Design of Asymmetric Nanofibers-Membranes Based on Polyvinyl Alcohol and Wool-Keratin for Wound Healing Applications

Keratin-containing scaffolds for tissue engineering applications: a review

In tissue engineering and regenerative medicine applications, the utilization of bioactive materials has become a routine tool. The goal of tissue engineering is to create new organs and tissues by combining cell biology, materials science, reactor engineering, and clinical research. As part of the growth pattern for primary cells in an organ, backing material is frequently used as a supporting material. A porous three-dimensional (3D) scaffold can provide cells with optimal conditions for proliferating, migrating, differentiating, and functioning as a framework. Optimizing the scaffolds' structure and altering their surface may improve cell adhesion and proliferation. A keratin-based biomaterials platform has been developed as a result of discoveries made over the past century in the extraction, purification, and characterization of keratin proteins from hair and wool fibers. Biocompatibility, biodegradability, intrinsic biological activity, and cellular binding motifs make keratin an attractive biomaterial for tissue engineering scaffolds. Scaffolds for tissue engineering have been developed from extracted keratin proteins because of their capacity to self-assemble and polymerize into intricate 3D structures. In this review article, applications of keratin-based scaffolds in different tissues including bone, skin, nerve, and vascular are explained based on common methods of fabrication such as electrospinning, freeze-drying process, and sponge replication method.

A review of the current state of natural biomaterials in wound healing applications

Skin, the largest biological organ, consists of three main parts: the epidermis, dermis, and subcutaneous tissue. Wounds are abnormal wounds in various forms, such as lacerations, burns, chronic wounds, diabetic wounds, acute wounds, and fractures. The wound healing process is dynamic, complex, and lengthy in four stages involving cells, macrophages, and growth factors. Wound dressing refers to a substance that covers the surface of a wound to prevent infection and secondary damage. Biomaterials applied in wound management have advanced significantly. Natural biomaterials are increasingly used due to their advantages including biomimicry of ECM, convenient accessibility, and involvement in native wound healing. However, there are still limitations such as low mechanical properties and expensive extraction methods. Therefore, their combination with synthetic biomaterials and/or adding bioactive agents has become an option for researchers in this field. In the present study, the stages of natural wound healing and the effect of biomaterials on its direction, type, and level will be investigated. Then, different types of polysaccharides and proteins were selected as desirable natural biomaterials, polymers as synthetic biomaterials with variable and suitable properties, and bioactive agents as effective additives. In the following, the structure of selected biomaterials, their extraction and production methods, their participation in wound healing, and quality control techniques of biomaterials-based wound dressings will be discussed.

Microemulsion-Based Keratin-Chitosan Gel for Improvement of Skin Permeation/Retention and Activity of Curcumin

Curcumin (Cur) is a kind of polyphenol with a variety of topical pharmacological properties including antioxidant, analgesic and anti-inflammatory activities. However, its low water solubility and poor skin bioavailability limit its effectiveness. In the current study, we aimed to develop microemulsion-based keratin-chitosan gel for the improvement of the topical activity of Cur. The curcumin-loaded microemulsion (CME) was formulated and then loaded into the keratin-chitosan (KCS) gel to form the CME-KCS gel. The formulated CME-KCS gel was evaluated for its characterization, in vitro release, in vitro skin permeation and in vivo activity. The results showed that the developed CME-KCS gel had an orange-yellow and gel-like appearance. The particle size and zeta potential of the CME-KCS gel were 186.45 ± 0.75 nm and 9.42 ± 0.86 mV, respectively. The CME-KCS gel showed desirable viscoelasticity, spreadability, bioadhesion and controlled drug release, which was suitable for topical application. The in vitro skin permeation and retention study showed that the CME-KCS gel had better in vitro skin penetration than the Cur solution and achieved maximum skin drug retention (3.75 ± 0.24 μg/cm²). In vivo experimental results confirmed that the CME-KCS gel was more effective than curcumin-loaded microemulsion (Cur-ME) in analgesic and anti-inflammatory activities. In addition, the CME-KCS gel did not cause any erythema or edema based on a mice skin irritation test. These findings indicated that the developed CME-KCS gel could improve the skin penetration and retention of Cur and could become a promising formulation for topical delivery to treat local diseases.

Hydrogel-Inducing Graphene-Oxide-Derived Core–Shell Fiber Composite for Antibacterial Wound Dressing

The study reveals the polymer–crosslinker interactions and functionality of hydrophilic nanofibers for antibacterial wound coatings. Coaxial electrospinning leverages a drug encapsulation protocol for a core–shell fiber composite with a core derived from polyvinyl alcohol and polyethylene glycol with amorphous silica (PVA-PEG-SiO2), and a shell originating from polyvinyl alcohol and graphene oxide (PVA-GO). Crosslinking with GO and SiO2 initiates the hydrogel transition for the fiber composite upon contact with moisture, which aims to optimize the drug release. The effect of hydrogel-inducing additives on the drug kinetics is evaluated in the case of chlorhexidine digluconate (CHX) encapsulation in the core of core–shell fiber composite PVA-PEG-SiO2-1x-CHX@PVA-GO. The release rate is assessed with the zero, first-order, Higuchi, and Korsmeyer–Peppas kinetic models, where the inclusion of crosslinking silica provides a longer degradation and release rate. CHX medicated core–shell composite provides sustainable antibacterial activity against Staphylococcus aureus.

Advanced Drug Delivery System for Management of Chronic Diabetes Wound Healing

The diabetic wound is excessively vulnerable to infection because the diabetic wound suggests delayed and incomplete healing techniques. Presently, wounds and ulcers related to diabetes have additionally increased the medical burden. A diabetic wound can impair mobility, lead to amputations, or even death. In recent times, advanced drug delivery systems have emerged as promising approaches for enhancing the efficacy of wound healing treatments in diabetic patients. This review aims to provide an overview of the current advancements in drug delivery systems in managing chronic diabetic wound healing. This review begins by discussing the pathophysiological features of diabetic wounds, including impaired angiogenesis, elevated reactive oxygen species, and compromised immune response. These factors contribute to delayed wound healing and increased susceptibility to infection. The importance of early intervention and effective wound management strategies is emphasized. Various types of advanced drug delivery systems are then explored, including nanoparticles, hydrogels, transferosomes, liposomes, niosomes, dendrimers, and nanosuspension with incorporated bioactive agents and biological macromolecules are also utilized for chronic diabetes wound management. These systems offer advantages such as sustained release of therapeutic agents, improved targeting and penetration, and enhanced wound closure. Additionally, the review highlights the potential of novel approaches such as antibiotics, minerals, vitamins, growth factors gene therapy, and stem cell-based therapy in diabetic wound healing. The outcome of advanced drug delivery systems holds immense potential in managing chronic diabetic wound healing. They offer innovative approaches for delivering therapeutic agents, improving wound closure, and addressing the specific pathophysiological characteristics of diabetic wounds.

Wool Keratin Nanofibers for Bioinspired and Sustainable Use in Biomedical Field

Keratin is a biocompatible and biodegradable protein as the main component of wool and animal hair fibers. Keratin-based materials support fibroblasts and osteoblasts growth. Keratin has been extracted by sulphitolysis, a green method (no harmful chemicals) with a yield of 38-45%. Keratin has been processed into nanofibers from its solutions by electrospinning. Electrospinning is a versatile and easy-to-use technique to generate nanofibers. It is an eco-friendly and economical method for the production of randomly and uniaxially oriented polymeric nanofibers. Thanks to their high specific surface area, nanofibers have great potential in the biomedical field. Keratin nanofibers have received significant attention in biomedical applications, such as tissue engineering and cell growth scaffolds, for their biocompatibility and bio-functionality. Accordingly, we propose an extensive overview of recent studies focused on the optimization of keratinbased nanofibers, emphasizing their peculiar functions for cell interactions and the role of additive phases in blends or composite systems to particularize them as a function of specific applications (i.e., antibacterial).

Preparation Methods and Functional Characteristics of Regenerated Keratin-Based Biofilms

The recycling, development, and application of keratin-containing waste (e.g., hair, wool, feather, and so on) provide an important means to address related environmental pollution and energy shortage issues. The extraction of keratin and the development of keratin-based functional materials are key to solving keratin-containing waste pollution. Keratin-based biofilms are gaining substantial interest due to their excellent characteristics, such as good biocompatibility, high biodegradability, appropriate adsorption, and rich renewable sources, among others. At present, keratin-based biofilms are a good option for various applications, and the development of keratin-based biofilms from keratin-containing waste is considered crucial for sustainable development. In this paper, in order to achieve clean production while maintaining the functional characteristics of natural keratin as much as possible, four important keratin extraction methods—thermal hydrolysis, ultrasonic technology, eco-friendly solvent system, and microbial decomposition—are described, and the characteristics of these four extraction methods are analysed. Next, methods for the preparation of keratin-based biofilms are introduced, including solvent casting, electrospinning, template self-assembly, freeze-drying, and soft lithography methods. Then, the functional properties and application prospects of keratin-based biofilms are discussed. Finally, future research directions related to keratin-based biofilms are proposed. Overall, it can be concluded that the high-value conversion of keratin-containing waste into regenerated keratin-based biofilms has great importance for sustainable development and is highly suggested due to their great potential for use in biomedical materials, optoelectronic devices, and metal ion detection applications. It is hoped that this paper can provide some basic information for the development and application of keratin-based biofilms.

Zwitterionic keratin coating on silk-Laponite fibrous membranes for guided bone regeneration

Implant-related infection is one of the main challenges in periodontal diseases. According to the zwitterionic properties of keratin, we aim to develop guided bone regeneration (GBR) membrane with antibacterial and bioactivity properties using a keratin coating. In this study, electrospun silk fibroin (SF)-Laponite (LAP) fibrous membranes were developed as GBR membranes, and keratin extracted from sheep wool was electrosprayed on them. Here, the role of electrospraying time (2, 3, and 4h) on the properties of the GBR membranes was investigated. After physicochemical characterization of the keratin-modified membranes, in vitro bioactivity and degradation rate of the membranes were studied in simulated body fluid and phosphate buffer saline, respectively. Moreover, proliferation and differentiation of mesenchymal stem cells were evaluated in contact with the keratin-modified SF-LAP membrane. Finally, the antibacterial activity of membranes against gram-positive bacteria (Staphylococcus aureus) was investigated. Results demonstrated the successful formation of homogeneous wool keratin coating on SF-LAP fibrous membranes using a simple electrospray process. While wool keratin coating significantly enhanced the elongation and hydrophilicity of the SF-LAP membrane, the mechanical strength was not changed. In addition, keratin coating significantly improved the bioactivity and degradation rate of SF-LAP membranes, owing to the carboxyl groups of amino acids in keratin coating. In addition, the synergic role of LAP nanoparticles and keratin coating drastically improved osteoblast proliferation and differentiation. Finally, the zwitterionic property of wool keratin coating originating from their equal positive (NH₃ ⁺ ) and negative (COO^- ) charges considerably improved the antibacterial activity of the SF-LAP membrane. Overall, keratin-coated SF-LAP fibrous membranes with significant mechanical and biological properties could have the potential for GBR membranes.

Electro Fluid Dynamics: A Route to Design Polymers and Composites for Biomedical and Bio-Sustainable Applications

In the last two decades, several processes have been explored for the development of micro and/or nanostructured substrates by sagely physically and/or chemically manipulating polymer materials. These processes have to be designed to overcome some of the limitations of the traditional ones in terms of feasibility, reproducibility, and sustainability. Herein, the primary aim of this work is to focus on the enormous potential of using a high voltage electric field to manipulate polymers from synthetic and/or natural sources for the fabrication of different devices based on elementary units, i.e., fibers or particles, with different characteristic sizes—from micro to nanoscale. Firstly, basic principles and working mechanisms will be introduced in order to correlate the effect of selected process parameters (i.e., an applied voltage) on the dimensional features of the structures. Secondly, a comprehensive overview of the recent trends and potential uses of these processes will be proposed for different biomedical and bio-sustainable application areas.

Protein and polysaccharide-based asymmetric mat with tuned bilayer configuration for enhanced wound healing efficiency

In this research we focused on the fabrication of an asymmetric bilayer membrane with core-shell/simple layer configuration providing the functions of needed hierarchically hydrophilicity and porosity, anti-infectious, tissue adhesion as well as degradation and integration with tissue, cells proliferation, and enhanced promotion of tissue regeneration. The bilayer membrane composed of collagen (Col), chitosan (CS), aloe vera (AV) and gelatin (Gel), not only simulates the features of the epidermis and dermis layer of a natural skin but also benefits from the materials necessary for the regeneration of injured skin tissue during the healing process. The results of full-thickness skin wound evaluation revealed that the fabricated asymmetric membrane could facilitate wound healing within 10 days mainly through enhancing cellular activities, enhancing collagen deposition, and promoting proliferation. Results of histopathological analysis and immunohistochemistry after 10 days of treatment, demonstrated more re-epithelialization and collagen density for the treated groups compared to the control group.

Hybrid-Based Wound Dressings: Combination of Synthetic and Biopolymers

Most commercialized wound dressings are polymer-based. Synthetic and natural polymers have been utilized widely for the development of wound dressings. However, the use of natural polymers is limited by their poor mechanical properties, resulting in their combination with synthetic polymers and other materials to enhance their mechanical properties. Natural polymers are mostly affordable, biocompatible, and biodegradable with promising antimicrobial activity. They have been further tailored into unique hybrid wound dressings when combined with synthetic polymers and selected biomaterials. Some important features required in an ideal wound dressing include the capability to prevent bacteria invasion, reduce odor, absorb exudates, be comfortable, facilitate easy application and removal as well as frequent changing, prevent further skin tear and irritation when applied or removed, and provide a moist environment and soothing effect, be permeable to gases, etc. The efficacy of polymers in the design of wound dressings cannot be overemphasized. This review article reports the efficacy of wound dressings prepared from a combination of synthetic and natural polymers.

Electrospun Sulfonatocalix[4]arene Loaded Blended Nanofibers: Process Optimization and In Vitro Studies

In the past decade, electrospun nanofibers made of biodegradable polymers have been used for different biomedical applications due to their flexible features in terms of surface area to volume ratio, pores, and fiber size, as well as their highly tunable surface properties. Recently, interest is growing in the use of supramolecular structures in combination with electrospun nanofibers for the fabrication of bioactive platforms with improved in vitro responses, to be used for innovative therapeutic treatments. Herein, sulfonatocalix[4]arene (SCX4) was synthesized from p-tert-butyl-calix[4]arene and embedded in electrospun nanofibers made of polycaprolactone (PCL) and gelatin (GEL). The supramolecular structure of SCX4 and its efficient entrapment into electrospun fibers was confirmed by NMR spectroscopy and FTIR analysis, respectively. SEM analysis supported via image analysis enabled the investigation of the fiber morphology at the sub-micrometric scale, showing a drastic reduction in fiber diameters in the presence of SCX4: 267 ± 14 nm (without SCX) to 115 ± 5 nm (3% SCX4). Moreover, it was demonstrated that SCX4 significantly contributes to the hydrophilic properties of the fiber surface, as was confirmed by the reduction in contact angles from 54 ± 1.4° to 31 ± 5.5° as the SCX4 amount increased, while no effects on thermal stability were recognized, as was confirmed by TGA analyses. In vitro tests also confirmed that SCX4 is not cytotoxic, but plays a supporting role in L929 interactions, as was validated by the cell viability of PGC15% after 7 days, with respect to the control. These preliminary but promising data suggest their use for the fabrication of innovative platforms able to bind SCX4 to bioactive compounds and molecules for different therapeutic applications, from molecular recognition to controlled drug delivery.

Keratin-based wound dressings: From waste to wealth

Keratin is a natural protein with a high content of cysteine residues (7-13%) and is widely found in hair, wool, horns, hooves, and nails. Keratin possesses abundant cell-binding motifs such as leucine-aspartate-valine (LDV), glutamate-aspartate-serine (EDS), and arginine-glycine-aspartate (RGD), which benefit cell attachment and proliferation. It has been confirmed that keratin plays important roles in every stage of wound healing, including hemostasis, inflammation, proliferation, and remodeling, making keratin-based materials good candidates for wound dressings. In combination with synthetic and natural polymers, keratin-based wound dressings in the forms of films, hydrogels, and nanofibers can be achieved with improved mechanical properties. This review focuses on the recent development of keratin-based wound dressings. Firstly, the physicochemical and biological properties of keratin, are systematically discussed. Secondly, the role of keratin in wound healing is proposed. Thirdly, the applications of keratin-based wound dressings are summarized, in terms of the forms and functionalization. Finally, the current challenges and future development of keratin-based wound dressings are presented.

An Overview on the Recent Advances in the Treatment of Infected Wounds: Antibacterial Wound Dressings

A wound can be surgical, cuts from an operation or due to accident and trauma. The infected wound, as a result of bacteria growth within the damaged skin, interrupts the natural wound healing process and significantly impacts the quality of life. Wound dressing is an important segment of the skincare industry with its economic burden estimated at $ 20.4 billion (in 2021) in the global market. The results of recent clinical trials suggest that the use of modern dressings can be the easiest, most accessible, and most cost-effective way to treat chronic wounds and, hence, holds significant promise. With the sheer number of dressings in the market, the selection of correct dressing is confusing for clinicians and healthcare workers. The aim of this research was to review widely used types of antibacterial wound dressings, as well as emerging products, for their efficiency and mode of action. In this review, we focus on introducing antibiotics and antibacterial nanoparticles as two important and clinically widely used categories of antibacterial agents. The perspectives and challenges for paving the way for future research in this field are also discussed. This article is protected by copyright. All rights reserved.