Polylactic Acid/Poly(vinylpyrrolidone) Co-Electrospun Fibrous Membrane as a Tunable Quercetin Delivery Platform for Diabetic Wounds

Diabetic wound infections (DWI) represent one of the most costly and disruptive complications in diabetic mellitus. The hyperglycemic state induces a persistent inflammation with immunological and biochemical impairments that promotes delayed wound healing processes and wound infection that often results in extended hospitalization and limb amputations. Currently, the available therapeutic options for the management of DWI are excruciating and expensive. Hence, it is essential to develop and improve DWI-specific therapies able to intervene on multiple fronts. Quercetin (QUE) exhibits excellent anti-inflammatory, antioxidant, antimicrobial and wound healing properties, which makes it a promising molecule for the management of diabetic wounds. In the present study, Poly-lactic acid/poly(vinylpyrrolidone) (PP) co-electrospun fibers loaded with QUE were developed. The results demonstrated a bimodal diameter distribution with contact angle starting from 120°/127° and go to 0° in less than 5 s indicating the hydrophilic nature of fabricated samples. The release QUE kinetics, analyzed in simulated wound fluid (SWF), revealed a strong initial burst release, followed by a constant and continuous QUE release. Moreover, QUE-loaded membranes present excellent antibiofilm and anti-inflammatory capacity and significantly reduce the gene expression of M1 markers tumor necrosis factor (TNF)-α, and IL-1β in differentiated macrophages. In conclusion, the results suggested that the prepared mats loaded with QUE could be a hopeful drug-delivery system for the effective treatment of diabetic wound infections.

Fiber Spinning from Cellulose Solutions in Imidazolium Ionic Liquids: Effects of Natural Antioxidants on Molecular Weight, Dope Discoloration, and Yellowing Behavior

Spinning of cellulosic fibers requires the prior dissolution of cellulose. 3-Alkyl-1-methylimidazolium ionic liquids have proven to be suitable solvents for that purpose, but the degradation of cellulose in the spinning dope can be severe. Suitable stabilizers are therefore required that prevent cellulose degradation, but do not adversely affect spinnability or the long-term yellowing behavior of the fibers. A group of twelve renewables-based antioxidants was selected for stabilizing 5% cellulose solutions in the ionic liquids and their effects on cellulose integrity, dope discoloration, and aging behavior were tested by gel permeation chromatography (GPC) and ISO brightness measurements. Propyl gallate (a gallic acid derivative), hydroxytyrosol (from olives), and tocopheramines (a vitamin E derivative) performed best in the three test categories, minimizing both cellulose degradation, chromophore formation in the spinning dope, and yellowing upon accelerating aging of the spun fibers. The use of these stabilizers for cellulose solutions in the imidazolium-based solvent system can therefore be recommended from the point of view of both performance and sustainability.

A U-Shaped Optical Fiber Temperature Sensor Coated with Electrospinning Polyvinyl Alcohol Nanofibers: Simulation and Experiment

This study describes the fabrication of an electrospun, U-shaped optical fiber sensor for temperature measurements. The sensor is based on single mode fibers and was fabricated into a U-shaped optical fiber sensor through flame heating. This study applied electrospinning to coat PVA, a polymer, onto the sensor layer to reduce its sensitivity to humidity. The sensor is used to measure temperature variations ranging from 30 °C to 100 °C. The objectives of this study were to analyze the sensitivity variation of the sensor with different sensor layer thicknesses resulting from different electrospinning durations, as well as to simulate the wavelength signals generated at different electrospinning durations using COMSOL. The results revealed that the maximum wavelength sensitivity, transmission loss sensitivity, and linearity of the sensor were 25 dBm/°C, 70 pm/°C, and 0.956, respectively. Longer electrospinning durations resulted in thicker sensor layers and higher sensor sensitivity, that wavelength sensitivity of the sensor increased by 42%.

Melt electrowriting reinforced composite membrane for controlled drug release

An in-house built hybrid manufacturing device, combining the pros of melt electrowriting (MEW) and melt electrospinning (MES), is firstly proposed to produce a reinforced nonwoven fabric applied in drug delivery systems. MEW is used to print regular PCL lattice, followed by the deposition of a PCL nonwoven fabric loaded with drugs, forming a MEW/MES composite scaffold. Tensile test results suggest that after combining with MEW lattice, the strength of the composite scaffold can have a two-fold improvement and the elongation to break can increase up to 900%. Solvent vapor annealing is applied to adjust drug release rate through controlling the crystallinity of PCL. Although the increased crystallinity restrained drug release, a shish-kebab-shaped fiber structure formed by the annealing facilitates drug release. This MEW-based hybrid printing method can greatly enhance the freedom of making complex scaffold and extend to other nanotechnologies to fabricate reinforced scaffold as well.

Melt electrowritten poly(caprolactone) lattices incorporated with silver nanoparticles for directional water transport antibacterial wound dressings

The composite dressing has excellent antibacterial ability and directional water transport effect, showing potential application in wound care.

Electrospun Nanofibers/Nanofibrous Scaffolds Loaded with Silver Nanoparticles as Effective Antibacterial Wound Dressing Materials

The treatment of wounds is expensive and challenging. Most of the available wound dressings are not effective and suffer from limitations such as poor antimicrobial activity, toxicity, inability to provide suitable moisture to the wound and poor mechanical performance. The use of inappropriate wound dressings can result in a delayed wound healing process. Nanosize range scaffolds have triggered great attention because of their attractive properties, which include their capability to deliver bioactive agents, high surface area, improved mechanical properties, mimic the extracellular matrix (ECM), and high porosity. Nanofibrous materials can be further encapsulated/loaded with metal-based nanoparticles to enhance their therapeutic outcomes in wound healing applications. The widely studied metal-based nanoparticles, silver nanoparticles exhibit good properties such as outstanding antibacterial activity, display antioxidant, and anti-inflammatory properties, support cell growth, making it an essential bioactive agent in wound dressings. This review article reports the biological (in vivo and in vitro) and mechanical outcomes of nanofibrous scaffolds loaded with silver nanoparticles on wound healing.

Konjac glucomannan/polyvinyl alcohol nanofibers with enhanced skin healing properties by improving fibrinogen adsorption

Skin tissue engineering aims to develop the effective healing strategy to repair the wound by optimizing skin scaffold materials. During the skin wound healing process, fibrin plays an important role due to the specific blood coagulation effect. In this study, the outstanding fibrin capability of konjac glucomannan (KGM) is demonstrated by the molecular dynamics simulation and confirmed by the protein adsorption experiments. A series of konjac glucomannan/polyvinyl alcohol (KGM/PVA) composites with different ratio are fabricated and their role in enhancing the skin repair is tested by in vitro cell culture and in vivo study. The E_ads (adsorption energy) between fibrin and KGM is about 30% larger than that between fibrin and PVA. The fibrinogen adsorption rates of PVA and KGM/PVA (5:5) composites can reach about 20% and 60%, respectively. The results show the blood adsorption capacity of KGM/PVA (5:5) composite can reach about 13 g/g. After 7 days of cell culture, the optical density values of 3T3 fibroblasts on KGM/PVA (5:5) composite could reach 0.8. The mechanical properties of the composites are also verified to meet the practical needs. Thus, we propose a potential wound dressing material strategy based on the materials design and the intrinsic properties of KGM.

Progress in electrospun composite nanofibers: composition, performance and applications for tissue engineering

The discovery of novel methods to fabricate optimal scaffolds that mimic both mechanical and functional properties of the extracellular matrix (ECM) has always been the "holy grail" in tissue engineering. In recent years, electrospinning has emerged as an attractive material fabrication method and has been widely applied in tissue engineering due to its capability of producing non-woven and nanoscale fibers. However, from the perspective of biomimicry, it is difficult for single-component electrospun fiber membranes to achieve the biomimetic purposes of the multi-component extracellular matrix. Based on electrospinning, various functional components can be efficiently and expediently introduced into the membranes, and through the complementation and correlation of the properties of each component, composite materials with comprehensive and superior properties are obtained while maintaining the primitive merits of each component. In this review, we will provide an overview of the attempts made to fabricate electrospinning-based composite tissue engineering materials in the past few decades, which have been divided into organic additives, inorganic additives and organic-inorganic additives.

Antibacterial Activities of Aliphatic Polyester Nanocomposites with Silver Nanoparticles and/or Graphene Oxide Sheets

Aliphatic polyesters such as poly(lactic acid) (PLA), polycaprolactone (PCL) and poly(lactic-co-glycolic) acid (PLGA) copolymers have been widely used as biomaterials for tissue engineering applications including: bone fixation devices, bone scaffolds, and wound dressings in orthopedics. However, biodegradable aliphatic polyesters are prone to bacterial infections due to the lack of antibacterial moieties in their macromolecular chains. In this respect, silver nanoparticles (AgNPs), graphene oxide (GO) sheets and AgNPs-GO hybrids can be used as reinforcing nanofillers for aliphatic polyesters in forming antimicrobial nanocomposites. However, polymeric matrix materials immobilize nanofillers to a large extent so that they cannot penetrate bacterial membrane into cytoplasm as in the case of colloidal nanoparticles or nanosheets. Accordingly, loaded GO sheets of aliphatic polyester nanocomposites have lost their antibacterial functions such as nanoknife cutting, blanket wrapping and membrane phospholipid extraction. In contrast, AgNPs fillers of polyester nanocomposites can release silver ions for destroying bacterial cells. Thus, AgNPs fillers are more effective than loaded GO sheets of polyester nanocomposiites in inhibiting bacterial infections. Aliphatic polyester nanocomposites with AgNPs and AgNPs-GO fillers are effective to kill multi-drug resistant bacteria that cause medical device-related infections.

Sputtering of Electrospun Polymer-Based Nanofibers for Biomedical Applications: A Perspective

Electrospinning has gained wide attention recently in biomedical applications. Electrospun biocompatible scaffolds are well-known for biomedical applications such as drug delivery, wound dressing, and tissue engineering applications. In this review, the synthesis of polymer-based fiber composites using an electrospinning technique is discussed. Formerly, metal particles were then deposited on the surface of electrospun fibers using sputtering technology. Key nanometals for biomedical applications including silver and copper nanoparticles are discussed throughout this review. The formulated scaffolds were found to be suitable candidates for biomedical uses such as antibacterial coatings, surface modification for improving biocompatibility, and tissue engineering. This review briefly mentions the characteristics of the nanostructures while focusing on how nanostructures hold potential for a wide range of biomedical applications.

Electrospun composite nanofibre fabrics containing green reduced Ag nanoparticles as an innovative type of antimicrobial insole

In this study, polyvinyl alcohol (PVA) nanofibrous membranes containing silver nanoparticles (Ag NPs) were successfully fabricated by the combination of electrospinning and a green reduction approach. Through the electrospinning technique, uniform and smooth nanofibres can be obtained, and the Ag NPs with a narrow size distributions are well dispersed in PVA nanofibres. The investigation indicates that the mass ratio of reductant tea polyphenols and AgNO₃ play a crucial role in controlling the size of the Ag NPs. More importantly, multi-layered fabrics with a layer of PVA/Ag NP nanofibrous membrane layered onto cotton substrates were developed and applied to shoe insoles. The fabricated shoe insoles with functionalized PVA nanofibres exhibit remarkable antimicrobial activity against both E. coli and S. aureus (i.e. antibacterial rate > 99%). The creation of such an encouraging fabric could establish a new optimization methodology for producing nanoengineered functional textiles.

This study aims to develop an antimicrobial insole with an electrospun nanofibre mat which contains green reduced Ag NPs by a facile fabrication method.

Ultrafine Ag Nanoparticles Encapsulated by Covalent Triazine Framework Nanosheets for CO2 Conversion

This paper describes the fabrication of covalent triazine framework nanosheet-encapsulated Ag nanoparticles (Ag⁰@CTFN) via a simple combination of the ultrasonic exfoliation and solution infiltration method. The as-prepared Ag⁰@CTFN displays an order layered-sheet structure with abundant micropores and mesopores, whereas ultrafine Ag nanoparticles are confined and stabilized in their interlayers through the interaction between N sites of triazine units and Ag nanoparticles. Considering that the Ag⁰@CTFN possesses the merits of high nitrogen, low density, and abundant basic sites, it was thus believed to have enough abilities to adsorb and activate CO₂ in the CO₂ conversion and catalysis. Importantly, the Ag⁰@CTFN, as a heterogeneous catalyst, showed highly catalytic activity in the carboxylation of various alkynes with CO₂ at ambient pressure and low temperature. This catalyst also exhibited good functional group tolerance and excellent stability without any significant loss of its activity after six recycles. This work not only achieves valuable and novel composite material but also provides the first application of covalent triazine framework nanosheets in chemical conversion of CO₂, opening a new field in preparing recyclable heterogeneous catalysts to accelerate the utilization of CO₂.

Electrospinning of casein nanofibers with silver nanoparticles for potential biomedical applications

Casein, a major protein content in the milk has been extensively used in drug delivery due to its unique structural features. Fabrication of nanofibers from casein along with nanoparticles for tissue engineering applications has been explored in this study. Nanofibers fabrication is achieved by co-electrospinning of casein with poly (ethylene oxide) in sodium dodecyl sulphate (SDS) aqueous solution. Stabilization of silver nanoparticles has been achieved by the presence of SDS in the nanofiber matrix. The influence of conductivity on the nanofiber fabrication has also been studied. The nanofibrous mats have been characterized using techniques such as scanning electron microscope (SEM) and high resolution-transmission electron microscope (HR-TEM). Antimicrobial properties of the nanofibers have been assessed and the cellular biocompatibility of the material has been evaluated using cultured fibroblast (NIH-3T3) cells. Silver nanoparticles incorporated nanofibers showed good antimicrobial property against both gram negative and gram positive bacteria. In addition, the nanofiber matrix exhibited good biocompatibility for the fibroblast cell proliferation. These results pave the way for extending the use of casein based nanofibers in the skin care applications.