellbeing, however, when the humidity reaches above 70% RH, subjects reported to be more tired . In spor® trans-epidermal water loss  was used as a reference. It is suggested that a distributed body network could be established to provide valuable information for improving athletes’ physical performance.The relationship between comfort, performance and humidity has inevitably led to a wide range of different materials being developed by textile and clothing manufacturers . ISO 1542 nanoparticles based optical fibre sensors show fast response time and appropriate RH range for measurement [Compared to electronic humidity sensors, an optical fibre sensor (OFS) offers several advantages such as light weight, miniature size, flexibility, simple configuration and insensitivity to electromagnetic fields . The diasurement .Previous research has shown different biomedical applications of RH measurements such as skin microenvironment  and brea2 NPs thin film for measurement of relative humidity and the other is a bare fibre used as a reference for bending losses compensation during exercise. Different tee-shirts are investigated: 100% cotton where the material will adsorb moisture and 100% polyester which has well known moisture wicking properties. These were selected to demonstrate that the properties of the fabric can affect humidity rather than to demonstrate the well-established differences between a natural and a synthetic garment.In this paper, an optical fibre sensing system is developed and applied for RH measurement during sports activity (in this case a cycling test). Each sensor consists of two optical fibres. One with Poly /SiO2 NPs, diameter 40–50nm) were purchased from Nissan Chemical, Japan. Deionised water (DI water), having resistivity of 18.2 megohm, was obtained from a water purification system .Potassium hydroxide (KOH), Sodium hydroxide (NaOH), Ethanol and Poly   were purchased from Sigma-Aldrich, UK. Silica Nanoparticles (SiO2 NPs coating and a reference fibre (REF) without any coating. The end of each fibre was perpendicular cleaved. Two fibres are tightly surrounded by a 900 µm furcation tube  and heat shrink tubing  for protecting the tip from mechanical damage. Two pairs of sensors are used in this study.The sensing probe is composed of two optical fibres  which are an optical fibre humidity sensor (OFHS) with PAH/SiO2 NPs was coated on the tip of an optical fibre using the Layer-by-Layer self-assembly method [2 NPs solution for 15 min. (b) and (c) processes were repeated to achieve the required thickness. The coated optical fibre was dried at room temperature in the laboratory for 24 h before use. For the layer by layer technique, the thickness of each layer is approximately equal to the diameter of SiO2 NPs i.e., a 40–50 nm/monolayer. To determine the optimum film thickness, sensors with 3, 7 and 11 layers were prepared. A thin film composed of PAH/SiOy method . The fab2 NPs coated optical fibre sensor has been described previously [2 NPs is approximately 1.22 and the intensity changes linearly with RH [The humidity sensing mechanism of a PAH/SiOeviously . The tot with RH .α) between two separate optical fibres from one batch are identical [Meanwhile, water vapour does not easily adhere to the smooth tip surface of the uncoated bare fibre, which means that the bare fibre with perpendicular cleaved tip has the potential to be a reference for reducing bending loss effect. Ideally, under the same bending conditions, the intensity-loss coefficients  is the intensity measured from the reference fibre at θ = 0 which can be made before measurements commence. As the (unknown) bending angle θ is the same in both reference and sensing fibres, α is then used to compensate the humidity sensing channel.OFSI is the intensity measured from the sensing optical fibre. In this work, the intensity change due to bending of the OFHS is compensated using a reference fibre. We define a term 2 NPs was imaged using a transmission optical microscope . The morphology of the functionalised fibre tip was studied using scanning electron microscopy (SEM) . The fibre before and after coating with PAH/SiOA climatic chamber  was used in the calibration process. According to the temperature humidity control range, 2 NPs bilayers were tested.The sensor response has previously modelled as linear ,20 and sFor verification, the sensing probe and commercial humidity sensor were placed 0.5 cm apart inside the climatic chamber. Using the calibration curve obtained from RH calibration experiment, the output signal from the sensing probe was confirmed in terms of RH unit. Thus, the RH in the climatic chamber was set from 55% RH to 95% RH and reversed with two cycles. In order to observe the performance in sports activities of the optical humidity sensing system, a cycling experiment was performed. 10 volunteers  participated in the cycling test using an indoor cycle  at room temperature (22 ± 1 °C). Each volunteer wore two sports T-shirts with different materials (100% cotton and 100% polyester) separately for the same cycling test. The two cycling tests were separated by 45 min in order to stabilise the physical condition of volunteers. All the T-shirts were laundered and conditioned in the lab for 24 h before testing. Ethical approval was provided by the Ethics Committee, Faculty of Engineering, University of Nottingham. In order to observe the performance in sports activities of the optical humidity sensing system, a cycling experiment was performed. 10 volunteers  participated in the cycling test using an indoor cycle  at room temperature (22 ± 1 °C). Each volunteer wore two sports T-shirts with different materials (100% cotton and 100% polyester) separately for the same cycling test. The two cycling tests were separated by 45 min in order to stabilise the physical condition of volunteers. All the T-shirts were laundered and conditioned in the lab for 24 h before testing. Ethical approval was provided by the Ethics Committee, Faculty of Engineering, University of Nottingham. The commercial humidity sensor BME280 was also used for verification of the signal from the optical fibre humidity sensor. BME280 and OFHS were embedded in a 3D-printed holder  is broadly repeatable and inversely proportional to the RH change measured by the commercial humidity sensor (black curve). Comparing the dynamic light changes of OFHS with different layers , 2 thin film. For all sensors, the light intensity change was observed to exhibit an approximately linear dependence on the change of RH (50–80%). It can be observed that the greater the number of layers leads to an increase in the sensitivity of the OFHS. For the sensor with 3 layers (red line), the sensitivity was 0.40 mV/% RH (R2 = 0.95), for 7 layers (dark blue line), the sensitivity was 0.96 mV/% RH (R2 = 0.88) and for 11 layers (orange line) the sensitivity increased to 3.02 mV/% RH (R2 = 0.96). The hysteresis value is ±1.17% RH for 11-layers humidity sensor. The hysteresis is defined as the difference between measurements of the humidity increase/decrease branch and the averaged curve of both branches, the sequence 50-85-50% RH is used as shown in the The RH results obtained from the developed OFHS with 11 layers and commercial sensor can be compared in In order to investigate the bending response of the sensor, the 11 layer sensing probe was further tested using the set-up shown in Cotton is a hydrophilic material and polyester has hydrophobic property ,27. It cpeak) of inner and outer sensors from the OFHS for volunteers wearing 100% cotton and 100% polyester T-shirts. As can be seen from peak readings with polyester were smaller than that in the cotton group. This confirms the performance of polyester as a moisture wicking material [material .The developed sensing system has enabled relative humidity to be measured during exercise. Due their flexibility and small diameter , optical fibre sensors can be easily integrated within textiles with the potential to form next generation smart garments. They are more unobtrusive than commercial electronic humidity sensors but, for future widespread use, need to be competitive on cost. The prototype demonstrated in this paper comprises several components such as an SLD, fibre optic coupler and optical switch that would limit its use to a laboratory-based testing tool. However, for widespread use in wearable sensing the system could be simplified and reduced in cost. For example, multiple LEDs and photodiodes could be used to replace the SLD and optical switch. The bill of materials for a single channel system with wireless electronics is estimated to be ~€25 with the most significant cost a wireless microcontroller. As with most electronics systems, this cost would reduce with higher volumes.The system is robust to motion artefacts due to the inclusion of a reference fibre that can be used to compensate for bending losses as shown in 2 = 0.96). In line with previous research ,29 a linThe measurement unit is currently a bench top system with a trailing optical fibre between it and the subject. In certain applications e.g., climatic chamber or treadmill exercise, this is not a significant problem, although bending losses will increase due to the long optical fibre cable between subject and measurement unit. However, for measurements on the field of play or workplace, a wearable unit with wireless communications is desirable. The instrumentation utilised here is relatively simple and compact, and so miniaturising the measurement unit will be a focus of future work. The system currently measures RH on the inside and outside of a garment at a single position but due to the small size of the sensors there is potential to increase this by increasing the number of sensors and number of channels on the optical switch, for example, 16 is likely to be deployed in the next version of the device. The system has been tested on two garments with well-known and different properties (100% cotton and 100% polyester). The aim was to demonstrate the potential of the sensor and not to characterise the materials. Future tests will investigate different materials, structures and multiple garment layers.2 nanoparticle film was used to measure changes in light intensity reflected from the tip of the fibre which are proportional to humidity. Bending losses were partially compensated by including an uncoated reference fibre which enables measurements to be made during exercise. A new approach to monitoring humidity in garments based on optical fibre sensing has been demonstrated. An optical fibre coated with an eleven-layer PAH/SiO2 = 0.96) when 11 bilayers of PAH/SiO2 NPs coated on the tip of fibre was used which was higher than that of 7  and 3 bilayers  of PAH/SiO2 nanoparticles. Measurements from 10 volunteers during a cycling test demonstrate the capability of the system to measure the effect of textile properties on humidity, with polyester providing better moisture wicking properties than cotton. The small size and flexibility of the sensors allow them to be easily integrated within garments with negligible effect on the moisture wicking properties and has the potential to be used as a tool for clothing developers designing moisture managing products. The response of the sensing system to RH concentration was linear with a sensitivity of 3.02 mV/% (R


Astrocytes have emerged as crucial regulators of neuronal network activity, synapse formation, and underlying behavioral and cognitive processes. Despite some pathways have been identified, the communication between astrocytes and neurons remains to be completely elucidated. Unraveling this communication is crucial to design potential treatments for neurological disorders like temporal lobe epilepsy (TLE). The BDNF and TrkB molecules have emerged as very promising therapeutic targets. However, their modulation can be accompanied by several off-target effects such as excitotoxicity in case of uncontrolled upregulation or dementia, amnesia, and other memory disorders in case of downregulation. Here, we show that BDNF and TrkB from astrocytes modulate neuronal dysfunction in TLE models. First, conditional overexpression of BDNF from astrocytes worsened the phenotype in the lithium-pilocarpine mouse model. Our evidences pointed out to the astrocytic pro-BDNF isoform as a major player of this altered phenotype. Conversely, specific genetic deletion of BDNF in astrocytes prevented the increase in the number of firing neurons and the global firing rate in an in vitro model of TLE. Regarding to the TrkB, we generated mice with a genetic deletion of TrkB specifically in hippocampal neurons or astrocytes. Interestingly, both lines displayed neuroprotection in the lithium-pilocarpine model but only the mice with genetic deletion of TrkB in astrocytes showed significantly preserved spatial learning skills. These data identify the astrocytic BDNF and TrkB molecules as promising therapeutic targets for the treatment of TLE. Activated astrocytes provide both excitatory and inhibitory effects on neighboring neurons2. Thus, astrocytes can modulate neuronal activity and, in turn, neurons exert functional changes in astrocytes upon neural activity such as modifications in gene expression, gliotransmitter release and intracellular calcium signals6. However, mechanisms underlying astrocyte–neuron reciprocal communication remain poorly understood.Correct function of neuronal networks depends on an appropriate modulation by astrocytes7. This expression pattern suggests that the BDNF–TrkB pathway could be a core system modulating astrocyte–neuron reciprocal communication. The neurotrophin BDNF is a key player in learning and memory processes, synaptic plasticity phenomena, and neuronal survival9 as well as TrkB, its main receptor11. However, BDNF and TrkB molecules have often opposed biological effects explained by the presence of the different TrkB isoforms and the antagonistic biological activity of mature (mBDNF) and precursor (pro-BDNF) forms of BDNF12. As an example, pro-BDNF can activate p75NTR to induce neurotoxicity whereas mBDNF can activate TrkB to induce neuroplasticity12. On the other hand, the truncated isoform of TrkB receptor (TrkB.T1) disrupts/counteracts the full-length (TrkB.FL) active receptor function14 by promoting the formation of non-functional heterodimers15. In contrast to the TrkB.FL-dependent signaling, TrkB.T1-mediated signaling has been suggested to mediate neurodegenerative processes in excitotoxic contexts16. Thus, excess of (pro)BDNF or TrkB.T1 protein levels as well as aberrant interaction between TrkB and p75NTR receptors may lead to neuronal dysfunction or death via induction of excitotoxicity-related molecular pathways17.Recent literature has shown that BDNF and TrkB are expressed in both neurons and astrocytes18. In particular, the increase in TrkB.T1 protein levels could be one of the underlying molecular mechanisms of neuronal death in TLE models19. However, whether astrocytes are regulating synaptic excitability or activation of neuronal populations in TLE-associated neurodegeneration via the BDNF and TrkB molecules remains elusive.A detrimental role of TrkB isoforms has been observed in temporal lobe epilepsy (TLE) modelsIn the present work we show that BDNF overexpression in astrocytes leads to enhanced excitability and neuronal cell death. Furthermore, we show that BDNF from astrocytes is necessary to increase the number of firing neurons in an in vitro model of TLE. In a second subset of results exploring the role of the astrocytic TrkB receptor, we show that a knockdown of total TrkB in astrocytes is beneficial in TLE. Concretely, we show that TrkB deletion in hippocampal astrocytes is neuroprotective in TLE models and preserves with higher rates hippocampal-related cognitive functions when compared to the genetic deletion of TrkB in neurons.23, we aimed to study the role of the neurotrophin produced by astrocytes in a TLE model by using wild-type (WT) mice and the pGFAP-BDNF transgenic mice as a gain-of-BDNF-function approach. In these mice, BDNF is overexpressed only under pathological conditions21. To do so, first we subjected pGFAP-BDNF mice and their WT controls to the lithium-pilocarpine model  increased significantly in field excitatory postsynaptic potentials (fEPSP) slopes with the increase in stimulus intensities  = 40.916; p < 0.001). Slopes of fEPSPs evoked in pGFAP-BDNF mice were significantly larger than those presented by WT animals for higher stimulus intensities  = 4.023; p ≤ 0.05) , we recorded input/output curves and paired-pulse facilitation at the CA3–CA1 synapse in the two groups of mice in vivo Fig. . The two05) Fig. . Altoget25. The two groups of mice presented a paired-pulse facilitation at short (20 and 40 ms) inter-pulse intervals  = 19.025; p < 0.001). Nevertheless, the pGFAP-BDNF group presented a significantly larger paired-pulse facilitation at the interval of 40 ms   for both groups of mice  of kainate Fig. . Both WTice Fig. . The preice Fig.  reduced ice Fig. . Overall23. To functionally explore the influence of astrocytic BDNF over the neuronal population response in an epileptic context we used a loss- and a gain-of-BDNF-function approach in vitro. We evaluated the activity of WT hippocampal neurons co-cultured with (i) BDNF−/− or BDNF+/+ astrocytes and (ii) WT or pGFAP-BDNF astrocytes upon epileptic induction with 4-aminopyrimidine (4-AP)26. Neuronal activity was assessed by in vitro calcium imaging using Fluo4-AM as a fluorescence calcium indicator. Firing activity was inferred from each individual neuron and then averaged and considered as one individual experiment. First, the results showed that 4-AP induced an increase of the firing frequency in both BDNF−/− and BDNF+/+ groups  expressing Cre-recombinase under the control of CAMKII or GFAP promoter, leading to the deletion of TrkB expression in principal neurons or astrocytes, respectively. We performed bilateral hippocampal injections of AAV-CaMKII-GFP, AAV-GFAP-GFP, AAV-CaMKII-Cre-GFP, or AAV-GFAP-Cre-GFP  or from astrocytes in the same hippocampal subregions, we used TrkBGFP Fig. . Next, tare Fig. .Fig. 5Eff/f-GFP-Veh) treated with vehicle. We did not detect significant changes in TrkB.FL expression either in the TrkBf/f-GFP-Pilo or in the TrkBf/f-CaMKII-Cre-Pilo groups   Fig. . These rf/f mice injected with AAV-GFP and treated with vehicle and TrkBf/f mice injected with AAV-GFP or with AAV-GFAP-Cre or with AAV-CaMKII-Cre and treated with pilocarpine . On day 7, we subjected the mice to the open field paradigm. Statistical analysis showed no significant differences between the groups TrkBf/f-GFAP-Cre-Pilo, TrkBf/f-CaMKII-Cre-Pilo, and TrkBf/f-GFP-Veh in spontaneous locomotor activity  was observed in both TrkBf/f-CaMKII-Cre-Pilo and TrkBf/f-GFAP-Cre-Pilo compared to TrkBf/f-GFP-Pilo  may have a key role in the development of SE, and that a reduction of TrkB.T1 (we cannot rule out an effect from undetected TrkB.FL downregulation) expression specifically in astrocytes is neuroprotective and rescues the performance in the NOL task. This is important since TrkB manipulation can alter synaptic plasticity and hippocampal-dependent learning47.TrkB receptor and its truncated isoform TrkB.T1 are expressed in astrocytes and neurons and could mediate the regulation of neuronal hyperactivation in the first stages of TLE48. Compared to our results, this differential effect can be explained by the different temporal approach of the BDNF release. Thus, an acute and sustained increase on BDNF levels during the first stages of TLE can induce an aberrant neuronal hyperexcitability and death while a late-onset and chronic treatment with this neurotrophin induces synaptic changes and promotes neuronal survival49.The role of BDNF and TrkB during different phases of TLE is complex. Previous work showed therapeutic effects of long-term BDNF supplementation in the epileptic hippocampus by reducing degenerating neurons50. Furthermore, TrkB.T1 was diminished/normalized in both groups of mice that have TrkB expression genetically disrupted in neurons or in astrocytes, validating the neuroprotective effect mediated by a reduction of TrkB.T1 expression after SE in a cell-specific manner. Upon excitotoxic conditions, a change in the TrkB isoforms occurs, decreasing the levels of TrkB.FL and increased TrkB.T151. The functional impact of TrkB.T1 increase has been controversial51. According to our results, normalization of TrkB.T1 levels might underlie the neuroprotective effect observed upon TrkB expression reduction, supporting the hypothesis of deleterious effect of TrkB.T1 increase in the epileptic context.Importantly, we found here an outstanding increase in the expression of TrkB.T1 as predicted51. Indeed, we observe a decrease in the phosphorylation of PLCγ upon pilocarpine treatment, which is a main affected molecular pathway by which SE-induced TrkB activation promotes its epileptogenic consequences52. Moreover, conditional reduction of TrkB expression in both neurons and astrocytes is able to rescue the decrease of both pPLCγ and pTrkB, probably due to the reduction of TrkB.T1 that hampers the activation of TrkB.FL receptor53. Conversely, pilocarpine treatment did not modify the BDNF-dependent phosphorylation of Akt as previously described51.Therefore, our results reveal for the first time a major participation of astrocytic TrkB in the cell death and cognitive deficits related to TLE models.TrkB-dependent signaling has been shown to be downregulated in excitotoxic models54. We cannot exclude that changes in phospho-Akt, among others, could have taken place during the first hours just after the pilocarpine treatment. Overall, our results point to astrocytic BDNF and TrkB as promising therapeutic targets for the treatment of TLE.Additionally, we have observed some effects probably due to a delayed time point in which we evaluated the mice. First, despite the weak neuronal death observed in mice genetically depleted of TrkB.T1 and TrkB.FL and treated with pilocarpine, we cannot discard that some neuronal death occurred during the first stages after pilocarpine treatment and we missed it out. Second, the presence of degenerating neurons in some hippocampal subregions (CA1 and CA3) but not in others (CA4) suggests differential sensitivity to pilocarpine of neurons from different hippocampal sub-fields. Thus, it is possible that these different degeneration dynamics have been neglected by focusing our experiments only in one time point. Third, although we observed neuroprotection in different hippocampal sub-fields, we did not detect changes in phospho-Akt, a well-known pathway involved in neuronal survival20. For TrkB deletion, TrkBf/f mice were generated in which the NTRK2 exon S was flanked with LoxP sequences55. We used P1–P3 BDNF+/+ and BDNF−/− mice56  to obtain astrocytes in vitro devoid of BDNF. Mouse genotyping for pGFAP-BDNF, TrkBf/f, and BDNF−/− mice was carried out from a tail biopsy as previously described57. The animals were housed with access to food and water ad libitum in a colony room kept at 19–22 °C and 40–60% humidity, under a 12:12 h light/dark cycle. Age of the mice was specified in each figure legend according to the experimental approach requirements. Experimental animals  were used in accordance with the ethical guidelines .For in vivo experiments in 10-week-old adult male mice  we used pGFAP-BDNF mice that express BDNF under the GFAP promoter12 GCs), rAAV5-GFAP-GFP , rAAV5-CaMKII-Cre-GFP , or rAAV5-GFAP-Cre-GFP . All the AAVs were purchased to the Virus Vector Core UNC . We used the following coordinates (millimeters) from bregma  and from skull ; anteroposterior: −2.0; Lateral +/−1.25, and dorsoventral: −1.3 (CA1) and −2.1 (GD). The cannula was left to deliver 1 μl of 1:1 virus in each depth during 2 min and five additional minutes were left to have complete virus diffusion. After 2 h of careful monitoring, mice were returned to their home cage for 3 weeks before starting the lithium-pilocarpine model and subsequent behavioral and biochemical analysis.Following anesthesia with ketamine/xylazine , we performed bilateral hippocampal injections of rAAV5-CaMKII-GFP  was stopped after approximately 120 min with an intraperitoneal injection of valium . Only animals that displayed 120 min of SE survived and showed the following levels of epileptic seizure were selected: mouth and facial movement, tremors, head nodding, and forelimb clonus.Animals were subjected to the lithium-pilocarpine model of TLE. Briefly, mice were treated intraperitoneally with lithium  20–23 h prior to administration of scopolamine, an anti-muscarinic molecule . Thirty minutes after the administration with methyl-scopolamine, animals were treated with pilocarpine . Control animals were injected with saline solution. Male, 8-month-old pGFAP-BDNF mice and their littermate wild-type (WT) controls of the same age and sex were prepared for the in vivo electrophysiological study of hippocampal functions. These experiments were carried out in the animal facilities of the Pablo de Olavide University. Upon their arrival animals were housed with access to food and water ad libitum and kept at 21 °C and 50% humidity, under a 12:12 h light/dark cycle. Experiments were carried out following European Union Council (2010/276:33–79/EU) guidelines and Spanish  regulations for the use of laboratory animals in chronic experiments. Experiments were also approved by the local Ethics Committee of Pablo de Olavide University (document no 06/03/2018/025).21, animals were anesthetized with 1.2% isoflurane  delivered via a mask adapted to mouse head . Then, animals were implanted with a bipolar stimulating electrode at the right Schaffer collateral-commissural pathway of the dorsal hippocampus  and with two recording electrodes at the ipsilateral stratum radiatum underneath the CA1 area . Electrodes were made of 50 μm, Teflon-coated tungsten wire . The final location of the recording electrodes was determined following the field potential depth profile evoked by paired  pulses presented to the stimulating electrode59. Two bare silver wires were affixed to the skull as ground. Electrodes were connected to a 6-pin socket  that was affixed with dental cement to the cranial bone. After surgery, animals were kept in individual cages provided with food and water ad libitum until the end of the experimental sessions.As already described60.To allow a proper recovery of the experimental animals, recording sessions were started 1 week after surgery. For input/output curves Fig. , monosyn61. Intervals between pair of pulses were set at 30 s to avoid unwanted interactions evoked by pre- or postsynaptic mechanisms.For the paired-pulse facilitation at the CA3–CA1 synapse Fig. , we used63. As illustrated in Fig. In order to determine the propensity of WT and pGFAP-BDNF mice to generate convulsive seizures, animals were injected (i.p.) with the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor agonist kainic acid  dissolved in 0,1 M phosphate-buffered saline (PBS) pH = 7.4 as previously described to increase hippocampal excitability in vivo+/+ and BDNF−/− mouse pups56 , and from P1 to P3 WT and pGFAP-BDNF mouse pups20 by hippocampal dissections. Extracted tissue was dissociated and placed in 25 cm2 flasks in an MEM 1Px conditioned media NM-15  with l-glutamine and Earle’s salts (Gibco-BRL) and placed in an incubator at 37 °C with 5% CO2. A tail biopsy was obtained from each pup for genotyping. After two passages cultures were purified by agitating in a shaker during 10 min at 400 r.p.m. Medium with undesired floating cells was replaced and flasks were placed in an incubator for 2 h at 37 °C. Next, flasks were agitated again for 16–18 h at 250 r.p.m. Finally, medium with floating cells was replaced with new medium. Once astrocytes reached confluence, they were seeded in 24-well plaques and allowed to reach confluence. Then, one day before the addition of hippocampal neurons, astrocyte cultures were pre-incubated with neurobasal medium  containing 1 ml per 50 ml of B27 supplement (Gibco-BRL) and 500 μl of GlutaMAX (100×) (Gibco-BRL). Hippocampal neurons were prepared from E18 B6CBA mouse embryos . The neuronal cell suspension was low density seeded in the 24-well plaques already containing astrocyte monolayer .Primary astrocyte cultures were obtained from P1 to P3 BDNF2, 2 mM; MgCl2, 1 mM. The recording chamber was mounted on an Olympus IX70 inverted microscope equipped with a Hamamatsu Orca Flash 4.0 V2  camera and Dual OptoLED power supply (Cairn Research Ltd) as a source of light. Fluorescence images were acquired at room temperature (RT) with a ×10 objective (20 frames/s). Neurons were recorded during 10 min for stabilization, afterward for induction of epileptiform activity, 100 μM 4-aminopirimidine or vehicle was added to the EM. After 5 min allowing the diffusion of the drug, activity was recorded during additional 10 min.Calcium fluorescence recordings were carried out at 15 DIV using cell-permeant calcium sensitive dye Fluo4-Acetoxymethyl ester (Fluo4-AM) . Cultures were incubated for 20 min at 37 °C in their own Neurobasal medium in the presence of 1 µM Fluo4. After incubation, cultures were placed in a 35 mm diameter glass bottom chamber  for recording. Recordings were carried out in pH-stable (7.4) external medium (EM). EM consisted of: HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid), 10 mM; NaCl, 128 mM; KCl, 4 mM; glucose, 10 mM; sucrose, 45 mM; CaCl64, a custom-made software package developed in Matlab (MathWorks). Recordings were first time-averaged across the whole recording to obtain a clear picture of the cell bodies. Cells were automatically detected as regions of interest (ROIs) using the time-averaged image. Traces were acquired for each ROI by spatially averaging between its pixels across the whole recording. Each trace was smoothed, and its baseline corrected. To estimate the baseline, a reference point was taken for each 50 s block, and its position within the block determined by the value closest to the 10% lower fluorescence percentile within that block. A smoothing spline was then fitted using this point set. This baseline was subtracted from the original trace and finally normalized to 100 × (F − F0)/F0 relative units.Analysis of calcium imaging recordings was performed with NETCALUsing a supervised machine learning approach, neuronal activity traces were selected. First, traces were visually examined and a subset belonging to neuronal activity class was manually selected. Then the classifier was trained with this subset using adaptive boosting (AdaBoost), machine learning meta-algorithm. The resulting classification was visually inspected and refined by changing the training set as required.65. For the underlying calcium model, a single decaying exponential with non-saturating dynamics with amplitude 1% ΔF0/F0 and decay 3 s was used on all experiments. Active neurons were considered when at least one spike was detected during the recording.Spikes were inferred using a modified Peeling method2 pellets, and stored at −80 °C until use. Briefly, the tissue was lysed by sonication in 150 ml of lysis buffer . After lysis, samples were centrifuged at 12,000 r.p.m. for 15 min. Supernatant proteins (15 mg) from total brain regions extracts were loaded in polyacrylamide gels (SDS–PAGE) at different polyacrylamide concentrations and transferred to nitrocellulose membranes  during 1 h. Membranes were blocked in TBS-T solution  plus 5% non-fat dry milk and 5% bovine serum albumin. Membranes were probed with the following antibodies: anti-BDNF rabbit 1:1000 , anti-GFAP rabbit 1:1000 , anti-TrkB mouse 1:1000 , anti-PLC1γ rabbit 1:1000 , anti-pPLC1γ (Tyr783) rabbit 1:1000 , anti-Akt rabbit 1:2000 , anti-pAkt (Thr308) rabbit 1:1000 , anti-pTrkB (Tyr816) rabbit 1:1000 , and anti-iNOS rabbit 1:1000 . All membranes were incubated with the primary antibodies overnight at 4 °C by shaking in PBS with 0.02% sodium azide. After washed with TBS-T, membranes were incubated with anti-rabbit or anti-mouse horseradish peroxidase-conjugated secondary antibodies . Secondary antibody binding was detected by the enhanced chemiluminescence substrate kit . For loading control a mouse monoclonal antibody for α-tubulin was used . ImageJ software was used to quantify the different densitometry immunoreactive bands relative to the intensity of the α-tubulin in the same membranes. Data are expressed as the mean ± SEM of band density.Animals were euthanized by cervical dislocation. The two hippocampi were dissected out, frozen using COMice were euthanized by cervical dislocation. Left hemispheres were removed and fixed for 72 h in 4% paraformaldehyde (PFA) in PBS. Forty-micrometer coronal sections were obtained using a Leica vibratome (Leica VT1000S). Next, free floating sections were washed three times in PBS, treated with NHCl for 30 min, and washed again three times with PBS. Floating sections were permeabilized and blocked with PBS containing 3% Triton X-100, 0.02% Azide, 2% BSA, and 3% NGS (Ab buffer) for 1 h at RT. After three washes in PBS, brain slices were incubated overnight at 4 °C with FITC-conjugated GFP primary antibody  for signal enhancement. Sections were washed three times and incubated for 2 h at RT with fluorescent secondary antibody Alexa Fluor 488 goat anti-mouse . Sections were analyzed using a two-photon confocal microscope (Leica SP5).To assess degenerating neurons in the hippocampus, mice were sacrificed 10 days after the administration of pilocarpine or vehicle. Left hemispheres were removed and kept in PFA during 3 days with constant shaking. At this point, PFA was replaced for PBS until the brains were cut. Forty-micrometer coronal sections were obtained using the Leica vibratome (Leica VT1000S). Brain sections were mounted with distilled water onto SuperFrost slides (Thermo Scientific™ SuperFrost™ Microscope Slides) and dried at RT. The tissue was fully dry within 30 min at which time it was immersed in 100% ethyl alcohol for 3 min followed by a 1 min change in 70% alcohol and a 1 min change in distilled water. The slides were then transferred to a solution of 0.06% potassium permanganate for 15 min and were gently shaken on a rotating platform. The slides were rinsed for 1 min in distilled water and were then transferred to the Fluoro-Jade staining solution where they are gently agitated for 30 min. A 0.01% stock solution of the dye was prepared by dissolving 10 mg Fluoro-Jade in 100 ml of distilled water. The 0.001% working solution of Fluoro-Jade was prepared by adding 10 ml of the stock Fluoro-Jade solution to 90 ml of 0.1% acetic acid in distilled water. After staining, the sections were rinsed with three 1 min changes of distilled water. Excess water was drained off, and the slides were rapidly air dried. When dry, the slides were immersed in xylene and then mounted with Mowiol mounting media.Sections were analyzed using an Olympus BX60 epifluorescent microscope equipped with an Orca-ER cooled CDD camera  with the Hokawo (Hamamatsu) image software acquisition. Three hippocampal sections were analyzed per animal and for each section five images were taken using the ×20 objective. To quantify the degenerating cells, the mean area of CA1, CA3, and CA4 was measured for each section and the number of Fluoro-Jade C (FJC)-positive cells inside this area was counted using FIJI software . The mean value of all animals from each group was obtained and represent as % related to the control group and as % related to the CA1 of the control group.71. First, materials for the SHIRPA evaluation consisted of a transparent Perspex viewing jar, a clean cage, a wire grid cage lid, and a stopwatch. During the procedure, each mouse was removed from the home cage, evaluated individually in the viewing jar, and then placed into the clean cage for further evaluation. Finally, animals were placed on the grid cage and last items were evaluated. The viewing jar and the testing cage were cleaned with 70° ethanol between animals to avoid the possibility of olfactory cues affecting behavior. The data from individual components of the modified SHIRPA were pulled to provide a general SHIRPA index as previously described72. For further information about the SHIRPA procedure, more detailed information is provided in the Mouse Phenome Database at the Jackson Laboratory’s website: https://phenome.jax.org/projects/Jaxpheno7/protocol#SHIRPA.To provide detailed mid-term general phenotype assessment 7–9 days after the pilocarpine treatment, mice were tested using the phenotype assessment protocol called SHIRPA, the OF, and the NOL test, all these tests have been used to detect mid-term behavioral alterations such as general neurological alterations, hyperlocomotion activity, and memory impairments induced by pilocarpineTo check spontaneous locomotor activity, anxiety-like parameters, and navigation we used the OF. Briefly, the apparatus consisted of a white square arena measuring 40 × 40 × 40 cm in length, width, and height, respectively. Dim light intensity was 60 lux throughout the arena. Animals were placed on the arena center and allowed to explore freely for 30 min. Spontaneous activity was measured. At the end of each trial, any defecation was removed, and the apparatus was wiped with 30% ethanol. Animals were tracked and recorded with SMART junior software .The NOL memory task evaluates spatial memory and is based on the ability of mice to recognize when a familiar object has been relocated. Exploration took place in an open-top arena with quadrangular form (45 × 45 cm). The light intensity was 40 lux throughout the arena. Mice were first habituated to the arena in the absence of objects . Some distal cues were placed throughout the procedure. On the third day during the acquisition phase mice were allowed to explore two duplicate objects (A1 and A2), which were placed close to the far corners of the arena for 10 min. After a delay of 24 h, one object was placed in the corner diagonally opposite. Thus, both objects in the phase were equally familiar, but one was in a new location. The position of the new object was counterbalanced between mice. Animals were tracked and recorded with SMART Junior software.F test to compare variances. In experiments with normal distribution statistical analysis were performed using the unpaired two-sided Student’s t-test (95% confidence), one-way ANOVA with the Tukey’s as post hoc tests, two-way ANOVA with the Bonferroni’s post hoc test as appropriate and indicated in the figure legends. Values of p < 0.05 were considered as statistically significant. Grubbs’ test was performed to determine the significant outlier values. All experiments in this study were blinded and randomized by blocks of animals. All mice bred for the experiments were used for preplanned experiments and randomized to experimental groups. Data were collected, processed, and analyzed randomly. The experimental design and handling of mice were identical across experiments. Littermates were used as controls with multiple litters (3–5) examined per experiments.Sample sizes were determined by using the power analysis method: 0.05 alpha value, 1 estimated sigma value, and 75% of power detection. All data are expressed as mean ± SEM. Normal distribution was tested with d’Agostino and Pearson omnibus, Shapiro–Wilk, and Kolmogorov–Smirnov normality tests. If at least one of them was passed, statistical analysis was performed using parametric statistical analysis. Otherwise non-parametric Mann–Whitney or Kruskal–Wallis or Dunn’s tests were used. Before pairs of comparisons we performed the


In recent years, the characteristics of the graphene/crystalline silicon junction have been frequently discussed in the literature, but study of the graphene/polycrystalline silicon junction and its potential applications is hardly found. The present work reports the observation of the electrical and optoelectronic characteristics of a graphene/polycrystalline silicon junction and explores one possible usage of the junction. The current–voltage curve of the junction was measured to show the typical exponential behavior that can be seen in a forward biased diode, and the photovoltage of the junction showed a logarithmic dependence on light intensity. A new phototransistor named the “photodiode–oxide–semiconductor field effect transistor (PDOSFET)” was further proposed and verified in this work. In the PDOSFET, a graphene/polycrystalline silicon photodiode was directly merged on top of the gate oxide of a conventional metal–oxide–semiconductor field effect transistor (MOSFET). The magnitude of the channel current of this phototransistor showed a logarithmic dependence on the illumination level. It is shown in this work that the PDOSFET facilitates a better pixel design in a complementary metal–oxide–semiconductor (CMOS) image sensor, especially beneficial for high dynamic range (HDR) image detection. The unique structural, electronic, and optical properties of graphene have made this two-dimensional material an attractive subject of research in recent years. While the high carrier mobility in graphene opened the door to its applications in high-speed electronics ,2,3,4, tInterestingly, while there have been a number of studies studying graphene/c-Si junctions and their application to photodetection ,29,30,314 and 105 cm−1 [2. Silver paste was respectively applied to the surface of exposed poly-Si and the surface of graphene to form the two electrical terminals of the graphene/n-type poly-Si junction. The reason for using silver paste as the contact material was that it could be easily applied to quickly finish sample preparation and it had been tested to form ohmic contacts with graphene and with n-type c-Si. It was speculated that the paste might still form ohmic contacts with n-type poly-Si. Before a graphene/poly-Si junction is used for applications, it is essential to have a look at its general electrical and optoelectronic characteristics. For this purpose, samples of graphene/n-type poly-Si junction were fabricated. A 300 nm-thick phosphorus-doped poly-Si film was deposited on an n-type Si wafer by using low pressure chemical vapor deposition (LPCVD) at a temperature of 620 °C. Because the optical absorption coefficient of poly-Si in the visible light band is between 10105 cm−1 , the thi105 cm−1 ,36. The RSH) of the graphene film was measured by using a four-point probe. Values between 250 Ω/square and 300 Ω/square were obtained for all the samples. The sheet resistance  at room temperature with the terminal of the poly-Si set at ground potential. I–V curve under the illumination of a halogen lamp. The optical power of the lamp was unknown. It can be seen from I–V curves do not show the simple exponential behavior of a single rectifying junction. Instead, they show the typical behavior of a metal–semiconductor–metal (MSM) structure with two asymmetric rectifying junctions [I–V curves and it is no longer straightforward to extract the exact values of junction parameters , we can still see that the dark current flowing through the single-layer graphene/n-type poly-Si junction increases exponentially with increasing forward bias voltage. The large ideality factor, n, of this disturbed forward bias characteristic was found by curve fitting to be about 10. The exponential dark I–V curve under forward bias implies that we should be able to see a logarithmic dependence on light intensity from the open-circuit photovoltage of the junction, as analyzed below.To see the graphene/n-type poly-Si junction behave like an ohmic junction or a Schottky junction, the dark unctions ,38. The I–V characteristic of a junction can be expressed asn is the ideality factor of the junction, sI is the dark reverse saturation current of the junction, and phI) of the PD is directly proportional to the incident light intensity. If at t = 0, a light starts to illuminate the junction under the open-circuit condition, the photocurrent does not flow out. It charges the junction capacitance (DC) and internally forward biases the junction at the same time. The dynamics can be described byThe general exponential dark phV), should follow the next equation:phI is the photocurrent, and t is the exposure time. The logarithmic response of the photovoltage to light intensity (via phI) is advantageous because it mimics human eyes’ response to brightness. Utilizing phV as the output signal allows one to detect a wide dynamic range of light intensity. Unlike the photocurrent that may easily saturate the subsequent reading circuit at high illuminance, the photovoltage allows the circuit to function properly because the signal is logarithmically compressed at high illuminance but still linear at low illuminance. When the incident light is weak or the exposure time is short, Equation (3) reduces tophI, sI, and DC are all proportional to the junction area, which means that it is not necessary to enlarge the device size of the PD in order to obtain a significant magnitude of photovoltage.Solving Equations (1) and (2) by the separation of the variables, with the zero initial condition I–V curve of the fabricated graphene/n-type poly-Si junction sample at room temperature shows an exponential characteristic under forward bias, it can be expected that if this junction is used as a PD, the photovoltage of the PD should exhibit a logarithmic dependence on the incident light intensity. Even though there exists an additional silver paste/poly-Si junction at the other side of the poly-Si, the photo-generated holes in the poly-Si can still flow to the graphene and build up the photovoltage. Since the measured dark The logarithmic behavior of the photovoltage of a PD makes this variable particularly useful for being adopted in CMOS image sensors as a signal to detect high dynamic range (HDR) images. Furthermore, the graphene/n-type poly-Si junction PD can bring even more benefit to this application because it can be implemented right on top of the gate oxide of a MOSFET in the pixel of a CMOS image sensor. GV) to a high value (VDD). Then, the Reset transistor is turned off and GV is reduced by the discharging mechanism due to the photocurrent phI generated from the PD. The amount of the voltage reduction (ΔV) at node G is a linear function of phI as shown in Equation (6):t is a specified discharging period, TC is the total capacitance at node G, DC is the capacitance of the PD, GC is the capacitance looking into the gate of the source follower (SF) transistor, and pC is the parasitic capacitance due to interconnect. A large fill factor of the PD in the pixel is preferred so that phI can be maximized and TC can be less influenced by GC and pC. After the discharging period,GV signal is output through the source follower to the column bus, and ΔV is used to represent the average light intensity during the discharging period. This linear operation principle has limitations: Firstly, for high light intensity, phI and ΔV can easily become too large and GV may be reduced too much to make the SF transistor functional. This saturation limits the detectable range of input light intensity. Secondly, for high resolution image sensors, there exists a tradeoff between the pixel size and the fill factor of the PD in a pixel. This limits the values of phI and DC, and the influence from GC and pC becomes obvious. Modifying the 3T pixel structure can resolve these limitations.Conventionally, the PD in the pixel is a monolithic P–N junction diode located beside the transistors. To operate the pixel, the Reset transistor is first turned on to set the voltage at node G (VREF) that makes the SF transistor always functional. In this way, the GV is first reset to VREF and then becomes the sum of VREF and the photovoltage of the PD after some exposure time t. The photovoltage of the PD can be expressed as Equation (3) except that DC should now be replaced by TC. Therefore, as explained in Equations (4) and (5), the GV in the modified pixel structure now behaves linearly at low light intensity but changes logarithmically at high light intensity. With the proper setting of VREF, the GV value does not exceed VDD and can always make the SF transistor functional. This natural compression of the signal allows the dynamic range of incident light intensity to be extremely wide, which makes the single-shot detection of high-contrast images possible. There is no need to take multiple shots of an HDR image at different exposure levels and then blend these images together for a composite image. Furthermore, if the original P–N junction PD is replaced with a graphene/n-type poly-Si junction PD that is directly fabricated on top of the gate oxide of the SF transistor, the parasitic capacitance pC can be eliminated and the tradeoff between pixel size and fill factor can be removed. That is, one can combine the PD and the SF transistor into a new integrated device, namely, the PD–oxide–semiconductor field effect transistor (PDOSFET), to maximize pixel performance. In this way, since the PD is directly stacked on the gate of the SF transistor, metallic interconnect is not needed and pC is completely eliminated. In addition, because the stacking makes the area of the PD the same as the gate area of the SF transistor, the photovoltage of the PD is independent of the area and there is no more area-competing issue between the PD and the MOSFET. Poly-Si/graphene PD offers unique advantages for this integration. The n-type poly-Si gate is an essential element in most CMOS technologies. All one needs to do is to apply a graphene film to the gate area to form the PD. Additionally, the graphene film has good thermal stability and can withstand the thermal cycles in subsequent fabrication processes. Therefore, one can apply it either before or after the poly-Si deposition process, which allows flexibility in designing the polarity of the PD. If graphene is placed above poly-Si, its transparency allows light to pass through and reach the poly-Si for optical absorption. Metal/poly-Si Schottky PD cannot provide these advantages.To verify the PDOSFET concept, a test device as schematically illustrated in 2O2. After rinsing in de-ionized (DI) water, the graphene was placed onto the Si wafer with gate oxide already grown on it, and the PC layer was subsequently removed with chloroform. The graphene was then patterned by lithography and RIE according to the designed gate pattern, followed by normal poly-Si gate deposition, lithography, and self-aligned CMOS processes in which the source and drain doping was implemented by using arsenic (As) ion implantation with an energy of 30 KeV and a dose of dI-gV and dI-dV characteristics of the fabricated PDOSFET in the dark were measured by using an Agilent 4156a semiconductor parameter analyzer. dI–gV curve of the PDOSFET under 3.3 V drain-to-source voltage (dsV). Normal turn-on behavior was observed. The threshold voltage for the channel to turn on is between 1 V and 1.5 V. By using the ATLAS device simulator from Silvaco, the threshold voltage of a MOSFET, the same as that for the PDOSFET shown in gV) so that the control of the surface potential at the channel surface by Vg becomes less effective. dI–dV characteristics of the PDOSFET under various gate bias voltages. Normal linear and saturation behaviors can be clearly recognized. The channel length of the fabricated PDOSFET is quite long; therefore, the short channel effect is hardly seen in The resultant PDOSFET looks just like a normal n-channel MOSFET (NMOSFET) except that a graphene layer is inserted between the n-type poly-Si gate and the gate oxide. That is, a PD is embedded right in the gate structure with minimal process modification. The device should be able to exhibit the normal dark electrical characteristics of an NMOSFET. To verify this, the outV) shows a logarithmic dependence on illuminance. This indicates that both the graphene/n-type poly-Si junction PD and the FET integrated in the PDOSFET functioned well. Under low illuminance, Vout changes linearly with light intensity to provide good resolution. At high illuminance, outV is compressed to prevent saturation. The feasibility of using a single PDOSFET in a pixel to replace the P–N junction PD and the SF transistor is thus verified. It should be mentioned that the modification from the conventional 3T pixel structure to the new 3T pixel structure with the PDOSFET is very slight and that the responsivity of the graphene/poly-Si PD is mainly determined by poly-Si, not by graphene. Therefore, except for the optical input dynamic range, most other performance parameters such as the quantum efficiency, conversion gain, noise, and image lag of the new pixel should be similar to those of the conventional pixel.When the PDOSFET is illuminated with light, the photovoltage developed at the PD should be able to effectively increase the gate voltage of the FET and thus increase the channel current. Therefore, when the PDOSFET is connected in a source follower configuration, the output voltage of the source follower should faithfully reflect the logarithmic behavior of the photovoltage of the PD. DSV = 5 V. Therefore, the observed logarithmic dependence of outV  on illuminance is certainly not due to (at least not dominated by) the optical absorption in the c-Si substrate. Instead, the graphene/n-type poly-Si PD on top of the gate dominates the optoelectronic behavior of the PDOSFET source follower.Although the thickness of the poly-Si gate was designed to be 300 nm to absorb most of the visible light, it cannot be ruled out that some long wavelength light may still travel through the gate and reach the c-Si region under the gate oxide. These photons may still generate electron–hole pairs and contribute to the increase in the drain current. However, if this influence exists and dominates, the magnitude of the drain current increase should be linearly proportional to the increasing illuminance. Besides, the photo-generated drain current of the MOSFET control device (without PD at the gate) under 49,000 Lux illumination was measured to be only 0.1 μA even at In addition, it was mentioned above that the source and drain areas of the PDOSFET were covered by metal in order to prevent the source and drain junctions from detecting light and contributing extra photocurrent. The effectiveness of this arrangement was investigated by measuring the dark and light drain currents when the gate voltage was set low to disable the channel. No change in the terminal current magnitude was observed with and without illumination. This confirms that the metal coverage on the source and drain regions effectively blocked the incident light.outV) was observed. For the fabricated large, long-channel PDOSFET, both the rise time and the fall time of outV were as short as 22 μs when the loading resistance was 100 kΩ, as shown in For most applications, it is desirable for the intrinsic operation speed of the phototransistor to be fast. Therefore, the transient response of the PDOSFET source follower was also investigated in this work. A white light-emitting diode (LED) was switched on/off by a voltage square wave to produce 5000 Lux light pulses onto the PDOSFET. The transient behavior of the source follower output voltage (One process issue about employing the proposed PDOSFET in mass production is the use of graphene in the front-end of standard, commercial CMOS processes. In such mass production processes, it is impossible to deposit the graphene layer by using slow techniques such as the transfer method. The direct wafer-level synthesis/deposition of graphene is needed. Besides, possible carbon contamination of the devices on the chip, due to the gases used in the graphene deposition process, must be avoided. Otherwise, graphene will not be usable in the front end of CMOS processes and it will be impossible to fabricate the PDOSFET. Although the new pixel structure shown in −2 dose to make it n-type. At the ohmic contact area, heavy doping was achieved by an additional ion implantation with 10 KeV of energy and a −2 dose. The area of the PD was designed to be As a remark, one possible way to implement the pixel structure shown in I–V curve of the junction was found to be exponential, and the junction responded to light, with its photovoltage being a logarithmic function of illuminance. A new phototransistor called the PDOSFET, in which the graphene/n-type poly-Si junction PD was directly integrated with an n-channel MOSFET, was proposed, fabricated, and functionally verified. The channel current of the PDOSFET was efficiently modulated by the photovoltage of the PD and thus responded to light intensity logarithmically. The proposed PDOSFET shows great potential for CMOS image sensor applications, especially for detecting HDR images.A graphene/n-type poly-Si junction PD was fabricated and characterized in this work. The dark


This paper reports an independently tunable graphene-based metamaterial absorber (GMA) designed by etching two cascaded resonators with dissimilar sizes in the unit cell. Two perfect absorption peaks were obtained at 6.94 and 10.68 μm with simple single-layer metal-graphene metamaterials; the peaks show absorption values higher than 99%. The mechanism of absorption was analyzed theoretically. The independent tunability of the metamaterial absorber (MA) was realized by varying the Fermi level of graphene under a set of resonators. Furthermore, multi-band and wide-band absorption were observed by the proposed structure upon increasing the number of resonators and resizing them in the unit cell. The obtained results demonstrate the multipurpose performance of this type of absorber and indicate its potential application in diverse applications, such as solar energy harvesting and thermal absorbing. Metamaterials are a type of artificially engineered electromagnetic material composed of periodically arranged sub-wavelength elements. They exhibit excellent properties and applications such as negative refractive index , opticalIn this paper, an independently tunable multipurpose single-layer GMA is proposed at mid-infrared frequencies. Two perfect absorption peaks are obtained; each resonant frequency can be independently tuned with a high absorption rate of 99% by varying the Fermi level of graphene under a set of resonators. The absorber remains effective over a wide range of angles under oblique incidence. In addition, multi-band and broadband absorption are observed when appropriately sized resonators are etched in the unit cell. All these results indicate that the proposed structure can be widely used in solar ray harvesting and thermal absorbing.d = 0.2 μm. Gate voltages Vg1 and Vg2 are applied to the two sets of graphene ribbons, and their Fermi levels are fE1 and fE2, respectively. The lengths of the resonator strips are l1 = 2.4 μm and l2 = 3.5 μm, and their widths are w1 = 0.48 μm and w2 = 0.7 μm. The periods of the unit cell are xP = 7.5 μm along the x direction and yP = 3.75 μm along the y direction. The dielectric layer has a thickness of 0.33 μm and comprises polytetrafluoroethylene with a relative permittivity of 2. The thickness of the ground plane is 0.3 μm, which is greater than its skin depth, ensuring that the transmission of electromagnetic waves can be completely suppressed. The relative permittivity of gold is defined as [A schematic diagram of the proposed GMA is illustrated in fined as :(1)εAu=1p = 1.37 × 1016 s−1 is the bulk plasmon frequency and γ0 = 4.08 × 1013 s−1 is the collision frequency.Here, ωσg, can be determined by the Kubo formula [fE > ħω/2), and the intraband contribution dominates the surface conductivity of graphene, while the interband transitions are negligible owing to Pauli blocking [The surface conductivity of graphene,  formula ,26; it cblocking . Conseque is the elementary charge, Bk is the Boltzmann constant, T = 300 K is the Kelvin temperature, ћ = h/2π is the reduced Planck’s constant, and ω is the applied angular frequency. Γ is the carrier scattering rate, which is kept constant at 2.4 THz for this study. cμ is the chemical potential, which is equal to the Fermi level of graphene when cµ > Bk.Here, σg as the Fermi level changes from 0.2 to 0.6 eV. It is evident that σg can be dynamically tuned by changing the Fermi level, which is highly convenient for designing tunable absorbers working within a specific frequency range. According to the Maxwell equations, Re (σg) is proportional to Im (εg), which represents the absorption losses in graphene [σg) when fE is changed. In addition, the spectral tuning can be measured by ∆Im (σg), which is explained in detail below.graphene . Thus, tAccording to the theory of multiple reflection and interference of the incident electromagnetic field, the absorption A (λ) can be obtained by A (λ) = 1 − R (λ) − T(λ), where R (λ) is the reflection and T (λ) is the transmission . Since tmin and λmax are the value of minimum and maximum wavelengths, respectively. Within the wavelength range from 4.5 to 13 μm, the value of E is 28.99% for the dual-band absorption structure. A larger value of absorption efficiency can be achieved via further reducing the wavelength range; the calculated E is 41.03% when the absorber works in the range of 6.5 to 11.5 μm. It should be noted that this range includes a large proportion of the atmospheric window which is the wave band with relatively high transmittance. The calculation means that nearly half of the incident light within the considered range could be absorbed. Therefore, the absorbers proposed in our research could acquire more of the incident energy, which will benefit the applications for light harvesting and thermal absorbing.Theoretical research on the proposed GMA was carried out using the finite elements solver COMSOL Multiphysics. When an s-polarized plane electromagnetic wave was incident on the double cross resonators, the absorption spectrum depicted by the solid curve in nversion . Here, λTo further demonstrate the absorption mechanism, a single-band absorber with one cross-shaped gold resonator was studied, as shown in x-axis direction, and those on the bottom flow in the opposite direction because of the reversed electric dipole moments. Consequently, a magnetic polariton (or “magnetic atom”) [y-axis. For both cases of wave incidence, the excited electromagnetic resonances confine and dissipate the electromagnetic energy in the absorber, resulting in perfect absorption close to 100%.In c atom”) ,31 is exc atom”) . For s-pfE1 increases from 0 to 0.6 eV, and the second peak with fE2 = 0 remains unchanged, as expected. fE1 and different fE2 values. Similar to the trend in the previous case, a blue shift evidently occurs for the second peak.The two absorption bands of the proposed GMA can be tuned as a whole or separately by different gate voltage loading methods on the two independent sets of graphene ribbons. As shown in fE1 and fE2 have the same increase from 0.4 to 0.6 eV, the absorption peak at the shorter wavelength shifts from 6.86 to 6.81 μm and that at the longer wavelength shifts from 10.37 to 10.22 μm. Assuming that the relative change in the resonant wavelengths is defined as δλ = 100 ×  denotes the graphene conductivity, W0 represents the stored electromagnetic energy in an uncovered metamaterial resonator. Thus, the spectral shift in the resonant frequency Re (∆ω) is related to Im (σg(ω)), and the corresponding amplitude modulation of absorption, Im (∆ω), is determined by Re (σg(ω)). The spectral shift is dominant over the amplitude modulation as Im (σg(ω)) > Re (σg(ω)), which is valid in the mid-infrared region [g(ω)) increases with wavelength for the same change in fE, as shown in It is important to note that the tuning efficiencies for the two resonance peaks are significantly different under the same variation in the applied gate voltages loaded on graphene; the second resonant peak exhibits a better response. For instance, when +λR2)/2 , the spe+λR2)/2 :(3)Δω=. The periods along the x and y directions are xP = 11.25 μm and yP = 3.75 μm, respectively. The other geometric parameters remain unchanged. In effε and effµ are the effective permittivity and permeability of the bulk multi-layer metamaterial. To satisfy the condition of matched impedances, the condition of effε = effµ is achieved by manipulating the spectral positions and strengths of the electric and magnetic resonances of the electromagnetic MAs [effε and effµ. The absorption peaks decrease slightly at 6.95 and 10.66 μm due to the mismatch between the dimensions of polytetrafluorethylene and the corresponding two resonators, resulting in an impedance mismatch between the structure and its surrounding [σg) at longer wavelengths for the same ∆fE.A triple-band absorber with three resonators of varied dimensions in the unit cell was designed, as shown in f vacuum ,36, wheretic MAs . The trirounding . Howeverl1 = 3.4 μm, l2 = 3.45 μm, and l3 = 3.5 μm, and their widths are wi = 0.2 × li . As depicted in Furthermore, a broadband absorber was designed using similarly sized resonators in the unit cell. As shown in In summary, an independently tunable multipurpose absorber with a single layer of metal-graphene metamaterials is proposed at mid-infrared frequencies. Compared with the previous work, the proposed dual-band absorber achieves independent tuning of two absorption peaks through reasonably designing the shape and arrangement of graphene and provides a flexible model for multi-band and broadband absorbers. The values of the absorption peaks are higher than 99%, and the structure does not hinder the wide-angle nature of MAs. The absorption spectrum is blue shifted when the Fermi level of graphene increases, and each resonance peak can be tuned independently. Triple-band and broadband absorbers were further achieved by appropriate design. The results of this study suggest that the proposed multipurpose structure can be widely used in light harvesting and thermal absorbing.


Tag questions are imperative, declarative, exclamative or interrogative statements that have been modified to include a question . Tag questions have been characterized as elderspeak because it suggests an expected response from the person with dementia, thus limiting his/her ability to make a decision independently. However, tag questions serve multiple functions in conversation. There is limited research on the multidimensional nature of tag questions in conversations between formal caregivers and their clients with dementia. Accordingly, the purpose of this study was to investigate the functions of tag questions used by formal caregivers in utterances coded as person-centered. Conversations (N= 87) between formal caregivers and a simulated person with dementia were video-recorded during a 5-minute care interaction involving morning care. Caregivers’ utterances were coded for the use of the following types of person-centered communication: recognition, negotiation, facilitation, and validation. During secondary data analysis, the person-centered utterances were analyzed for the use and function of tag questions. Conversational analyses revealed two broad functions of tag questions: gather information and facilitate a desired action. Tag questions used to gather information included the following specific functions: acknowledge response, establish common ground, state fact or opinion, initiate topic, conversational joking, state what is being done and questions. Tag questions that facilitated a desired reaction included the following specific functions: offers, advice and suggestions and requests and commands. Findings from the current study reveal that tag questions are not exclusively elderspeak and can be used to illicit conversation.


Although several reports indicate that the morphologic and electronic properties of the coating, as well as its surface features , play a key role in the biological interaction, these kinds of interactions have not been fully understood yet. In this review, we report and classify the cellular interaction mechanisms observed in graphene and hexagonal boron nitride (hBN) coatings. Graphene and hBN were chosen as study materials to gauge the effect of two atomic-thick coatings with analogous lattice structure yet dissimilar electrical properties upon contact with living matter, allowing to discern among the observed effects and link them to specific material properties. In our analysis, we also considered the influence of crystallinity and surface roughness, detailing the mechanisms of interaction that make specific coatings of these 2DMs either hostile toward bacterial cells or innocuous for mammalian cells. In doing this, we discriminate among the material and surface properties, which are often strictly connected to the 2DM production technique, coating deposition and post-processing method. Building on this knowledge, the selection of 2DM coatings based on their specific characteristics will allow to engineer desired functionalities and devices. Antibacterial coatings to prevent biofouling, biocompatible platforms suitable for biomedical applications  could be realized in the next future. Overall, a clear understanding on how the 2DM coating’s properties may modulate a specific bacterial or cellular response is crucial for any future innovation in the field.Two-dimensional material (2DM) coatings exhibit complex and controversial interactions with biological matter, having shown in different contexts to induce bacterial cell death and contribute to mammalian cell growth and proliferation  Other than being present in most of the Earth’s habitats, bacteria live in symbiotic and parasitic relationships with plants and animals. Bacteria are ubiquitous in mammals, and while they are necessary for the development of a balanced immune system, the disruption of microbiomes can negatively affect the health of an individual. Nowadays, bacterial pathogenic agents represent a major public health issue . The useAnother concern regarding bacteria is their adhesion to surfaces, and the consequent issue of biofouling. Biofouling refers to the formation of a biofilm consisting of a complex community of one or several microbial species on the surface of an object, which can impair its functionality, e.g., by promoting corrosion. Biofouling and related issues can cause damage to objects, equipment and structures, and often lead to significant financial loss . In the in vivo conditions. Suitable substrate materials should be able to guide cell growth and modulation, bioactive molecule delivery, physicochemical cue generation, while having similar mechanical properties to the native tissue  are a class of atomic-thick materials that are the subject of intense research efforts, motivated by a wide range of useful properties of high interest in several technological fields . In the 2-bonded carbon atoms arranged in a hexagonal lattice  are archetypal 2DMs that have drawn the attention of researchers . Graphen lattice   supports for monitoring and modulating excitable cell activity  new systems capable of inducing tissue regeneration or restoring cell-to-cell communication; (ii) specific diagnostic tools for the activity . Graphenactivity . Howeveraterials .Graphene and hBN have been recently found to induce specific cellular responses in different contexts. Taking into consideration the issues related to bacterial infection and the relevance of degenerative diseases, the different biological interactions of these materials can be exploited toward the following aims: (1) inducing bacterial cell death, e.g., to design medical instruments and mitigate the spreading of infections in hospital environment, and to produce anti-biofouling coatings ; (2) stiIn this paper, we reviewed the literature describing the various kinds of interactions that pristine graphene and hBN coatings respectively show with different bacterial species and different types of mammalian cells. Following this “Introduction,” the section “2DM coatings and cellular interaction” will report and comment on the main interaction mechanisms taking place when graphene and hBN coatings are used to interface bacterial and mammalian cells. The section “Coating applications” will then build on this by detailing the current and prospective applications for such coatings in the biomedical field. In the “Conclusion,” the main results and perspectives on the topic will be summarized.In this section, we report on the studied interactions between GBM coatings and bacteria, correlating them to the structural and electrical characteristics of the various coatings. Current literature on the antimicrobial mechanisms in GBMs such as GO and rGO, initially reported in 2010 , has beeIn the case of atomically smooth, CVD-grown graphene coatings, the main antibacterial mechanism is determined by its electronic conductivity  Lu et a. RegardiStaphylococcus aureus and Gram- (G-) (Escherichia coli) were used to investigate the antibacterial properties of monolayer graphene film on Cu, semiconductor Ge and insulator SiO2. The study showed that while graphene on Cu and Ge could inhibit the proliferation of both bacteria types, the same did not occur on SiO2 , where the bacterial cells will not be in contact with exposed flake edges, the antibacterial effects have been shown to arise from electronic conductivity of the basal plane, which induces cell oxidation without reactive oxygen species (ROS) production . This ef on SiO2 . On the ell wall . The conell wall . CVD-graell wall . Prolifereported . Usuallyreported .2 presented a wrinkled surface as a result from the differential thermal expansion on Cu. This situation, coupled with bilayer regions, and micrometric damages resultant from the transfer process, exposed the underlying SiO2 and contribute to the overall roughness of the material. They have observed that the coatings impact surface energy and electrostatic interactions with bacteria, decreasing bacterial adhesion through reduction of the expression levels of genes related to adhesion in Halomonas spp. CAM2, a typical biofilm producing species. In graphene coated SiO2, the substrate has a significant surface state density just below the conduction band, which donates electrons to graphene to balance the chemical potential at the interface. This leads to a n-type graphene coating, repelling negatively charged bacteria in solution, and to an observable decrease in wettability  have more consistently shown to induce the formation of pores in the cell membrane that lead to osmotic imbalance and death. However, the two types of cells attached to the control surfaces remained viable, contrarily to the two other types of fabricated graphene surfaces – rough (GN-R) and smooth (GN-S). The differences in bactericidal activity in the two surfaces can be accounted for by taking into consideration three parameters: exposed edge length (LGN), graphene orientation (θGN), and edge length density (dedge). GN-R exhibits a higher number of viable S. aureus cells due to its decreased edge density. S. aureus are smaller than P. aeruginosa, making it possible for them to colonize the free space between edges  physical insertion of the sharp edges in the membrane and subsequent extraction of phospholipids ; (2) proen edges .S. aureus biofilm formation was observed in samples with the smaller flake size (obtained with the longest sonication times)  . Besidesn times) . By fullin vitro (cell lines and primary cultures) and in vivo (rodent) models, the majority of them focused on the functionalized forms of graphene: GO and rGO , respectively  before neuronal seeding has been used by A controversial aspect, which is necessary to mention, concerns the common practice of pre-coating graphene-based substrates. The practice of pre-coating graphene with poly-Beyond the possible application in neurological diseases/disorders, graphene also represents an attractive material for non-neuronal tissue engineering. The possibility to use graphene as a platform that supports and promotes cell adhesion, proliferation, and maturation, pushed the researchers to investigate its interaction with non-excitable cells. Aiming at an extended knowledge about the interaction of graphene with mammalian cells, it is also useful to study how graphene can interact with cancer cells. In a way similar to its interaction with bacteria, graphene shows toxic effects when put in contact with tumor derived cells. Despite the need for further investigation in this field, in recent years some preliminary studies suggest the possibility to use graphene as anti-neoplastic agent. in vivo studies investigating the toxicology, distribution and clearance of graphene is gradually increasing. Nonetheless, the vast majority concerns the functionalized form of graphene, in particular GO, given its capability to better interact with the biological matter . Authors treated intravenously mice with graphene nanosheets at 20 mg/kg for 3 months and demonstrated that the material localized preferentially at the level of the reticuloendothelial system (RES), liver and spleen. Interestingly, graphene nanosheets were gradually cleared by both renal and fecal excretion. No significant toxicity was detected by blood analysis and histological examinations, leading authors to encourage further studies in this field  rats treated with control ambient air; (ii) rats treated with a low concentration of graphene (0.68 mg/m3); and (iii) rats treated with high concentration of graphene (3.86 mg/m3). No significant alterations were detected in animal and organ weight and in the levels of protein expression . Despite alveolar macrophage ingestion of graphene was observed in both material-treated groups, no severe toxic effect was detected at the concentration and time points used  and, in accordance with in vitro (HEK cells) and in vivo (zebrafish) toxicity of graphene and GO of three different sizes . Authors demonstrated that in vitro both the small and the large size of graphene and GO increased DNA damage, ROS formation and the expression of associated critical genetic markers. Injection of both graphene and GO in zebrafish induced ROS generation and developmental alterations. In general, a significant higher toxicity was reported for smaller size graphene (in particular for GO) that showed a stronger ability to decrease the survival rate and induce the acute toxicity , including other BN structures. m growth . Studiesm growth   bacteria. The results showed significant antibacterial activity  have dominated the vast majority of publications, leaving contrasting results, and unanswered questions . In recein vitro on a mouse hippocampal cell line (mHippo E14). Authors treated cells with hBN and its degradation product (BA), fixing the range of exposure at 4.4–440 μm/mL (for 24 and 72 h). No cytotoxic effects, no changes in cell cycle, ROS production and DNA damage were detected for hBN concentration lower than 22 μm/mL. In addition, both hBN and BA favored the cell survival after exposure to doxorubicin (an anti-neoplastic agent), by reducing oxidative stress (e stress  (Taskin e stress .® CRL 2120TM) and Madin-Darby canine kidney cells. At the highest concentration of 0.4 mg/mL, the hBN NPs caused mild cytotoxic effect on CRL-2120 cells  had higher uptake capacity when compared to human dermal fibroblasts, explaining the different proliferation effect of hBN in these cell lines. Nevertheless, improvement of proliferation and migration in both types of cells was observed. Angiogenesis ability of HUVECs treated with hBN showed promising results. Additionally, it was found that hBN might also improve the wound healing process by lowering ROS due to its antioxidant capacity, similarly to BA; it was found that hBN can rescue cells from apoptosis, and that at low concentrations, it did not depolarize the mitochondria nor disrupt F-actin formation .in vivo in Wistar albino rat subjects. Biochemical, hematologic and histopathology parameters were examined for 24 h after intravenous injection of different doses of hBN NPs. Hematological and biochemical parameters showed no changes except in the 1600 and 3200 μg/kg dose groups. Histological detections on these groups indicated the hBN NP treatment induced significant damage in the liver, kidney, heart, spleen, and pancreas. The results also indicated that hBN NPs with diameter of 121 nm could hold promise in biomedical applications, where low doses between 50 and 800 μg/kg are not toxic (+). Cell viability tests confirmed that hBNs do not exhibit neurotoxic effects. Flow cytometry analysis determined that hBN significantly decreased apoptotic cells in the experimental PD model  formed separated islands. In addition, MSCs seeded onto graphene showed a spindle-shape morphology, allowing a higher proliferation with a possible differentiation toward osteoblast lineage. On the contrary, MSCs plated onto SiO2 presented a more polygonal cell shape, typical of non-differentiated cells. Author also tested the cell adherence and concluded that cells plated onto graphene showed a weaker and smaller contact with the support, corresponding to an active state of the cells  showed rounded and irregular morphology, probably due to the poor adhesion. By adding in the maintaining medium a protein cocktail to favor osteogenic differentiation, the cells plated onto the graphene uncoated supports did not express protein markers of differentiation after 15 days of treatment; on the contrary MSCs plated onto graphene coated substrates remarkably differentiated into osteoblasts at a comparable rate to the differentiation with the bone morphogenic protein-2 (BMP-2) (in vivo effects of a CVD-grown monolayer graphene-coated Ti disks implanted in the back subcutaneous area of nude mice. Authors incubated in vitro human adipose-derived stem cells (hASCs) and human bone marrow mesenchymal stem cells (hBMMSCs) on the top of their support before implanting them into the mice. No evident in vivo toxicity was reported; in addition, they demonstrated that CVD graphene favored cell adhesion, proliferation and differentiation toward an osteogenic faith, in accordance with in vivo osteogenesis and the molecular mechanisms at the base of this process. Authors generated MSC-impregned graphene scaffolds and implanted them into immunocompromised (SCID) mice at 28 days of life. Without the addition of any osteogenic inducers, graphene scaffolds were able to promote osteogenic differentiation of MSC by increasing the expression of bone-related markers (RUNX2 and OPN)  analyses and histological observations were performed. Authors demonstrated that microstructure parameters  and the new bone formation were significantly enhanced in animals implanted with the graphene-coated Ti6-Al4-V (he cells . Nayak e (BMP-2) . In addi (BMP-2) . Liu et and OPN) . Li K. ei6-Al4-V .Due to its biocompatibility and electrical properties, graphene has been regarded as an advanced and viable interface for enhancing neuronal activity or improving the record of electrical cell signal. Li et al. demonstrated that CVD graphene is able to promote neurite sprouting and outgrowth (associated with a significant increase of GAP-43 protein expression), concluding that the graphene-coated substrate could have a prominent impact on the cell early developing stages . In accoThrough a theoretical approach, they speculated that monolayer graphene effects on neurons might be maximized when graphene is deposited in an electrically insulation support , compared to a suspended condition. Authors concluded that the alteration in the spontaneous synaptic transmission could be justify by the different ratio between cells with adaptive/tonic phenotypes. Notably, authors did not exclude a potential contribution of astrocytes in the surface ion concentration alterations, since astrocytes are able to regulate the extracellular medium between neurons and the substrate .per se is not sufficient to promote the electrical activity of neuronal networks, suggesting that other material features  have to be taken into account in the design of future graphene-based implants . The hippocampal neuron cells exhibited healthy morphology and spontaneous electrical activity after 19–21 days in culture. The electrical measurements did not harm the cells. The performance of the GFETs degrades slightly with time , by creating a suitable microenvironment for the stem cells. When interfacing neuronal stem cells, a graphene coating is able per se to boost neurite sprouting and maturation and, when interaction with mesenchymal stem cells, drive their maturation specifically toward osteoblast or cardiomyogenic lineage in both in vitro and in vivo systems. Besides its ability to favor stem cell maturation, when interfacing excitable cells, monolayer graphene films revealed also to enhance synaptic transmission by increasing spontaneous intracellular Ca2+ spikes and neuronal firing by altering extracellular K+ concentration. Traditionally, authors attributed these phenomena to the high electrical conductivity graphene. However, this feature alone is not enough to promote the electrical activity of neuronal networks, and hence other characteristics of the coating  must be considered when designing graphene-based interfaces and implants. As a final and crucial remark, the in vivo biocompatibility of graphene is still debated. Few works reported in the last decade alert about the possible in vivo toxicity of graphene and its derivatives. A peculiar aspect that troubles the scientific community regards the possibility of graphene to permanently deposits in the organs , causing chronic inflammatory processes. Nonetheless, the long-term persistence of graphene in the organisms has not been clearly demonstrated and in most of the cases the toxicity reduces over time; in addition, phenomena of graphene clearance through feces has been reported. On the other hand, the possibility to use 2D graphene as an in vivo therapeutical tool is still an open question. Graphene-coated prosthesis has been successfully employed to favor bone tissue regeneration; in addition, cancer cell aggregations seem permeable to graphene sheets and capable to retain them. This interesting phenomenon leads researcher to investigate the possibility to use graphene in the antineoplastic therapies.With regards to mammalian cells, CVD graphene coatings produced revealed to be highly suitable for cell interfacing. Nonetheless, no universal consensus exists yet on the physio-chemical mechanism underlying the favorable interaction between cells and graphene, despite some authors attributed the excellent biocompatibility to the absence of ROSs formation or to the capability of graphene of directly interacting with specific molecules in the mammalian cell membrane . Overall, the absence of an evident As a partial conclusion about the mechanisms of interaction with the two kinds of cells, we underline that although a graphene coating in certain conditions can induce bacterial cell death, the mammalian cells seem to be generally unharmed by it. Based on these interactions, applications for graphene have surfaced. CVD graphene coatings have shown to be able to hinder bacterial adherence and coating due to electrostatic interactions at the surface. Additionally, its lattice size allows it to be impermeable to Cu and Ni ions, blocking the bacteria at the surface to metabolize the substrate. CVD graphene has also been used for sensing applications in neuroscience and medicine in the form of sensors, wearable devices and scaffolding due to its softness, electrical conductivity, and biocompatibility.Due to the limited availability of literature regarding hBN coatings and their interaction with bacteria and cells, we have reviewed not only cases where this material was deposited on a substrate, but also those investigating its behavior in liquid solutions and in nanocomposites, in order to provide a more comprehensive overview. In the case of 2D hBN coatings, studies conducted experimentally with LPE samples and via simulations showed antibacterial effects related to the exposed flake edges (as shown for graphene), which promoted cellular membrane disruption and temperature-dependent lipid extraction. However, studies conducted in atomically smooth hBN coatings  have revealed no antibacterial activity of the basal plane, further highlighting the role of a sufficiently high electrical conductivity in bacterial death. Electrostatic interactions seemed to contribute toward an inhibition of bacterial adhesion. Despite their markedly different electrical conductivity, both graphene and hBN coatings have shown to be effective against biocorrosion of metal substrates by reducing the number of adhered bacteria, with the reduced cellular adhesion being consequence of the atomic smoothness of the coatings. In both cases, the small lattice size in graphene and hBN allows them to act as impermeable barriers, blocking the migration of aggressive metabolites and avoiding biocorrosion of the underlying metallic substrate.With regards to mammalian cells, hBN has shown to be cytotoxic in liquid solution above certain concentrations and in a shape-dependent manner. Cytotoxicity studies conducted with hBN in liquid solution for different nanoflake sizes show that when the size is small enough it becomes possible for mammalian cells to internalize them and cause an increase in ROS production. Overall, 2D hBN materials have shown promise in bone tissue scaffolding, wound healing, and treatment of neurodegenerative diseases such as Parkinson’s. For further understanding the potential of this kind of materials, the cytotoxicity will need to be ascertained to address some of the inconsistencies present in literature.In conclusion, the current scenario suggests that, notwithstanding the substantial amount of studies in the field, further investigation is still needed before two-dimensional materials such as graphene and hBN can fulfill their potential in advanced biomedical applications. This is particularly true in the case of hBN, where most interactions with living matter still needs to be understood and detailed.JS and MM: data acquisition and writing original draft. JR: data revision and support on writing. PA: data interpretation and evaluation. AC: conceptualization, coordination, writing, and funding acquisition. All authors: final writing.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.