A Review of Keratin-Based Biomaterials for Biomedical Applications

Keratinization and cornification of avian skin appendages during development. Insights from immunolabeling and electron microscopic studies

The basal cytoskeleton of avian keratinocytes consists in a number of Intermediate Filament Keratins (IFKs, also indicated as alpha-keratins), poor (soft) or rich (hard) in cysteine. In keratinocytes of developing skin appendages Corneous Beta Proteins (CBPs, formerly termed beta-keratins), build most of the corneous material of developing scutate scales, claws, beak and feathers. CBPs derive from a gene locus termed Epidermal Differentiation Complex (EDC), unrelated to genes for IFKs. CBPs and IFKs belong to two different gene families that evolved independently during the evolution of birds. The evolution of feathers derived from the initial morphogenesis of barb ridges containing specialized proteins. During feather development, the framework of IFKs that combine with CBPs in differentiating keratinocytes, barb and barbule cells, give rise to resistant but flexible corneocytes in feathers and hard corneocytes in scales, claws and beaks. Here, we mainly deal with avian IFKs that are accumulated during the development of skin derivatives of birds, especially downfeathers. The latter are corneous appendages and, when mature, are composed from a prevalent mass of feather-CBPs (fCBPs, formerly indicated as feather beta-keratins). During development fCBPs are deposited over a IFKs cytoskeleton formed in barb and barbule cells, and these small beta-proteins rapidly overcame in amount IFKs, generating the corneous barbs and barbules of downfeathers. This process likely occurs through electrostatic interactions between acidic IFKs and basic CBPs, and later by the formation of covalent bonds (-S-S- and epsilon-bonds). Proteome and molecular studies have sequenced most of IFKs and CBPs of feathers in some species of birds. Most of the proteins extracted from feathers are fCBPs, while a lower amount is constituted from IFKs and other minor proteins.

Recombinant keratin: Comprehensive review of synthesis, hierarchical assembly, properties, and applications

Keratin has gained attention for its remarkable mechanical properties, thermal stability, and beneficial biological properties, such as promoting hemostasis and wound healing. Traditionally, keratin has been extracted from natural sources, including human hair, wool, and feathers, and processed into biomaterials, including films, hydrogels, and nanoparticles, primarily for biomedical applications. However, extraction methods often result in heterogeneous keratin mixtures with residual impurities and structural degradation due to harsh purification conditions, complicating efforts to understand how specific keratins and their hierarchical assemblies contribute to desired material properties. Recombinant keratin technology addresses these challenges by enabling the synthesis of individual keratin types with high purity and batch-to-batch consistency. These advancements facilitate studies on how individual and combined keratins at various assembly stagesfrom molecular components and heterodimers to intermediate filaments (IFs) and IF networksimpact material properties. Moreover, this technology allows for precise genetic modifications, potentially leading to engineered keratin variants with tailored characteristics for targeted applications. Despite these advantages, translating recombinant keratin into practical applications requires overcoming key manufacturing challenges, such as optimizing large-scale production and improving purification efficiency. This review presents the current state of recombinant keratin research by highlighting its advancements and exploring current biomaterial applications. While its applications remain limited compared to extracted keratin at this early stage, its potential offers future opportunities for extending its use in advanced material design and beyond biomedical fields. STATEMENT OF SIGNIFICANCE: Keratin and keratinized structures provide essential protection to tissues against mechanical stress and environmental damage, serving as foundational elements across diverse biological systems. This review discusses advancements in recombinant keratin technology, enabling high-purity, reproducible synthesis with controlled composition modifications that effectively overcome the limitations of traditional extraction methods. The innovations deepen our understanding of hierarchical assembly in keratin structures across various length scales, along with their reinforcing mechanisms and mechanical and biofunctional properties. These insights lay the groundwork for biomaterials tailored to regenerative medicine, wound healing, and other biomedical applications. By focusing on the unique capabilities of recombinant keratin, this review offers a valuable resource for future advancements in high-performance biomaterials across biomedical and biotechnological fields.

Exploring the Functional Properties of Hydrolyzed Keratin: Filling the Knowledge Gap on Surface Active, Emulsifying, and Thickening Properties

Hydrolyzed keratin (HK) refers to any hydrolysate of keratin of a different origin derived by acid, alkali, enzymatic, or other methods of hydrolysis. HK is water soluble and has distinct chemical-physical properties compared to fibrous keratin. Although HK is employed across various technological sectors, there is a notable gap in the literature regarding the detailed chemical-physical properties of commercially available HKs. This study aims to address this gap by providing a thorough analysis of the surface-active, emulsifying, and thickening properties of three commercially available HKs. The results reveal relevant differences among HKs marketed under the International Nomenclature Cosmetic Ingredient (INCI) name "Hydrolyzed Keratin," with variations in their chemical-physical properties, primarily influenced by molecular weight. Specifically, HKs with a higher average M w (>3000 Da) and protein content demonstrate enhanced emulsifying and thickening capabilities. Conversely, HKs with low M w (<1000 Da) do not show surface-active properties suitable for the preparation of emulsions. Therefore, this study underscores the need for the standardization of commercially available HK products to obtain biomaterials with tailored and specific chemical-physical properties, enhancing their potential applications in cosmetic and pharmaceutical topical formulations.

Bilayer vascular grafts separately composited with nitric oxide-releasing keratin conjugates and hydrogen sulfide-releasing heparin conjugates

Gasotransmitters such as nitric oxide (NO) and hydrogen sulfide (H2S) play crucial roles in various physiological and pathological processes, including angiogenesis, vascular homeostasis, thrombosis, inflammation, and remodeling. In addition to playing their respective roles, these two gasotransmitters act synergistically to regulate physiological pathways. This study designed and fabricated bilayer tissue-engineered vascular grafts with respective dual NO and H2S release capability for vascular cell regulation according to the spatiotemporal regulation strategy. Keratin/methacrylated arginine conjugate (KMA) was prepared and then electrospun with poly(ε-caprolactone) (PCL) with NO release potential, serving as the inner layer of grafts. For the outer layer of grafts with H2S release capability, heparin/4-aminobenzothioamide conjugate (HAT) was synthesized and then coaxially electrospun with PCL. These two conjugates could retain keratin's good biocompatibility and heparin's anticoagulation nature. The bilayer grafts selectively promoted the proliferation of HUVECs and inhibited the abnormal proliferation of HUASMCs. More importantly, the release of NO and H2S can stimulate the secretion of the other, thus resulting in a synergistic effect. In addition, these grafts exhibited antibacterial, antioxidant, and anti-inflammatory properties. Furthermore, the grafts could modulate macrophage polarization toward the M2 phenotype. In rat models with abdominal aorta replacement for 1 month of implantation, the grafts facilitated rapid endothelialization with enhanced anticoagulant and anti-calcification properties. These findings suggest that these bilayer grafts are promising candidates for small-diameter tissue-engineered vascular grafts.

Development of keratin-based fibers fabricated by interfacial polyelectrolyte complexation for suture applications

Interfacial Polyelectrolyte Complexation (IPC) is a convenient way to produce composite, micro-scale fibers. In this paper, we report the successful development of novel keratin-based IPC fibers and also demonstrate the feasibility of using these fibers as sutures through a proof-of-concept in vivo study. Two composite fibers were produced: chitosan-keratin (CK) and keratin-keratin (KK). These fibers were evaluated for their physico-chemical, mechanical and biochemical properties. In the dry state, the CK fiber had a greater Young's modulus of about 2 GPa while the KK fiber registered a longer strain-at-break of about 100 % due to the strain-stiffening effect. Notably, the keratins were found to assemble into amyloids within the composite fibers based on Congo red staining and Wide-Angle X-Ray Scattering. Functionally, both fibers were malleable could be weaved, braided and knotted. When used as sutures to close incisional wounds in mice over 21 days, these fibers were found to elicit minimal host tissue response and were partially degraded over the duration. Interestingly, the KK fiber evoked a lower extent of immune cell response and fibrous capsule encapsulation that was comparable to commercial, non-absorbable Dafilon® sutures. This work demonstrated the possibility of producing keratin-based IPC fibers which may find practicality as medical sutures.

An Integrated Modular Vaccination System for Spatiotemporally Separated Perioperative Cancer Immunotherapy

The perioperative period is crucial for determining postoperative tumor recurrence and metastasis. Various factors in postoperative lesions can diminish the therapeutic effect of conventional chemoradiotherapy, while emerging immunotherapy is restricted. The combination use of inflammatory inhibitors during treatment is also controversial. Here, a modular microneedle prepared from engineered keratin proteins is reported, which spatially and temporally differentiates the microenvironment of immune cell activation required for immunotherapy from that of wound healing. The recombinant keratin-84-T-based needle root layer, mainly retained in the epidermis, facilitated dendritic cell recruitment to achieve maximum antigen presentation of loaded vaccines. Meanwhile, the recombinant keratin-81-1Aα-based needle tip layer, located within the dermis, rapidly mitigated inflammatory responses while promoting tissue repair and regeneration. Unlike simply mixing immunotherapy and wound treatment, this spatiotemporal segmentation approach maximized the efficacy of immune therapeutics while promoting wound healing, making it suitable for application throughout the perioperative period.

Unlocking the Potential of Keratin: A Comprehensive Exploration from Extraction and Structural Properties to Cross-Disciplinary Applications

The rapid expansion of the livestock and poultry industry has led to a considerable increase in slaughter byproducts; however, exploring their potential applications still needs to be improved. These underutilized byproducts, which include nails, hides, skins, and bones, represent a significant loss of valuable biological resources. Among these materials, keratin has garnered considerable attention due to its unique properties as a natural biopolymer. Keratin exhibits outstanding mechanical properties and biocompatibility and has attracted increasing attention for its recovery and conversion into relevant application materials. However, natural keratin typically has a high sulfur content, complex 3D structure, and abundant hydrogen and disulfide bonds, which cause challenges in application. Current extraction for keratin includes physical, chemical, biological, and hybrid approaches. Combining multiple methods synergistically enhances protein extraction efficiency and purity, and facilitates the exploration of structure and functional properties. This review encompasses the structural characteristics, properties, extraction methods, and research progress related to keratin. The preparation and application of keratin composite materials in different forms, such as fibers, films, hydrogels, and scaffolds, are illustrated. Applications in several fields, including biomedicine, flexible electronic components, environmental materials and food packaging are discussed. Hopefully, this paper will provide a comprehensive understanding and guidance for further development and application of keratin materials.

Human keratin matrix in addition to standard of care accelerates healing of venous ulcers: a case series

OBJECTIVE

Venous leg ulcers (VLUs) are often large and complicated wounds that, despite combinations of advanced wound care techniques and systemic treatment of underlying vascular issues, take many months to heal and have high rates of recurrence. In this study, we investigated the efficacy of a novel wound care solution-human keratin matrix (HKM).

METHOD

A case series of VLUs were treated with HKM in conjunction with indicated vascular intervention and standard of care (SoC) procedures. For analysis, these wounds were divided into very large (>200 cm2) and smaller (<35 cm2) wounds.

RESULTS

The cohort comprised 16 VLUs (very large=7; smaller=9). Very large VLUs were reduced in size by an average of 71% within 10 weeks, and showed a 50% size reduction within four applications of HKM. Smaller VLUs reduced by 50% in size within the first three weeks of treatment, and 88.9% of these wounds healed completely with an average of 4.5 HKM applications over an average of 6.5 weeks.

CONCLUSION

The results of this series highlight the potential of HKM, in combination with indicated systemic interventions and SoC, as an effective treatment for hard-to-heal (chronic) VLUs, even in very large wounds.

Keratinous and corneous-based products towards circular bioeconomy: A research review

Keratins and corneous proteins are key components of biomaterials used in a wide range of applications and are potential substitutes for petrochemical-based products. Horns, hooves, feathers, claws, and similar animal tissues are abundant sources of α-keratin and corneous β-proteins, which are by-products of the food industry. Their close association with the meat industry raises environmental and ethical concerns regarding their disposal. To promote an eco-friendly and circular use of these materials in novel applications, efforts have focused on recovering these residues to develop sustainable, non-animal-related, affordable, and scalable procedures. Here, we review and examine biotechnological methods for extracting and expressing α-keratins and corneous β-proteins in microorganisms. This review highlights consolidated research trends in biomaterials, medical devices, food supplements, and packaging, demonstrating the keratin industry's potential to create innovative value-added products. Additionally, it analyzes the state of the art of related intellectual property and market size to underscore the potential within a circular bioeconomic model.

β-Cyclodextrin/dialdehyde glucan-coated keratin nanoparticles for oral delivery of insulin

Successful oral insulin administration can considerably enhance the quality of life (QOL) of diabetes patients who must frequently take insulin injections. However, Oral insulin administration is seriously hampered by gastrointestinal enzymes, wide pH range, mucus and mucosal layers, which limit insulin oral bioavailability to ≤2 %. Herein, we developed a simple, inexpensive and safe dual β-cyclodextrin/dialdehyde glucan-coated keratin nanoparticle (β-CD-K-IN-DG). The resulted β-CD-K-IN-DG not only gave the ultra-high insulin loading (encapsulation efficiency (98.52 %)), but also protected insulin from acid and enzymatic degradation. This β-CD-K-IN-DG had a notable hypoglycemic effect, there was almost 80 % insulin release after 4 h of incubation under hyperglycemic conditions. Ex vivo results confirmed that β-CD-K-IN-DG possessed high mucus-penetration ability. Transepithelial transport and uptake mechanism studies revealed that bypass transport pathway and endocytosis promoted β-CD-K-IN-DG entered intestinal epithelial cells, thus increased the bioavailability of insulin (12.27 %). The improved stability of insulin during in vivo transport implied that β-CD-K-IN-DG might be a potential tool for the effective oral insulin administration.

Development and Evaluation of Microencapsulated Oregano Essential Oil as an Alternative Treatment for Candida albicans Infections

Vulvovaginal candidiasis (VVC) is characterized as a very common fungal infection that significantly affects women's health worldwide. Essential oils (EOs) are currently being evaluated as an alternative therapy. The development of efficient techniques such as micro- or nanoencapsulation for protecting and controlling release is essential to overcome the limitations of EO applications. Therefore, the aim of this study was to develop and characterize oregano EO-loaded keratin microparticles (OEO-KMPs) as a potential treatment for VVC. OEO-KMPs were produced using high-intensity ultrasonic cycles and characterized in terms of morphological and physicochemical parameters. In vitro evaluation included assessing the toxicity of the OEO-KMPs and their effect against Candida albicans using microdilution and agar diffusion, while the activity against biofilm was quantified using colony forming units (CFU). The efficacy of the OEO-KMPs in an in vivo VVC mouse model was also studied. Female BALB/c mice were intravaginally infected with C. albicans, 24 h postinfection animals were treated intravaginally with 15 μL of OEO-KMPs and 24 h later vaginal fluid was analyzed for C. albicans and Lactobacillus growth (CFU mL-1). The results showed the stability of the OEO-KMPs over time, with high encapsulation efficiency and controlled release. This nanoparticle size facilitated penetration and completely inhibited the planktonic growth of C. albicans. In addition, an in vitro application of 2.5% of the OEO-KMPs eradicated mature C. albicans biofilms while preserving Lactobacillus species. In in vivo, a single intravaginal application of OEO-KMPs induced a reduction in C. albicans growth, while maintaining Lactobacillus species. In conclusion, this therapeutic approach with OEO-KMPs is promising as a potential alternative or complementary therapy for VVC while preserving vaginal microflora.

Exploring keratin composition variability for sustainable thermal insulator design

In pursuing sustainable thermal insulation solutions, this study explores the integration of human hair and feather keratin with alginate. The aim is to assess its potential in thermal insulation materials, focusing on the resultant composites' thermal and mechanical characteristics. The investigation uncovers that the type and proportion of keratin significantly influence the composites' porosity and thermal conductivity. Specifically, higher feather keratin content is associated with lesser sulfur and reduced crosslinking due to shorter amino acids, leading to increased porosity and pore sizes. This, in turn, results in a decrease in β-structured hydrogen bond networks, raising non-ordered protein structures and diminishing thermal conductivity from 0.044 W/(m·K) for pure alginate matrices to between 0.033 and 0.038 W/(m·K) for keratin-alginate composites, contingent upon the specific ratio of feather to hair keratin used. Mechanical evaluations further indicate that composites with a higher ratio of hair keratin exhibit an enhanced compressive modulus, ranging from 60 to 77 kPa, demonstrating the potential for tailored mechanical properties to suit various applications. The research underscores the critical role of sulfur content and the crosslinking index within keratin's structures, significantly impacting the thermal and mechanical properties of the matrices. The findings position keratin-based composites as environmentally friendly alternatives to traditional insulation materials.

Synthesis of Keratin Nanoparticles Extracted from Human Hair through Hydrolysis with Concentrated Sulfuric Acid: Characterization and Cytotoxicity

Human hair, composed primarily of keratin, represents a sustainable waste material suitable for various applications. Synthesizing keratin nanoparticles (KNPs) from human hair for biomedical uses is particularly attractive due to their biocompatibility. In this study, keratin was extracted from human hair using concentrated sulfuric acid as the hydrolysis agent for the first time. This process yielded KNPs in both the supernatant (KNPs-S) and precipitate (KNPs-P) phases. Characterization involved scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Zeta potential analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TG). KNPs-S and KNPs-P exhibited average diameters of 72 ± 5 nm and 27 ± 5 nm, respectively. The hydrolysis process induced a structural rearrangement favoring β-sheet structures over α-helices in the KNPs. These nanoparticles demonstrated negative Zeta potentials across the pH spectrum. KNPs-S showed higher cytotoxicity (CC50 = 176.67 µg/mL) and hemolytic activity, likely due to their smaller size compared to KNPs-P (CC50 = 246.21 µg/mL), particularly at concentrations of 500 and 1000 µg/mL. In contrast, KNPs-P did not exhibit hemolytic activity within the tested concentration range of 32.5 to 1000 µg/mL. Both KNPs demonstrated cytocompatibility with fibroblast cells in a dose-dependent manner. Compared to other methods reported in the literature and despite requiring careful washing and neutralization steps, sulfuric acid hydrolysis proved effective, rapid, and feasible for producing cytocompatible KNPs (biomaterials) in single-step synthesis.

Development of Innovative Biocomposites with Collagen, Keratin and Hydroxyapatite for Bone Tissue Engineering

This study follows the process for the development of an innovative biomimetic composite derived from bovine collagen with keratin, with hydroxyapatite being hybridized into its architecture, and it builds a comprehensive evaluation of the composite's characteristics. The novel biomimetic materials are tailored with special traits to be achieved for the repair of osteochondral defects (OCDs). The purpose of the present research is to create a reliable effective alternative to existing bone graft materials while leveraging the intrinsic properties of the components for enhanced osteoinduction and integration. The composites were characterized based on their morphological properties, including water absorption, through scanning electron microscopy (SEM), and their structural properties were characterized by Fourier-Transform Infrared Spectroscopy (FTIR). Biological performance was assessed in vitro using human bone marrow mesenchymal stem cells (BMSCs), focusing on cytotoxicity, cell viability, and the ability to support cell colonization with forthcoming results. This in vivo study illustrates the real potential that this class of novel composites exhibits in regard to bone and cartilage tissue engineering and encourages further exploration and development for future clinical applications.

Keratin from Animal By-Products: Structure, Characterization, Extraction and Application-A Review

Keratin is a structural fibrous protein and the core constituent of animal by-products from livestock such as wool, feathers, hooves, horns, and pig bristles. This natural polymer is also the main component of human hair and is present at an important percentage in human and animal skin. Significant amounts of keratin-rich animal tissues are discarded worldwide each year, ca. 12 M tons, and the share used for keratin extraction and added-value applications is still very low. An important stream of new potential raw materials, represented by animal by-products and human hair, is thus being lost, while a large-scale valorization could contribute to a circular bioeconomy and to the reduction in the environmental fingerprint of those tissues. Fortunately, scientific research has made much important progress in the last 10-15 years in the better understanding of the complex keratin architecture and its variability among different animal tissues, in the development of tailored extraction processes, and in the screening of new potential applications. Hence, this review aims at a discussion of the recent findings in the characterization of keratin and keratin-rich animal by-product structures, as well as in keratin recovery by conventional and emerging techniques and advances in valorization in several fields.

Unveiling Trends: Nanoscale Materials Shaping Emerging Biomedical Applications

The realm of biomedical materials continues to evolve rapidly, driven by innovative research across interdisciplinary domains. Leveraging big data from the CAS Content Collection, this study employs quantitative analysis through natural language processing (NLP) to identify six emerging areas within nanoscale materials for biomedical applications. These areas encompass self-healing, bioelectronic, programmable, lipid-based, protein-based, and antibacterial materials. Our Nano Focus delves into the multifaceted utilization of nanoscale materials in these domains, spanning from augmenting physical and electronic properties for interfacing with human tissue to facilitating intricate functionalities like programmable drug delivery.

Caldanaerobacter subterraneus subsp. keratinolyticus subsp. nov., a Novel Feather-Degrading Anaerobic Thermophile

Caldanaerobacter subterraneus subsp. keratinolyticus subsp. nov. strain KAk was isolated from a geothermal hot spring located in Kazakhstan. Growth occurred at temperatures ranging from 50 to 80 °C, with approximately 70 °C as optimum. It also thrived in pH conditions ranging from 4.0 to 9.0, with the best growth occurring at 6.8. Under optimal conditions in a glucose-containing medium, the cells were predominantly observed singly, in pairs, or less frequently in chains, and did not form endospores. However, under conditions involving growth with merino wool or feathers, or under suboptimal conditions, the cells of strain KAk exhibited a notably elongated and thinner morphology, with lengths ranging from 5 to 8 µm, and spores were observed. The KAk strain exhibited efficient degradation of feather keratin and merino wool at temperatures ranging from 65 to 70 °C. Analysis of the 16S rRNA gene sequence placed KAk within the genus Caldanaerobacter, family Thermoanaerobacteraceae, with the highest similarity to C. subterraneus subsp. tengcongensis MB4T (98.84% sequence identity). Furthermore, our analysis of the draft genome sequence indicated a genome size of 2.4 Mbp, accompanied by a G+C value of 37.6 mol%. This study elucidated the physiological and genomic characteristics of strain KAk, highlighting its keratinolytic capabilities and distinctiveness compared to other members of the genus Caldanaerobacter.

Keratin-PNIPAM Hybrid Microgels: Preparation, Morphology and Swelling Properties

Combinations of synthetic polymers, such as poly(N-isopropylacrylamide) (PNIPAM), with natural biomolecules, such as keratin, show potential in the field of biomedicine, since these hybrids merge the thermoresponsive properties of PNIPAM with the bioactive characteristics of keratin. This synergy aims to produce hybrids that can respond to environmental stimuli while maintaining biocompatibility and functionality, making them suitable for various medical and biotechnological uses. In this study, we exploit keratin derived from wool waste in the textile industry, extracted via sulfitolysis, to synthesize hybrids with PNIPAM microgel. Utilizing two distinct methods-polymerization of NIPAM with keratin (HYB-P) and mixing preformed PNIPAM microgels with keratin (HYB-M)-resulted in hybrids with 20% and 25% keratin content, respectively. Dynamic light scattering (DLS) and transmission electron microscopic (TEM) analyses indicated the formation of colloidal systems with particle sizes of around 110 nm for HYB-P and 518 nm for HYB-M. The presence of keratin in both systems, 20% and 25%, respectively, was confirmed by spectroscopic (FTIR and NMR) and elemental analyses. Distinct structural differences were observed between HYB-P and HYB-M, suggesting a graft copolymer configuration for the former hybrid and a complexation for the latter one. Furthermore, these hybrids demonstrated temperature responsiveness akin to PNIPAM microgels and pH responsiveness, underscoring their potential for diverse biomedical applications.

Bridging Nature and Engineering: Protein-Derived Materials for Bio-Inspired Applications

The sophisticated, elegant protein-polymers designed by nature can serve as inspiration to redesign and biomanufacture protein-based materials using synthetic biology. Historically, petro-based polymeric materials have dominated industrial activities, consequently transforming our way of living. While this benefits humans, the fabrication and disposal of these materials causes environmental sustainability challenges. Fortunately, protein-based biopolymers can compete with and potentially surpass the performance of petro-based polymers because they can be biologically produced and degraded in an environmentally friendly fashion. This paper reviews four groups of protein-based polymers, including fibrous proteins (collagen, silk fibroin, fibrillin, and keratin), elastomeric proteins (elastin, resilin, and wheat glutenin), adhesive/matrix proteins (spongin and conchiolin), and cyanophycin. We discuss the connection between protein sequence, structure, function, and biomimetic applications. Protein engineering techniques, such as directed evolution and rational design, can be used to improve the functionality of natural protein-based materials. For example, the inclusion of specific protein domains, particularly those observed in structural proteins, such as silk and collagen, enables the creation of novel biomimetic materials with exceptional mechanical properties and adaptability. This review also discusses recent advancements in the production and application of new protein-based materials through the approach of synthetic biology combined biomimetics, providing insight for future research and development of cutting-edge bio-inspired products. Protein-based polymers that utilize nature's designs as a base, then modified by advancements at the intersection of biology and engineering, may provide mankind with more sustainable products.

Material-specific binding peptides empower sustainable innovations in plant health, biocatalysis, medicine and microplastic quantification

Material-binding peptides (MBPs) have emerged as a diverse and innovation-enabling class of peptides in applications such as plant-/human health, immobilization of catalysts, bioactive coatings, accelerated polymer degradation and analytics for micro-/nanoplastics quantification. Progress has been fuelled by recent advancements in protein engineering methodologies and advances in computational and analytical methodologies, which allow the design of, for instance, material-specific MBPs with fine-tuned binding strength for numerous demands in material science applications. A genetic or chemical conjugation of second (biological, chemical or physical property-changing) functionality to MBPs empowers the design of advanced (hybrid) materials, bioactive coatings and analytical tools. In this review, we provide a comprehensive overview comprising naturally occurring MBPs and their function in nature, binding properties of short man-made MBPs (<20 amino acids) mainly obtained from phage-display libraries, and medium-sized binding peptides (20-100 amino acids) that have been reported to bind to metals, polymers or other industrially produced materials. The goal of this review is to provide an in-depth understanding of molecular interactions between materials and material-specific binding peptides, and thereby empower the use of MBPs in material science applications. Protein engineering methodologies and selected examples to tailor MBPs toward applications in agriculture with a focus on plant health, biocatalysis, medicine and environmental monitoring serve as examples of the transformative power of MBPs for various industrial applications. An emphasis will be given to MBPs' role in detecting and quantifying microplastics in high throughput, distinguishing microplastics from other environmental particles, and thereby assisting to close an analytical gap in food safety and monitoring of environmental plastic pollution. In essence, this review aims to provide an overview among researchers from diverse disciplines in respect to material-(specific) binding of MBPs, protein engineering methodologies to tailor their properties to application demands, re-engineering for material science applications using MBPs, and thereby inspire researchers to employ MBPs in their research.

Ethnopharmacological uses of fauna among the people of central Punjab, Pakistan

Introduction

The utilization of fauna and fauna-based byproducts in ethnomedicinal usages has been a longstanding human activity, practiced across various cultures worldwide. This study focuses on investigating the utilization of animal-based traditional medicine by the people of Pakistan, specifically in the Gujranwala area.

Methods

Data collection took place from January to September 2019 through interviews with local communities. Ethnomedicinal applications of animal products were analyzed using several indices, including Relative Frequency of Citation (RFC), Relative Popularity Level (RPL), Folk Use Value (FL), and Relative Occurrence Percentage (ROP).

Results

The study identified the use of different body parts of 54 species of animals in treating various diseases and health issues. These include but are not limited to skin infections, sexual problems, pain management (e.g., in the backbone and joints), eyesight issues, immunity enhancement, cold, weakness, burns, smallpox, wounds, poisoning, muscular pain, arthritis, diabetes, fever, epilepsy, allergies, asthma, herpes, ear pain, paralysis, cough, swelling, cancer, bronchitis, girls' maturity, and stomach-related problems. Certain species of fauna were noted by informers with high "frequency of citation" (FC), ranging from 1 to 77. For instance, the black cobra was the most frequently cited animal for eyesight issues (FC = 77), followed by the domestic rabbit for burn treatment (FC = 67), and the Indus Valley spiny-tailed ground lizard for sexual problems (FC = 66). Passer domesticus and Gallus gallus were noted to have the highest ROP value of 99.

Discussion

The findings of this study provide valuable preliminary insights for the conservation of fauna in the Gujranwala region of Punjab, Pakistan. Additionally, screening these animals for medicinally active compounds could potentially lead to the development of novel animal-based medications, contributing to both traditional medicine preservation and modern pharmaceutical advancements.

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.

Keratin as an effective coating material for in vitro stem cell culture, induced differentiation and wound healing assays

The utilization of stem cells in tissue engineering holds great promise as efficient tools for tissue regeneration and in treating numerous musculoskeletal diseases. However, several limiting factors, such as precise delivery and control of differentiation of these stem cells as well as mimicking the microenvironment required to modulate stem cell behaviour in-vivo, have given rise to an urgent need for the development of new biomaterials which could be tailored to enhance cell renewal and/or direct cell fates. Keratin-rich biological materials offer several advantages, such as biocompatibility, tailorable mechanical properties, huge bioavailability, non-toxicity, non-immunogenic, and intrinsic tissue repair and/or regeneration capabilities, which makes them highly valued. In the present work, we report the preparation of keratin-based bio-materials from goat hair waste and its effectiveness as a coating material for in vitro culture and induced differentiation of mesenchymal stem cells (MSC's) and primary goat fibroblast cells. Since no known keratinase enzymes are expressed as such in human and/or animal systems, these keratin biomaterials could be used to slow the rate of degradation and deliver keratin-loaded stem cell scaffolds to induce their directed differentiation in vivo. The generated keratin materials have been characterized for surface morphology, protein structures, size and other properties using SDS-PAGE, LC/MS-MS, SEM, FTIR etc. Also, in vitro cell culture assays such as cell adhesion, viability using MTT, live dead assays, differentiation assays and in vitro scratch/wound healing assays were performed. Our results provide important data supporting tissue engineering applications of these keratinous biomaterials by combining the unique biological characteristics of goat hair-derived keratin material with the regenerative power of stem cells and their combinatorial use in applications such as disease treatment and injury repair as well as their use in the preparation of wound healing products, such as dressings and bandages, for management of clinical care in animals.

New Inhibitor Based on Hydrolyzed Keratin Peptides for Stainless Steel Corrosion in Physiological Serum: An Electrochemical and Thermodynamic Study

Reducing the impact of some biological fluids on bioimplants involves the control of surface characteristics by modeling the interface architecture and assembling ecofriendly thin films to retard corrosion. Therefore, a mixture of hydrolyzed keratin peptides (HKER) was investigated as a corrosion inhibitor for 304L stainless steel (SS) in physiological serum (PS), using electrochemical measurements associated with optical microscopy and atomic force microscopy (AFM). The tests, performed for various concentrations of the inhibitor at different temperatures, showed that the inhibition efficiency (IE) decreased with a rise in temperature and proportionally increased with the HKER concentration, reaching its maximum level, around 88%, at 25 °C, with a concentration of 40 g L-1 HKER in physiological serum. The experimental data best fitted the El-Awady adsorption model. The activation parameters (Ea, ∆Ha and ∆Sa) and the adsorption ones (∆Gads0, ∆Hads, ∆Sads) have highlighted a mixed action mechanism of HKER, revealing that physisorption prevails over chemisorption. AFM parameters, such as the average roughness (Ra), root-mean-square roughness (Rq) and maximum peak-to-valley height (Rp-v), confirmed HKER adsorption, indicating that a smoother surface of the 304L stainless steel was obtained when immersed in a PS-containing inhibitor, compared to the surface designed in blank solution, due to the development of a protective layer on the alloy surface.

Keratin protein nanofibers from merino wool yarn: a top-down approach for the disintegration of hierarchical wool architecture to extract α-keratin protein nanofibers

We report the extraction of keratin nanofibers from the medulla of a parent yarn after denaturing the cuticle and cortex microstructures of a merino wool yarn. Controlled alkaline hydrolysis, followed by high-speed blending in acetic acid, allowed for the extraction of keratin protein nanofibers with an average diameter of 25 nm and a length of less than 3 μm. SEM and AFM analyses showed the removal of cuticle cells from the yarn. FT-IR and DSC analyses confirmed the hydrolysis and denaturation of the sheet protein matrix of cuticle cells. XPS analysis provided strong evidence for the gradual removal of the epicuticle, cuticle cells, and cortex of the hierarchical wool structure with an increase in alkaline hydrolysis conditions. It was confirmed that the merino wool yarn subjected to hydrolysis under alkaline conditions exposed its internal fibrillar surface. In an acetic acid medium, these fibrillar surfaces obtained a surface charge, which further supported the defibrillation of the structure into its individual nanofibrils during high-speed blending. The extracted nanostructures constitute mainly α-helical proteins. The morphology of the nanofibers is composed of a uniform circular cross-section based on the images obtained using AFM, TEM, and SEM. The extracted nanofibers were successfully fabricated into transparent sheets that can be used in several applications.

Nitric Oxide-Releasing Porous Coating with Antibacterial Activity and Blood Compatibility

Nitric oxide (NO)-releasing coating is promising to enhance the biocompatibility of medical devices. In this study, polyurethane (PU) and S-nitrosated keratin (KSNO) were dissolved with dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF) to prepare a coating solution. This solution is facile to form a porous coating on various substrates based on solvent-evaporation-induced phase separation (SEIPS). The coating could continuously release NO up to 200 h in the presence of ascorbic acid (Asc). In addition, the coating could accelerate endothelialization by promoting the viability of human umbilical vein endothelial cells (HUVECs) while inhibiting the proliferation of human umbilical artery smooth muscle cells (HUASMCs). Furthermore, the coating had good antibacterial activity and blood compatibility. Taken together, this universal coating provides wider potential applications in the field of cardiovascular implants.

Keratin- and VEGF-Incorporated Honey-Based Sponge-Nanofiber Dressing: An Ideal Construct for Wound Healing

To overcome the drawbacks of single-layered wound dressings, bilayer dressings are now introduced as an alternative to achieve effective and long-term treatment. Here, a bilayer dressing composed of electrospun nanofibers in the bottom layer (BL) and a sponge structure as the top layer (TL) is presented. Hydrophilic poly(acrylic acid) (PAAc)-honey (Hny) with interconnected pores of 76.04 μm was prepared as the TL and keratin (Kr), Hny, and vascular endothelial growth factor (VEGF) were prepared as the BL. VEGF indicates a gradual release over 7 days, promoting angiogenesis, as proven by the chick chorioallantoic membrane assay and in vivo tissue histomorphology observation. Additionally, the fabricated dressing material indicated a satisfactory tensile profile, cytocompatibility for human keratinocyte cells, and the ability to promote cell attachment and migration. The in vivo animal model demonstrated that the full-thickness wound healed faster when it was covered with PAAc-Hny/Hny-Kr-VEGF than in other groups. Additionally, faster blood vessel formation, collagen synthetization, and epidermal layer generation were also confirmed, which have proven efficient healing acceleration in wounds treated with synthesized bilayer dressings. Our findings indicated that the fabricated material can be promising as a functional wound dressing.

Scales of non-avian reptiles and their derivatives contain corneous beta proteins coded from genes localized in the Epidermal Differentiation Complex

The evolution of modern reptiles from basic reptilian ancestors gave rise to scaled vertebrates. Scales are of different types, and their corneous layer can shed frequently during the year in lepidosaurians (lizards, snakes), 1-2 times per year in the tuatara and in some freshwater turtle, irregularly in different parts of the body in crocodilians, or simply wore superficially in marine and terrestrial turtles. Lepidosaurians possess tuberculate, non-overlapped or variably overlapped scales with inter-scale (hinge) regions. The latter are hidden underneath the outer scale surface or may be more exposed in specific body areas. Hinge regions allow stretching during growth and movement so that the skin remains mechanically functional. Crocodilian and turtles feature flat and shield scales (scutes) with narrow inter-scale regions for stretching and growth. The epidermis of non-avian reptilian hinge regions is much thinner than the exposed outer surface of scales and is less cornified. Despite the thickness of the epidermis, scales are mainly composed of variably amount of Corneous Beta Proteins (CBPs) that are coded in a gene cluster known as EDC (Epidermal Differentiation Complex). These are small proteins, 100-200 amino acid long of 8-25 kDa, rich in glycine and cysteine but also in serine, proline and valine that participate to the formation of beta-sheets in the internal part of the protein, the beta-region. This region determines the further polymerization of CBPs in filamentous proteins that, together a network of Intermediate Filament Keratins (IFKs) and other minor epidermal proteins from the EDC make the variable pliable or inflexible corneous material of reptilian scales, claws and of turtle beak. The acquisition of scales and skin derivatives with different mechanical and material properties, mainly due to the evolution of reptile CBPs, is essential for the life and different adaptations of these vertebrates.

Recent advances in keratin for biomedical applications

The development of keratin-based biomaterials provides an approach to addressing related environmental pollutants and turns waste into wealth. Keratin possesses various merits, such as biocompatibility, biodegradability, hemostasis, non-immunogenicity, antibacterial activity, antioxidation, multi-responsiveness, and abundance in nature. Additionally, keratin biomaterials have been extensively employed in various biomedical applications such as drug delivery, wound healing, and tissue engineering. This review focuses on the properties and biomedical applications of keratin biomaterials. It is anticipated to provide valuable insights for the research and development of keratin biomaterials.

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.

Considerations and recommendations on camouflage in alopecia in Black women

Alopecia is among the leading dermatological concerns affecting Black women. For many women, hair is a central component of identity and self-expression, the loss of which can have significant psychosocial effects. Hair camouflage is often utilized to minimize the visibility of hair loss, provide aesthetic benefits, and improve quality of life. The versatility and affordability of hair camouflage allows patients with alopecia to conceal hair loss, increasing self-confidence, and decreasing social stigma. However, hair camouflage practices often involve adhesives, chemicals, and/or high-tension braiding, all of which can exacerbate alopecia. Accordingly, special considerations should be made to protect patients' natural hair from damage while using these styling practices. A better understanding of best practices for some of the most widely used camouflage options-wigs, extensions, topical hair fibers, and micropigmentation-can help clinicians establish rapport with Black women and optimize individually-tailored therapeutic plans during active treatment and end-stage hair loss.

Polymeric biomaterials for wound healing

Skin indicates a person's state of health and is so important that it influences a person's emotional and psychological behavior. In this context, the effective treatment of wounds is a major concern, since several conventional wound healing materials have not been able to provide adequate healing, often leading to scar formation. Hence, the development of innovative biomaterials for wound healing is essential. Natural and synthetic polymers are used extensively for wound dressings and scaffold production. Both natural and synthetic polymers have beneficial properties and limitations, so they are often used in combination to overcome overcome their individual limitations. The use of different polymers in the production of biomaterials has proven to be a promising alternative for the treatment of wounds, as their capacity to accelerate the healing process has been demonstrated in many studies. Thus, this work focuses on describing several currently commercially available solutions used for the management of skin wounds, such as polymeric biomaterials for skin substitutes. New directions, strategies, and innovative technologies for the design of polymeric biomaterials are also addressed, providing solutions for deep burns, personalized care and faster healing.

Magnetic Analysis of MgFe Hydrotalcites as Powder and Dispersed in Thin Films within a Keratin Matrix

Hydrotalcites (HTlcs) are a class of nanostructured layered materials that may be employed in a variety of applications, from green to bio technologies. In this paper, we report an investigation on HTlcs made of Mg and Fe, recently employed to improve the growth in vitro of osteoblasts within a keratin sponge. We carried out an analysis of powder materials and of HTlcs dispersed in keratin and spin-coated on a Si/SiO₂ substrate at different temperatures. A magnetic study of the powders was carried out with a Quantum Design Physical Property Measurement System equipped with a Vibrating Sample Magnetometer. The data gathered prove that these HTlcs are fully paramagnetic, and keratin showed a very small magnetic response. Optical and Atomic Force Microscopy analyses of the thin films provide a detailed picture of clusters randomly dispersed in the films with various dimensions. The magnetic properties of these films were characterized using the Nano Magneto Optical Kerr Effect (NanoMOKE) down to 7.5 K. The data collected show that the local magnetic properties can be mapped with a micrometric resolution distinguishing HTlc regions from keratin ones. This approach opens new perspectives in the characterization of these composite materials.

Protein-Based Hydrogels and Their Biomedical Applications

Hydrogels made from proteins are attractive materials for diverse medical applications, as they are biocompatible, biodegradable, and amenable to chemical and biological modifications. Recent advances in protein engineering, synthetic biology, and material science have enabled the fine-tuning of protein sequences, hydrogel structures, and hydrogel mechanical properties, allowing for a broad range of biomedical applications using protein hydrogels. This article reviews recent progresses on protein hydrogels with special focus on those made of microbially produced proteins. We discuss different hydrogel formation strategies and their associated hydrogel properties. We also review various biomedical applications, categorized by the origin of protein sequences. Lastly, current challenges and future opportunities in engineering protein-based hydrogels are discussed. We hope this review will inspire new ideas in material innovation, leading to advanced protein hydrogels with desirable properties for a wide range of biomedical applications.

An in vitro analysis of the hemostatic efficacy of fibrinogen precipitation with varied keratin fraction compositions

In preclinical studies, human hair has demonstrated effective hemostatic properties, potentially attributed to keratin proteins facilitating rapid conversion of fibrinogen to fibrin during coagulation. However, the rational use of human hair keratin for hemostasis remains unclear, given its complex mixture of proteins with diverse molecular weights and structures, leading to variable hemostatic capacity. To optimize the rational utilization of human hair keratin for hemostasis, we investigated the effects of different keratin fractions on keratin-mediated fibrinogen precipitation using a fibrin generation assay. Our study focused on high molecular weight keratin intermediate filaments (KIFs) and lower molecular weight keratin-associated proteins (KAPs) combined in various ratios during the fibrin generation. Scanning electron microscope analysis of the precipitates revealed a filamentous pattern with a broad distribution of fiber diameters, likely due to the diversity of keratin mixtures involved. An equal proportion of KIFs and KAPs in the mixture yielded the most extensive precipitation of soluble fibrinogen in an in vitro study, potentially due to structure-induced exposure of active sites. However, all hair protein samples exhibited diverse catalytic behaviors compared to thrombin, highlighting the potential of utilizing specific hair fractions to develop hair protein-based hemostatic materials with optimized capacity.

Innovative Wound Healing Hydrogel Containing Chicken Feather Keratin and Soy Isoflavone Genistein: In Vivo Studies

The current study was performed to isolate keratin from chicken feathers with an intention to develop a keratin-genistein wound-healing hydrogel, along with its in vivo analysis. Pre-formulation aspects were analysed by using FTIR; SEM; HPTLC, while gel was characterized for gel strength, viscosity, spreadability, drug content, etc. Additionally, an in vivo study along with biochemical factors against pro-inflammatory factors and histopathological studies were conducted to determine possible wound-healing and anti-inflammatory effects. Pre-formulation studies revealed the presence of amide bonds with region of dense fibrous keratin and an internal porous network in extracted keratin, which corresponds with standard keratin. Evaluation of optimised keratin-genistein hydrogel indicated the development of neutral, non-sticky hydrogel which spread evenly on the skin. In vivo studies in rats indicate higher degrees of wound-healing in combined hydrogel (94.65%) for a duration of 14 days as compared to an individual hydrogel formulation with the development of the epidermis and excessive proliferation of fibrous connective tissue indicating wound repair. Furthermore, the hydrogel inhibited the overexpression of IL-6 gene along with other pro-inflammatory factors, indicating its anti-inflammatory effects. In order to find out the possibility of closure of wounds and anti-inflammatory properties of the novel product, an in vivo investigation into the healing of wounds in laboratory animals was carried out through biochemical (ELISA and qRT-PCR) analyses against inflammatory markers (IL-2, IL-6, IL-1, IL-10, and COX-2) and histopathological (liver, skin, and the kidneys) investigations. Based on the results, we conclude that keratin-genistein hydrogel is a promising therapeutic molecule for the management of wound repair.

Assessment of the Efficacy of an LL-37-Encapsulated Keratin Hydrogel for the Treatment of Full-Thickness Wounds

Wound healing remains a burdensome healthcare problem due to moisture loss and bacterial infection. Advanced hydrogel dressings can help to resolve these issues by assisting and accelerating regenerative processes such as cell migration and angiogenesis because of the similarities between their composition and structure with natural skin. In this study, we aimed to develop a keratin-based hydrogel dressing and investigate the impact of the delivery of LL-37 antimicrobial peptide using this hydrogel in treating full-thickness rat wounds. Therefore, oxidized (keratose) and reduced (kerateine) keratins were utilized to prepare 10% (w/v) hydrogels with different ratios of keratose and kerateine. The mechanical properties of these hydrogels with compressive modulus of 6-32 kPa and tan δ <1 render them suitable for wound healing applications. Also, sustained release of LL-37 from the keratin hydrogel was achieved, which can lead to superior wound healing. In vitro studies confirmed that LL-37 containing 25:75% of keratose/kerateine (L-KO25:KN75) would result in significant fibroblast proliferation (∼85% on day 7), adhesion (∼90 cells/HPF), and migration (73% scratch closure after 12 h and complete closure after 24 h). Also, L-KO25:KN75 is capable of eradicating both Gram-negative and Gram-positive bacteria after 18 h. According to in vivo assessment of L-KO25:KN75, wound closure at day 21 was >98% and microvessel density (>30 vessels/HPF at day 14) was significantly superior in comparison to other treatment groups. The mRNA expression of VEGF and IL-6 was also increased in the L-KO25:KN75-treated group and contributed to proper wound healing. Therefore, the LL-37-containing keratin hydrogel ameliorated wound closure, and also angiogenesis was enhanced as a result of LL-37 delivery. These results suggested that the L-KO25:KN75 hydrogel could be a sustainable substitute for skin tissue regeneration in medical applications.

Chlorhexidine-loaded polysulfobetaine/keratin hydrogels with antioxidant and antibacterial activity for infected wound healing

Multifunctional hydrogel dressings are promising for wound healing. In the study, chlorhexidine(CHX) loaded double network hydrogels were prepared by free radical polymerization of sulfobetaine and oxidative self-crosslinking of reduced keratin. The introduced keratin and CHX endowed hydrogels with cytocompatibility, antioxidant capability as well as enhanced antibacterial activity due to the antifouling property of polysulfobetaine. These hydrogels exhibited acidity, glutathione(GSH), and trypsin triple-responsive release behaviors, resulting in the accelerated release of CHX under wound microenvironments. Intriguingly, the freeze-drying hydrogels could be ground to powders and sprinkled on the irregular wound bed, followed by absorbing wound fluid to reform hydrogel in situ. These aerogel powders were more convenient for sterilization, formulation, and storage. Further, these aerogel powders could be rejected after being mixed with an appropriate amount of water. In vivo infected wound healing confirmed that the aerogel powder dressing significantly promoted collagen deposition and reduced inflammation, thereby accelerating the closure and regeneration of skin wounds. Taken together, these degradable aerogel powders have great potential applications for wound healing.

Nitric oxide releasing poly(vinyl alcohol)/S-nitrosated keratin film as a potential vascular graft

Nitric oxide (NO) releasing vascular graft is promising due to its merits of thromboembolism reduction and endothelialization promotion. In this study, keratin-based NO donor of S-nitrosated keratin (KSNO) was blended with poly(vinyl alcohol) (PVA) and further crosslinked with sodium trimetaphosphate (STMP) to afford PVA/KSNO biocomposite films. These films could release NO sustainably for up to 10 days, resulting in the promotion of HUVECs growth and the inhibition of HUASMCs growth. In addition, these films displayed good blood compatibility and antibacterial activity. Taken together, these films have potential applications in vascular grafts.

Exploring the Effects of Wetting and Free Fatty Acid Deposition on an Atomistic Hair Fiber Surface Model Incorporating Keratin-Associated Protein 5-1

The complex development of cosmetic and medical formulations relies on an ever-growing accuracy of predictive models of hair surfaces. Hitherto, modeling efforts have focused on the description of 18-methyl eicosanoic acid (18-MEA), the primary fatty acid covalently attached to the hair surface, without explicit modeling of the protein layer. Herein, the molecular details of the outermost surface of the human hair fiber surface, also called the F-layer, were studied using molecular dynamics (MD) simulations. The F-layer is composed primarily of keratin-associated proteins KAP5 and KAP10, which are decorated with 18-MEA on the outer surface of a hair fiber. In our molecular model, we incorporated KAP5-1 and evaluated the surface properties of 18-MEA through MD simulations, resulting in 18-MEA surface density, layer thickness, and tilt angles in agreement with previous experimental and computational studies. Subsequent models with reduced 18-MEA surface density were also generated to mimic damaged hair surfaces. Response to wetting of virgin and damaged hair showed rearrangement of 18-MEA on the surface, allowing for water penetration into the protein layer. To demonstrate a potential use case for these atomistic models, we deposited naturally occurring fatty acids and measured 18-MEA's response in both dry and wet conditions. As fatty acids are often incorporated in shampoo formulations, this work demonstrates the ability to model the adsorption of ingredients on hair surfaces. This study illustrates, for the first time, the complex behavior of a realistic F-layer at the molecular level and opens up the possibility of studying the adsorption behavior of larger, more complex molecules and formulations.

Human hair proteins as natural reactive oxygen species scavengers for in vitro applications

Human hair proteins are recognized for their intrinsically high cysteine content. They can be solubilized while preserving their highly reductive thiol groups for free radical scavenging applications. The presence of aromatic and nucleophilic amino acids such as methionine, serine, phenylalanine, and threonine further contribute to the antioxidative potential of this material. Herein, utilizing the DPPH (2,2-diphenyl-1-picrylhydrazyl) and acellular 2',7'-dichlorodihydrofluorescein diacetate (H₂ DCFDA) assays, keratins are demonstrated to possess the highest radical scavenging activity among the studied hair proteins. Consequently, protection against hydrogen peroxide-induced oxidative stress in human dermal fibroblasts (HDFs) cultured in human hair keratin supplemented media is demonstrated. Quenching of reactive oxygen species in the HDF is observed using the CellROX Green dye and the expression levels of antioxidant (HMOX1, SOD2, GPX1) and tumor suppressor (TP53) genes is analyzed using qPCR. Collectively, this study presents further evidence and demonstrates the in vitro application potential of hair proteins, especially keratins, as an antioxidizing supplement.

DNA and protein analyses of hair in forensic genetics

Hair is one of the most common pieces of biological evidence found at a crime scene and plays an essential role in forensic investigation. Hairs, especially non-follicular hairs, are usually found at various crime scenes, either by natural shedding or by forcible shedding. However, the genetic material in hairs is usually highly degraded, which makes forensic analysis difficult. As a result, the value of hair has not been fully exploited in forensic investigations and trials. In recent years, with advances in molecular biology, forensic analysis of hair has achieved remarkable strides and provided crucial clues in numerous cases. This article reviews recent developments in DNA and protein analysis of hair and attempts to provide a comprehensive solution to improve forensic hair analysis.

Mechanical anisotropy of hair affected by genetic diseases highlights structural information related to differential crosslinking in keratins

Previous work with Atomic Force Microscope (AFM) nanoindentation, on longitudinal and cross-sections of the human hair fibre, allowed for the derivation of a model for the mechanical behaviour of human hair, called the Anisotropic Index. Expanding that research further, and by applying this model, the nanomechanical behaviour of hairs from patients with the disease Trichothiodystrophy (TTD) has been examined and structural insights, gained from combining the AFM results with Differential Scanning Calorimetry (DSC) experiments and tensile measurements, suggests that TTD-affected hairs have a relatively increased amount of Keratin Intermediate Filaments, contained in compartments of differing crosslinking extent. The associated calculations of axial and transverse Young's Moduli deliver values in good agreement with the measured fibre mechanics. Furthermore, comparing these findings with the results previously obtained from the study of hairs from patients with the disease Monilethrix, it is shown that the Anisotropic Index correlates well with the known deficiencies in both hair types obtained from such patients and allows for discerning between the Control hair and from those affected by the two diseases. AFM nanoindentation along and across the fibre axis and the Anisotropic Index thus appear to reveal structural details of hair not otherwise acquirable, whilst DSC may offer a quick and simple method for distinguishing between different severities of TTD.

Effect of ultrasound on keratin valorization from chicken feather waste: Process optimization and keratin characterization

Chicken feather (CF) has been deemed as one of the main poultry byproducts with a large amount produced globally. However, the robust chemical nature of chicken feathers has been limiting in its wide-scale utilization and valorization. The study proposed a strategy of keratin regeneration from chicken feather combining ultrasound and Cysteine (Cys)-reduction for keratin regeneration. First, the ultrasonic effect on feather degradation and keratin properties was systematically explored based on Cys-reduction. Results showed that the feather dissolution was significantly improved by increasing both ultrasonic time and power, and the former had a greater impact on keratin yield. However, the treatment time over 4 h led to a decrease of keratin yield, producing more soluble peptides, > 9.7 % of which were < 0.5 kDa. Meanwhile, prolonging time decreased the thermal stability with weight loss at a lower temperature and amino acids content (e.g., Ser, Pro and Gly) of keratin. Conversely, no remarkable damage in chemical structure and thermal stability of regenerated keratin was observed by only increasing ultrasonic power, while the keratin solubility was notably promoted and reached 745.72 mg·g^-1 in NaOH (0.1 M) solution (400 W, 4 h). The regenerated keratin under optimal conditions (130 W, 2.7 h, and 15 % of Cys) possessed better solubility while without obvious damage in chemical structure, thermal stability, and amino acids composition. The study illustrated that ultrasound physically improved CF degradation and keratin solubility without nature damage and provided an alternative for keratin regeneration involving no toxic reagent, probably holding promise in the utilization and valorization of feather waste.

Emerging Antimicrobial and Immunomodulatory Fiber-Based Scaffolding Systems for Treating Diabetic Foot Ulcers

Diabetic foot ulcers (DFUs) are one of the main complications of diabetes and are characterized by their complexity and severity, which are frequently aggravated by overexpressed inflammatory factors and polymicrobial infections. Most dressing systems offer a passive action in the treatment of DFUs, being frequently combined with antibiotic or immunomodulatory therapies. However, in many instances due to these combined therapies' inability to properly fight microbial presence, and provide a suitable, breathable and moist environment that is also capable of protecting the site from secondary microbial invasions or further harm, aggravation of the wound state is unavoidable and lower limb amputations are necessary. Considering these limitations and knowing of the urgent demand for new and more effective therapeutic systems for DFU care that will guarantee the quality of life for patients, research in this field has boomed in the last few years. In this review, the emerging innovations in DFU dressing systems via fiber-based scaffolds modified with bioactive compounds have been compiled; data focused on the innovations introduced in the last five years (2017-2022). A generalized overview of the classifications and constraints associated with DFUs healing and the bioactive agents, both antimicrobial and immunomodulatory, that can contribute actively to surpass such issues, has also been provided.

Molecular Structure and Dynamics in Wet Gecko β-Keratin

Molecular dynamics simulations are performed to investigate the molecular picture of water sorption in gecko keratin and the influence of relative humidity (RH) on the local structure and dynamics in water-swollen keratin. At low RHs, water sorption occurs through hydrogen bonding of water with the hydrophilic groups of keratin. At high RHs (>80%), additional water molecules connect to the first "layer" of amide-connected water molecules (multimolecular sorption) through hydrogen bonds, giving rise to a sigmoidal shape of the sorption isotherm. This causes the formation of large chain-like clusters surrounding the hydrophilic groups of keratin, which upon a further increase of the RH form a percolating water network. An examination of the dynamics of water molecules sorbed in keratin demonstrates that there are two states, bound and free, for water. The dynamics of water in these states depends on the RH. At low RHs, large-scale translational motions of tightly bound water molecules to keratin are needed to remake the entire hydration shell of the keratin. At high RHs (>80%), the water molecules more quickly exchange between the two states. The center-of-mass mean-square displacement of water molecules indicates a hopping motion of water molecules in the keratin solvation shell. The hopping mechanism is more pronounced at RHs < 80%. At higher RHs, water translation through water clusters (water network) dominates. We have observed two regimes for the dependence of dynamical properties on the RH: a regime of gradual increase of the dynamics over 10% < RH < 80% and a regime of drastic dynamic acceleration at RH > 80%. The latter regime begins exactly where the water uptake and the volume swelling also increase much more and where a drastic change in the elastic properties of gecko keratin has been observed. A nearly linear relation between the relaxation times for all dynamical processes and the water content of gecko keratin is observed.

Recent advances in bioengineered scaffold for in vitro meat production

In vitro meat production via stem cell technology and tissue engineering provides hypothetically elevated resource efficiency which involves the differentiation of muscle cells from pluripotent stem cells. By applying the tissue engineering technique, muscle cells are cultivated and grown onto a scaffold, resulting in the development of muscle tissue. The studies related to in vitro meat production are advancing with a seamless pace, and scientists are trying to develop various approaches to mimic the natural meat. The formulation and fabrication of biodegradable and cost-effective edible scaffold is the key to the successful development of downstream culture and meat production. Non-mammalian biopolymers such as gelatin and alginate or plant-derived proteins namely soy protein and decellularized leaves have been suggested as potential scaffold materials for in vitro meat production. Thus, this article is aimed to furnish recent updates on bioengineered scaffolds, covering their formulation, fabrication, features, and the mode of utilization.

Advances in Stimuli-responsive Hydrogels for Tissue Engineering and Regenerative Medicine Applications: A Review Towards Improving Structural Design for 3D Printing

The physicochemical properties of polymeric hydrogels render them attractive for the development of 3D printed prototypes for tissue engineering in regenerative medicine. Significant effort has been made to design hydrogels with desirable attributes that facilitate 3D printability. In addition, there is significant interest in exploring stimuli-responsive hydrogels to support automated 3D printing into more structurally organised prototypes such as customizable bio-scaffolds for regenerative medicine applications. Synthesizing stimuli-responsive hydrogels is dependent on the type of design and modulation of various polymeric materials to open novel opportunities for applications in biomedicine and bio-engineering. In this review, the salient advances made in the design of stimuli-responsive polymeric hydrogels for 3D printing in tissue engineering are discussed with a specific focus on the different methods of manipulation to develop 3D printed stimuli-responsive polymeric hydrogels. Polymeric functionalisation, nano-enabling and crosslinking are amongst the most common manipulative attributes that affect the assembly and structure of 3D printed bio-scaffolds and their stimuli- responsiveness. The review also provides a concise incursion into the various applications of stimuli to enhance the automated production of structurally organized 3D printed medical prototypes.

Silk fibroin microgels as a platform for cell microencapsulation

Cell microencapsulation has been utilized for years as a means of cell shielding from the external environment while facilitating the transport of gases, general metabolites, and secretory bioactive molecules at once. In this light, hydrogels may support the structural integrity and functionality of encapsulated biologics whereas ensuring cell viability and function and releasing potential therapeutic factors once in situ. In this work, we describe a straightforward strategy to fabricate silk fibroin (SF) microgels (µgels) and encapsulate cells into them. SF µgels (size ≈ 200 µm) were obtained through ultrasonication-induced gelation of SF in a water-oil emulsion phase. A thorough physicochemical (SEM analysis, and FT-IR) and mechanical (microindentation tests) characterization of SF µgels were carried out to assess their nanostructure, porosity, and stiffness. SF µgels were used to encapsulate and culture L929 and primary myoblasts. Interestingly, SF µgels showed a selective release of relatively small proteins (e.g., VEGF, molecular weight, M_W = 40 kDa) by the encapsulated primary myoblasts, while bigger (macro)molecules (M_W = 160 kDa) were hampered to diffusing through the µgels. This article provided the groundwork to expand the use of SF hydrogels into a versatile platform for encapsulating relevant cells able to release paracrine factors potentially regulating tissue and/or organ functions, thus promoting their regeneration.

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.