Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

Advances in bioinspired nanomaterials managing microbial biofilms and virulence: A critical analysis

Microbial virulence and biofilm formation stand as a big concern against the goal of achieving a green and sustainable future. Microbial pathogenesis is the process by which the microbes (bacterial, fungal, and viral) cause illness in their respective host organism. 'Nanotechnology' is a state-of-art discipline to address this problem. The use of conventional techniques against microbial proliferation has been challenging against the environment. To tackle this problem, there has been a revolution in this multi-disciplinary field, to address the aspect of bioinspired nanomaterials in the antibiofilm and antimicrobial sector. Bioinspired nanomaterials prove to be a potential antibiofilm and antimicrobial agent as they are non-hazardous to the environment and mostly synthesized using a single-step reduction protocol. They exhibit synergistic effects against bacterial, fungal, and viral pathogens and thereby, control the virulence. In this literature review, we have elucidated the potential of bioinspired nanoparticles as well as nanomaterials as a promising anti-microbial treatment pedagogy and throw light on the advancements in how smart photo-switchable platforms have been designed to exhibit both bacterial releasing as well as bacterial-killing properties. Certain limitations and possible outcomes of these bio-based nanomaterials have been discussed in the hope of achieving a green and sustainable ecosystem.

Silver-loaded poly(vinyl alcohol)/polycaprolactone polymer scaffold as a biocompatible antibacterial system

A chronic nonhealing wound poses a significant risk for infection and subsequent health complications, potentially endangering the patient's well-being. Therefore, effective wound dressings must meet several crucial criteria, including: (1) eliminating bacterial pathogen growth within the wound, (2) forming a barrier against airborne microbes, (3) promoting cell proliferation, (4) facilitating tissue repair. In this study, we synthesized 8 ± 3 nm Ag NP with maleic acid and incorporated them into an electrospun polycaprolactone (PCL) matrix with 1.6 and 3.4 µm fiber sizes. The Ag NPs were anchored to the matrix via electrospraying water-soluble poly(vinyl) alcohol (PVA), reducing the average sphere size from 750 to 610 nm in the presence of Ag NPs. Increasing the electrospraying time of Ag NP-treated PVA spheres demonstrated a more pronounced antibacterial effect. The resultant silver-based material exhibited 100% inhibition of gram-negative Escherichia coli and gram-positive Staphylococcus aureus growth within 6 h while showing non-cytotoxic effects on the Vero cell line. We mainly discuss the preparation method aspects of the membrane, its antibacterial properties, and cytotoxicity, suggesting that combining these processes holds promise for various medical applications.

Antifungal Activity of Chitosan/Poly(Ethylene Oxide) Blend Electrospun Polymeric Fiber Mat Doped with Metallic Silver Nanoparticles

In this work, the implementation of advanced functional coatings based on the combination of two compatible nanofabrication techniques such as electrospinning and dip-coating technology have been successfully obtained for the design of antifungal surfaces. In a first step, uniform and beadless electrospun nanofibers of both polyethylene oxide (PEO) and polyethylene (PEO)/chitosan (CS) blend samples have been obtained. In a second step, the dip-coating process has been gradually performed in order to ensure an adequate distribution of silver nanoparticles (AgNPs) within the electrospun polymeric matrix (PEO/CS/AgNPs) by using a chemical reduction synthetic process, denoted as in situ synthesis (ISS). Scanning electron microscopy (SEM) has been used to evaluate the surface morphology of the samples, showing an evolution in average fiber diameter from 157 ± 43 nm (PEO), 124 ± 36 nm (PEO/CS) and 330 ± 106 nm (PEO/CS/AgNPs). Atomic force microscopy (AFM) has been used to evaluate the roughness profile of the samples, indicating that the ISS process induced a smooth roughness surface because a change in the average roughness Ra from 84.5 nm (PEO/CS) up to 38.9 nm (PEO/CS/AgNPs) was observed. The presence of AgNPs within the electrospun fiber mat has been corroborated by UV-Vis spectroscopy thanks to their characteristic optical properties (orange film coloration) associated to the Localized Surface Plasmon Resonance (LSPR) phenomenon by showing an intense absorption band in the visible region at 436 nm. Energy dispersive X-ray (EDX) profile also indicates the existence of a peak located at 3 keV associated to silver. In addition, after doping the electrospun nanofibers with AgNPs, an important change in the wettability with an intrinsic hydrophobic behavior was observed by showing an evolution in the water contact angle value from 23.4° ± 1.3 (PEO/CS) up to 97.7° ± 5.3 (PEO/CS/AgNPs). The evaluation of the antifungal activity of the nanofibrous mats against Pleurotus ostreatus clearly indicates that the presence of AgNPs in the outer surface of the nanofibers produced an important enhancement in the inhibition zone during mycelium growth as well as a better antifungal efficacy after a longer exposure time. Finally, these fabricated electrospun nanofibrous membranes can offer a wide range of potential uses in fields as diverse as biomedicine (antimicrobial against human or plant pathogen fungi) or even in the design of innovative packaging materials for food preservation.

Antimicrobial and anti-biofilm activities of bio-inspired nanomaterials for wound healing applications

Chronic wounds are ubiquitously inhabited by bacteria, and they remain a challenge as they cause significant discomfort and because their treatment consumes huge clinical resources. To reduce the burden that chronic wounds place upon both patients and health services, a wide variety of approaches have been devised and investigated. Bioinspired nanomaterials have shown great success in wound healing when compared to existing approaches, showing better ability to mimic natural extracellular matrix (ECM) components and thus to promote cell adhesion, proliferation, and differentiation. Wound dressings that are based on bioinspired nanomaterials can be engineered to promote anti-inflammatory mechanisms and to inhibit the formation of microbial biofilms. We consider the extensive potential of bioinspired nanomaterials in wound healing, revealing a scope beyond that covered previously.

Current status and progress in research on dressing management for diabetic foot ulcer

Diabetic foot ulcer (DFU) is a major complication of diabetes and is associated with a high risk of lower limb amputation and mortality. During their lifetime, 19%-34% of patients with diabetes can develop DFU. It is estimated that 61% of DFU become infected and 15% of those with DFU require amputation. Furthermore, developing a DFU increases the risk of mortality by 50%-68% at 5 years, higher than some cancers. Current standard management of DFU includes surgical debridement, the use of topical dressings and wound decompression, vascular assessment, and glycemic control. Among these methods, local treatment with dressings builds a protective physical barrier, maintains a moist environment, and drains the exudate from DFU wounds. This review summarizes the development, pathophysiology, and healing mechanisms of DFU. The latest research progress and the main application of dressings in laboratory and clinical stage are also summarized. The dressings discussed in this review include traditional dressings (gauze, oil yarn, traditional Chinese medicine, and others), basic dressings (hydrogel, hydrocolloid, sponge, foam, film agents, and others), bacteriostatic dressings, composite dressings (collagen, nanomaterials, chitosan dressings, and others), bioactive dressings (scaffold dressings with stem cells, decellularized wound matrix, autologous platelet enrichment plasma, and others), and dressings that use modern technology (3D bioprinting, photothermal effects, bioelectric dressings, microneedle dressings, smart bandages, orthopedic prosthetics and regenerative medicine). The dressing management challenges and limitations are also summarized. The purpose of this review is to help readers understand the pathogenesis and healing mechanism of DFU, help physicians select dressings correctly, provide an updated overview of the potential of biomaterials and devices and their application in DFU management, and provide ideas for further exploration and development of dressings. Proper use of dressings can promote DFU healing, reduce the cost of treating DFU, and reduce patient pain.

Multi-material electrospinning: from methods to biomedical applications

Electrospinning as a versatile, simple, and cost-effective method to engineer a variety of micro or nanofibrous materials, has contributed to significant developments in the biomedical field. However, the traditional electrospinning of single material only can produce homogeneous fibrous assemblies with limited functional properties, which oftentimes fails to meet the ever-increasing requirements of biomedical applications. Thus, multi-material electrospinning referring to engineering two or more kinds of materials, has been recently developed to enable the fabrication of diversified complex fibrous structures with advanced performance for greatly promoting biomedical development. This review firstly gives an overview of multi-material electrospinning modalities, with a highlight on their features and accessibility for constructing different complex fibrous structures. A perspective of how multi-material electrospinning opens up new opportunities for specific biomedical applications, i.e., tissue engineering and drug delivery, is also offered.

Cyclic desorption based efficacy of polyvinyl alcohol-chitosan variant resins for multi heavy-metal removal

The simultaneous removal of Cu, Pb and Fe from water bodies has been targeted in this work with polyvinyl alcohol (PVA) and chitosan (low, medium, and high molecular weight) derivative and with cyclic desorption efficacy target. For a varied range of adsorbent loading (0.2-2 g L^-1), initial concentration (187.7-563.1 mg L^-1 for Cu, 5.2-15.6 mg L^-1 for Pb, and 61.85-185.55 mg L^-1 for Fe), and resin contact time (5 to 720 min), batch adsorption-desorption studies were conducted. After first adsorption-desorption cycle, the optimum absorption capacity was 6.85 mg g^-1 for Pb, 243.90 mg g^-1 for Cu, and 87.72 mg g^-1 for Fe for the high molecular weight chitosan grafted polyvinyl alcohol resin (HCSPVA). The alternate kinetic and equilibrium models were analyzed along with the interaction mechanism between metal ions and functional groups. The cyclic desorption studies were carried out with simple eluent systems such as HCl, HNO₃, H₂SO₄, KOH, and NaOH. The experiments revealed that the HCSPVA derivative has been an impressive, reusable, and effective sorbent for the mitigation of Pb, Fe, and Cu in complex wastewater systems. This is due to its easy synthesis, excellent adsorption capacity, quick sorption rate, and remarkable regeneration capabilities.

Recent Advances in Silver Nanoparticles Containing Nanofibers for Chronic Wound Management

Infections are the primary cause of death from burns and diabetic wounds. The clinical difficulty of treating wound infections with conventional antibiotics has progressively increased and reached a critical level, necessitating a paradigm change for enhanced chronic wound care. The most prevalent bacterium linked with these infections is Staphylococcus aureus, and the advent of community-associated methicillin-resistant Staphylococcus aureus has posed a substantial therapeutic challenge. Most existing wound dressings are ineffective and suffer from constraints such as insufficient antibacterial activity, toxicity, failure to supply enough moisture to the wound, and poor mechanical performance. Using ineffective wound dressings might prolong the healing process of a wound. To meet this requirement, nanoscale scaffolds with their desirable qualities, which include the potential to distribute bioactive agents, a large surface area, enhanced mechanical capabilities, the ability to imitate the extracellular matrix (ECM), and high porosity, have attracted considerable interest. The incorporation of nanoparticles into nanofiber scaffolds constitutes a novel approach to “nanoparticle dressing” that has acquired significant popularity for wound healing. Due to their remarkable antibacterial capabilities, silver nanoparticles are attractive materials for wound healing. This review focuses on the therapeutic applications of nanofiber wound dressings containing Ag-NPs and their potential to revolutionize wound healing.

Polysaccharide Electrospun Nanofibers for Wound Healing Applications

As a type of biological macromolecule, natural polysaccharides have been widely used in wound healing due to their low toxicity, good biocompatibility, degradability and reproducibility. Electrospinning is a versatile and simple technique for producing continuous nanoscale fibers from a variety of natural and synthetic polymers. The application of electrospun nanofibers as wound dressings has made great progress and they are considered one of the most effective wound dressings. This paper reviews the preparation of polysaccharide nanofibers by electrospinning and their application prospects in the field of wound healing. A variety of polysaccharide nanofibers, including chitosan, starch, alginate, and hyaluronic acid are introduced. The preparation strategy of polysaccharide electrospun nanofibers and their functions in promoting wound healing are summarized. In addition, the future prospects and challenges for the preparation of polysaccharide nanofibers by electrospinning are also discussed.

Single unit functionally graded bioresorbable electrospun scaffold for scar-free full-thickness skin wound healing

Full-thickness wounds are difficult to heal spontaneously. Scaffolds, meant for treating full-thickness wounds, should ensure proper tissue regeneration, both structurally and functionally. An ideal scaffold should mimic the physical, mechanical and biochemical properties of natural skin. However, available mono- or bi-layer skin scaffolds lack in the precise architecture and functionality, thus, failing to provide scar-free regeneration of full-thickness skin wounds. These unmet challenges of scar-free skin regeneration have been addressed in the present study for the first time. This research deals with the synthesis of a low-cost, structurally and functionally graded single unit biodegradable polymeric scaffold. The functional gradient in this scaffold was achieved by varying polymer concentration and electrospinning parameters. This gradient in the scaffold provided the required microenvironment for proper functional and structural reconstruction of all the layers of natural skin. The mechanical property of the scaffold matched that of the natural skin. Besides, the degradation kinetics of the scaffold was in coordination with the regeneration time for the full-thickness wound. The porosity and hydrophilicity gradients of the scaffold helped it mimic the in vivo hypodermal, dermal and epidermal microenvironments of the skin, simultaneously. Co-culturing PCS-201 (dermal fibroblasts) and HaCaT (keratinocytes) on the scaffold resulted in successful regeneration through cellular proliferation, differentiation and organization of the skin tissue. The scaffold also displayed better wound healing in vivo, in terms of speedy wound closure and proper tissue regeneration, in comparison to the standard treatment. Altogether, this study successfully established a simple, one-step synthesis process of a functionally graded, bioresorbable scaffold for scar-free, native-like, structural and functional regeneration of full-thickness skin wounds. Due to cost-effectiveness, easy synthesis process and microarchitectural features, the designed scaffold possesses a potential of translation to a good commercial wound healing product.

An asymmetric wettable PCL/chitosan composite scaffold loaded with IGF-2 for wound dressing

An effective dressing is essential for wound healing. In fact, the wettability performance is one of the most important factors of a wound dressing. The fundamental functions of a wound dressing involve the absorption of excess exudates and maintenance of optimal moisture at the wound by controlling water evaporation. Here, we designed a type of chitosan (CS) sponge and PCL nanofibrous membrane composite dressing with asymmetric wettability surfaces as wound healing materials for biomedical applications. The hydrophobic surfaces of the composite dressing were waterproof and could efficiently control the water vapor transmission rate, whereas the hydrophilic surface of the CS sponge had good cytocompatibility and water-absorbing capability. Insulin-like growth factor-2 (IGF-2) was added to the CS sponge, and exhibited a stimulatory effect on fibroblasts migration and proliferation. Therefore, the fabricated CS sponge and PCL membrane composite dressing had excellent cytocompatibility, vapor transmission rate, and liquid absorption and asymmetric wettability, suggesting its potential as a promising alternative to traditional wound dressing.

Advances in Electrospun Hybrid Nanofibers for Biomedical Applications

Electrospun hybrid nanofibers, based on functional agents immobilized in polymeric matrix, possess a unique combination of collective properties. These are beneficial for a wide range of applications, which include theranostics, filtration, catalysis, and tissue engineering, among others. The combination of functional agents in a nanofiber matrix offer accessibility to multifunctional nanocompartments with significantly improved mechanical, electrical, and chemical properties, along with better biocompatibility and biodegradability. This review summarizes recent work performed for the fabrication, characterization, and optimization of different hybrid nanofibers containing varieties of functional agents, such as laser ablated inorganic nanoparticles (NPs), which include, for instance, gold nanoparticles (Au NPs) and titanium nitride nanoparticles (TiNPs), perovskites, drugs, growth factors, and smart, inorganic polymers. Biocompatible and biodegradable polymers such as chitosan, cellulose, and polycaprolactone are very promising macromolecules as a nanofiber matrix for immobilizing such functional agents. The assimilation of such polymeric matrices with functional agents that possess wide varieties of characteristics require a modified approach towards electrospinning techniques such as coelectrospinning and template spinning. Additional focus within this review is devoted to the state of the art for the implementations of these approaches as viable options for the achievement of multifunctional hybrid nanofibers. Finally, recent advances and challenges, in particular, mass fabrication and prospects of hybrid nanofibers for tissue engineering and biomedical applications have been summarized.

PVP/Highly Dispersed AgNPs Nanofibers Using Ultrasonic-Assisted Electrospinning

Silver nanoparticles (AgNPs) are novel materials with antibacterial, antifungal, and antiviral activities over a wide range. This study aimed to prepare polyvinylpyrrolidone (PVP) electrospinning composites with uniformly distributed AgNPs. In this study, starch-capped ~2 nm primary AgNPs were first synthesized using Atmospheric pressure Pulsed Discharge Plasma (APDP) at AC 10 kV and 10 kHz. Then, 0.6 wt.% AgNPs were mixed into a 10 wt.% PVP ethanol-based polymer solution and coiled through an Ultrasonic-assisted Electrospinning device (US-ES) with a 50 W and 50 kHz ultrasonic generator. At 12 kV and a distance of 10 cm, this work successfully fabricated AgNPs-PVP electrospun fibers. The electrospun products were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), High-Resolution TEM (HR-TEM), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Thermogravimetric (TG), and X-ray Photoelectron Spectroscopy (XPS) methods.

Design, preparation and in vitro characterization of biomimetic and bioactive chitosan/polyethylene oxide based nanofibers as wound dressings

Chitosan-based nanofibers (CS-NFs) are excellent artificial extracellular matrices (ECMs) due to the resemblance of CS with the glycosaminoglycans of the natural ECMs. Despite this excellent feature, the poor electrospinnability and mechanical properties of CS are responsible for important limitations in respect to its biomedical applications. To improve the CS's physico-chemical properties, new bioactive and biomimetic CS-NFs were formulated with polyethylene oxide (PEO), having incorporated different active components (ACs) with important beneficial effects for healing. Manuka honey (trophic and antimicrobial effects), propolis (antimicrobial effects), Calendula officinalis infusion (antioxidant effect, reepithelialization stimulating agent), insulin (trophic effect), and L-arginine (angiogenic effect) were selected as ACs. SEM morphology analysis revealed well-alignment, unidirectional arrays, with small diameters, no beads, and smooth surfaces for developed CS_PEO-ACs NFs. The developed NFs showed good biodegradability (NFs mats lost up to 60% of their initial weight in PBS), increased hemocompatibility (hemolytic index less than 4%), and a reduced cytotoxicity degree (cell viability degree more than 90%). In addition, significant antioxidant and antimicrobial effects were noted for the developed NFs which make them suitable for chronic wounds, due to the role of oxidative stress and infection risk in delaying normal wound healing. The most suitable for wound healing applications seems to be CS_PEO@P_C which showed an improved hemolysis index (2.92 ± 0.16%), is non-toxic (cell viability degree more than 97%), and has also significant radical scavenging effect (DPPH inhibition more than 65%). In addition, CS_PEO@P_C presents increased antimicrobial effects, more noticeably for Staphylococcus aureus strain, which is a key feature in preventing wound infection and delaying the healing process. It can be concluded that the developed CS/PEO-ACs NFs are very promising biomaterials for wound care, especially CS_PEO@P_C.

Biotechnological Applications of Polymeric Nanofiber Platforms Loaded with Diverse Bioactive Materials

This review article highlights the critical research and formative works relating to nanofiber composites loaded with bioactive materials for diverse applications, and discusses the recent research on the use of electrospun nanofiber incorporating bioactive compounds such as essential oils, herbal bioactive components, plant extracts, and metallic nanoparticles. Inevitably, with the common advantages of bioactive components and polymer nanofibers, electrospun nanofibers containing bioactive components have attracted intense interests for their applications in biomedicine and cancer treatment. Many studies have only concentrated on the production and performance of electrospun nanofiber loaded with bioactive components; in this regard, the features of different types of electrospun nanofiber incorporating a wide variety of bioactive compounds and their developing trends are summarized and assessed in the present article, as is the feasible use of nanofiber technology to produce products on an industrial scale in different applications.

Recent advances in polymer scaffolds for biomedical applications

The review provides insights into current advancements in electrospinning-assisted manufacturing for optimally designing biomedical devices for their prospective applications in tissue engineering, wound healing, drug delivery, sensing, and enzyme immobilization, and others. Further, the evolution of electrospinning-based hybrid biomedical devices using a combined approach of 3 D printing and/or film casting/molding, to design dimensionally stable membranes/micro-nanofibrous assemblies/patches/porous surfaces, etc. is reported. The influence of various electrospinning parameters, polymeric material, testing environment, and other allied factors on the morphological and physico-mechanical properties of electrospun (nano-/micro-fibrous) mats (EMs) and fibrous assemblies have been compiled and critically discussed. The spectrum of operational research and statistical approaches that are now being adopted for efficient optimization of electrospinning process parameters so as to obtain the desired response (physical and structural attributes) has prospectively been looked into. Further, the present review summarizes some current limitations and future perspectives for modeling architecturally novel hybrid 3 D/selectively textured structural assemblies, such as biocompatible, non-toxic, and bioresorbable mats/scaffolds/membranes/patches with apt mechanical stability, as biological substrates for various regenerative and non-regenerative therapeutic devices.

New Hyaluronic Acid/Polyethylene Oxide-Based Electrospun Nanofibers: Design, Characterization and In Vitro Biological Evaluation

Natural compounds have been used as wound-healing promoters and are also present in today's clinical proceedings. In this research, different natural active components such as propolis, Manuka honey, insulin, L-arginine, and Calendula officinalis infusion were included into hyaluronic acid/poly(ethylene)oxide-based electrospun nanofiber membranes to design innovative wound-dressing biomaterials. Morphology and average fiber diameter were analyzed by scanning electron microscopy. Chemical composition was proved by Fourier transform infrared spectroscopy, which indicated successful incorporation of the active components. The nanofiber membranes with propolis and Calendula officinalis showed best antioxidant activity, cytocompatibility, and antimicrobial properties against pathogen strains Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa and had an average diameter of 217 ± 19 nm with smooth surface aspect. Water vapor transmission rate was in agreement with the range suitable for preventing infections or wound dehydration (~5000 g/m2 24 h). Therefore, the developed hyaluronic acid/poly(ethylene)oxide nanofibers with additional natural components showed favorable features for clinical use as wound dressings.

Multidrug-loaded electrospun micro/nanofibrous membranes: Fabrication strategies, release behaviors and applications in regenerative medicine

Electrospun micro/nanofibrous membranes (EFMs) have been widely investigated as local drug delivery systems. Multiple drugs can be simultaneously incorporated into one EFM to create synergistic effects, reduce side effects, and play their respective roles in the complex physiological processes of tissue regeneration and postoperative adhesion prevention. Due to the versatile electrospinning techniques, sustained and programmed release behaviors of multiple drugs could be achieved by modulating the structure of the EFMs and the location of the drugs. In this review, various multidrug incorporation approaches based on electrospinning are overviewed. In particular, the advantages and limitations of each drug incorporation technique, the methods to control drug release and the effect of one drug release on another are discussed. Then the applications of multidrug-loaded EFMs in regenerative medicine, including wound healing, bone regeneration, vascular tissue engineering, nerve regeneration, periodontal regeneration and adhesion prevention are comprehensively reviewed. Finally, the future perspectives and challenges in the research of multidrug-loaded EFMs are discussed.

Chitosan based-nanoparticles and nanocapsules: Overview, physicochemical features, applications of a nanofibrous scaffold, and bioprinting

Recent advancements in the synthesis, properties, and applications of chitosan as the second after cellulose available biopolymer in nature were discussed in this review. A general overview of processing and production procedures from A to Z was highlighted. Chitosan exists in three polymorphic forms which differ in degree of crystallinity (α, β, and γ). Thus, the degree of deacetylation, crystallinity, surface area, and molecular mass significantly affect most applications. Otherwise, the synthesis of chitosan nanofibers is suffering from many drawbacks that were recently treated by co-electrospun with other polymers such as polyvinyl alcohol (PVA), polyethylene oxide (PEO), and polycaprolactone (PCL). Ultimately, this review focuses on the area of new trend utilization of chitosan nanoparticles as nanospheres and nanocapsules, in cartilage and bone regenerative medicine. Owing to its biocompatibility, bioavailability, biodegradability, and costless synthesis, chitosan is a promising biopolymeric structure for water remediation, drug delivery, antimicrobials, and tissue engineering.

Antimicrobial Double-Layer Wound Dressing Based on Chitosan/Polyvinyl Alcohol/Copper: In vitro and in vivo Assessment

PURPOSE

Today, the development of wounds and their side effects has become a problematic issue in medical science research. Hydrogel-based dressings are some of the best candidates for this purpose due to their ability to keep the wound bed clean, as well as provide proper moisture, tissue compatibility and an antimicrobial effect for wound healing. On the other hand, copper and its compounds have been used experimentally for many years in studies as an antimicrobial substance. Various studies have been performed determining the antimicrobial properties of this element, during which significant effects on infection have been shown.

METHODS

Chitosan/polyvinyl alcohol/copper nanofibers were successfully prepared by incorporating Cu onto a polymer electrospun using an electrospinning technique. A double-layer nanofiber composed of poly(vinyl alcohol) and chitosan incorporated with Cu nanoparticles as a protective layer and a second layer composed of polyvinylpyrrolidone (PVP) nanofibers which was adjacent to the damaged cells was prepared. The prepared nanofiber was characterized by TGA, FT-IR, TEM, SEM-EDS, and X-ray powder diffraction. The antimicrobial efficiency of the nanofibers was demonstrated through biological tests on some Gram-positive and Gram-negative bacteria. Finally, the prepared hydrogel formulations were prepared to evaluate their effect on the healing process of rat open wounds.

RESULTS

In this study, data from SEM, TEM, EDS, and XRD confirmed the formation of uniform fibers with nanodiameters and the presence of Cu nanoparticles onto the electrospun nanofibers. The antibacterial activity of copper was observed against all of the selected bacteria, but the Gram-positive bacteria were more sensitive compared to Gram-negative bacteria.

CONCLUSION

According to the obtained results, the hydrogel wound dressing prepared in this research can be effective in caring for open wounds in the early stages of wound healing and preventing the occurrence of prolonged open wounds.

Synthesis of Fe3O4/Ag nanohybrid ferrofluids and their applications as antimicrobial and antifibrotic agents

To date, the search for creating stable ferrofluids with excellent properties for biomedical application is one of the challenging scientific and practical investigations. In this study, novel Fe3O4/Ag nanohybrid ferrofluids from iron sand were synthesized using a double-layer method. The Fe3O4/Ag nanocomposites exhibited stable crystallite sizes of 11.8 12.1 nm and 36.8-37.2 nm for Fe3O4 and Ag, respectively. The lattice parameters of the spinel structure Fe3O4 and face-centered cubic Ag were respectively 8.344 Å and 4.091 Å. With increasing Ag amount, the crystallite phase of Ag in the nanocomposites increased from 40.2% to 77.2%. The XPS results confirmed that Fe3O4/Ag nanocomposites were successfully prepared, where Fe3O4 mixed well with Ag via strong ionic bonding. The FTIR results confirmed the presence of Fe3O4/Ag, oleic acid, and dimethyl sulfoxide as the filler, first layer, and second layer, respectively. The as-prepared ferrofluids exhibited superparamagnetic behavior, where the saturation magnetization decreased with increasing Ag content. The Fe3O4/Ag nanohybrid ferrofluids exhibited excellent antimicrobial performance against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Candida albicans. More importantly, the Fe3O4/Ag nanohybrid ferrofluids decreased the progression of liver fibrosis-related inflammation and fibrogenic activity on hepatic stellate cells.

Morphology of electrospun PVA nanofibers enhanced with graphene oxide, poly (3,4-ethylenedioxythiophene): Polystyrene sulfonate (PEDOT:PSS) and multiwalled carbon nanotubes

Morphology of poly(vinyl alcohol) (PVA) nanofibers was studied while varying needle-collector distance and concentrations of graphene oxide, poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), and functionalized multiwalled carbon nanotubes. Most notably, we found that variations in PVA nanofiber diameter of ~ 34 nm exist in the radial area of electrospinning; the variation is believed to be the result of a fringing electric field effect at the edge of the collector plates. Needle-collector distance was varied between 10 and 17 cm, and FESEM images revealed average fiber diameter decreased from 173 nm to 144 nm with no obvious change in morphology at both nanofiber diameters. Similarly, electrospinning of PVA-GO solution at 17 cm resulted in nanofibers with decreased average diameter of 197 nm (σ = 97 nm), compared with PVA alone (349 nm, σ = 87 nm) with no obvious change in morphology. The average diameter of PVA nanofibers then increased with added PEDOT:PSS to 244 nm, σ = 75 nm. PVA-MWCNT samples at 2 wt% and 4 wt% showed no beading, while at 6, 8, and 10 wt%, beads were prevalent in the fibers. The presence of beads could be the result of re-agglomeration of MWCNTs in the electrospinning solution at higher wt%. No clear trend was found with increasing concentrations of MWCNTs, with average nanofiber diameters varying in the range of 115 – 206 nm.

Physical-Chemical Crosslinked Electrospun Colocasia esculenta Tuber Protein-Chitosan-Poly(Ethylene Oxide) Nanofibers with Antibacterial Activity and Cytocompatibility

Background

Electrospun nanofibers based on Colocasia esculenta tuber (CET) protein are considered as a promising material for wound dressing applications. However, the use of these nanofibers in aqueous conditions has poor stability. The present study was performed to obtain insights into the crosslinked electrospun CET’s protein–chitosan (CS)–poly(ethylene oxide) (PEO) nanofibers and to evaluate their potential for wound dressing applications.

Methods

The electrospun nanofibers were crosslinked with glutaraldehyde (GA) vapor and heat treatment (HT) to enhance their physicochemical stability. The crosslinked nanofibers were characterized by protein profiles, morphology structures, thermal behavior, mechanical properties, and degradation behavior. Furthermore, the antibacterial properties and cytocompatibility were analyzed by antibacterial assessment and cell proliferation.

Results

The protein profiles of the electrospun CET’s protein–CS–PEO nanofibers before and after HT crosslinking contained one major bioactive protein with a molecular weight of 14.4 kDa. Scanning electron microscopy images of the crosslinked nanofibers indicated preservation of the structure after immersion in phosphate buffered saline. The crosslinked nanofibers resulted in higher ultimate tensile strength and lower ultimate strain compared to the non-crosslinked nanofibers. GA vapor crosslinking showed higher water stability compared to HT crosslinking. The in vitro antibacterial activity of the crosslinked nanofibers showed a stronger bacteriostatic effect on Staphylococcus aureus than on Escherichia coli. Human skin fibroblast cell proliferation on crosslinked GA vapor and HT nanofibers with 1% (w/v) CS and 2% (w/v) CET’s protein demonstrated the highest among all the other crosslinked nanofibers after seven days of cell culture. Cell proliferation and cell morphology results revealed that introducing higher CET’s protein concentration on crosslinked nanofibers could increase cell proliferation of the crosslinked nanofibers.

Conclusion

These results are promising for the potential use of the crosslinked electrospun CET’s protein–CS–PEO nanofibers as bioactive wound dressing materials.

Anthocyanin Colorimetric Strip for Volatile Amine Determination

Food freshness is one of the main concerns of consumers. Food spoilage is mainly caused by contamination and microbial growth in which the latter produces volatile amines in the process. Several methods have been used to determine volatile amines to indicate food freshness, and indicator films are deemed as the most time-efficient and economical. In this study, anthocyanin was extracted from mangosteen rind as a natural dye indicator and was incorporated in a chitosan/PVA polymer matrix. The film with different concentrations of anthocyanin extract (5%, 15%, and 25%) was prepared and tested for their sensitivity to 136 ppm ammonia vapor followed by colorimetric analysis using ImageJ software. The film with 25% anthocyanin yielded the most visible color change upon exposure to ammonia vapor. The color changed from pink to yellowish-brown within 14 minutes of exposure. The RGB-converted images of the film with 25% anthocyanin extract showed gradual loss of red coloration being replaced by cyan spots. FTIR spectra showed incorporation of anthocyanin to the chitosan/PVA matrix with the decrease in the intensity of the C-N stretching peak. Thermogravimetric analysis showed that the film has high thermal stability with onset temperature of 310.43°C. Thus, the film developed is an excellent candidate for optimization and production of a thermally stable amine detector for food products.

Antibiotic Delivery Strategies to Treat Skin Infections When Innate Antimicrobial Defense Fails

The epidermal skin barrier protects the body from a host of daily challenges, providing protection against mechanical insults and the absorption of chemicals and xenobiotics. In addition to the physical barrier, the epidermis also presents an innate defense against microbial overgrowth. This is achieved through the presence of a diverse collection of microorganisms on the skin (the "microbiota") that maintain a delicate balance with the host and play a significant role in overall human health. When the skin is wounded, the local tissue with a compromised barrier can become colonized and ultimately infected if bacterial growth overcomes the host response. Wound infections present an immense burden in healthcare costs and decreased quality of life for patients, and treatment becomes increasingly important because of the negative impact that infection has on slowing the rate of wound healing. In this review, we discuss specific challenges of treating wound infections and the advances in drug delivery platforms and formulations that are under development to improve topical delivery of antimicrobial treatments.

Graphene oxide coated shell-core structured chitosan/PLLA nanofibrous scaffolds for wound dressing

Graphite oxide (GO) and chitosan (CS) nanofibers have aroused intense interest as wound dressing due to their physicochemical, antimicrobial properties and nanotopography. In this study, GO nanosheets were coated on shell (chitosan, CS)-core (L-polylactic acid, PLLA) structured nanofibrous scaffolds to create a synergistic microenvironment for wound healing. Through scanning electron microscopy (SEM) and atomic force microscopy (AFM) tests, results showed that the surface of GO-coated CS/PLLA nanofibers presented corrugated wrinkles and rougher than that of CS/PLLA nanofibers, and the GO nanosheets did not destroy the structure of nanofibers. X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) demonstrated that GO nanosheets were successfully coated on CS/PLLA nanofibrous scaffolds. Furthermore, the coatings of GO nanosheets significantly improved the hydrophilicity of CS/PLLA nanofibrous scaffolds. GO-coated CS/PLLA nanofibrous scaffolds revealed more excellent antimicrobial activity to Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) than that of CS/PLLA nanofibrous scaffolds, meanwhile, they promoted the proliferation of pig iliac endothelial cells (PIECs). Rats wounds covered by GO-coated CS/PLLA nanofibrous scaffolds were healed better than other groups on pathological section. This type of nanofibrous scaffolds with GO nanosheets would possess an excellent potential in wound healing process.

A novel bilayer zein/MMT nanocomposite incorporated with H. perforatum oil for wound healing

Recently, layered structures composed of nanofibers have gained attention as a novel material to mimic skin tissue in wound healing applications. The aim of this study is to develop a novel hybrid bilayer material composed of zein based composite film and nanofiber layers as a wound dressing material. The upper layer was composed of H. perforatum oil incorporated zein film including MMT and the bottom layer was comprised of 3D electrospun zein/MMT nanofibers to induce wound healing with the controlled release of H. perforatum oil. The bilayer composites were characterized in terms of mechanical test, WVP, water uptake and surface wettability. Antimicrobial activity of the wound dressings against microorganisms were investigated by disc diffusion method. In vitro cytotoxicity of monolayer film and bilayer structure was performed using WST-1 assay on HS2 keratinocyte and 3T3 cell lines. Results indicated that the prepared monolayer films showed appropriate mechanical and gas barrier properties and surface wettability for wound healing. Controlled release of H. perforatum oil was obtained from fabricated membranes up to 48 h. Bilayer membranes showed antimicrobial activity against E. coli, S. aureus, and C. albicans and did not show any toxic effect on NIH3T3 mouse fibroblast and HS2 keratinocyte cell lines. In vitro scratch assay results indicated that H. perforatum oil had a wound healing effect by inducing fibroblast migration. The proliferation study supported these results by increasing fibroblast proliferation on H. perforatum oil loaded bilayer membranes.

The effect of collection substrate on electrospun ciprofloxacin-loaded poly(vinylpyrrolidone) and ethyl cellulose nanofibers as potential wound dressing materials

In this work, nanofibers based on hydrophilic poly(vinylpyrrolidone) (PVP) and hydrophobic ethyl cellulose (EC) were generated via electrospinning. A model antibiotic, ciprofloxacin (CIF), was also incorporated into the fibers. Fibers were collected on both a foil substrate and a commercial gauze, the latter in the interests of developing a smart fabric. Electron microscopy images revealed that the fibers collected on both foil and fabric were homogeneous and cylindrical. Infrared spectroscopy, X-ray diffraction and differential scanning calorimetry demonstrated that CIF was successfully loaded into the fibers and present in the amorphous physical form. In vitro drug release tests were conducted to simulate drug release from the formulations into a wound site, and as expected the hydrophilic fibers showed much faster release than their hydrophobic analogues. CIF was released through a combined mechanism of polymer erosion and drug diffusion, and the EC nanofibers displayed close to zero-order release over three days. Fibroblast cells are able to grow and proliferate on the fibers. Finally, inhibition zone assays revealed that the growth of both Gram positive and Gram negative bacteria could be effectively inhibited as a result of the presence of CIF in the fibers. There were no marked differences between the fibers collected on foil and on gauze, and electrospinning can be performed directly onto a gauze substrate to prepare a smart fabric.

Fabrication of Electrospun Polymer Nanofibers with Diverse Morphologies

Fiber structures with nanoscale diameters offer many fascinating features, such as excellent mechanical properties and high specific surface areas, making them attractive for many applications. Among a variety of technologies for preparing nanofibers, electrospinning is rapidly evolving into a simple process, which is capable of forming diverse morphologies due to its flexibility, functionality, and simplicity. In such review, more emphasis is put on the construction of polymer nanofiber structures and their potential applications. Other issues of electrospinning device, mechanism, and prospects, are also discussed. Specifically, by carefully regulating the operating condition, modifying needle device, optimizing properties of the polymer solutions, some unique structures of core⁻shell, side-by-side, multilayer, hollow interior, and high porosity can be obtained. Taken together, these well-organized polymer nanofibers can be of great interest in biomedicine, nutrition, bioengineering, pharmaceutics, and healthcare applications.

Silver nanoparticles coated with dodecanethiol used as fillers in non-cytotoxic and antifungal PBAT surface based on nanocomposites

In the present study, we report the preparation of antifungal and non-cytotoxic polymer nanocomposites with potential application in biomedical materials. Dodecanethiol-protected silver nanoparticles (AgNPs-DDT) were synthesized by a reduction/precipitation method and dispersed in chloroform to obtain stable colloidal dispersions. PBAT-based nanocomposites containing 0.25, 0.5 and 2 wt% AgNPs-DDT were prepared by casting method. The incorporation of AgNPs-DDT in PBAT matrix resulted in nanocomposites which combine improved mechanical performance and antifungal properties with a non-cytotoxic characteristic.