Effect of discarded keratin-based biocomposite hydrogels on the wound healing process in vivo

Synergistic potential of gellan gum methacrylate and keratin hydrogel for visceral hemostasis and skin tissue regeneration

In recent years, the development of biodegradable hydrogels as an alternative over the traditional wound dressing has become increasingly significant. These specific hydrogels are able to offer suitable microenvironments to further aid the process of tissue or organ regeneration. However, application of biodegradable hydrogels in clinical medicine remains uncommon due to most biodegradable hydrogels struggle with achieving satisfactory adhesiveness property, high mechanical support and cell compatibility simultaneously. In order to overcome these constraints and enhance the applicability of biodegradable hydrogels, methods have been employed in this study. By reacting gellan gum with methacrylic anhydride and incorporating a biodegradable protein, keratin, we endowed the hydrogels with high pliability via photo-polymerization chain extension, thereby obtaining a biodegradable hydrogel with exceptional properties. Through a series of in vitro tests, GGMA/keratin hydrogels exhibited great cell compatibility via providing an appropriate environment for cell proliferation. Furthermore, this hydrogel not only exhibits extraordinary adhesive ability on visceral tissues but also extends to scenarios involving skin or organ damage, offering valuable assistance in wound healing. Our design provides a suitable platform for cell proliferation and tissue regeneration, which shows prospects for future medical research and clinical applications.

Keratin/Copper Complex Electrospun Nanofibers for Antibacterial Treatments: Property Investigation and In Vitro Response

The frontiers of antibacterial materials in the biomedical field are constantly evolving since infectious diseases are a continuous threat to human health. In this work, waste-wool-derived keratin electrospun nanofibers were blended with copper by an optimized impregnation procedure to fabricate antibacterial membranes with intrinsic biological activity, excellent degradability and good cytocompatibility. The keratin/copper complex electrospun nanofibers were multi-analytically characterized and the main differences in their physical-chemical features were related to the crosslinking effect caused by Cu2+. Indeed, copper ions modified the thermal profiles, improving the thermal stability (evaluated by differential scanning calorimetry and thermogravimetry), and changed the infrared vibrational features (determined by infrared spectroscopy) and the chemical composition (studied by an X-ray energy-dispersive spectroscopy probe and optical emission spectrometry). The copper impregnation process also affected the morphology, leading to partial nanofiber swelling, as evidenced by scanning electron microscopy analyses. Then, the membranes were successfully tested as antibacterial materials against gram-negative bacteria, Escherichia coli. Regarding cytocompatibility, in vitro assays performed with L929 cells showed good levels of cell adhesion and proliferation (XTT assay), and no significant cytotoxic effect, in comparison to bare keratin nanofibers. Given these results, the material described in this work can be suitable for use as antibiotic-free fibers for skin wound dressing or membranes for guided tissue regeneration.

Human Hair Keratin-Based Hydrogels in Regenerative Medicine: Current Status and Future Directions

Regenerative medicine (RM) is a multidisciplinary field that utilizes the inherent regenerative potential of human cells to generate functionally and physiologically acceptable human cells, tissues, and organs in vivo or ex vivo. An appropriate biomaterial scaffold with desired physicochemical properties constitutes an important component of a successful RM approach. Among various forms of biomaterials explored until the present day, hydrogels have emerged as a versatile candidate for tissue engineering and regenerative medicine (TERM) applications such as scaffolds for spatial patterning and delivering therapeutic agents, or substrates to enhance cell growth, differentiation, and migration. Although hydrogels can be prepared from a variety of synthetic polymers as well as biopolymers, the latter are preferred for their inherent biocompatibility. Specifically, keratins are fibrous proteins that have been recently explored for constructing hydrogels useful for RM purposes. The present review discusses the suitability of keratin-based biomaterials in RM, with a particular focus on human hair keratin hydrogels and their use in various RM applications.

Preparation of quaternized N-halamine modified graphene oxide based antibacterial hydrogel and wound healing of bacterial infection

In clinical practice, the wound on the surface of the skin is prone to bacterial infection, for which healing of infected wounds has always been a tremendous challenge for clinics and research institutions. We developed a multifunctional bactericidal, recyclable, and slow-release graphene oxide-based hydrogel for bacterial wound healing and real-time monitoring of bacterial infection in this study. At the same time, the material has a sensing function, which can be used in the connection between the injured skin and the continuous detection equipment. QNGH (quaternarized N-halamine-grafted GO hydrogel) is manufactured by hydrogen bonding between quaternized N-halamine-modified graphene oxide and polyvinyl alcohol (PVA). The results show that in the mouse model of full-thickness skin repair, the hydrogel can continuously release germicidal ions and recyclability, promoting wound healing and contraction. Further, the graphene oxide-based hydrogel has excellent strain sensing performance. It detects the bending and stretching movements of different parts of the human body quickly, stably, and sensitively to show an excellent real-time monitoring performance of human motion. The sensing function of the hydrogel further broadens its application field. Therefore, this hydrogel material is expected to be a candidate material for sensing devices at the wound.

Biopolymer-Based Wound Dressings with Biochemical Cues for Cell-Instructive Wound Repair

Regenerative medicine is an active research sphere that focuses on the repair, regeneration, and replacement of damaged tissues and organs. A plethora of innovative wound dressings and skin substitutes have been developed to treat cutaneous wounds and are aimed at reducing the length or need for a hospital stay. The inception of biomaterials with the ability to interact with cells and direct them toward desired lineages has brought about innovative designs in wound healing and tissue engineering. This cellular engagement is achieved by cell cues that can be biochemical or biophysical in nature. In effect, these cues seep into innate repair pathways, cause downstream cell behaviours and, ultimately, lead to advantageous healing. This review will focus on biomolecules with encoded biomimetic, instructive prompts that elicit desired cellular domino effects to achieve advanced wound repair. The wound healing dressings covered in this review are based on functionalized biopolymeric materials. While both biophysical and biochemical cues are vital for advanced wound healing applications, focus will be placed on biochemical cues and in vivo or clinical trial applications. The biochemical cues aforementioned will include peptide therapy, collagen matrices, cell-based therapy, decellularized matrices, platelet-rich plasma, and biometals.

Nigella/honey/garlic/olive oil co-loaded PVA electrospun nanofibers for potential biomedical applications

The current work focuses on the formation of nanofibrous mats without the use of toxic solvents and metallic nanoparticles utilizing polyvinyl alcohol (PVA) and a blend of nigella, honey, garlic, and olive oil. Using deionized water (DI) water as a solvent, nanofibrous mats composed of PVA/nigella/honey (PNH) and PVA/garlic/honey/olive oil (PGHO) were developed. Methanol extraction was utilized to extract the therapeutic components of nigella sativa. Antibacterial and moisture management tests (MMT) were employed to examine the antibacterial and absorbance characteristics of the PNH and PGHO nanofibrous. Scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) tests were employed to analyze the morphological and chemical characteristics. PGHO showed thermal stability up to 245 °C, and PNH withstands until 225 °C. PNH and PGHO both exhibited antibacterial activity against Staphylococcus aureus (S. aureus), with inhibition zones of 36 mm and 35 mm, respectively. The synthesized materials exhibited excellent absorbance properties, thermal stability, cytotoxicity, and the production of thin nanofibers with an average diameter between 150 and 170 nm. The samples were characterized using FTIR spectra, which confirmed the presence of all components in the developed samples. To date, extensive research on electrospinning for biomedical applications has been undertaken using a variety of hazardous solvents and metallic nanoparticles. Briefly, our objective is to develop nanofibrous materials from plant extracts through a process called "green electrospinning" to observe the synergistic effect of multiple biocomponents incorporated nanofibers avoiding toxic solvents and metallic compounds for potential biomedical applications.

Electrospun non-wovens potential wound dressing material based on polyacrylonitrile/chicken feathers keratin nanofiber

Electrospinning nanofibers have a tremendous interest in biomedical applications such as tissue engineering, drug administration, and wound healing because of their ability to replicate and restore the function of the natural extracellular matrix found in tissues. The study’s highlight is the electrospinning preparation and characterization of polyacrylonitrile with chicken feather keratin as an additive. In this study, keratin was extracted from chicken feather waste using an environmentally friendly method and used to reinforce polymeric nanofiber mats. Scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy were used to examine the morphology and the structure of the prepared nanofiber mats. The effect of keratin on the porosity and the tensile strength of reinforcing nanofibers is investigated. The porosity ratio of the nanofiber mats goes up from 24.52 ± 2.12 for blank polyacrylonitrile (PAN (NF)) to 90.89 ± 1.91% for polyacrylonitrile nanofiber with 0.05 wt% keratin (PAN/0.05% K). Furthermore, keratin reinforcement improves the nanofiber's mechanical properties, which are important for wound dressing application, as well as its antibacterial activity without causing hemolysis (less than 2%). The best antibacterial activities were observed against Pseudomonas aeruginosa (30 ± 0.17 mm inhibition zone) and Staphylococcus aureus (29 ± 0.31 mm inhibition zone) for PAN/0.05% K sample, according to the antibacterial test. This research has a good potential to broaden the use of feather keratin-based nanofibers in wound healing.

A keratin/chitosan sponge with excellent hemostatic performance for uncontrolled bleeding

Uncontrolled bleeding leads to a higher fatality rate in the situation of surgery, traffic accidents and warfare. Traditional hemostatic materials such as bandages are not ideal for uncontrolled or incompressible bleeding. Therefore, it is of great significance to develop a new medical biomaterial with excellent rapid hemostatic effect. Keratin is a natural, biocompatible and biodegradable protein which contains amino acid sequences that induce cell adhesion. As a potential biomedical material, keratin has been developed and paid attention in tissue engineering fields such as promoting wound healing and nerve repair. Herein, a keratin/chitosan (K/C) sponge was prepared to achieve rapid hemostasis. The characterizations of K/C sponge were investigated, including SEM, TGA, liquid absorption and porosity, showing that the high porosity up to 90.12 ± 2.17 % resulted in an excellent blood absorption. The cytotoxicity test and implantation experiment proved that the K/C sponge was biocompatible and biodegradable. Moreover, the prepared K/C sponge showed better hemostatic performance than chitosan sponge (CS) and the commercially available gelatin sponge in both rat tail amputation and liver trauma bleeding models. Further experiments showed that K/C sponge plays a hemostatic role through the endogenous coagulation pathway, thus shortening the activated partial thromboplastin time (APTT) effectively. Therefore, this study provided a K/C sponge which can be served as a promising biomedical hemostatic material.

Valorization of Human Hair and Its Derivatives in Tissue Engineering: A Review

Human hair is a potential biomaterial for biomedical applications. Improper disposal of human hair may pose various adverse effects on the environment and human health. Therefore, proper management of human hair waste is pivotal. Human hair fiber and its derivatives offer various advantages as biomaterials such as biocompatibility, biodegradability, low toxicity, radical scavenging, electroconductivity, and intrinsic biological activity. Therefore, the favorable characteristics of human hair have rendered its usage in tissue engineering (TE) applications including skin, cardiac, nerve, bone, ocular, and periodontal. Moreover, the strategies by utilizing human hair as a biomaterial for TE applications may reduce the accumulation of human hair. Thus, it also improves human hair waste management while promoting natural, environmental-friendly, and nontoxic materials. Furthermore, promoting sustainable materials production will benefit human health and well-being. Hence, this article reviews and discusses human hair characteristics as sustainable biomaterials and their recent application in TE applications. Impact Statement This review article highlights the sustainability aspects of human hair as raw biomaterials and various elements of human hair that could potentially be used in tissue engineering (TE) applications. Furthermore, this article discusses numerous benefits of human hair, highlighting its value as biomaterials in bioscaffold development for TE applications. Moreover, this article reviews the role and effect of human hair in various TE applications, including skin, cardiac, nerve, bone, ocular, and periodontal.

Protein-Based Hydrogels: Promising Materials for Tissue Engineering

The successful design of a hydrogel for tissue engineering requires a profound understanding of its constituents' structural and molecular properties, as well as the proper selection of components. If the engineered processes are in line with the procedures that natural materials undergo to achieve the best network structure necessary for the formation of the hydrogel with desired properties, the failure rate of tissue engineering projects will be significantly reduced. In this review, we examine the behavior of proteins as an essential and effective component of hydrogels, and describe the factors that can enhance the protein-based hydrogels' structure. Furthermore, we outline the fabrication route of protein-based hydrogels from protein microstructure and the selection of appropriate materials according to recent research to growth factors, crucial members of the protein family, and their delivery approaches. Finally, the unmet needs and current challenges in developing the ideal biomaterials for protein-based hydrogels are discussed, and emerging strategies in this area are highlighted.

Protein materials as sustainable non- and minimally invasive strategies for biomedical applications

Protein-based materials have found applications in a wide range of biomedical fields because of their biocompatibility, biodegradability and great versatility. Materials of different physical forms including particles, hydrogels, films, fibers and microneedles have been fabricated e.g. as carriers for drug delivery, factors to promote wound healing and as structural support for the generation of new tissue. This review aims at providing an overview of the current scientific knowledge on protein-based materials, and selected preclinical and clinical studies will be reviewed in depth as examples of the latest progress within the field of protein-based materials, specifically focusing on non- and minimally invasive strategies mainly for topical application.

Keratin Biomaterials in Skin Wound Healing, an Old Player in Modern Medicine: A Mini Review

Impaired wound healing is a major medical problem. To solve it, researchers around the world have turned their attention to the use of tissue-engineered products to aid in skin regeneration in case of acute and chronic wounds. One of the primary goals of tissue engineering and regenerative medicine is to develop a matrix or scaffold system that mimics the structure and function of native tissue. Keratin biomaterials derived from wool, hair, and bristle have been the subjects of active research in the context of tissue regeneration for over a decade. Keratin derivatives, which can be either soluble or insoluble, are utilized as wound dressings since keratins are dynamically up-regulated and needed in skin wound healing. Tissue biocompatibility, biodegradability, mechanical durability, and natural abundance are only a few of the keratin biomaterials' properties, making them excellent wound dressing materials to treat acute and chronic wounds. Several experimental and pre-clinical studies described the beneficial effects of the keratin-based wound dressing in faster wound healing. This review focuses exclusively on the biomedical application of a different type of keratin biomaterials as a wound dressing in pre-clinical and clinical conditions.

Waste Reutilization in Polymeric Membrane Fabrication: A New Direction in Membranes for Separation

In parallel to the rapid growth in economic and social activities, there has been an undesirable increase in environmental degradation due to the massively produced and disposed waste. The need to manage waste in a more innovative manner has become an urgent matter. In response to the call for circular economy, some solid wastes can offer plenty of opportunities to be reutilized as raw materials for the fabrication of functional, high-value products. In the context of solid waste-derived polymeric membrane development, this strategy can pave a way to reduce the consumption of conventional feedstock for the production of synthetic polymers and simultaneously to dampen the negative environmental impacts resulting from the improper management of these solid wastes. The review aims to offer a platform for overviewing the potentials of reutilizing solid waste in liquid separation membrane fabrication by covering the important aspects, including waste pretreatment and raw material extraction, membrane fabrication and characterizations, as well as the separation performance evaluation of the resultant membranes. Three major types of waste-derived polymeric raw materials, namely keratin, cellulose, and plastics, are discussed based on the waste origins, limitations in the waste processing, and their conversion into polymeric membranes. With the promising material properties and viability of processing facilities, recycling and reutilization of waste resources for membrane fabrication are deemed to be a promising strategy that can bring about huge benefits in multiple ways, especially to make a step closer to sustainable and green membrane production.

Keratose hydrogel for tissue regeneration and drug delivery

Keratin (KRT), a natural fibrous structural protein, can be classified into two categories: "soft" cytosolic KRT that is primarily found in the epithelia tissues (e.g., skin, the inner lining of digestive tract) and "hard" KRT that is mainly found in the protective tissues (e.g., hair, horn). The latter is the predominant form of KRT widely used in biomedical research. The oxidized form of extracted KRT is exclusively denoted as keratose (KOS) while the reduced form of KRT is termed as kerateine (KRTN). KOS can be processed into various forms (e.g., hydrogel, films, fibers, and coatings) for different biomedical applications. KRT/KOS offers numerous advantages over other types of biomaterials, such as bioactivity, biocompatibility, degradability, immune/inflammatory privileges, mechanical resilience, chemical manipulability, and easy accessibility. As a result, KRT/KOS has attracted considerable attention and led to a large number of publications associated with this biomaterial over the past few decades; however, most (if not all) of the published review articles focus on KRT regarding its molecular structure, biochemical/biophysical properties, bioactivity, biocompatibility, drug/cell delivery, and in vivo transplantation, as well as its applications in biotechnical products and medical devices. Current progress that is directly associated with KOS applications in tissue regeneration and drug delivery appears an important topic that merits a commentary. To this end, the present review aims to summarize the current progress of KOS-associated biomedical applications, especially focusing on the in vitro and in vivo effects of KOS hydrogel on cultured cells and tissue regeneration following skin injury, skeletal muscle loss, peripheral nerve injury, and cardiac infarction.

Antibacterial polyvinyl alcohol/bacterial cellulose/nano-silver hydrogels that effectively promote wound healing

The lack of antibacterial properties limits the application of bacterial cellulose hydrogels in wound dressings. To overcome this deficiency, silver nanoparticles (AgNPs) were introduced as antibacterial agents into a polyvinyl alcohol (PVA)/bacterial cellulose (BC) solution. A freeze-thaw method promoted formation of PVA/BC/Ag hydrogels and improved their mechanical properties. The physicochemical and biological properties of this hydrogel were systematically characterized. Those results showed the hydrogels contained a porous three-dimensional reticulum structure and had high mechanical properties. Also, the hydrogels possessed outstanding antibacterial properties and good biocompatibilities. More importantly, it effectively repaired wound defects in mice models and wound healing reached 97.89% within 15 days, and far exceeded other groups and indicated its potential for use in wound treatment applications.

Development of antibacterial nanofibrous wound dressing and conceptual reaction mechanism to deactivate the viral protein by Nigella sativa extract

Nigella sativa (N. sativa) is extensively used as medicinal plant all over the world. It has the potential properties as the antiviral and antibacterial application. Its seed contain thymoquinone (TQ), thymohydroquinone (THQ), thymol (THY), p-cymene as major and other minor components. TQ and THQ exhibit broad spectrum of antimicrobial properties against the activity of bacteria, viruses, parasites, schistosoma and fungi. This work provides credence to the fabrication of antibacterial nanofibrous membrane by electrospinning machine from N. sativa extract with polyvinyl alcohol (PVA) solution for wound dressing. The morphology of the developed membrane is also characterized using scanning electron microscope. Fourier transform infrared spectroscopy (FTIR) data has been showed that the functional groups of N. sativa are present in the prepared PVA-N. sativa nanofibrous membrane and its antibacterial activity was investigated. The disk diffusion method has been used to evaluate the antibacterial activity of PVA-N. sativa nanofibrous membrane against Staphylococcus aureus (S. aureus) bacteria and the inhibition zone with a value of 10 mm is formed. Considering the inherent properties of N. sativa, a conceptual reaction mechanism has been proposed to deactivate the viral proteins by the action of TQ and THQ.

Novel porous chitosan/N-halamine structure with efficient antibacterial and hemostatic properties

In this work, a novel chitosan based structure (CS/EVC) with low density, high porosity, three-dimensional porous structure and great adsorption capability has been prepared by using 1,2-epoxy-4-vinyl cyclohexane (EVC) as a cross-linker. After immersing CS/EVC in N-halamine 1-chloro-2,2,5,5-tetramethyl-4-imidazolinone (MC) solution, antibacterial CS/EVC/MC compounds were obtained. Compared with chitosan and CS/EVC controls, CS/EVC/MC showed excellent antimicrobial activities, which could inactivate both more than 6 logs (×1/1,000,000) of Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 8099) within 30 and 10 min, respectively. Moreover, the relatively low blood clotting index of CS/EVC/MC and the activation of platelets adhering to the surfaces indicated that the CS/EVC/MC sample is potential to promote the agglutination abilities of blood cells and simultaneously control wound bleeding. In addition, in vitro cytotoxicity test showed that the CS/EVC/MC had no cytotoxicity. The material might thus have a great potential for biomedical applications.

From fabric to tissue: Recovered wool keratin/polyvinylpyrrolidone biocomposite fibers as artificial scaffold platform

Keratin extracted from wool fibers has recently gained attention as an abundant source of renewable, biocompatible material for tissue engineering and drug delivery applications. However, keratin extraction and processing generally require a copious use of chemicals, not only bearing consequences for the environment but also possibly compromising the envisioned biological outcome. In this study, we present, for the first time, keratin-PVP biocomposite fibers obtained via an all-water co-electrospinning process and explored their properties modulation as a result of different thermal crosslinking treatments. The protein-based fibers featured homogenous morphologies and average diameters in the range of 170-290 nm. The thermomechanical stability and response to a wet environment can be tuned by acting on the curing time; this can be achieved without affecting the 3D fibrous network nor the intrinsic hydrophilic behavior of the material. More interestingly, our protein-based membranes treated at 170 °C for 18 h successfully sustained the attachment and growth of primary human dermal fibroblasts, a cellular model which can recapitulate more faithfully the physiological human tissue conditions. Our proposed approach can be viewed as pivotal in designing tunable protein-based scaffolds for the next generation of skin tissue growth devices.

Synthesis, characterization, and their some chemical and biological properties of PVA/PAA/nPS hydrogel nanocomposites: Hydrogel and wound dressing

The nanocomposite hydrogels were prepared by dispersing of the nanopomegranate seed particles into poly(vinyl alcohol)/poly(acrylic acid) blend matrix in an aqueous medium by the solvent casting method. These hydrogels were characterized using scanning electron microscopy, Fourier transform infrared spectra, differential scanning calorimetry, and optical contact angle instruments. The nanopomegranate seed, blend, and hydrogel nanocomposites were tested for microbial activity. In addition, cytocompatibilities of these blend and hydrogel nanocomposites/composites were tested on human lymphocyte with in vitro MTS cell viability assays. Fourier transform infrared spectra revealed that esterification reaction took place among functional groups in the structure of poly(vinyl alcohol) and poly(acrylic acid). The hydrophilic properties of all hydrogels decreased with increasing nanopomegranate seed content. The mean diameters of the nanopomegranate seed particles were about 88 nm. Nanopomegranate seed particles demonstrated antibacterial properties against gram-positive bacteria, Staphylococcus aureus, and gram-negative bacteria, Escherichia coli. The lymphocyte viabilities increased after addition of nanopomegranate seeds into the polymer blend. The swelling behavior of blend and hydrogels was dependent on the cross-linking density created by the reaction between poly(vinyl alcohol)/poly(acrylic acid) blend and nanopomegranate seed. Scanning electron microscopy images were highly consistent with Fourier transform infrared spectra, differential scanning calorimetry, and antibacterial activity results.

Lignin-mediated green synthesis of AgNPs in carrageenan matrix for wound dressing applications

Carrageenan-based functional wound dressing materials were prepared through a one-pot green synthesis of silver nanoparticles (AgNPs) using lignin as a reducing and capping agent in the carrageenan matrix cross-linked with divalent cations such as CaCl₂, CuCl₂, and MgCl₂. The wound healing efficacy of the hydrogel film was evaluated using Sprague-Dawley rats. Crosslinking with divalent cations improved the physical properties of carrageenan-based hydrogels containing AgNPs such as strength, flexibility, swelling ratio, and release rate of Ag ions depending on the type of crosslinking agent used. The carrageenan-based hydrogels were biocompatible against the mouse fibroblast cell line (L929 cell line). Carra/Lig/AgNPs/MgCl₂ hydrogel significantly healed the wounds in Sprague-Dawley rats within two weeks, reducing the wound area to <3%, which was further confirmed by histological analysis with the epidermis and mature glands. Carrageenan-based multifunctional hydrogels have a high potential for wound dressing applications.

New Developments in Medical Applications of Hybrid Hydrogels Containing Natural Polymers

New trends in biomedical applications of the hybrid polymeric hydrogels, obtained by combining natural polymers with synthetic ones, have been reviewed. Homopolysaccharides, heteropolysaccharides, as well as polypeptides, proteins and nucleic acids, are presented from the point of view of their ability to form hydrogels with synthetic polymers, the preparation procedures for polymeric organic hybrid hydrogels, general physico-chemical properties and main biomedical applications (i.e., tissue engineering, wound dressing, drug delivery, etc.).

Carboxymethyl cellulose-human hair keratin hydrogel with controlled clindamycin release as antibacterial wound dressing

This study offers a new antibacterial wound dressing from carboxymethyl cellulose (CMC)-human hair keratin with topical clindamycin delivery. Keratin was successfully extracted from human hair. Different sponges fabricated by changing CMC to keratin ratio were characterized and compared. Halloysite nanotubes were used as carriers to control the clindamycin release. Various characterization techniques were used to determine the effects of keratin addition on the structure, morphology, physical properties, drug release, antibacterial activity, and cellular behavior of CMC hydrogels. As proved by SEM and EDS, porous structure with interconnected pores was successfully formed and clindamycin-loaded HNTs were uniformly dispersed within the porous structures. Increasing the keratin in CMC hydrogel not only lowered its water vapor transmission rate to a suitable range for wound healing but also improved the water stability of CMC hydrogel. The in vitro release study indicated that clindamycin was released slower in samples containing higher keratin and the Fickian diffusion mechanism controlled their release profile. The fabricated dressing effectively inhibits S. aureus bacterial colonies growth after 24 h. Fibroblast culturing on the fabricated sponges indicated that cellular attachment, proliferation, and spreading were significantly enhanced with increasing the keratin amount.

Phosphorylated Zein as Biodegradable and Aqueous Nanocarriers for Pesticides with Sustained-Release and anti-UV Properties

Zein's prevalent hydrophobic character is one of the major challenges associated with ineffective utilization as an aqueous nanocarrier for pesticides. Herein, we report an effective approach to hydrophilic modification of zein by phosphorylation using nontoxic sodium tripolyphosphate (STP), thereby improving the water-solubility, foliage wettability, and adhesion ability of zein as a nanocarrier for sustained release of pesticides. The procedure relied on zein grafted with STP via N- and O- phosphate bonds and encapsulation of avermectin (AVM) as a hydrophobic model drug using phosphorylated zein (P-Zein), which achieved pH sensitivity to controlled release of AVM in various applicable environments. The chemical interaction between zein and STP was confirmed by Fourier transform infrared, thermogravimetric analysis, and differential scanning calorimetric. Scanning electron microscopy, dynamic light scattering, and zeta potential technique were applied to investigate their structural characteristics and stability, from which it was found that AVM encapsulated in P-Zein (AVM@P-Zein) formed uniform nanoparticles with average sizes in the range of 174-278 nm under different conditions, and had an excellent stability in aqueous solution. Besides, AVM@P-Zein facilitated the wettability on the foliage surface evidenced from contact angle values owing to the amphiphilic character after phosphorylation as well as enhanced the adhesion ability between liquid and leaf, restricting the pesticide runoff. Ultraviolet-visible spectroscopy was employed to explore the anti-UV property and encapsulation as well as release behavior, which revealed that the presence of P-Zein like a shell protects AVM from UV photolysis with encapsulation efficiency of approximately 81.52%, and the release of AVM from P-Zein showed pH-responsive behavior ascribed to protonation and deprotonation of phosphate under various pH conditions fitting to Elovich kinetic model, achieving the relatively more rapid release under acidic conditions. More importantly, AVM@P-Zein retained the toxicity for insecticidal effect.

Self-assembly behavior of the keratose proteins extracted from oxidized Ovis aries wool fibers

Water soluble keratose proteins were obtained from an Ovis Aries wool using peracetic acid oxidation. The wool samples and the extracted keratose proteins were characterized by using FTIR, XRD, SEM and TGA techniques. Fractions of α-keratose (MW = 43-53 kDa) along with protein species with molecular weights between 23 kDa and 33 kDa were identified in the SDS-PAGE analysis result of the extracted protein mixture. DLS and AFM experiments indicated that self-assembled globular nanoparticles with diameters between 15 nm and 100 nm formed at 5 mg/ml keratose concentration. On the other hand, upon incubation of 10 w % keratose solutions at 37 °C and 50 °C, interconnected keratose hydrogels with respective storage modulus (G') values of 0.17 ± 0.03 kPa and 3.7 ± 0.5 kPa were obtained. It was shown that the keratose hydrogel prepared at 37 °C supported L929 mouse fibroblast cell proliferation which suggested that these keratose hydrogels could be promising candidates in soft tissue engineering applications.

In vitro and in vivo Assessment of Keratose as a Novel Excipient of Paclitaxel Coated Balloons

Purpose: Drug coated balloons (DCB) are continually improving due to advances in coating techniques and more effective excipients. Paclitaxel, the current drug choice of DCB, is a microtubule-stabilizing chemotherapeutic agent that inhibits smooth muscle cell proliferation. Excipients work to promote coating stability and facilitate paclitaxel transfer and retention at the target lesion, although current excipients lack sustained, long-term paclitaxel retention. Keratose, a naturally derived protein, has exhibited unique properties allowing for tuned release of various therapeutic agents. However, little is known regarding its ability to support delivery of anti-proliferative agents such as paclitaxel. The goal of this project was to thus demonstrate the feasibility of keratose as a DCB-coating excipient to promote the release and delivery of paclitaxel. Methods: Keratose was combined with paclitaxel in vitro and the release kinetics of paclitaxel and keratose were evaluated through high performance liquid chromatograph-mass spectroscopy (HPLC-MS) and spectrophotometry, respectively. A custom coating method was developed to deposit keratose and paclitaxel on commercially available angioplasty balloons via an air spraying method. Coatings were then visualized under scanning electron microscopy and drug load quantified by HPLC-MS. Acute arterial transfer of paclitaxel at 1 h was assessed using a novel ex vivo model and further evaluated in vivo in a porcine ilio-femoral injury model. Results: Keratose demonstrated tunable release of paclitaxel as a function of keratose concentration in vitro. DCB coated via air spraying yielded consistent drug loading of 4.0 ± 0.70 μg/mm2. Under scanning electron microscopy, the keratose-paclitaxel DCB showed uniform coverage with a consistent, textured appearance. The acute drug transfer of the keratose-paclitaxel DCB was 43.60 ± 14.8 ng/mg at 1 h ex vivo. These measurements were further confirmed in vivo as the acute 1 h arterial paclitaxel levels were 56.60 ± 66.4 ng/mg. Conclusion: The keratose-paclitaxel coated DCB exhibited paclitaxel uptake and achieved acute therapeutic arterial tissue levels, confirming the feasibility of keratose as a novel excipient for DCB.

The Hair Follicle: An Underutilized Source of Cells and Materials for Regenerative Medicine

The hair follicle is one of only two structures within the adult body that selectively degenerates and regenerates, making it an intriguing organ to study and use for regenerative medicine. Hair follicles have been shown to influence wound healing, angiogenesis, neurogenesis, and harbor distinct populations of stem cells; this has led to cells from the follicle being used in clinical trials for tendinosis and chronic ulcers. In addition, keratin produced by the follicle in the form of a hair fiber provides an abundant source of biomaterials for regenerative medicine. In this review, we provide an overview of the structure of a hair follicle, explain the role of the follicle in regulating the microenvironment of skin and the impact on wound healing, explore individual cell types of interest for regenerative medicine, and cover several applications of keratin-based biomaterials.

Keratin: dissolution, extraction and biomedical application

Keratinous materials such as wool, feathers and hooves are tough unique biological co-products that usually have high sulfur and protein contents. A high cystine content (7-13%) differentiates keratins from other structural proteins, such as collagen and elastin. Dissolution and extraction of keratin is a difficult process compared to other natural polymers, such as chitosan, starch, collagen, and a large-scale use of keratin depends on employing a relatively fast, cost-effective and time efficient extraction method. Keratin has some inherent ability to facilitate cell adhesion, proliferation, and regeneration of the tissue, therefore keratin biomaterials can provide a biocompatible matrix for regrowth and regeneration of the defective tissue. Additionally, due to its amino acid constituents, keratin can be tailored and finely tuned to meet the exact requirement of degradation, drug release or incorporation of different hydrophobic or hydrophilic tails. This review discusses the various methods available for the dissolution and extraction of keratin with emphasis on their advantages and limitations. The impacts of various methods and chemicals used on the structure and the properties of keratin are discussed with the aim of highlighting options available toward commercial keratin production. This review also reports the properties of various keratin-based biomaterials and critically examines how these materials are influenced by the keratin extraction procedure, discussing the features that make them effective as biomedical applications, as well as some of the mechanisms of action and physiological roles of keratin. Particular attention is given to the practical application of keratin biomaterials, namely addressing the advantages and limitations on the use of keratin films, 3D composite scaffolds and keratin hydrogels for tissue engineering, wound healing, hemostatic and controlled drug release.

An investigation of konjac glucomannan-keratin hydrogel scaffold loaded with Avena sativa extracts for diabetic wound healing

We have developed a novel hydrogel composed of konjac glucomannan (KGM), human hair proteins (KER), and an ethanolic extract of Avena sativa (OAT) and evaluated its potential as a dressing material for diabetic wounds. KGM is an excellent biocompatible gelling agent that stimulates fibroblast proliferation and immunomodulation. Human hair proteins (KER) are biocompatible, biodegradable, and possess abundant cell adhesion sites. KER also promotes fibroblast attachment and proliferation, keratinocyte migration, and collagen expression, which can accelerate wound healing. OAT consists of oat β-glucans and several anti-inflammatory and antioxidant moieties that can reduce prolonged inflammation in chronic wounds. SEM images confirm the highly porous architecture of the scaffolds. When immersed in PBS, KGM+KER+OAT hydrogels absorb 7.5 times their dry weight. These hydrogels display a measured rate of degradation in lysozyme. KGM+KER+OAT hydrogels showed no significant cytotoxicity against NIH/3T3 fibroblasts. DAPI and SEM images obtained after 48h of cell culture illustrate the attachment and infiltration of fibroblasts. In vivo studies performed using a diabetic rat excision wound model showed that KGM+KER+OAT hydrogels significantly accelerated wound healing compared to the control and the KGM+KER hydrogels.

Biomacromolecules as carriers in drug delivery and tissue engineering

Natural biomacromolecules have attracted increased attention as carriers in biomedicine in recent years because of their inherent biochemical and biophysical properties including renewability, nontoxicity, biocompatibility, biodegradability, long blood circulation time and targeting ability. Recent advances in our understanding of the biological functions of natural-origin biomacromolecules and the progress in the study of biological drug carriers indicate that such carriers may have advantages over synthetic material-based carriers in terms of half-life, stability, safety and ease of manufacture. In this review, we give a brief introduction to the biochemical properties of the widely used biomacromolecule-based carriers such as albumin, lipoproteins and polysaccharides. Then examples from the clinic and in recent laboratory development are summarized. Finally the current challenges and future prospects of present biological carriers are discussed.

Comparative study of kerateine and keratose based composite nanofibers for biomedical applications

In this work, two forms of keratins, kerateine (KR) and keratose (KO), were fabricated respectively into electrospun nanofibers by combination with polyurethane (PU). The differences of the structure and material properties between KR and KO based fibers were investigated by SEM observation, ATR-FTIR, XRD, contact angle, tensile test, in vitro degradation and cytocompatibility assay. The results indicated that the KR based nanofibers exhibited a higher tensile modulus, lower fracture strain and slower degradation rate, mainly due to the reformation of disulfide crosslinking between the regenerated cysteines in KR after the reductive extraction. The KO based nanofibers demonstrated a stronger hydrophilic property and higher water uptake ability due to the cysteic acid residues resulting from the oxidative extraction. Furthermore, the combination of keratins, regardless of KR or KO, could obviously improve the cytocompatibility of PU, especially in the cell attachment stage.

Fabrication of bi-layer scaffold of keratin nanofiber and gelatin-methacrylate hydrogel: Implications for skin graft

Bi-layer scaffold composed of human hair keratin/chitosan nanofiber mat and gelatin methacrylate (GelMA) hydrogel was fabricated by using electrospinning and photopolymerization techniques. To prepare the nanofiber layer, the blend solution of human hair keratin and chitosan (mixture ratio: 5/5) was electrospun using formic acid as a solvent in the presence of poly(ethylene glycol), followed by cross-linking with glutaraldehyde. The tensile strength of the human hair keratin/chitosan nanofiber mat was much higher than that of pure human hair keratin nanofiber mat. Meanwhile, the blend nanofiber mat was relatively more compatible with HaCaT cell proliferation and keratinocyte differentiation than the pure chitosan nanofiber mat. The bi-layer scaffold was prepared by photopolymerization of GelMA under the cross-linked nanofiber mat. To evaluate the feasibility as a skin graft, human fibroblast was encapsulated in the hydrogel layer and HaCaT cells were cultured on the nanofiber layer and they were co-cultured for 10days. As a result, the encapsulated fibroblasts proliferated in the hydrogel matrix and HaCaT cells formed a cell layer on the top of scaffold, mimicking dermis and epidermis of skin tissue.

Hair growth promoting activity of discarded biocomposite keratin extract

Keratin biomaterial has been used in regenerative medicine owing to its in-vivo and in-vitro biocompatibility. The present study was aimed to investigate the hair growth promoting activity of keratin extract and its mechanism of action. Keratin extract was topically applied on the synchronized depilated dorsal skin of telogenic C57BL/6 mice and promoted hair growth by inducing the anagen phase. The histomorphometric observation indicated significantly increases the number, shaft of hair follicles and deep subcutis area in the keratin extract treated group in contrast to the control group, which was considered an indication of anagen phase induction. Subsequently, the quantitative real-time polymerase chain reaction analysis revealed that fibroblast growth factor-10, vascular endothelial growth factor, insulin-like growth factor-1, β-catenin, and Shh were expressed earlier in the keratin extract-treated group than in the control group. Besides, keratin extract has been observed to be biocompatible when analyzed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and 4',6-diamidino-2-phenylindole staining using immortalized human keratinocyte cells, showing more than 90% cell viability. Our study demonstrated that keratin extract stimulating hair follicle growth by inducing the growth phase; anagen in telogenic C57BL/6 mice and thus the topical application of keratin extract may represent a promising biomaterial for the management and applications of hair follicle disorder.

Novel bilayer wound dressing based on electrospun gelatin/keratin nanofibrous mats for skin wound repair

A bilayer membrane (GKU) with a commercial polyurethane wound dressing as an outer layer and electrospun gelatin/keratin nanofibrous mat as an inner layer was fabricated as a novel wound dressing. Scanning electron micrographs showed that gelatin/keratin nanofibers had a uniform morphology and bead-free structure with average fiber diameter of 160.4nm. 3-(4,5-Dimethylthiazolyl)-2,5-diphenyltetrazolium bromide assay using L929 fibroblast cells indicated that the residues released from the gelatin/keratin composite nanofibrous mat accelerated cell proliferation. Cell attachment experiments revealed that adhered cells spread better and migrated deeper into the gelatin/keratin nanofibrous mat than that into the gelatin nanofibrous mat. In animal studies, compared with the bilayer membrane without keratin, gauze and commercial wound dressing, Comfeel®, GKU membrane gave much more number of blood vessels and a greater reduction in wound area at 4days, and better wound repair at 14days with a thicker epidermis and larger number of newly formed hair follicles. GKU membrane, thus, could be a good candidate for wound dressing applications.

Cellulose nanocrystal-reinforced keratin bioadsorbent for effective removal of dyes from aqueous solution

High-efficiency and recyclable three-dimensional bioadsorbents were prepared by incorporating cellulose nanocrystal (CNC) as reinforcements in keratin sponge matrix to remove dyes from aqueous solution. Adsorption performance of dyes by CNC-reinforced keratin bioadsorbent was improved significantly as a result of adding CNC as filler. Batch adsorption results showed that the adsorption capacities for Reactive Black 5 and Direct Red 80 by the bioadsorbent were 1201 and 1070mgg^-1, respectively. The isotherms and kinetics for adsorption of both dyes on bioadsorbent followed the Langmuir isotherm model and pseudo-second order model, respectively. Desorption and regeneration experiments showed that the removal efficiencies of the bioadsorbent for both dyes could remain above 80% at the fifth recycling cycles. Moreover, the bioadsorbent possessed excellent packed-bed column operation performance. Those results suggested that the adsorbent could be considered as a high-performance and promising candidate for dye wastewater treatment.

Sustainable and smart keratin hydrogel with pH-sensitive swelling and enhanced mechanical properties

Protein based hydrogels are a very interesting type of biomaterials with many probed strengths related to their source and chemical structure. Biocompatibility and biodegradability are accompanied by affordability when it comes to low cost sources. The main keratin source is agroindustrial waste, such as feathers, horns, hooves, hair and wool. Thus, the main cost of keratin hydrogels derives from their processing. Here is presented a new strategy for the obtaining of a keratin hydrogel with enhanced mechanical properties using low cost reagents. This keratin hydrogel is stiff enough to allow handling without special cares and also presenting a reversible pH-responsive behavior. The minimum swelling is observed at low pH due to a collapsed and disordered protein network with water tightly adsorbed to the hydrophilic sites. The swelling rises significantly above pH6 and the maximum swelling appears above pH8 where an expanded network allows water to enter to the pores.

Honey/PVA hybrid wound dressings with controlled release of antibiotics: Structural, physico-mechanical and in-vitro biomedical studies

Hydrogel/honey hybrids manifest an attractive design with an exclusive therapeutic property that promotes wound healing process. The greater the concentration of honey within the formulation, the better the biomedical properties that will be achieved. However, an increase in the percentage of honey can negatively affect the physico-chemical and mechanical properties of hybrid hydrogels. The need exists, therefore, to prepare wound dressings that contain high honey density with optimal biomedical, mechanical and physicochemical properties. In this study, a simple method for the preparation of a highly concentrated honey/PVA hybrid hydrogel with borax as the crosslinking agent is reported. Comprehensive evaluations of the morphology, swelling kinetics, permeability, bio-adhesion, mechanical characteristics, cytotoxicity, antibacterial property, cell proliferation ability and their controlling release properties were conducted as a function of crosslinking density. All the borax-induced hydrogels showed acceptable biocompatibility, and the incorporation of 1% borax in the hydrogel formulation produced optimal behaviours for wound addressing applications.