Antimicrobial Peptide‐Based Electrospun Fibers for Wound Healing Applications

GO/AgNW aided sustained release of ciprofloxacin loaded in Starch/PVA nanocomposite mats for wound dressings application

Compared to conventional bandages, which do not meet all wound care requirements, nanofiber wound dressings could provide a potentially excellent environment for healing. In the present research, nanocomposite membrane based on starch (St) - polyvinyl alcohol (PVA) nanofibers containing ciprofloxacin antibiotic drug loaded on graphene oxide‑silver nanowire (GO-AgNWs) hybrid nanoparticles is produced by electrospinning process. Morphological studies showed that the length and diameter of silver nanowires are 21 ± 9.17 μm and 82 ± 10.52 nm, respectively. The contact angle of 57.1° due to the hydrophilic nature of nanofibers, also the swelling degree of 679.51 % and, the water vapor permeability of 2627 ± 56 (g/m2.day) can be expressed as a confirmation of the ability of this wound dressing to manage secretions around the wound. In evaluating the antibacterial activity of these nanocomposite membranes against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria, the most potent antibacterial effect is in the case of nanofibers containing a high percentage of starch and nanoparticles carrying ciprofloxacin; with non-growth halos of 47.58 mm and 22.06 mm was recorded. The release of ciprofloxacin drug in vitro was reported to be 61.69 % during 24 h, and the final release rate was 82.17 %. Despite the biocompatibility and cell viability of 97.74 % and the biodegradability rate of 28.51 %, the StP-GOAgNWCip nanocomposite membrane can be introduced as a suitable candidate for wound dressing.

Advancements in Regenerative Hydrogels in Skin Wound Treatment: A Comprehensive Review

This state-of-the-art review explores the emerging field of regenerative hydrogels and their profound impact on the treatment of skin wounds. Regenerative hydrogels, composed mainly of water-absorbing polymers, have garnered attention in wound healing, particularly for skin wounds. Their unique properties make them well suited for tissue regeneration. Notable benefits include excellent water retention, creating a crucially moist wound environment for optimal healing, and facilitating cell migration, and proliferation. Biocompatibility is a key feature, minimizing adverse reactions and promoting the natural healing process. Acting as a supportive scaffold for cell growth, hydrogels mimic the extracellular matrix, aiding the attachment and proliferation of cells like fibroblasts and keratinocytes. Engineered for controlled drug release, hydrogels enhance wound healing by promoting angiogenesis, reducing inflammation, and preventing infection. The demonstrated acceleration of the wound healing process, particularly beneficial for chronic or impaired healing wounds, adds to their appeal. Easy application and conformity to various wound shapes make hydrogels practical, including in irregular or challenging areas. Scar minimization through tissue regeneration is crucial, especially in cosmetic and functional regions. Hydrogels contribute to pain management by creating a protective barrier, reducing friction, and fostering a soothing environment. Some hydrogels, with inherent antimicrobial properties, aid in infection prevention, which is a crucial aspect of successful wound healing. Their flexibility and ability to conform to wound contours ensure optimal tissue contact, enhancing overall treatment effectiveness. In summary, regenerative hydrogels present a promising approach for improving skin wound healing outcomes across diverse clinical scenarios. This review provides a comprehensive analysis of the benefits, mechanisms, and challenges associated with the use of regenerative hydrogels in the treatment of skin wounds. In this review, the authors likely delve into the application of rational design principles to enhance the efficacy and performance of hydrogels in promoting wound healing. Through an exploration of various methodologies and approaches, this paper is poised to highlight how these principles have been instrumental in refining the design of hydrogels, potentially revolutionizing their therapeutic potential in addressing skin wounds. By synthesizing current knowledge and highlighting potential avenues for future research, this review aims to contribute to the advancement of regenerative medicine and ultimately improve clinical outcomes for patients with skin wounds.

Development of hybrid electrospun alginate-pulverized moringa composites

The consideration of biopolymers with natural products offers promising and effective materials with intrinsic and extrinsic properties that are utilized in several applications. Electrospinning is a method known for its unique and efficient performance in developing polymer-based nanofibers with tunable and diverse properties presented as good surface area, morphology, porosity, and fiber diameters during fabrication. In this work, we have developed an electrospun sodium alginate (SA) incorporated with pulverized Moringa oleifera seed powder (PMO) as a potential natural biosorbent material for water treatment applications. The developed fibers when observed using a scanning electron microscope (SEM), presented pure sodium alginate with smooth fiber (SAF) characteristics of an average diameter of about 515.09 nm (±114.33). Addition of pulverized Moringa oleifera at 0.5%, 2%, 4%, 6%, and 8% (w/w) reduces the fiber diameter to an average of about 240 nm with a few spindle-like pulverized Moringa oleifera particles beads of 300 nm (±77.97) 0.5% particle size and 110 nm (±32.19) with the clear observation of rougher spindle-like pulverized Moringa oleifera particle beads of 680 nm (±131.77) at 8% of alginate/Moringa oleifera fiber (AMF). The results from the rheology presented characteristic shear-thinning or pseudoplastic behaviour with a decline in viscosity, with characteristic behaviour as the shear rate increases, indicative of an ideal polymer solution suitable for the spinning process. Fourier transform infrared spectroscopy (FT-IR) shows the presence of amine and amide functional groups are prevalent on the alginate-impregnated moringa with water stability nanofibers and thermogravimetric analysis (TGA) with change in degradation properties in a clear indication and successful incorporation of the Moringa oleifera in the electrospun fiber. The key findings from this study position nanofibers as sustainable composites fiber for potential applications in water treatment, especifically heavy metal adsorption.

Fibrous matrices facilitate pleurocidin killing of wound associated bacterial pathogens

Conventional wound infection treatments neither actively promote wound healing nor address the growing problem of antibacterial resistance. Antimicrobial peptides (AMPs) are natural defense molecules, released from host cells, which may be rapidly bactericidal, modulate host-immune responses, and/or act as endogenous mediators for wound healing. However, their routine clinical use has hitherto been hindered due to their instability in the wound environment. Here we describe an electrospun carrier system for topical application of pleurocidin, demonstrating sufficient AMP release from matrices to kill wound-associated pathogens including Acinetobacter baumannii and Pseudomonas aeruginosa. Pleurocidin can be incorporated into polyvinyl alcohol (PVA) fiber matrices, using coaxial electrospinning, without major drug loss with a peptide content of 0.7% w/w predicted sufficient to kill most wound associated species. Pleurocidin retains its activity on release from the electrospun fiber matrix and completely inhibits growth of two strains of A. baumannii (AYE; ATCC 17978) and other ESKAPE pathogens. Inhibition of P. aeruginosa strains (PAO1; NCTC 13437) is, however, matrix weight per volume dependent, with only larger/thicker matrices maintaining complete inhibition. The resulting estimation of pleurocidin release from the matrix reveals high efficiency, facilitating a greater AMP potency. Wound matrices are often applied in parallel or sequentially with the use of standard wound care with biocides, therefore the presence and effect of biocides on pleurocidin potency was tested. It was revealed that combinations displayed additive or modestly synergistic effects depending on the biocide and pathogens which should be considered during the therapy. Taken together, we show that electrospun, pleurocidin-loaded wound matrices have potential to be investigated for wound infection treatment.

Synergistic Combination of Antimicrobial Peptides and Cationic Polyitaconates in Multifunctional PLA Fibers

Combining different antimicrobial agents has emerged as a promising strategy to enhance efficacy and address resistance evolution. In this study, we investigated the synergistic antimicrobial effect of a cationic biobased polymer and the antimicrobial peptide (AMP) temporin L, with the goal of developing multifunctional electrospun fibers for potential biomedical applications, particularly in wound dressing. A clickable polymer with pendent alkyne groups was synthesized by using a biobased itaconic acid building block. Subsequently, the polymer was functionalized through click chemistry with thiazolium groups derived from vitamin B1 (PTTIQ), as well as a combination of thiazolium and AMP temporin L, resulting in a conjugate polymer-peptide (PTTIQ-AMP). The individual and combined effects of the cationic PTTIQ, Temporin L, and PTTIQ-AMP were evaluated against Gram-positive and Gram-negative bacteria as well as Candida species. The results demonstrated that most combinations exhibited an indifferent effect, whereas the covalently conjugated PTTIQ-AMP displayed an antagonistic effect, potentially attributed to the aggregation process. Both antimicrobial compounds, PTTIQ and temporin L, were incorporated into poly(lactic acid) electrospun fibers using the supercritical solvent impregnation method. This approach yielded fibers with improved antibacterial performance, as a result of the potent activity exerted by the AMP and the nonleaching nature of the cationic polymer, thereby enhancing long-term effectiveness.

Highly active nisin coated polycaprolactone electrospun fibers against both Staphylococcus aureus and Pseudomonas aeruginosa

In this study, a wound dressing of electrospun polycaprolactone (PCL) fibers incorporating the antimicrobial peptide (AMP) nisin was fabricated. Nisin was physically adsorbed to the PCL fibers and tested for antibacterial activity against both Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). The PCL fibers had an average diameter of 1.16 μm ± 0.42 μm and no significant change in diameter occurred after nisin adsorption. X-ray photoelectron spectroscopy (XPS) analysis of the fibers detected nitrogen indicative of adsorbed nisin and the signal was used to quantify the levels of coverage on the fiber surfaces. In vitro nisin release studies showed a burst release profile with 80 % of the nisin being released from the fibers within 30 min. Air plasma pre-treatment of the PCL fibers to render them hydrophilic improved nisin loading and release. Antibacterial testing was performed using minimum inhibitory concentration (MIC) and surface attachment assays. The released nisin remained active against both Gram positive S. aureus and Gram negative P. aeruginosa, which has previously been difficult to achieve with single polymer fiber systems. Mammalian cell culture of the nisin coated fibers with L-929 mouse fibroblasts and human epidermal keratinocytes (HEKa) showed that the nisin did not have a significant effect on the biocompatibility of the PCL fibers. The results presented here demonstrate that the physical adsorption, which is a post-treatment, overcomes the potential limitations of harsh chemicals and fabrication conditions of electrospinning from organic solvents and provides a drug loading system having effective antibacterial properties in wound dressings.

In Situ Precision Cell Electrospinning as an Efficient Stem Cell Delivery Approach for Cutaneous Wound Healing

Mesenchymal stem cell (MSC) therapies have been brought forward as a promising treatment modality for cutaneous wound healing. However, current approaches for stem cell delivery have many drawbacks, such as lack of targetability and cell loss, leading to poor efficacy of stem cell therapy. To overcome these problems, in the present study, an in situ cell electrospinning system is developed as an attractive approach for stem cell delivery. MSCs have a high cell viability of over 90% even with a high applied voltage of 15 kV post-cell electrospinning process. In addition, cell electrospinning does not show any negative effect on the surface marker expression and differentiation capacity of MSCs. In vivo studies demonstrate that in situ cell electrospinning treatment can promote cutaneous wound healing through direct deposition of bioactive fish gelatin fibers and MSCs onto wound sites, leading to a synergic therapeutic effect. The approach enhances extracellular matrix remodeling by increasing collagen deposition, promotes angiogenesis by increasing the expression of vascular endothelial growth factor (VEGF) and forming small blood vessels, and dramatically reduces the expression of interleukin-6 (IL-6) during wound healing. The use of in situ cell electrospinning system potentially provides a rapid, no touch, personalized treatment for cutaneous wound healing.

Bromelain- and Silver Nanoparticle-Loaded Polycaprolactone/Chitosan Nanofibrous Dressings for Skin Wound Healing

A cutaneous wound is caused by various injuries in the skin, which can be wrapped with an efficient dressing. Electrospinning is a straightforward adjustable technique that quickly and continuously generates nanofibrous wound dressings containing antibacterial and anti-inflammatory agents to promote wound healing. The present study investigated the physicochemical and biological properties of bromelain (BRO)- and silver nanoparticle (Ag NPs)-loaded gel-based electrospun polycaprolactone/chitosan (PCL/CS) nanofibrous dressings for wound-healing applications. Electron microscopy results showed that the obtained nanofibers (NFs) had a uniform and homogeneous morphology without beads with an average diameter of 176 ± 63 nm. The FTIR (Fourier transform infrared) analysis exhibited the loading of the components. Moreover, adding BRO and Ag NPs increased the tensile strength of the NFs up to 4.59 MPa. BRO and Ag NPs did not significantly affect the hydrophilicity and toxicity of the obtained wound dressing; however, the antibacterial activity against E. coli and S. aureus bacteria was significantly improved. The in vivo study showed that the wound dressing containing BRO and Ag NPs improved the wound-healing process within one week compared to other groups. Therefore, gel-based PCL/CS nanofibrous dressings containing BRO and Ag NPs could be a promising solution for healing skin wounds.

Development of Neuropeptide Hemokinin-1 Analogues with Antimicrobial and Wound-Healing Activity

Wound healing is a complex process that can be delayed in some pathological conditions, such as infection and diabetes. Following skin injury, the neuropeptide substance P (SP) is released from peripheral neurons to promote wound healing by multiple mechanisms. Human hemokinin-1 (hHK-1) has been identified as an SP-like tachykinin peptide. Surprisingly, hHK-1 shares similar structural features with antimicrobial peptides (AMPs), but it does not display efficient antimicrobial activity. Therefore, a series of hHK-1 analogues were designed and synthesized. Among these analogues, AH-4 was found to display the greatest antimicrobial activity against a broad spectrum of bacteria. Furthermore, AH-4 rapidly killed bacteria by membrane disruption, similar to most AMPs. More importantly, AH-4 showed favorable healing activity in all tested mouse full-thickness excisional wound models. Overall, this study suggests that the neuropeptide hHK-1 can be used as a desirable template for developing promising therapeutics with multiple functions for wound healing.

Antibacterial and antioxidant double-layered nanofibrous mat promotes wound healing in diabetic rats

Diabetic wounds are problematic to heal owing to microbial infections as well as decreased proliferation and high concentrations of reactive oxygen species. In this study, a double-layered nanofibrous mat containing grape seed extract (GSE) and silver sulfadiazine (SSD) was fabricated. A synthetic biodegradable polymer, e.g., polycaprolactone (PCL), and a natural material (i.e., collagen) were employed as wound dressing substances. The results showed that GSE possesses antioxidant activity which can be helpful in reducing free radicals. The platform exhibited antibacterial activity against gram-positive and -negative bacteria. The double-layered nanofibrous mat containing GSE and SSD not only was not toxic but also amplified the cell proliferation compared to a pure mat, showing the effect of plant extract. After induction of a round wound, the animals were divided into three groups, namely (1) normal group (receiving + GSE/-GSE nanofiber), (2) diabetic group (receiving + GSE/-GSE nanofiber), and (3) control group (receiving gauze). In vivo evaluation demonstrated no significant differences in the healing process of normal rats. Surprisingly, fully repaired skin was observed on day 14 in the double-layered nanofibrous mat containing GSE in the normal and diabetic groups whereas the wound of diabetic rats treated with pure mat was not completely healed. The macroscopic and microscopic results after 14 days showed the following order in wound repair: Normal/ + GES > Diabetic/ + GSE > Normal/-GES > Diabetic/-GSE > control (with gauze) (p < 0.05). Accordingly, the double-layered nanofibrous mat containing GSE and SSD used in the present study could be considered as a suitable wound dressing in order to shorten healing time and prevent infection during the wound healing process.

Biodegradable Electrospun Scaffolds as an Emerging Tool for Skin Wound Regeneration: A Comprehensive Review

Skin is designed to protect various tissues, and because it is the largest and first human bodily organ to sustain damage, it has an incredible ability to regenerate. On account of extreme injuries or extensive surface loss, the normal injury recuperating interaction might be inadequate or deficient, bringing about risky and disagreeable circumstances that request the utilization of fixed adjuvants and tissue substitutes. Due to their remarkable biocompatibility, biodegradability, and bioactive abilities, such as antibacterial, immunomodulatory, cell proliferative, and wound mending properties, biodegradable polymers, both synthetic and natural, are experiencing remarkable progress. Furthermore, the ability to convert these polymers into submicrometric filaments has further enhanced their potential (e.g., by means of electrospinning) to impersonate the stringy extracellular grid and permit neo-tissue creation, which is a basic component for delivering a mending milieu. Together with natural biomaterial, synthetic polymers are used to solve stability problems and make scaffolds that can dramatically improve wound healing. Biodegradable polymers, commonly referred to as biopolymers, are increasingly used in other industrial sectors to reduce the environmental impact of material and energy usage as they are fabricated using renewable biological sources. Electrospinning is one of the best ways to fabricate nanofibers and membranes that are very thin and one of the best ways to fabricate continuous nanomaterials with a wide range of biological, chemical, and physical properties. This review paper concludes with a summary of the electrospinning (applied electric field, needle-to-collector distance, and flow rate), solution (solvent, polymer concentration, viscosity, and solution conductivity), and environmental (humidity and temperature) factors that affect the production of nanofibers and the use of bio-based natural and synthetic electrospun scaffolds in wound healing.

Recent Advances in Using Natural Antibacterial Additives in Bioactive Wound Dressings

Wound care is a global health issue with a financial burden of up to US $96.8 billion annually in the USA alone. Chronic non-healing wounds which show delayed and incomplete healing are especially problematic. Although there are more than 3000 dressing types in the wound management market, new developments in more efficient wound dressings will require innovative approaches such as embedding antibacterial additives into wound-dressing materials. The lack of novel antibacterial agents and the misuse of current antibiotics have caused an increase in antimicrobial resistance (AMR) which is estimated to cause 10 million deaths by 2050 worldwide. These ongoing challenges clearly indicate an urgent need for developing new antibacterial additives in wound dressings targeting microbial pathogens. Natural products and their derivatives have long been a significant source of pharmaceuticals against AMR. Scrutinising the data of newly approved drugs has identified plants as one of the biggest and most important sources in the development of novel antibacterial drugs. Some of the plant-based antibacterial additives, such as essential oils and plant extracts, have been previously used in wound dressings; however, there is another source of plant-derived antibacterial additives, i.e., those produced by symbiotic endophytic fungi, that show great potential in wound dressing applications. Endophytes represent a novel, natural, and sustainable source of bioactive compounds for therapeutic applications, including as efficient antibacterial additives for chronic wound dressings. This review examines and appraises recent developments in bioactive wound dressings that incorporate natural products as antibacterial agents as well as advances in endophyte research that show great potential in treating chronic wounds.

Dendritic Nanogels Directed Dual-Encapsulation Topical Delivery System of Antimicrobial Peptides Targeting Skin Infections

Antimicrobial peptides (AMPs) are promising antibacterial agents in the fight against multidrug resistant pathogens. However, their application to skin infections is limited by the absence of a realizable topical delivery strategy. Herein, a hybrid hierarchical delivery system for topical delivery of AMPs is accomplished through the incorporation of AMPs into dendritic nanogels (DNGs) and their subsequent embedding into poloxamer gel. The high level of control over the crosslink density and the number of chosen functionalities makes DNGs ideal capsules with tunable loading capacity for DPK-060, a human kininogen-derived AMP. Once embedded into the poloxamer gel, DPK-060 encapsulated in DNGs displays a slower release rate compared to those entrapped directly in the gels. In vitro EpiDerm Skin Irritation Tests show good biocompatibility, while MIC and time-kill curves reveal the potency of the peptide toward Staphylococcus aureus. Anti-infection tests on ex vivo pig skin and in vivo mouse infection models demonstrate that formulations with 0.5% and 1% AMPs significantly inhibit the growth of S. aureus. Similar outcomes are observed for an in vivo mouse surgical site infection model. Importantly, when normalizing the bacteria inhibition to released/free DPK-060 at the wound site, all formulations display superior efficacy compared to DPK-060 in solution.

Therapeutic applications of electrospun nanofibers impregnated with various biological macromolecules for effective wound healing strategy - A review

A Non-healing infected wound is an ever-growing global epidemic, with increasing burden of mortality rates and management costs. The problems of chronic wound infections and their outcomes will continue as long as their underlying causes like diabetic wounds grow and spread. Commercial wound therapies employed have limited potential that inhibits pivotal functions and tissue re-epithelialization properties resulting in wound infections. Nanomaterial based drug delivery formulations involving biological macromolecules are developing areas of interest in wound healing applications which are utilized in the re-epithelialization of skin with cost-effective preparations. Research conducted on nanofibers has shown enhanced skin establishment with improved cell proliferation and growth and delivery of bioactive organic molecules at the wound site. However, drug targeted delivery with anti-scarring properties and tissue regeneration aspects have not been updated and discussed in the case of macromolecule impregnated nanofibrous mats. Hence, this review focuses on the brief concepts of wound healing and wound management, therapeutic commercialized wound dressings currently available in the field of wound care, effective electrospun nanofibers impregnated with different biological macromolecules and advancement of nanomaterials for tissue engineering have been discussed. These new findings will pave the way for producing anti-scarring high effective wound scaffolds for drug delivery.

Solvent modulation in peptide sub-microfibers obtained by solution blow spinning

Peptides possess high chemical diversity at the amino acid sequence level, which further translates into versatile functions. Peptides with self-assembling properties can be processed into diverse formats giving rise to bio-based materials. Peptide-based spun fibers are an interesting format due to high surface-area and versatility, though the field is still in its infancy due to the challenges in applying the synthetic polymer spinning processes to protein fibers to peptides. In this work we show the use of solution blow-spinning to produce peptide fibers. Peptide fiber formation was assisted by the polymer poly (vinyl pyrrolidone) (PVP) in two solvent conditions. Peptide miscibility and further self-assembling propensity in the solvents played a major role in fiber formation. When employing acetic acid as solvent, peptide fibers (0.5 μm) are formed around PVP fibers (0.75 μm), whereas in isopropanol only one type of fibers are formed, consisting of mixed peptide and PVP (1 μm). This report highlights solvent modulation as a mean to obtain different peptide sub-microfibers via a single injection nozzle in solution blow spinning. We anticipate this strategy to be applied to other small peptides with self-assembly propensity to obtain multi-functional proteinaceous fibers.

A Straightforward Approach towards Antibacterial and Anti-Inflammatory Multifunctional Nanofiber Membranes with Sustained Drug Release Profiles

Preventing bacterial infection and controlling the inflammatory response occupy important positions in wound treatment. Although loading wound dressings with antibacterial or anti-inflammatory drugs/molecules is an effective approach to address these issues, simultaneous sustained release of these drugs remains challenging. Herein, hydrophilic polyhexamethylene guanidine hydrochloride (PHGC) and hydrophobic indomethacin (Indo) are loaded in hydrophilic polyvinyl alcohol (PVA) and hydrophobic polycaprolactone (PCL) nanofibers respectively by bidirectional electrospinning to form an antibacterial and anti-inflammatory PCL-Indo/PVA-PHGC wound dressing. The fabricated nanofiber membrane exhibits 100% disinfection activity to both Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria because of the release of the broad-spectrum antibacterial molecule PHGC. Additionally, the loading of Indo in the nanofiber membrane enhances the expression level of IL-10, while inhibiting those of IL-6 and TNF-α in the RAW264.7 mouse cells. In the interwoven membrane of PCL and PVA fibers, the release of hydrophobic Indo is hindered by hydrophilic PHGC and PVA fibers, and similarly, the release of hydrophilic PHGC is hindered by hydrophobic Indo and PCL fibers. In conclusion, the PCL-Indo/PVA-PHGC nanofiber membrane has excellent antibacterial, anti-inflammatory, and sustained-release effects, and thus regulates the immune microenvironment of the cells to potentially promote wound healing.

Antimicrobial peptides for bone tissue engineering: Diversity, effects and applications

Bone tissue engineering has been becoming a promising strategy for surgical bone repair, but the risk of infection during trauma repair remains a problematic health concern worldwide, especially for fracture and infection-caused bone defects. Conventional antibiotics fail to effectively prevent or treat bone infections during bone defect repair because of drug-resistance and recurrence, so novel antibacterial agents with limited resistance are highly needed for bone tissue engineering. Antimicrobial peptides (AMPs) characterized by cationic, hydrophobic and amphipathic properties show great promise to be used as next-generation antibiotics which rarely induce resistance and show potent antibacterial efficacy. In this review, four common structures of AMPs (helix-based, sheet-based, coil-based and composite) and related modifications are presented to identify AMPs and design novel analogs. Then, potential effects of AMPs for bone infection during bone repair are explored, including bactericidal activity, anti-biofilm, immunomodulation and regenerative properties. Moreover, we present distinctive applications of AMPs for topical bone repair, which can be either used by delivery system (surface immobilization, nanoparticles and hydrogels) or used in gene therapy. Finally, future prospects and ongoing challenges are discussed.

Understanding the Origin of Tensile Response in a Graphene Textile Strain Sensor with Negative Differential Resistance

The flexible strain sensors based on the textile substrate have natural flexibility, high sensitivity, and wide-range tensile response. However, the textile's complex and anisotropic substructure leads to a negative differential resistance (NDR) response, lacking a deeper understanding of the mechanism. Therefore, we examined a graphene textile strain sensor with a conspicuous NDR tensile response, providing a requisite research platform for mechanism investigation. The pioneering measurement of single fiber bundles confirmed the existence of the NDR effect on the subgeometry scale. Based on the in situ characterization of tensile morphology and measurement, we conducted quantitative behavior analyses to reveal the origin of tensile electrical responses in the full range comprehensively. The results showed that the dominant factor in generating the NDR effect is the relative displacement of fibers within the textile bundles. Based on the neural spiking-like tensile response, we further demonstrated the application potential of the textile strain sensor in threshold detection and near-sensor signal processing. The proposed NDR behavior model would provide a reference for the design and application of wearable intelligent textiles.

Electrospun fibers loaded with antimicrobial peptides for treatment of wound infections

The widespread resistance of clinically relevant bacteria against established antibiotics emphasizes the urgent need for novel therapeutics. In this context, wound infections constitute a specific challenge, as most systemically applied antibiotics are insufficiently available at the site of infection. Therefore, the local treatment of infected wounds poses a particular challenge regarding the appropriate release kinetics of actives and their residence time in the wound bed. Consequently, design and development of novel, drug-loaded wound dressings constitute a major research focus for the effective treatment of wound infections. In this study, we employed electrospinning to design drug-loaded wound dressings, incorporating the therapeutically promising antimicrobial peptide tyrothricin. By parallel electrospinning, we combined different ratios of water-soluble polyvinyl pyrrolidone and water-insoluble methacrylate copolymer (EudragitE), in order to take advantage of their specific mechanical stability and dissolution properties. We fabricated fiber mats constituting mechanically stable wound dressings with a controlled drug release profile, combining an initial burst release above the minimal inhibitory concentration of known wound pathogens and a subsequent prolonged antimicrobial effect of the active ingredient. Antimicrobial activity against Staphylococcusaureus and Staphylococcusepidermidis was successfully proven, thereby introducing our tyrothricin-loaded fiber mats as a promising prospective therapy against typical wound-associated pathogens.

The potential application of natural products in cutaneous wound healing: A review of preclinical evidence

Under normal circumstances, wound healing can be summarized as three processes. These include inflammation, proliferation, and remodeling. The vast majority of wounds heal rapidly; however, a large percentage of nonhealing wounds have still not been studied significantly. The factors affecting wound nonhealing are complex and diverse, and identifying an effective solution from nature becomes a key goal of research. This study aimed to highlight and review the mechanisms and targets of natural products (NPs) for treating nonhealing wounds. The results of relevant studies have shown that the effects of NPs are associated with PI3K-AKT, P38MAPK, fibroblast growth factor, MAPK, and ERK signaling pathways and involve tumor growth factor (TNF), vascular endothelial growth factor, TNF-α, interleukin-1β, and expression of other cytokines and proteins. The 25 NPs that contribute to wound healing were systematically summarized by an inductive collation of the six major classes of compounds, including saponins, polyphenols, flavonoids, anthraquinones, polysaccharides, and others, which will further direct the attention to the active components of NPs and provide research ideas for further development of new products for wound healing.

Development of a Hot-Melt-Extrusion-Based Spinning Process to Produce Pharmaceutical Fibers and Yarns

Fibers and yarns are part of everyday life. So far, fibers that are also used pharmaceutically have mainly been produced by electrospinning. The common use of spinning oils and the excipients they contain, in connection with production by melt extrusion, poses a regulatory challenge for pharmaceutically usable fibers. In this publication, a newly developed small-scale direct-spinning melt extrusion system is described, and the pharmaceutically useful polyvinyl filaments produced with it are characterized. The major parts of the system were newly developed or extensively modified and manufactured cost-effectively within a short time using rapid prototyping (3D printing) from various materials. For example, a stainless-steel spinneret was developed in a splice design for a table-top melt extrusion system that can be used in the pharmaceutical industry. The direct processing of the extruded fibers was made possible by a spinning system developed called Spinning-Rosi, which operates continuously and directly in the extrusion process and eliminates the need for spinning oils. In order to prevent instabilities in the product, further modifications were also made to the process, such as a the moisture encapsulation of the melt extrusion line at certain points, which resulted in a bubble-free extrudate with high tensile strength, even in a melt extrusion line without built-in venting.

Guanidinium-rich lipopeptide functionalized bacteria-absorbing sponge as an effective trap-and-kill system for the elimination of focal bacterial infection

Focal bacterial infections are often difficult to treat due to the rapid emergence of antibiotic-resistant bacteria, high risk of relapse, and severe inflammation at local lesions. To address multidrug-resistant skin and soft tissue infections, a bacteria-absorbing sponge was prepared to involve a "trap-and-kill" mechanism. The system describes a guanidinium-rich lipopeptide functionalized lyotropic liquid-crystalline hydrogel with bicontinuous cubic networks. Amphiphilic lipopeptides can be spontaneously anchored to the lipid-water interface, exposing their bacterial targeting sequences to enhance antibacterial trapping/killing activity. Computational simulations supported our structural predictions, and the sponge was confirmed to successfully remove ∼98.8% of the bacteria in the medium. Release and degradation behavior studies indicated that the bacteria-absorbing sponge could degrade, mediate enzyme-responsive lipopeptide release, or generate ∼200 nm lipopeptide nanoparticles with environmental erosion. This implies that the sponge can effectively capture and isolate high concentrations of bacteria at the infected site and then sustainably release antimicrobial lipopeptides into deep tissues for the eradication of residual bacteria. In the animal experiment, we found that the antibacterial performance of the bacterial-absorbing sponge was significant, which demonstrated not only a long-term inhibition effect to disinfect and avoid bacterial rebound, but also a unique advantage to protect tissue from bacterial attack. STATEMENT OF SIGNIFICANCE: Host defense peptides/peptidomimetics (HDPs) have shown potential for the elimination of focal bacterial infections, but the application of their topical formulations suffers from time-consuming preparation processes, indistinctive toxicity reduction effects, and inefficient bacterial capture ability. To explore new avenues for the development of easily prepared, low-toxicity and high-efficiency topical antimicrobials, a guanidinium-rich lipopeptide was encapsulated in a lyotropic liquid-crystalline hydrogel (denoted as "bacteria-absorbing sponge") to achieve complementary superiorities. The superior characteristic of the bacteria-absorbing sponge involves a "trap-and-kill" mechanism, which undergoes not only a long-term inhibition effect to disinfect and avoid bacterial rebound, but also effective bacterial capture and isolating action to confine bacterial diffusion and protect tissues from bacterial attack.

Progress in hydrogels for skin wound repair

As the first defensive line between the human body and the outside world, the skin is vulnerable to damage from the external environment. Skin wounds can be divided into acute wounds (mechanical injuries, chemical injuries and surgical wounds, etc.) and chronic wounds (burns, infections, diabetes, etc.). In order to manage skin wound, a variety of wound dressings have been developed, including gauze, films, foams, nanofibers, hydrocolloids and hydrogels. Recently, hydrogels have received much attention because of their natural extracellular matrix (ECM)-mimik structure, tunable mechanical properties, and facile bioactive substance delivery capability. They show great potential application in skin wound repair. This paper first introduces the anatomy and function of the skin, the process of wound healing and conventional wound dressings, and then introduces the composition and construction methods of hydrogels. Next, this paper introduces the necessary properties of hydrogels in skin wound repair and the latest research progress of hydrogel dressings for skin wound repair. Finally, the future development goals of hydrogel materials in the field of wound healing are proposed. This article is protected by copyright. All rights reserved.

Melittin from Bee Venom Encapsulating Electrospun Fibers as a Potential Antimicrobial Wound Dressing Patches for Skin Infections

Skin infection compromises the body’s natural defenses. Several antibiotics are no longer effective owing to the evolution of antimicrobial-resistant (AMR) bacteria, hence, the constant development of novel antibacterial agents. Naturally occurring antibacterial agents may be potential candidates for AMR bacterial infection treatments; however, caution should be taken when administering such agents due to the high incidence of toxicity. A fibrous material system from a biocompatible polymer that could be used as a skin patch for skin infections treatment caused by AMR bacteria is proposed in this study. Bee venom’s active ingredient, melittin, was fabricated using electrospinning technology. Scanning electron microscopy showed that melittin-loaded fibers had smooth surfaces with no signs of beads or pores. The average diameter of this fibrous system was measured to be 1030 ± 160 nm, indicating its successful preparation. The melittin fibers’ drug loading and entrapment efficiency (EE%) were 49 ± 3 µg/mg and 84 ± 5%, respectively. This high EE% can be another successful preparatory criterion. An in vitro release study demonstrated that 40% of melittin was released after 5 min and achieved complete release after 120 min owing to the hydrophilic nature of the PVP polymer. A concentration of ≤10 µg/mL was shown to be safe for use on human dermal fibroblasts HFF-1 after 24-h exposure, while an antibacterial MIC study found that 5 μg/mL was the effective antimicrobial concentration for S. aureus, A. baumannii, E. coli and Candida albicans yeast. A melittin-loaded fibrous system demonstrated an antibacterial zone of inhibition equivalent to the control (melittin discs), suggesting its potential use as a wound dressing patch for skin infections.

Polymer Conjugates of Antimicrobial Peptides (AMPs) with d-Amino Acids (d-aa): State of the Art and Future Opportunities

In recent years, antimicrobial peptides (AMPs) have enjoyed a renaissance, as the world is currently facing an emergency in terms of severe infections that evade antibiotics’ treatment. This is due to the increasing emergence and spread of resistance mechanisms. Covalent conjugation with polymers is an interesting strategy to modulate the pharmacokinetic profile of AMPs and enhance their biocompatibility profile. It can also be an effective approach to develop active coatings for medical implants and devices, and to avoid biofilm formation on their surface. In this concise review, we focus on the last 5 years’ progress in this area, pertaining in particular to AMPs that contain d-amino acids, as well as their role, and the advantages that may arise from their introduction into AMPs.

A pilot and open trial to evaluate topical Bacterial Cellulose bio-curatives in the treatment of cutaneous leishmaniasis caused by L. braziliensis

The treatment of cutaneous leishmaniasis (CL) in Brazil using pentavalent antimony (Sb^v) is associated with a high failure rate and long time to heal. Moreover, standard Sb^v treatment cures only 50-60% of the cases. In this pilot clinical trial, we evaluated the topical use of bacterial cellulose (BC) bio-curatives + Sb^v in the treatment of CL caused by L. braziliensis, in Bahia, Brazil. A total of 20 patients were randomized in two groups assigned to receive either parenteral Sb^v alone or parenteral Sb^v plus topically applied BC bio-curatives. CL patients treated with Sb^v + topical BC bio-curatives had a significantly higher cure rate at 60 days post initiation of treatment compared to CL patients treated with Sb^v alone (P=0.01). At day 90 post initiation of treatment, cure rate was similar in the two groups as was overall healing time. Adverse effects or local reactions to topical BC application were not observed. This pilot trial shows that the potential use of a combined therapy consisting of topical BC bio-curatives and parenteral Sb^v in favoring healing of CL lesions caused by L. braziliensis, at an early time point.

Optical clearing of tissues: Issues of antimicrobial phototherapy and drug delivery

This review presents principles and novelties in the field of tissue optical clearing (TOC) technology, as well as application for optical monitoring of drug delivery and effective antimicrobial phototherapy. TOC is based on altering the optical properties of tissue through the introduction of immersion optical cleaning agents (OCA), which impregnate the tissue of interest. We also analyze various methods and kinetics of delivery of photodynamic agents, nanoantibiotics and their mixtures with OCAs into the tissue depth in the context of antimicrobial and antifungal phototherapy. In vitro and in vivo studies of antimicrobial phototherapies, such as photodynamic, photothermal plasmonic and photocatalytic, are summarized, and the prospects of a new TOC technology for effective killing of pathogens are discussed.

Antimicrobial peptide-based materials: opportunities and challenges

The multifunctional properties of antimicrobial peptides (AMPs) make them attractive candidates for the treatment of various diseases. AMPs are considered alternatives to antibiotics due to the rising number of multidrug-resistant...

Collagen-Based Nanofibers for Skin Regeneration and Wound Dressing Applications

Skin regeneration after an injury is very vital, but this process can be impeded by several factors. Regenerative medicine is a developing biomedical field with the potential to decrease the need for an organ transplant. Wound management is challenging, particularly for chronic injuries, despite the availability of various types of wound dressing scaffolds in the market. Some of the wound dressings that are in clinical practice have various drawbacks such as poor antibacterial and antioxidant efficacy, poor mechanical properties, inability to absorb excess wound exudates, require frequent change of dressing and fails to offer a suitable moist environment to accelerate the wound healing process. Collagen is a biopolymer and a major constituent of the extracellular matrix (ECM), making it an interesting polymer for the development of wound dressings. Collagen-based nanofibers have demonstrated interesting properties that are advantageous both in the arena of skin regeneration and wound dressings, such as low antigenicity, good biocompatibility, hemostatic properties, capability to promote cellular proliferation and adhesion, and non-toxicity. Hence, this review will discuss the outcomes of collagen-based nanofibers reported from the series of preclinical trials of skin regeneration and wound healing.

Fabrication and characterization of an antibacterial chitosan/silk fibroin electrospun nanofiber loaded with a cationic peptide for wound-dressing application

Wound infections are still problematic in many cases and demand new alternatives for current treatment strategies. In recent years, biomaterials-based wound dressings have received much attention due to their potentials and many studies have been performed based on them. Accordingly, in this study, we fabricated and optimized an antibacterial chitosan/silk fibroin (CS/SF) electrospun nanofiber bilayer containing different concentrations of a cationic antimicrobial peptide (AMP) for wound dressing applications. The fabricated CS/SF nanofiber was fully characterized and compared to the electrospun silk fibroin and electrospun chitosan alone in vitro. Then, the release rate of different concentrations of peptide (16, 32, and 64 µg/ml) from peptide-loaded CS/SF nanofiber was investigated. Finally, based on cytotoxic activity, the antibacterial activity of scaffolds containing 16 and 32 µg/ml of the peptide was evaluated against standard and multi-drug resistant strains of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa isolated from burn patients. The peptide-loaded CS/SF nanofiber displayed appropriate mechanical properties, high water uptake, suitable biodegradation rate, a controlled release without cytotoxicity on Hu02 human foreskin fibroblast cells at the 16 and 32 µg/ml concentrations of peptide. The optimized CS/SF containing 32 μg/ml peptide showed strong antibacterial activity against all experimental strains from standard to resistance. The results showed that the fabricated antimicrobial nanofiber has the potential to be applied as a wound dressing for infected wound healing, although further studies are needed in vivo.

Nanofibers as drug-delivery systems for antimicrobial peptides

Microbial infections are a major worldwide public health problem because a number of microorganisms can show drug resistance. Antimicrobial peptides (AMPs) are small biomolecules that present antimicrobial and immunomodulatory activities. Despite their great potential, there are still many barriers to the formulation of these molecules. In this context, nanotechnological approaches such as nanofibers are candidate drug-delivery systems for AMP formulations. These nanomaterials have a large contact surface and may carry several AMPs (single or multilayer), directing them to specific targets. Thus, this review describes the main advances related to the use of nanofibers as drug-delivery systems for AMPs. These strategies can contribute directly to the design of new multifunctional wound dressings, coatings for prostheses, and tissue engineering applications.

Characteristics and therapeutic applications of antimicrobial peptides

The demand for novel antimicrobial compounds is rapidly growing due to the phenomenon of antibiotic resistance in bacteria. In response, numerous alternative approaches are being taken including use of polymers, metals, combinatorial approaches, and antimicrobial peptides (AMPs). AMPs are a naturally occurring part of the immune system of all higher organisms and display remarkable broad-spectrum activity and high selectivity for bacterial cells over host cells. However, despite good activity and safety profiles, AMPs have struggled to find success in the clinic. In this review, we outline the fundamental properties of AMPs that make them effective antimicrobials and extend this into three main approaches being used to help AMPs become viable clinical options. These three approaches are the incorporation of non-natural amino acids into the AMP sequence to impart better pharmacological properties, the incorporation of AMPs in hydrogels, and the chemical modification of surfaces with AMPs for device applications. These approaches are being developed to enhance the biocompatibility, stability, and/or bioavailability of AMPs as clinical options.

Current approaches and future prospects of nanofibers: a special focus on antimicrobial drug delivery

Antibacterial nanofibers have a great potential for effective treatment of infections. They act as drug reservoir systems that release higher quantities of antibacterial agents/drug in a controlled manner at infection sites and prevent drug resistance, while concomitantly decreasing the systemic toxicity. With this drug delivery system, it is also possible to achieve multiple drug entrapment and also simultaneous or sequential release kinetics at the site of action. Therefore, advances in antibacterial nanofibers as drug delivery systems were overviewed within this article. Recently published data on antibacterial drug delivery was also summarised to provide a view of the current state of art in this field. Although antibacterial use seems to be limited and one can ask that 'what is left to be discovered?'; recent update literatures in this field highlighted the use of nanofibers from very different perspectives. We believe that readers will be benefiting this review for enlightening of novel ideas.

Latest Advances on Bacterial Cellulose-Based Antibacterial Materials as Wound Dressings

At present, there are various wound dressings that can protect the wound from further injury or isolate the external environment in wound treatment. Whereas, infection and slow self-healing still exist in wound healing process. Therefore, it is urgent to develop an ideal wound dressing with good biocompatibility and strong antibacterial activity to promote wound healing. Bacterial cellulose is a kind of promising biopolymer because it can control wound exudate and provide a moist environment for wound healing. However, the lack of antibacterial activity limits its application. In this paper, the advantages of bacterial cellulose as wound dressings were introduced, and the preparation and research progress of bacterial cellulose-based antibacterial composites in recent years were reviewed, including adding antibiotics, combining with inorganic antibacterial agents or organic antibacterial agents. Finally, the existing problems and future development direction of bacterial cellulose-based antibacterial wound dressings were discussed.

Bio-Based Electrospun Fibers for Wound Healing

Being designated to protect other tissues, skin is the first and largest human body organ to be injured and for this reason, it is accredited with a high capacity for self-repairing. However, in the case of profound lesions or large surface loss, the natural wound healing process may be ineffective or insufficient, leading to detrimental and painful conditions that require repair adjuvants and tissue substitutes. In addition to the conventional wound care options, biodegradable polymers, both synthetic and biologic origin, are gaining increased importance for their high biocompatibility, biodegradation, and bioactive properties, such as antimicrobial, immunomodulatory, cell proliferative, and angiogenic. To create a microenvironment suitable for the healing process, a key property is the ability of a polymer to be spun into submicrometric fibers (e.g., via electrospinning), since they mimic the fibrous extracellular matrix and can support neo- tissue growth. A number of biodegradable polymers used in the biomedical sector comply with the definition of bio-based polymers (known also as biopolymers), which are recently being used in other industrial sectors for reducing the material and energy impact on the environment, as they are derived from renewable biological resources. In this review, after a description of the fundamental concepts of wound healing, with emphasis on advanced wound dressings, the recent developments of bio-based natural and synthetic electrospun structures for efficient wound healing applications are highlighted and discussed. This review aims to improve awareness on the use of bio-based polymers in medical devices.

Overview of Host Defense Peptides and Their Applications for Plastic and Reconstructive Surgeons

BACKGROUND

Host defense peptides are a family of endogenous short peptides that are found in all living beings and play a critical role in innate immunity against infection.

METHODS

A nonsystematic review of host defense peptides was conducted with specific interest in properties and applications relevant to plastic and reconstructive surgery.

RESULTS

In addition to their direct antimicrobial actions against pathogens, including multidrug-resistant bacteria, they also demonstrate important functions in immunomodulation, tumor cell lysis, and tissue regeneration. These properties have made them a topic of clinical interest for plastic surgeons because of their potential applications as novel antibiotics, wound healing medications, and cancer therapies. The rising clinical interest has led to a robust body of literature describing host defense peptides in great depth and breadth. Numerous mechanisms have been observed to explain their diverse functions, which rely on specific structural characteristics. However, these peptides remain mostly experimental, with limited translation to clinical practice because of numerous failures to achieve acceptable results in human trials.

CONCLUSIONS

Despite the broad ranging potential of these peptides for use in the field of plastic and reconstructive surgery, they are rarely discussed in the literature or at scientific meetings. In this review, the authors provide a summary of the background, structure, function, bacterial resistance, and clinical applications of host defense peptides with the goal of stimulating host defense peptide-based innovation within the field of plastic and reconstructive surgery.

Electrospun Nanocomposites Containing Cellulose and Its Derivatives Modified with Specialized Biomolecules for an Enhanced Wound Healing

Wound healing requires careful, directed, and effective therapies to prevent infections and accelerate tissue regeneration. In light of these demands, active biomolecules with antibacterial properties and/or healing capacities have been functionalized onto nanostructured polymeric dressings and their synergistic effect examined. In this work, various antibiotics, nanoparticles, and natural extract-derived products that were used in association with electrospun nanocomposites containing cellulose, cellulose acetate and different types of nanocellulose (cellulose nanocrystals, cellulose nanofibrils, and bacterial cellulose) have been reviewed. Renewable, natural-origin compounds are gaining more relevance each day as potential alternatives to synthetic materials, since the former undesirable footprints in biomedicine, the environment, and the ecosystems are reaching concerning levels. Therefore, cellulose and its derivatives have been the object of numerous biomedical studies, in which their biocompatibility, biodegradability, and, most importantly, sustainability and abundance, have been determinant. A complete overview of the recently produced cellulose-containing nanofibrous meshes for wound healing applications was provided. Moreover, the current challenges that are faced by cellulose acetate- and nanocellulose-containing wound dressing formulations, processed by electrospinning, were also enumerated.

Topical antimicrobial peptide formulations for wound healing: Current developments and future prospects

Antimicrobial peptides (AMPs) are the natural antibiotics recognized for their potent antibacterial and wound healing properties. Bare AMPs have limited activity following topical application attributable to their susceptibility to environment (hydrolysis, oxidation, photolysis), and wound (alkaline pH, proteolysis) related factors as well as minimal residence time. Therefore, the formulation of AMPs is essential to enhance stability, prolong delivery, and optimize effectiveness at the wound site. Different topical formulations of AMPs have been developed so far including nanoparticles, hydrogels, creams, ointments, and wafers to aid in controlling bacterial infection and enhance wound healing process in vivo. Herein, an overview is provided of the AMPs and current understanding of their formulations for topical wound healing applications along with suitable examples. Furthermore, future prospects for the development of effective combination AMP formulations are discussed. STATEMENT OF SIGNIFICANCE: Chronic wound infection and subsequent development of antibiotic resistance are serious clinical problems affecting millions of people worldwide. Antimicrobial peptides (AMPs) possess great potential in effectively killing the bacteria with minimal risk of resistance development. However, AMPs susceptibility to degradation following topical application limits their antimicrobial and wound healing effects. Therefore, development of an optimized topical formulation with high peptide stability and sustained AMP delivery is necessary to maximize the antimicrobial and wound healing effects. The present review provides an overview of the state-of-art in the field of topical AMP formulations for wound healing. Current developments in the field of topical AMP formulations are reviewed and future prospects for the development of effective combination AMP formulations are discussed.

Wound healing properties of magnesium mineralized antimicrobial nanofibre dressings containing chondroitin sulphate – a comparison between blend and core–shell nanofibres

Effect of chondroitin sulphate incorporated PCL/gelatin as blends or core–shell composite nanofibres are compared in terms of their biocompatibility for skin cells and wound healing in porcine model of partial thickness burns.