Times Higher Response Research Articles

Anisotropic optoelectronic properties of lead-free Cs3Bi2I9 single-crystal photodetectors

Lead-free halide perovskites have attracted widespread research interest due to their excellent optoelectronic properties and environmental friendliness. As one of the bismuth iodide compounds, Cs3Bi2I9 perovskite has been extensively explored in the field of photovoltaic devices and radiation detectors due to their non-toxic lead-free components and excellent stability. In this work, we successfully grow large-sized Cs3Bi2I9 single crystals (SC) with (l00) and (00l) crystal exposure facets by inverse temperature crystallization method. Under 525 nm light illumination with the intensity 15 mW cm−2 and 7 V bias, the (l00) Cs3Bi2I9 SC shows 2 times higher photocurrent, 3.6 times higher responsivity, and 2.8 times higher detectivity than the (00l) Cs3Bi2I9 SC, respectively. Superior response time in the scale of millisecond is obtained in both (l00) and (00l) Cs3Bi2I9 SCs. Based on the first-principle calculation, the (l00) SC possesses a higher charge distribution density and a wider dispersion distribution than (00l) SC, suggesting that more electrons in the (l00) SC can be excited in a wider range. The tighter arrangement of Cs+ and [BiI6]− octahedra in the (l00) SC than (00l) SC leads to the anisotropic photoelectric performance in (l00) and (00l) Cs3Bi2I9 SCs. Our results provide a strategy for the oriental growth of Cs3Bi2I9 SCs and the design of anisotropic optoelectronic devices with excellent performance.

Achieving Room-Temperature ppb-Level H2S Detection in a Au-SnO2 Sensor with Low Voltage Enhancement Effect.

Although semiconductor metal oxide-based sensors are promising for gas sensing, low-power and room temperature operation (24 ± 1 °C) remains desirable for practical applications particularly considering the request of energy saving or net zero emission. In this study, we demonstrate a Au/SnO2-based ultrasensitive H2S gas sensor with a limit of detection (LOD) of 2 ppb, operating at very low voltages (0.05 to 0.5 V) at room temperature. The Au/SnO2-based sensor showed approximately 7 times higher response (the ratio of change in the current to initial current) of ∼270% and 4 times faster recovery (126 s) compared to the pure SnO2-based sensor when exposed to 500 ppb H2S gas concentration at 0.5 V operating voltage at relative humidity (RH) 17.5 ± 2.5%. The enhancement can be attributed to the catalytic characteristics of AuNPs, increasing the number of adsorbed oxygen species on sensing material surfaces. Additionally, AuNPs aid in forming flower-petal-like Au/SnO2 nanostructures, offering a larger surface area and more active sites for H2S sensing. Moreover, at low voltage (<1 V), the localized dipoles at the Au/SnO2 interface may further enhance the absorption of polar oxygen molecules and hence promote the reaction between H2S and oxygen species. This low-power, ultrasensitive H2S sensor outperforms high-powered alternatives, making it ideal for environmental, food safety, and healthcare applications.

Electrochemical detection of manganese ions using aptamer-based layers

Heavy metals are one of the major pollutants found in drinking water and their abnormal level may pose a threat to human's health and life. Manganese also belongs to heavy metals group, and it is generally used in production of batteries, fertilizers, and ceramics. Even though, Mn is necessary for proper development of central nervous system, its elevated concentration might lead to certain diseases such as epilepsies, cell death in focal cerebral ischemia as well as neurodegenerative diseases such as Huntington and Alzheimer. Hence, it is crucial to elaborate novel methods for manganese ions detection that could be applied for in situ analysis of water samples.Herein, we present the studies on the electrochemical detection of manganese ions using aptamer-modified electrodes. This is the first attempt of application of aptamer strands as receptor layers for electrochemical analysis of manganese ions and for that purpose gold disk electrodes served as transducers, which were further modified with disulfide - based aptamers and 6-mercapto-1-hexanol blocking agent. The electrochemical measurements concerned the choice of the conditions for formation of aptamer receptor layer as well as the type of redox indicator that served as the source of current signal. The studies referred to the definition of aptasensor working parameters including the verification of the possibility of manganese ion detection in cell culture media. It was shown that it was possible to detect Mn2+ ions within 25 nM–1 μM concentration and the proposed aptasensor exhibited high selectivity towards target analyte for which at least 2 – times higher response was recorded than for interfering ions. Moreover, the possibility of Mn2+ detection in real samples was depicted followed by stability and regeneration studies.

In Situ Cancer-Cell-Triggered Visible Changes in Mechanical Properties, Electroconductivity, and Adhesiveness of a MnO2@PD-Based Mineralized Hydrogel.

Herein, a cancer-specific dopamine-conjugated sp2-rich carbonized polymer dot (PD)-encapsulated mesoporous MnO2 (MnO2@PD)-mineralized hydrogel biosensor was developed that offers cancer-induced observable in situ alterations in fluorescence (FL), electrochemical, and mechanophysical properties. Cancer-triggered MnO2 degradation in the hydrogel, prompted by increased levels of glutathione (GSH) and reactive oxygen species (ROS) such as H2O2, leads to PD release and FL restoration, thereby controlling changes in the pore structure and increasing hydrogen bonding, resulting in physiologically visible alterations in mechanical stretchability, viscosity, swelling behavior, and adhesiveness. The pore size of the matrix increased from 21.83 to 36.81 m2/g upon GSH treatment, affecting the viscosity and swellability of the system. The resistance increased from 21.96 ± 1.16 to 30.69 ± 2.01 and 32.21 ± 2.54 kΩ, respectively, confirming the dependence of conductivity changes on H2O2 and GSH treatments. The in vitro treatment with cancer cells (HeLa, PC-3, and B16F10) facilitated a tunable electrochemical sensing performance via redox-mediated MnO2 breakdown by intracellular ROS and GSH, whereas hydrogels treated with normal cells (CHO-K1) showed minimal changes. Cancer-microenvironment-derived water-drop sensing showed three times higher response as compared to the normal cell-treated hydrogel. The sensing capability of the fabricated sensor was validated based on bending-induced relative resistance changes under dry and wet conditions. Moreover, the integration of the developed sensor with a wireless sensor enabled real-time monitoring with a smartphone.

Room temperature operated flexible La-ZnO/MWCNTs sensor for ppb level carbon monoxide detection

The advancement of gas sensors with ppb level concentration experiences profound challenges. In this research, Lanthanum (La)-Zinc Oxide (ZnO)/multi-walled carbon nanotubes (MWCNTs) composites were successfully fabricated and loaded on a flexible polyimide substrate where interdigitated electrodes (thickness: 300 µm and spacing: 300 µm) were prepared using a laser carbonation technique for room temperature (RT) carbon monoxide (CO) gas detection. The synthesized composites were characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, UV–visible spectrophotometry, x-ray diffraction, and Fourier transform infrared spectroscopy. When compared to the La-ZnO composite, the addition of MWCNTs on the synthesized composite-based sensor exhibited ∼8 times higher response than La-ZnO to 100 ppm CO at 27 °C. The response of the La-ZnO/MWCNTs composite sensors to 20 ppm CO was tested at six different relative humidity (RH) levels ranging from 0% to 90% in the increments of 20% RH. These sensors exhibited humidity tolerant properties, as evidenced by their responses to different humidity levels. Even when exposed to 90% RH, the sensor only showed ∼13% reduction in response compared to 0% RH, indicating that it is a humidity tolerant sensor. Furthermore, the La-ZnO/MWCNTs sensor has excellent selectivity and can detect low CO concentrations of 100 ppb. As a result, the proposed high-performance flexible sensor has a lot of potential for use in wearable devices to sense CO gas at RT for trace level detection.

Reversible room temperature ammonia sensor based on the synthesized MoS2/PANI nanocomposites

Successful fabrication and optimization of molybdenum disulfide (MoS2)/polyaniline (PANI) nanocomposite-based room temperature ammonia sensors have been reported in this work. The hydrothermal technique was used to synthesize nanocomposites of MoS2 and PANI at different amounts of PANI. For this, the precursor values were changed by choosing three different values of 0.65 (MP1), 1.1 (MP2), and 2.2 (MP3) for the ammonium heptamolybdate/PANI weight ratio. Successful fabrication of nanocomposites was confirmed by Raman analysis and x-ray diffraction. According to FESEM images, MoS2/PANI nanocomposites have been composed of 1D-PANI nanofibers covered by 2D-MoS2 nanosheets and created a porous morphology that influenced their sensing characteristics significantly. The samples’ ability to detect ammonia at room temperature was examined by fabricating sensor devices using the synthesized MoS2, PANI, and nanocomposites. The fabricated sensor using MP2 showed much better gas-sensing properties than other samples. This sensor showed about 4.6 and 1.6 times higher response than pristine PANI and MoS2 sensors for 10 ppm of ammonia, respectively, with better selectivity toward ammonia than other gas species. This research shows that compositing PANI with MoS2 significantly improves the gas detection performance of MoS2.

Twistable and tailorable Cu-doped SnO2@PANI textile for wearable ammonia sensing

Herein, a twistable and tailorable NH3 sensor utilizing hollow porous Cu-doped SnO2@PANI (PCS) composite was assembled on a flexible non-woven fabric substrate by in-situ polymerization technique and its gas sensing performance was tested at room temperature (∼25 °C). The results indicated that the well-designed PCS sensor to 50 ppm NH3 exhibited six times higher response (25.4) than the pristine PANI sensor (4.5). The PCS flexible sensor still possessed a response (1.53) for 10 ppb NH3, and the detection limit could reach 5.2 ppb for NH3. Meanwhile, the PCS flexible sensor demonstrated excellent flexibility with response decreases of only 1.97 % after 1000 times bending (120°), and 2.11 % after 100 times folding (150°) and long-term stability through 42 days of monitoring (maintaining 98.4 % response). Furthermore, the PCS sensor displayed insensitivity to relative humidity (20 % − 75 % RH), and the low sensing temperature could reach − 15 °C. The enhanced sensing performance of the PCS sensor was attributed to the synergistic effect of the vital role of abundant oxygen vacancy and − OH groups, as well as the hollow porous interconnected structure and the p-n heterojunction between Cu-doped SnO2 and PANI. This work provides more opportunities to design smart wearable devices for detecting ppb-level NH3 at room temperature.

Improvement in gas sensitivity of carbon nanotube to volatile organic compounds by covering zinc oxide nanowire

Carbon nanotubes (CNTs) have been utilized in many gas sensor structures, individually or in hybrid form with other materials to enhance their gas sensing properties. CNT and CNT–ZnO nanowire structures were fabricated by plasma-enhanced chemical vapor deposition (PECVD) and hydrothermal growth methods to explore and compare their gas sensing properties. The morphologies of the fabricated samples were characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy. Gas sensing properties of fabricated samples were assessed at different atmospheric and thermal conditions. Results verified CNT–ZnO has two times higher response than the CNT sample toward volatile organic compounds vapor at room temperature. A longer lifetime and more stability are other advantages of the CNT–ZnO hybrid. Moreover, it is shown that increasing the length of ZnO nanowires exhibits a higher response to examined analytes. It was found that increasing the temperature causes different sensing regimes in CNT and CNT–ZnO samples. At all ranges of temperatures, the resistance of CNT samples increased in the presence of reducing gases while CNT–ZnO samples exhibited similar behavior only below ∼90 °C. At elevated temperatures, their resistances decreased in response to the same gases.

Light-Controlled Recruitable Hybridization Chain Reaction on Exosome Vehicles for Highly Sensitive MicroRNA Imaging in Living Cells.

Sensitive imaging of intracellular microRNA (miRNA) in living cells is of great significance. Isothermal hybridization chain reaction (HCR)-based methods, although have been widely used to monitor intracellular low-abundance miRNA, are still subjected to the challenges of limited signal amplification efficiency and compromised imaging resolution. In this work, we design a light-controlled recruitable HCR (LCR-HCR) strategy that enables us to well overcome these limitations. Exosomes as delivery and recruitment vehicles are modified with three cholesterol-modified hairpins (H1, H2, and H3), in which H1 is for anchoring target miRNA and H2 and H3 with photocleavable linkers (PC-linkers) are designed for spatiotemporal HCR. By controllably releasing probes with high local concentrations to efficiently trigger HCR and further recruiting the generated double-stranded DNA (dsDNA) polymers instead of dispersion in the cytoplasm, the LCR-HCR method can significantly improve the imaging contrast by confining all of the reactants on exosome vehicles. For a proof-of-concept demonstration, the miR-21 was analyzed by LCR-HCR with a limit of detection (LOD) down to 3.3 pM (corresponding to 165 amol per 50 μL) in vitro and four times higher response than traditional HCR in vivo. In general, the LCR-HCR method provides a powerful tool for sensitive miRNA imaging in living cells and cancer diagnosis.

Decoration of laser-ablated ZnO nanoparticles over sputtered deposited SnO2 thin film based formaldehyde sensor

Heterojunction based metal oxide semiconductors have a great potential to detect toxic gases and volatile organic compounds. Here, we report a synthesis technique to obtain ZnO nanoparticles (NPs) via laser ablation method in ambient atmosphere using a nanosecond pulse laser. The laser ablated ZnO NPs were used for the decoration of sputtered deposited SnO2 thin film to realize n-type ZnO/n-type SnO2 heterojunction based formaldehyde (HCHO) gas sensor. Fabricated ZnO/SnO2 sensor shows 3 times higher response (response = 20) to 50 ppm HCHO, faster response-recovery dynamics (τres = 4 s and τrec = 30 s) and better selectivity compared to pristine SnO2 sensor at lower operating temperature (250 °C). The ZnO/SnO2 heterojunction based sensor also can detect < 0.25 ppm HCHO, which allows for lower detectable limit of sub-ppm HCHO. Therefore, the ZnO/SnO2 sensor shows enhanced sensing performance due to oxygen vacancies and n-n heterojunction structures provides more effective electrons for oxygen adsorption which speeds up the electronic transport at the interface of two materials. Synthesis of metal oxide composite NPs using pulse laser ablation method could be a promising alternative rapid route for the fabrication of highly sensitive gas sensors to detect most common indoor air pollutant.

Highly Selective and Low-Power Carbon Monoxide Gas Sensor Based on the Chain Reaction of Oxygen and Carbon Monoxide to WO3.

Carbon monoxide (CO) poisoning can easily occur in industrial and domestic settings, causing headaches, loss of consciousness, or death from overexposure. Commercially available CO gas sensors consume high power (typically 38 mW), whereas low-power gas sensors using nanostructured materials with catalysts lack reliability and uniformity. A low-power (1.8 mW @ 392 °C), sensitive, selective, reliable, and practical CO gas sensor is presented. The sensor adopts floated WO3 film as a sensing material to utilize the unique reaction of lattice oxide of WO3 with CO gas. The sensor locally modulates the electron concentration in the WO3 film, allowing O2 and CO gases to react primarily in different sensing areas. Electrons generated by the CO gas reaction can be consumed for O2 gas adsorption in a remote area, and this promotes the additional reaction of CO gas, boosting sensitivity and selectivity. The proposed sensor exhibits a 39.5 times higher response than the conventional resistor-type gas sensor fabricated on the same wafer. As a proof of concept, sensors with In2O3 film are fabricated, and the proposed sensor platform shows no advantage in detecting CO gas. Fabrication of the proposed sensor is reproducible and inexpensive due to conventional silicon-based processes, making it attractive for practical applications.

High Responsivity Si-Ge Waveguide Avalanche Photodiodes Enhanced by Loop Reflector

We present a loop reflector-assisted silicon-germanium waveguide avalanche photodiode with improved responsivity. Compared to the same APD without the reflector, it has 1.49 times higher responsivity, ~ 1.12 A/W, without compromising the speed performance. It exhibits a 3 dB-bandwidth of ~ 25 GHz, a build-up time limited gain-bandwidth product of ~ 296 GHz, a highest gain-bandwidth product of ~ 497 GHz. Clear eye diagrams are measured at both 32 Gbps NRZ and 64 Gbps PAM4 modulation, and a 1 ~ 2 dB better sensitivity up to -15.7 dBm with 32 Gbps NRZ at a BER of 2.4 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> .

MXene modulated SnO2 gas sensor for ultra-responsive room-temperature detection of NO2

Continuous exposure to high concentration of nitrogen dioxide (NO2) severely affects the human respiratory system. Besides, NO2 has been recently observed to foster COVID-19, resulting in increased fatality rate; thus highly selective gas sensors are required for detecting NO2 at sub-ppb level. In this direction, we have synthesized two-dimensional MXene-based tin oxide (SnO2) heterostructures with varying MXene wt% (10–40 wt%) using a facile hydrothermal method for room-temperature NO2 detection. The synthesized heterostructures have been structurally, optically, and electrically characterized using a suite of characterization techniques, namely, X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller techniques. The optimal incorporation of MXene in SnO2 nanoparticles effectively decumulates them, increasing the specific surface area of heterostructures and thereby exposing large number of adsorption sites. 20-wt% SnO2/MXene heterostructures-based sensor exhibits nearly five times higher response (231%) toward 30-ppb NO2 at room temperature with shorter response time (146 s) and recovery time (102 s) than pristine SnO2. Moreover, the sensor showed high selectivity, sensitivity, repeatability, reproducibility, and stable sensing response under humid conditions. The assembly of these results suggests that SnO2/MXene platform provides a pathway for realizing highly responsive NO2 sensors. Herein, possible gas sensing mechanism based on the formation of SnO2/MXene heterostructures has been discussed.

Layered SnS2/porous nickel foil based Schottky junction: An excellent ammonia sensor at room temperature

In recent years, layered materials has gained immense attention in the field of gas sensing owing to their extraordinary electrical, optical and catalytic properties. Their gas sensing performance can further be improved by switching from ohmic to schottky based sensor due to exponential change of conductance in analyte environment. In most of the Schottky based gas sensor, the surface of the sensing material is covered by metal electrode which reduces the sensing performance. Herein, we have fabricated 2D SnS2 (thickness: 5.62 ± 1.26 nm) based Schottky junction for ammonia detection operated at room temperature using porous nickel foil which allows the analyte molecule to maximize the interaction with the sensing material. We have compared the performance of the Schottky junction sensor with that of SnS2 based ohmic sensor. The Schottky junction based sensor has 140.7 times higher response than SnS2 based ohmic sensor at 360 ppm. The response of the sensor exhibits exponential behavior with ammonia concentration which is explained by estimated barrier height modulation from 0.83 eV (in air) to 0.69 eV (at 225 ppm). In addition, the long term stability over six months of the sensor makes it a promising candidate for practical ammonia sensor operated at room temperature.

Porous Mn-doped Co3O4 nanosheets: Gas sensing performance and interfacial mechanism investigation with In situ DRIFTS

Unraveling the gas-solid interfacial sensing mechanism during gas sensing is very essential for the development of high-performance gas sensors. In this work, the Mn-doped Co3O4 porous nanosheets with 5.6 times higher response than pristine Co3O4 and short response/recovery time (55/30 s) for 100 ppm toluene gas is synthesized. More importantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is conducted to investigate the gas-solid interfacial sensing mechanism over 3-Mn-Co3O4. The interfacial reaction species have been monitored, such as methylbenzene, benzyl alcohol, benzaldehyde, benzoic acid, carbon monoxide, and water molecule. These species originate from the elementary and overall reactions during toluene gas sensing. The dynamic evolution of surface species could be divided into three stages of adsorption reaction, reaction balance, and desorption reaction. Furthermore, combined with the density function theory simulation calculation, the gas-solid interfacial sensing mechanism over 3-Mn-Co3O4 is proposed. Toluene molecule reacts with the surface active oxygen species resulting in the occurrence of a series of elementary reactions and the generation of intermediates. The products of overall reaction are CO2 and H2O during gas sensing. Our work implements a meaningful exploration of in situ DRIFTS in gas-sensing field and provides a distinctive view to understand the gas-soild interfacial gas-sensing mechanism.

Use of botulinum toxin type a in psychiatry - new perspectives and future potential

IntroductionFor almost three decades, botulinum toxin type A (BT-A) has been used for medical purposes. Evidence of the potential use of BT-A is emerging for psychiatric disorders, like unipolar and bipolar depression, borderline personality disorder (BPD), late dyskinesia, amongst others. This may represent a new role of BT-A treatment and could expand the therapeutic arsenal in psychiatry.ObjectivesThe goal is to review current evidence regarding BT-A and psychiatry disorders.MethodsLiterature review of BT-A use in psychiatric conditions using Medline database.ResultsThere’s evidence supporting the use of BT-A in resistant unipolar depression, with studies showing an 8 and 4 times higher response and remission rates comparing with placebo. Beneficial effects were also found in bipolar depression. Preliminary data suggest that BT-A therapy may also be effective in the treatment of mental disorders characterized by an excess of negative emotions, such as BPD. The underlying mechanism might be the “facial feedback hypothesis”. Hyperhidrosis is a common comorbidity in social anxiety disorder and may itself give rise to depressive or anxiety symptoms. BT-A has proved to be a safe and effective treatment for hyperhidrosis. BT-A can also be safely used for dystonia secondary to the use of psychiatric medication, when there’s an inadequate response to anticholinergic medication. Also, BT-A injections in the salivary glands have been investigated for treating clozapine-induced sialorrhea and studies reported successful reduction in hypersalivation.ConclusionsAlthough more studies are needed to evaluate the potential of BT-A in psychiatry, there is growing evidence of its potential use for some psychiatric conditions.

Heterostructures of mesoporous hollow Zn2SnO4/SnO2 microboxes for high-performance acetone sensors

Metal oxide Semiconductors with porous hollow heterostructures can provide significant advantages for gas sensing by facilitating the increase of free electron density and the diffusion of target gases. Herein, mesoporous hollow Zn2SnO4/SnO2 microboxes were successfully synthesized by using a facile ZnSn(OH)6-sacrificial template method. In synergy with the special mesoporous hollow structure and the n-n heterojunction formed between Zn2SnO4 and SnO2, the Zn2SnO4/SnO2 composites exhibited excellent acetone-sensing properties. Compared with the pure SnO2 sensor, the Zn2SnO4/SnO2 sensor not only displayed a 2 times higher response (20.1) toward 100 ppm acetone as well as excellent selectivity and stability at the optimal operating temperature of 250 °C, but still maintained a perceived response (2.4) even when the concentration of acetone was down to 1 ppm. In addition, the enhanced sensing mechanism of Zn2SnO4/SnO2 microboxes was also discussed in detail. This work indicates that the mesoporous hollow Zn2SnO4/SnO2 microboxes can be very promising sensing material for the application of acetone gas sensors.

SnO2 nanoparticles incorporated CuO nanopetals on graphene for high-performance room-temperature NO2 sensor

Metal oxide semiconductors (MOS)-based sensor are promising for monitoring hazardous NO2. However, the high operating temperature (e.g., 100–400 °C) significantly restricts practical applications. Herein a high-performance room-temperature NO2 sensor based on binary MOS and reduced graphene oxide (rGO) is demonstrated. Response of SnO2-CuO/rGO towards 50 ppm NO2 is 8–15 times higher than those of CuO/rGO and SnO2/rGO counterparts. Meanwhile, good selectivity (6 times higher response over other inorganic gases), long-term stability (decay < 5% for 7 days) and low limit of detection (150 ppb) are achieved, which can be interpreted by the p-n heterostructure and synergistic effect.

Abstract QS20: Correlation Between Different Tissue Expansion Protocols And Changes In Gene Expression

Purpose: Tissue expansion (TE) relies on skin growth in response to mechanical forces. Although TE is widely used in reconstructive surgery, there has been minimal investigation into the transcriptional activity in the skin under stretch. The present study evaluates the molecular response of skin to TE to identify pathways that could potentially be manipulated to improve the efficacy of TE and investigate the effect of eight TE protocols on expression of mechanosensitive genes. Methods: Using a porcine TE model, the transcriptome was mapped (RNA-seq analysis) in the skin samples that were stretched by inflation of expanders with 30ml or 60ml saline for 1 hour to 14 days. Contralateral unexpanded sites served as controls. Differentially expressed genes were detected with NOIseq (FC>2 and probability>0.8). qRT-PCR analysis was performed to verify results obtained by RNA-seq. Statistical analysis was performed using GraphPad Prism 7 software. The significance of obtained results was calculated using the unpaired student’s t-test. P-values≤0.05 were considered significant. Results: Differential analysis revealed significant changes in the expression of 220 genes (P<0.005), representing a diverse response pattern. qPCR analysis on biopsies collected from apical (a), middle (m) and periphery (p) of expanders showed that expression of mechanosensitive genes depends on magnitude of mechanical forces. The highest increase of MMP1 expression (FC=41-787, P>0.001) was detected in the apical biopsies, exposed on the highest pressure. In biopsies “m” the increase in MMP1 expression was 4-8 times smaller than in biopsies “a”, but still significantly higher than in control (FC=52-175, P>0.001). In biopsies “p” the MMP1 expression was not significantly changed. The evaluation of SFRP2 expression at 3 days after fill with 30ml saline revealed 5 times higher response (P=0.001) when additional injection with the same volume was performed 7 days earlier, suggesting that multiple injections stimulate the molecular response of skin in TE more effectively. The opposite effect was observed for double injection with 60ml saline, indicating that when pressure is too high this can negatively affect the molecular response and limit skin growth and regeneration. Conclusions: RNA-seq analysis revealed numerous genes responding to tissue expansions that are involved in a variety of biological processes including homeostasis, proliferation, differentiation, and inflammation. To achieve the most effective stimulation of skin growth, real-time evaluation of pressure within the expanders will be incorporated in subsequent studies. Understanding the correlation between time of expansion, magnitude of pressure and molecular response of skin in TE may help to optimize clinical outcomes, leading to the most efficient recruitment of new skin and make expansion feasible even in compromised tissue beds.

Room temperature gas sensor based on tin dioxide@ polyaniline nanocomposite assembled on flexible substrate: ppb-level detection of NH3

The SnO2@ Polyaniline (PANI) nanocomposites were successfully synthesized via a combined approach of hydrothermal and in-situ polymerization. The morphology and structure of the materials were characterized using SEM and TEM. The specific surface area was analyzed by the Brunauer-Emmett-Teller (BET) equation. The results showed that the materials had micro-structure and large specific surface area. The prepared materials were loaded on flexible polyethylene terephthalate (PET) substrate and their gas sensing properties were investigated at room temperature. Comparing with PANI sensor, the 20 mol% SnO2@ Polyaniline (PASn20) sensor exhibited 6.2 times higher response (Rgas/Rair = 29.8) to 100 ppm NH3 at room temperature. Furthermore, the PASn20 sensor possessed the ability to detect low NH3 concentrations of 10–200 ppb and outstanding selectivity. The enhanced sensing performance was attributed to the micro-structure with large specific surface area and the formation of p-n heterojunctions at the surface between PANI and SnO2.