Preparation of Translucent and Flexible Human Hair Protein Films and Their Properties

Protein scaffolds in human clinics

Fundamental clinical areas such as drug delivery and regenerative medicine require biocompatible materials as mechanically stable scaffolds or as nanoscale drug carriers. Among the wide set of emerging biomaterials, polypeptides offer enticing properties over alternative polymers, including full biocompatibility, biodegradability, precise interactivity, structural stability and conformational and functional versatility, all of them tunable by conventional protein engineering. However, proteins from non-human sources elicit immunotoxicities that might bottleneck further development and narrow their clinical applicability. In this context, selecting human proteins or developing humanized protein versions as building blocks is a strict demand to design non-immunogenic protein materials. We review here the expanding catalogue of human or humanized proteins tailored to execute different levels of scaffolding functions and how they can be engineered as self-assembling materials in form of oligomers, polymers or complex networks. In particular, we emphasize those that are under clinical development, revising their fields of applicability and how they have been adapted to offer, apart from mere mechanical support, highly refined functions and precise molecular interactions.

Keratin - Based materials for biomedical applications

Keratin constitutes the major component of the feather, hair, hooves, horns, and wool represents a group of biological material having high cysteine content (7-13%) as compared to other structural proteins. Keratin -based biomaterials have been investigated extensively over the past few decades due to their intrinsic biological properties and excellent biocompatibility. Unlike other natural polymers such as starch, collagen, chitosan, the complex three-dimensional structure of keratin requires the use of harsh chemical conditions for their dissolution and extraction. The most commonly used methods for keratin extraction are oxidation, reduction, steam explosion, microbial method, microwave irradiation and use of ionic liquids. Keratin -based materials have been used extensively for various biomedical applications such as drug delivery, wound healing, tissue engineering. This review covers the structure, properties, history of keratin research, methods of extraction and some recent advancements related to the use of keratin derived biomaterials in the form of a 3-D scaffold, films, fibers, and hydrogels.

Keratinous materials: Structures and functions in biomedical applications

Keratins are a family of fibrous proteins anticipated to possess wide-ranging biomedical applications due to their abundance, physicochemical properties and intrinsic biological activity. This review mainly focuses on the biomaterials derived from three major sources of keratins; namely human hair, wool and feather, that have effective applications in tissue engineering, wound healing and drug delivery. This article offers five viewpoints regarding keratin i) an introduction to keratin protein extraction and keratin-based scaffold fabrication methods ii) applications in nerve and bone tissue engineering iii) a review on the keratin dressings applied to different types of wounds to facilitate wound healing and thereby repair the skin iv) the utilization of keratinous materials as a carrier system for therapeutics with a controlled manner v) a discussion regarding the main challenges for using keratin in biomedical applications as well as its future prospects.

Borrowing From Nature: Biopolymers and Biocomposites as Smart Wound Care Materials

Wound repair is a complex and tightly regulated physiological process, involving the activation of various cell types throughout each subsequent step (homeostasis, inflammation, proliferation, and tissue remodeling). Any impairment within the correct sequence of the healing events could lead to chronic wounds, with potential effects on the patience quality of life, and consequent fallouts on the wound care management. Nature itself can be of inspiration for the development of fully biodegradable materials, presenting enhanced bioactive potentialities, and sustainability. Naturally-derived biopolymers are nowadays considered smart materials. They provide a versatile and tunable platform to design the appropriate extracellular matrix able to support tissue regeneration, while contrasting the onset of adverse events. In the past decades, fabrication of bioactive materials based on natural polymers, either of protein derivation or polysaccharide-based, has been extensively exploited to tackle wound-healing related problematics. However, in today's World the exclusive use of such materials is becoming an urgent challenge, to meet the demand of environmentally sustainable technologies to support our future needs, including applications in the fields of healthcare and wound management. In the following, we will briefly introduce the main physico-chemical and biological properties of some protein-based biopolymers and some naturally-derived polysaccharides. Moreover, we will present some of the recent technological processing and green fabrication approaches of novel composite materials based on these biopolymers, with particular attention on their applications in the skin tissue repair field. Lastly, we will highlight promising future perspectives for the development of a new generation of environmentally-friendly, naturally-derived, smart wound dressings.

Human Hair “Waste” and Its Utilization: Gaps and Possibilities

Human hair is considered a waste material in most parts of the world and its accumulation in waste streams causes many environmental problems; however, it has many known uses. Preventing waste of such a material requires both addressing the problems in the current usage and developing its utilization systems at locations where they are missing. With focus on developing systematic utilization of human hair waste, this paper first reviews the possible uses of human hair gathered from large scale trades, local/traditional knowledge, upcoming innovations, and scientific research; along with the socioeconomic systems that have evolved around the known uses. Concerns and gaps in these systems are identified and possible directions to address these gaps are discussed. For expanding hair utilization to new contexts, important considerations such as knowledge, skill, and technology requirements and potential markets are discussed. Finally, a policy framework for socially and environmentally healthy utilization of human hair is outlined. This study shows that human hair is a highly versatile material with significant potential in several critical areas such as agriculture, medical applications, construction materials, and pollution control. Moreover, these uses are diverse enough for entrepreneurs ranging from unskilled to highly technical individuals and for the wide variety of human hair waste available in different locations.

Structure-property relationships of meta-kerateine biomaterials derived from human hair

The structure-property relationships of kerateine materials were studied by separating crude hair extracts into two protein sub-fractions, referred to as α- and γ-kerateines, followed by their de novo recombination into meta-kerateine hydrogels, sponges and films. The kerateine fractions were characterized using electrophoresis and mass spectrometry, which revealed that the α-fraction contained complexes of type I and type II keratins and that the γ-fraction was primarily protein fragments of the α-fraction along with three proteins of the KAP-1 family. Meta-kerateine materials with increased amounts of γ-kerateines showed diminished physical, mechanical and biological characteristics. Most notably, materials with higher γ-content formed less elastic and less solid-like hydrogels and sponges that were less hydrolytically stable. In addition, a model biological assay showed that meta-kerateine films with greater amounts of γ-kerateines were less supportive of hepatocyte attachment. Investigation into the mechanism of attachment revealed that hepatocyte adhesion to meta-kerateines is not mediated by the β1 integrin subunit, despite the presence of LDV binding motifs within the type I α-keratins. This work to define the role of protein composition on biomaterial function is essential for the optimization of keratin biomaterials for biomedical applications.

A Review of Keratin-Based Biomaterials for Biomedical Applications

Advances in the extraction, purification, and characterization of keratin proteins from hair and wool fibers over the past century have led to the development of a keratin-based biomaterials platform. Like many naturally-derived biomolecules, keratins have intrinsic biological activity and biocompatibility. In addition, extracted keratins are capable of forming self-assembled structures that regulate cellular recognition and behavior. These qualities have led to the development of keratin biomaterials with applications in wound healing, drug delivery, tissue engineering, trauma and medical devices. This review discusses the history of keratin research and the advancement of keratin biomaterials for biomedical applications.

Biomineralization of calcium phosphate on human hair protein film and formation of a novel hydroxyapatite-protein composite material

Human hair protein can be used not only as a totally biodegradable material but also as a "self-originated" material, which may avoid an undesirable immune reaction, if it has been prepared from a certain individual and implanted into the same person. In this study, a novel organic-inorganic composite, which contains human hair proteins and hydroxyapatite, was investigated as biomineral-scaffolding materials. The human hair protein was extracted by our original "Shindai method" (Nakamura et al., Biol Pharm Bull 2002;25:569-572; Fujii et al., Biol Pharm Bull 2004;27:89-93). The extracts were exposed to CaCl(2) solution for fabrication into flat films, which mainly consisted of alpha-keratin. After washing with distilled water, approximately 3 Ca(2+) ions per 1 keratin molecule bound to the film. The Ca(2+)-binding was slightly sensitive to the ionic strengths, and only Mg(2+) inhibited binding of Ca(2+). A composite of the human hair protein and calcium phosphate was prepared via alternate soaking processes using CaCl(2) and Na(2)HPO(4) solutions. As the soaking cycle proceeded, the film weight increased and its color became white, indicating successful deposition of calcium phosphate. The diameters of deposited calcium phosphate particles were about 2-4 microm. The proteins were not solubilized and degraded during the soaking processes. FTIR and WAXD analyses indicated that calcium phosphate was first deposited as amorphous, then transformed into crystalline monohydrogen calcium phosphate during the earlier soaking cycle, and, via octacalcium phosphate, finally converted into hydroxyapatite after 20 cycles. The present human hair protein/hydroxyapatite composite film is a "self-originated" and also an intact proteinaceous material without chemical modification, and thus, a promising material for hard tissue engineering.

Effects of human hair and nail proteins and their films on rat mast cells

Human hair and nail are valuable materials for producing individual corresponding biocompatible materials. A rapid and convenient protein extraction method (Shindai method) and novel procedures for preparing their protein films from their extracts have been developed using human hair and nail. The effects of the human hair and nail proteins and their films on histamine release from rat peritoneal mast cells were investigated. Both protein solutions and their films, mainly consisting of keratins and matrix proteins, did not induce histamine release from the mast cells. Scanning electron microscopy (SEM) also showed that the mast cells were only slightly affected by adding the human hair and nail proteins or by incubating on their protein films. The IgE-dependent histamine release was inhibited by the hair and nail proteins and their films. Incubation of the mast cells with the hair and nail proteins prior to the addition of the IgE serum resulted in a high inhibition (50%) of the histamine release, while the inhibition was approximately 10% when the protein solutions were mixed with the mast cells after incubation with the IgE serum. These results suggest that the human hair and nail proteins and their films will be useful materials for antiallergic actions.