Nanofiber Hydrogel Research Articles

Inducing Immunomodulatory Effects on Human Macrophages by Multifunctional NCO-sP(EO-stat-PO)/Gelatin Hydrogel Nanofibers.

Endowing materials and scaffolds with immunomodulatory properties has evolved into a very active field of research. However, combining such effects with multifunctionality regarding cell adhesion and manipulation is still challenging due to the intricate nature of cell-substrate interactions that require fine-tuning of scaffold properties. Here, we reported electrospinning of a well-known biopolymer, gelatin, together with six-arm star-shaped poly(ethylene oxide-stat-propylene oxide) prepolymer with isocyanate end groups (NCO-sP(EO-stat-PO)) as a reactive prepolymer cross-linker. Covalent coupling of two components during and after processing yielded a network of hydrogel fibers that was remarkably stable under aqueous and also proteolytic conditions without the need for extra cross-linking, with a significant increase in stability with increasing NCO-sP(EO-stat-PO) content. When seeded with human macrophages, cells adhered and spread on the fibers and were found highly viable after 7 days of culture across all scaffolds. Furthermore, hybrid fibrous meshes upregulated the expression of a prohealing gene, CD206, while downregulating proinflammatory genes, IL-1β and IL-8. Markedly, NCO-sP(EO-stat-PO)-rich samples induced a significantly reduced release of proinflammatory cytokines, IL-1β, IL-6, and IL-8. Finally, we successfully conjugated IL-4 to NCO-sP(EO-stat-PO) that effectively steered macrophages into a prohealing M2 type, demonstrating additional and robust control over the immunomodulatory feature of the scaffolds.

Clinical Use of the Self-Assembling Peptide RADA16: A Review of Current and Future Trends in Biomedicine.

RADA16 is a synthetic peptide that exists as a viscous solution in an acidic formulation. In an acidic aqueous environment, the peptides spontaneously self-assemble into β-sheet nanofibers. Upon exposure and buffering of RADA16 solution to the physiological pH of biological fluids such as blood, interstitial fluid and lymph, the nanofibers begin physically crosslinking within seconds into a stable interwoven transparent hydrogel 3-D matrix. The RADA16 nanofiber hydrogel structure closely resembles the 3-dimensional architecture of native extracellular matrices. These properties make RADA16 formulations ideal topical hemostatic agents for controlling bleeding during surgery and to prevent post-operative rebleeding. A commercial RADA16 formulation is currently used for hemostasis in cardiovascular, gastrointestinal, and otorhinolaryngological surgical procedures, and studies are underway to investigate its use in wound healing and adhesion reduction. Straightforward application of viscous RADA16 into areas that are not easily accessible circumvents technical challenges in difficult-to-reach bleeding sites. The transparent hydrogel allows clear visualization of the surgical field and facilitates suture line assessment and revision. The shear-thinning and thixotropic properties of RADA16 allow its easy application through a narrow nozzle such as an endoscopic catheter. RADA16 hydrogels can fill tissue voids and do not swell so can be safely used in close proximity to pressure-sensitive tissues and in enclosed non-expandable regions. By definition, the synthetic peptide avoids potential microbiological contamination and immune responses that may occur with animal-, plant-, or mineral-derived topical hemostats. In vitro experiments, animal studies, and recent clinical experiences suggest that RADA16 nanofibrous hydrogels can act as surrogate extracellular matrices that support cellular behavior and interactions essential for wound healing and for tissue regenerative applications. In the future, the unique nature of RADA16 may also allow us to use it as a depot for precisely regulated drug and biopharmaceutical delivery.

Soft-fiber-reinforced tough and fatigue resistant hydrogels

Soft-fiber-reinforced tough and fatigue resistant hydrogels

Cu–Ag Alloy Nanoparticles in Hydrogel Nanofibers for the Catalytic Reduction of Organic Compounds

Nanoalloys or alloy nanoparticles containing multiple metals are of great interest because the combination of multiple metals in close proximity can grant enhanced properties including stability, activity, and selectivity arising from synergism that cannot be accessed by the combination of individual metals. In this study, we have produced nanoalloys in stable flexible electrospun hydrogel nanofibers composed of poly(acrylic acid) and poly(allylamine hydrochloride). The hydrogel fibers were loaded with metal ions such as copper and silver through an immersion in metal salt solutions followed by a chemical reduction to form the metal nanoparticles. The hydrogel matrix allowed for the absorption of metal ions into the fibers and provided a viscous environment to promote the formation of alloy particles in the small diameter range (<25 nm). The proposed fabrication process is advantageous in terms of simplicity, controllability, and versatility. The reductions of 4-nitrophenol and methylene blue were performed to test and compare the catalytic activity of monometallic nanoparticles and copper–silver bimetallic nanoparticles. The copper–silver bimetallic nanoparticles demonstrated preferred selectivity for the reduction of 4-nitrophenol and higher catalytic activity for the reduction of methylene blue. Overall, we have developed promising stable flexible nanocomposites for catalytic reduction of organic redox compounds, and other catalytic nanoalloy systems could be further studied by modification of the procedure.

Bioinspired sequentially crosslinked nanofibrous hydrogels with robust adhesive and stretchable capability for joint wound dressing

Despite recent progress in hydrogel wound dressings, joint wound treatment remains an ongoing challenge due to their poor adhesive and stretchable properties. Herein, inspired by protein secretion-curing process of natural marine mussels, an adhesive nanofibrous hydrogel is developed via a sequential crosslinking strategy. Firstly, to avoid uncontrolled self-polymerization of dopamine (DA), DA grafted gelatin (GT) nanofibers are fabricated via electrospinning under pH value around 4. Further, the fibrous hydrogels are in-situ crosslinked under pH value of about 8 to strengthen the intermolecular interaction within fibers. The DA crosslinked GT fibrous hydrogels via Michael addition and Schiff base reaction exhibit superior adhesive and tensile properties which are 1.5 times and 3.1 times higher than those of GT fibrous hydrogels, respectively. The in vitro cytocompatibility tests and in vivo wound healing study further prove that GT grafted DA nanofibrous hydrogels are able to accelerate wound healing. Taken together, we demonstrate a simple and versatile strategy for generating adhesive and stretchable nanofibrous hydrogel, showing a great potential for joint wound care.

Review of electrospun hydrogel nanofiber system: Synthesis, Properties and Applications

AbstractHydrogel‐based nanofibers or vice versa are a relatively new class of nanomaterials, in which hydrogels are structured in nanofibrous form. Structure and size of the material directly governs its functionality, therefore, in hydrogel science, the nanofibrous form of hydrogels enables its usage in targeted applications. Hydrogel nanofiber system combines the desirable properties of both hydrogel and nanofiber like flexibility, soft consistency, elasticity, and biocompatibility due to high water content, large surface area to volume ratio, low density, small pore size and interconnected pores, high stiffness, tensile strength, and surface functionality. Swelling behavior is a critical property of hydrogels that is significantly increased in hydrogel nanofibers due to their small size. Electrospinning is the most popular method to fabricate “hydrogel nanofibers,” while other processes like self‐assembly, solution blowing and template synthesis also exist. Merging the characteristics of both hydrogels and nanofibers in one system allows applications in drug delivery, tissue engineering, actuation, wound dressing, photoluminescence, light‐addressable potentiometric sensor (LAPS), waterproof breathable membranes, and enzymatic immobilization. Treatment of wastewater, detection, and adsorption of metal ions are also emerging applications. In this review paper, we intend to summarize in detail about electrospun “hydrogel nanofiber” in relation to its synthesis, properties, and applications.

A Chemically Self‐Charging Flexible Solid‐State Zinc‐Ion Battery Based on VO2 Cathode and Polyacrylamide–Chitin Nanofiber Hydrogel Electrolyte

AbstractConventional self‐charging systems are generally complicated and highly reliant on the availability of energy sources. Herein, a chemically self‐charging, flexible solid‐state zinc ion battery (ssZIB) based on a vanadium dioxide (VO2) cathode and a polyacrylamide‐chitin nanofiber (PAM‐ChNF) hydrogel electrolyte is developed. With a power density of 139.0 W kg‐1, the ssZIBs can deliver a high energy density of 231.9 Wh kg‐1. The superior electrochemical performance of the ssZIBs is attributed to the robust tunnel structure of the VO2 cathode and the entangled network of PAM‐ChNF electrolyte, which provide efficient pathways for ion diffusion. Impressively, the designed ssZIBs can be chemically self‐charged by the redox reaction between the cathode and oxygen in ambient conditions. After oxidation for 6 h in air, the ssZIBs manifest a high discharging capacity of 263.9 mAh g‐1 at 0.2 A g‐1, showing excellent self‐rechargeability. With the assistance of a small amount of acetic acid added to the hydrogel electrolyte, the galvanostatic discharging and chemical self‐charging cycles can reach 20. More importantly, such ssZIBs are able to operate well at chemical or/and galvanostatic charging hybrid modes, demonstrating superior reusability. This work brings a new prospect for designing flexible chemically self‐charging ssZIBs for portable self‐powered systems.

Self-assembling peptide hydrogels facilitate vascularization in two-component scaffolds

One of the major constraints against using polymeric scaffolds as tissue-regenerative matrices is a lack of adequate implant vascularization. Self-assembling peptide hydrogels can sequester small molecules and biological macromolecules, and they can support infiltrating cells in vivo. Here we demonstrate the ability of self-assembling peptide hydrogels to facilitate angiogenic sprouting into polymeric scaffolds after subcutaneous implantation. We constructed two-component scaffolds that incorporated microporous polymeric scaffolds and viscoelastic nanoporous peptide hydrogels. Nanofibrous hydrogels modified the biocompatibility and vascular integration of polymeric scaffolds with microscopic pores (pore diameters: 100–250 µm). In spite of similar amphiphilic sequences, charges, secondary structures, and supramolecular nanostructures, two soft hydrogels studied herein had different abilities to aid implant vascularization, but had similar levels of cellular infiltration. The functional difference of the peptide hydrogels was predicted by the difference in the bioactive moieties inserted into the primary sequences of the peptide monomers. Our study highlights the utility of soft supramolecular hydrogels to facilitate host-implant integration and control implant vascularization in biodegradable polyester scaffolds in vivo. Our study provides useful tools in designing multi-component regenerative scaffolds that recapitulate vascularized architectures of native tissues.

Engineering hiPSC-CM and hiPSC-EC laden 3D nanofibrous splenic hydrogel for improving cardiac function through revascularization and remuscularization in infarcted heart

Cell therapy has been a promising strategy for cardiac repair after myocardial infarction (MI), but a poor ischemic environment and low cell delivery efficiency remain significant challenges. The spleen serves as a hematopoietic stem cell niche and secretes cardioprotective factors after MI, but it is unclear whether it could be used for human pluripotent stem cell (hiPSC) cultivation and provide a proper microenvironment for cell grafts against the ischemic environment. Herein, we developed a splenic extracellular matrix derived thermoresponsive hydrogel (SpGel). Proteomics analysis indicated that SpGel is enriched with proteins known to modulate the Wnt signaling pathway, cell-substrate adhesion, cardiac muscle contraction and oxidation-reduction processes. In vitro studies demonstrated that hiPSCs could be efficiently induced into endothelial cells (iECs) and cardiomyocytes (iCMs) with enhanced function on SpGel. The cytoprotective effect of SpGel on iECs/iCMs against oxidative stress damage was also proven. Furthermore, in vivo studies revealed that iEC/iCM-laden SpGel improved cardiac function and inhibited cardiac fibrosis of infarcted hearts by improving cell survival, revascularization and remuscularization. In conclusion, we successfully established a novel platform for the efficient generation and delivery of autologous cell grafts, which could be a promising clinical therapeutic strategy for cardiac repair and regeneration after MI.

Multi-scale structuring of cell-instructive cellulose nanocrystal composite hydrogel sheets via sequential electrospinning and thermal wrinkling

Structured hydrogel sheets offer the potential to mimic the mechanics and morphology of native cell environments in vitro; however, controlling the morphology of such sheets across multiple length scales to give cells consistent multi-dimensional cues remains challenging. Here, we demonstrate a simple two-step process based on sequential electrospinning and thermal wrinkling to create nanocomposite poly(oligoethylene glycol methacrylate)/cellulose nanocrystal hydrogel sheets with a highly tunable multi-scale wrinkled (micro) and fibrous (nano) morphology. By varying the time of electrospinning, rotation speed of the collector, and geometry of the thermal wrinkling process, the hydrogel nanofiber density, fiber alignment, and wrinkle geometry (biaxial or uniaxial) can be independently controlled. Adhered C2C12 mouse myoblast muscle cells display a random orientation on biaxially wrinkled sheets but an extended morphology (directed preferentially along the wrinkles) on uniaxially wrinkled sheets. While the nanofiber orientation had a smaller effect on cell alignment, parallel nanofibers promoted improved cell alignment along the wrinkle direction while perpendicular nanofibers disrupted alignment. The highly tunable structures demonstrated are some of the most complex morphologies engineered into hydrogels to-date without requiring intensive micro/nanofabrication approaches and offer the potential to precisely regulate cell-substrate interactions in a “2.5D” environment (i.e. a surface with both micro- and nano-structured topographies) for in vitro cell screening or in vivo tissue regeneration. Statement of significanceWhile structured hydrogels can mimic the morphology of natural tissues, controlling this morphology over multiple length scales remains challenging. Furthermore, the incorporation of secondary morphologies within individual hydrogels via simple manufacturing techniques would represent a significant advancement in the field of structured biomaterials and an opportunity to study complex cell-biomaterial interactions. Herein, we leverage a two-step process based on electrospinning and thermal wrinkling to prepare structured hydrogels with microscale wrinkles and nanoscale fibers. Fiber orientation/density and wrinkle geometry can be independently controlled during the electrospinning and thermal wrinkling processes respectively, demonstrating the flexibility of this technique for creating well-defined multiscale hydrogel structures. Finally, we show that while wrinkle geometry is the major determinant of cell alignment, nanofiber orientation also plays a role in this process.

Scaffolds from Self-Assembling Tetrapeptides Support 3D Spreading, Osteogenic Differentiation, and Angiogenesis of Mesenchymal Stem Cells.

The apparent rise of bone disorders demands advanced treatment protocols involving tissue engineering. Here, we describe self-assembling tetrapeptide scaffolds for the growth and osteogenic differentiation of human mesenchymal stem cells (hMSCs). The rationally designed peptides are synthetic amphiphilic self-assembling peptides composed of four amino acids that are nontoxic. These tetrapeptides can quickly solidify to nanofibrous hydrogels that resemble the extracellular matrix and provide a three-dimensional (3D) environment for cells with suitable mechanical properties. Furthermore, we can easily tune the stiffness of these peptide hydrogels by just increasing the peptide concentration, thus providing a wide range of peptide hydrogels with different stiffnesses for 3D cell culture applications. Since successful bone regeneration requires both osteogenesis and vascularization, our scaffold was found to be able to promote angiogenesis of human umbilical vein endothelial cells (HUVECs) in vitro. The results presented suggest that ultrashort peptide hydrogels are promising candidates for applications in bone tissue engineering.

Antifreezing ionotronic skin based on flexible, transparent, and tunable ionic conductive nanocellulose hydrogels

Ionic hydrogels with excellent flexibility and good conductivity have great potential in diverse electric devices. However, it remains challenging to improve the biocompatibility of ionic hydrogels. Here, natural and environment-friendly cellulose nanofiber hydrogels were prepared without adding any organic active materials. The cellulose hydrogel networks with free metal ions (Li+/Ca2+/K+) were obtained by soaking in ion aqueous solution of different concentrations in order to endow tunable conductivity, thus a new kind of transparent ionic hydrogels with both excellent sensing performance obtained by a simple, low-cost and harmless process. The free metal ions locked in the negatively charged nanocellulose network through electrostatic interaction provided adjustable conductivity and sensing performance. Hydrogels doped with 4 mol L−1 lithium ions exhibited the best sensing performance with the conductivity of 4.36 × 10–4 S cm−1, and the current response value was as high as 127%. It was worth noting that the strain-sensitive performance of calcium ions was generally excellent even at low temperatures (−30 °C). The antifreezing of the hydrogel improved its service under extreme environment. This kind of hydrogel has great application prospects in artificial intelligence products, such as human healthy monitoring equipment and soft robotics at subzero temperature.

Strong fatigue-resistant nanofibrous hydrogels inspired by lobster underbelly

•Hierarchical assembly of welded and high-crystalline bouligand structure in hydrogels •Mechanics-guided design of high fatigue resistance for nanofibrous hydrogels •Fatigue characterization of nanofibers in synthetic hydrogels •High-velocity microparticle impacts on synthetic nanofibrous hydrogels Nanofibrous hydrogels are pervasive in animal and plant bodies and have been widely seen in engineering applications. Electrospinning is one of the most widely used methods for the fabrication of nanofibrous hydrogels. Whereas the biological nanofibrous hydrogels can maintain high strength and high toughness under multiple cycles of mechanical loads, such fatigue-resistant properties have not been achieved in electrospun nanofibrous hydrogels. Here, we report a bioinspired design of strong and fatigue-resistant nanofibrous hydrogels that can closely mimic the bouligand structure of the natural hydrogel in the lobster underbelly. The resultant nanofibrous hydrogel can reach high nominal strength up to 8.4 MPa and high fatigue threshold up to 770 J/m2. We further demonstrate the superior impact resistance of the bioinspired bouligand-type nanofibrous hydrogel with specific penetration energy of 40 kJ/kg. We show that it is critical to weld the interfaces between nanofibers and introduce intrinsically high-energy phases (nanocrystalline domains) into nanofibers. Nanofibrous hydrogels are pervasive in animal and plant bodies and have been widely seen in engineering applications. Electrospinning is one of the most widely used methods for the fabrication of nanofibrous hydrogels. Whereas the biological nanofibrous hydrogels can maintain high strength and high toughness under multiple cycles of mechanical loads, such fatigue-resistant properties have not been achieved in electrospun nanofibrous hydrogels. Here, we report a bioinspired design of strong and fatigue-resistant nanofibrous hydrogels that can closely mimic the bouligand structure of the natural hydrogel in the lobster underbelly. The resultant nanofibrous hydrogel can reach high nominal strength up to 8.4 MPa and high fatigue threshold up to 770 J/m2. We further demonstrate the superior impact resistance of the bioinspired bouligand-type nanofibrous hydrogel with specific penetration energy of 40 kJ/kg. We show that it is critical to weld the interfaces between nanofibers and introduce intrinsically high-energy phases (nanocrystalline domains) into nanofibers.

Nanofibrous hydrogel-reduced graphene oxide membranes for effective solar-driven interfacial evaporation and desalination

• The photothermal membrane has excellent light absorbing ability. • The evaporator has a high evaporation rate and energy conversion efficiency. • The evaporator exhibits stable solar-driven desalination performance. • Water in the hybrid hydrogel membrane has a low vaporization enthalpy. • Intermediate water dominates the interfacial evaporation. Interfacial evaporation from light-absorbing, porous materials have offered an exciting opportunity to utilize sustainable renewable solar energy for desalination. However, the efforts to understand the fundamental mechanisms governing the interfacial evaporation have greatly lagged behind performance studies. Herein, a hybrid nanofibrous hydrogel-reduced graphene oxide (NHrG) membrane is demonstrated in this work. We experimentally characterized the state of water in the NHrG membrane and proved the presence of intermediate water in the porous membrane. By monitoring the vaporization enthalpy as a function of membrane saturation, we demonstrated that the vaporization of intermediate water dominates the interfacial evaporation process, thus playing a key role in lowering the vaporization enthalpy. The lowered enthalpy value together with other factors, such as the high light absorption efficiency enabled by reduced graphene oxide (rGO) and the porous hydrophilic network induced by electrospun hydrogel nanofibers, led to a highly efficient solar-driven interfacial evaporator. The NHrG membrane had an evaporation rate of up to 1.85 kg m −2 h −1 with a high energy conversion efficiency of 95.4% under one sun irradiation. In addition, the evaporator exhibited excellent desalination performance in treating fresh seawater and achieved high removal of salt as well as heavy metal ions. Our study provides important knowledge for performance optimization and process design.

Nanofibrous hydrogels embedded with phase-change materials: Temperature-responsive dressings for accelerating skin wound healing

Wound environment-responsive materials show great potential in skin repair. Herein, a temperature-responsive fibrous hydrogel was developed with the aid of the phase-change material of natural fatty acids. The extracellular matrix-like methacrylate gelatin (GelMA) nanofibrous hydrogels were fabricated via electrospinning and UV-crosslinking, followed by a depot of fatty acids/aspirin (ASP) encapsulated polydopamine (PDA). The as-prepared fibrous hydrogels showed a significantly faster ASP release at 40 °C compared with those of 25 °C and 37 °C, and an “on-off” drug release was achieved at heating and cooling cycles between 40 °C and 25 °C. The in vitro cell culture tests and in vivo wound healing study proved that GelMA-PDA-ASP nanofibrous hydrogels facilitated the cell growth and accelerated wound repair. Taken together, the thermosensitive drug-releasing nanofibrous hydrogel, showed a great potential for wound care.

An optimized preparation of nanofiber hydrogels derived from natural carbohydrate polymers and their drug release capacity under different pH surroundings

Cellulose and chitin, as the two important natural carbohydrate polymers, have possibility to disassemble to biomass derived polysaccharide nanofibers. The 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized nanocellulose and nanochitin based hydrogel was fabricated via acid gas phase coagulation. It was observed that hydrogels began to form when the pH was lower than 3. When 0.1 mL of acetic acid coagulation bath was provided, 10 h were enough to form sufficient physical crosslinking. Moreover, the release time of amygdalin loaded in the hydrogel could be more than 60 h with a release amount of 80 % due to the uniform network and water-bearing structure. Meanwhile, the release capacity of hydrogels showed diversity at different pH surroundings, which was attributed to the existence of carboxyl groups on the oxidized nanofiber. The results suggested the possible application of the produced nanofiber hydrogels in some specific areas, such as drug delivery, wound dressing, and food packaging.

Rheological properties of cellulose nanofiber hydrogel for high-fidelity 3D printing

Optimization of the rheological properties of the matrix is ​​critical for high-fidelity matrix-assisted 3D printing (MAP), which enables the free-form fabrication of fluidic soft materials. This report describes the generic criteria observable in the printing process of cellulose nanofiber (CNF) hydrogels: the sharpness of an angled line, the cross-sectional ratio of a feature, the surface roughness of features, and the completeness of multi-line writing. The concentration and physical properties of the CNF affects the printing fidelity by changing the values of the four criteria, which are closely related to the rheological properties of the matrix. The printing fidelity can be enhanced by the optimal combination of the inks and the CNF matrix. Hydrophilic and hydrophobic inks are printed in the CNF matrix demonstrating as a universal matrix for free-form fabrication with liquid inks.

Peptide-based scaffolds for the culture and maintenance of primary human hepatocytes

We report here the use of a nanofibrous hydrogel as a 3D scaffold for the culture and maintenance of functional primary human hepatocytes. The system is based on the cooperative assembly of a fiber-forming peptide component, fluorenylmethyloxycarbonyl-diphenylalanine (Fmoc-FF), and the integrin-binding functional peptide ligand, Fmoc-arginine-glycine-aspartic acid (Fmoc-RGD) into a nanofibrous gel at physiological pH. This Fmoc-FF/RGD hydrogel was formulated to provide a biomimetic microenvironment with some critical features such as mechanical properties and nanofiber morphology, which were optimized to support hepatocyte culture. The material was shown to support maintenance and function of encapsulated primary human hepatocytes as indicated by actin staining, qRT-PCR, and functional cytochrome P450 assays. The designed gel was shown to outperform Matrigel in cytochrome P450 functional assays. The hydrogel may prove useful for liver development and disease models, as well as providing insights into the design of future implantable scaffolds for the regeneration of liver tissue in patients with liver disease.

Herbal Extract Loaded Chitosan/PEO Nanocomposites as Antibacterial Coatings of Orthopaedic Implants

One of the most substantial complications in orthopedic surgeries is implant associated infection. While the implant interface can be a permissive surface for bacterial colonization, an appropriate coating on the implant can effectively hinder biofilm formation. To this aim, henna and thyme extract loaded into a chitosan (CS)/polyethylene oxide (PEO) based nanofibrous hydrogel. CS/PEO/henna and CS/PEO/thymus extract nanofibers were fabricated via two-nozzle electrospinning. The proper weight ratio of CS/PEO/herbal extract was optimized. The appropriate ratio of CS/PEO and the most suitable extract concentrations was obtained to be 7/3 (v/v) and 1 % (v/v), respectively. Contact angle measurements showed an appropriate degree of hydrophilicity in all groups including herbal loaded electrospun nanosheets. Tensile strength measurements showed that inclusion of henna and thymus made minor changes in tensile strength and strain of herbal loaded nanofiber, compared to control CS/PEO fibers. Then antibacterial tests were performed and the fibers either by themselves or when used as coating on orthopedic screws exhibited a good inhibition zone against both gram negative and gram positive bacteria. The coatings showed no adverse effect on the red blood cells in leading to hemolysis. Cytocompatibility assay indicated that the prepared nanofibrous hydrogel coating was absolutely biocompatible as tested with fibroblast cells. The results of this study indicated that our henna and thyme extracts loaded CS/PEO coatings can be used in various medical fields such as wound dressing and implantation coating to prevent bacterial adhesion, growth and generally, infection.

Development of a novel label-free impedimetric electrochemical sensor based on hydrogel/chitosan for the detection of ochratoxin A

Ochratoxin A (OTA) is one of the most abundant mycotoxins that contaminate various food products. Herein, we propose a novel label-free impedimetric electrochemical sensor consisting of chitosan/dipeptide nanofibrous hydrogel and immobilized DNA probes with OTA aptamer for the detection of OTA. The thin film of chitosan/dipeptide nanofibrous hydrogel was used as sensing interface and carrier for hybridization chain reaction (HCR) of OTA aptamer and DNA2 strand to form DNA concatemer. The concatemer was dissociated to single-stranded DNA (ssDNA) in the presence of target OTA, and the signal amplification was further implemented by introducing RecJf exonuclease, which could digest the single-stranded DNA resulting in OTA recycle. Electrochemical impedance spectroscopy (EIS) has been employed to characterize the properties of the fabricated sensor. A linear detection range of 0.1–100 ng mL−1 was obtained for OTA with a low detection limit of 0.03 ng mL−1. Furthermore, the developed sensor was demonstrated in white wine to detect OTA, indicating that the proposed impedimetric sensor has a promising potential application in the food industry.