Self-Assembly of Solubilized Human Hair Keratins

Biocompatibility and wound-healing prospect of KAPs-depleted residual hair biomaterial

This work is an in-depth investigation of the in vitro and in vivo biocompatibility of processed and treated residual human hair samples with intact cuticle layers. The specimens included oxidized hair with minimal melanin (BLH) and hair with medium- (M-KAP) and low- (L-KAP) amounts of keratin associated proteins (KAPs), confirmed through gel electrophoresis, electron microscopy, trichrome histological staining, and tensile biomechanics, in comparison to the untreated regular hair (REG) control. All hair groups, high KAPs (H-KAPs: REG and BLH), M-KAP, and L-KAP, are non-cytotoxic in the adipose fibroblast's response to their extracts based on the ISO 10993-5 medical device biomaterial testing standard. In vivo mouse subcutaneous implantation (ISO 10993-6, local effects) at 2 weeks showed a foreign body response (FBR) with thin fibrous encapsulation at 28% relative skin dermis thickness; but the L-KAP implant mitigated a significant decrease in FBR area compared to H-KAPs and a lower number of immune cells of mostly macrophages and mast cells on the biomaterial's surface. In the bulk of the capsules, blood vessels and collagen extracellular matrix densities were similar among groups. These findings suggest that small globular KAPs diffuse out of the cortex to the host-biomaterial interface which induce a slightly-elevated FBR but limited to the implant's surface vicinity. For translatability, we evaluated the effectiveness of the residual hair with the most depleted KAPs (L-KAP) in a 10 mm-diameter, splinted, and full-thickness mouse skin excision wound. Treatment with the L-KAP mesh exhibited an 8% healing improvement per day compared to the untreated control: significantly reducing the projected complete healing time by 30%. On-going research focuses on purer keratin-based and macromolecularly organized residual hair biomaterials for drug-delivery as they are deemed the most biocompatible.

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.

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.

Optical evaluation of internal damage to human hair based on second near-infrared window polarization microscopy

OBJECTIVE

Hair beauty treatments glorify human life. As a side effect, there is a risk of deteriorating the health of the hair. Optically polarized microscopy has been used for many decades to evaluate hair conditions owing to its ease of use and low operating costs. However, the low biopermeability of light hinders the observation of detailed structures inside hair. The aim of this study is to establish an evaluation technique of internal damages in a hair by utilizing a near-infrared (NIR) light with a wavelength of 1000-1600 nm, called "second NIR window".

METHODS

We built a laser scanning transmission microscope system with an indium gallium arsenide detector, a 1064 nm laser source, and optical circular polarization to visualize the anisotropy characterization of keratin fibres in hair. Samples of Asian black hair before and after bleaching, after permanent-waving, after lithium bromide (LiBr) treatment, and after heating was observed. Some parameters reflecting intra-hair damage were quantitatively compared with the parameters in digitally recorded images with analytical developments.

RESULTS

The light transmittance of black hair was dramatically improved by utilizing the second NIR window. Numerical analysis of circular polarization in hair quantified the internal damage in chemically or thermally treated hair and found two different types of damage. The present method enabled quantitative evaluation of the condition changes in the cortex; for example, a decrease in circular polarizability by LiBr treatment and restoration by replacing the LiBr solution with water. In addition, black speckles were observed after the heat treatment. Longer heating and wetting times increased the appearance probability and size of the speckles. According to quantitative analyses, the emergence of black spots was independent of polarizability changes, indicating that they were not pores.

CONCLUSION

Circular polarization microscopy based on near-infrared optics in the second NIR window provides an effective evaluation method for quantifying intra-hair damage caused by cosmetic treatments. The present method provides noninvasive, easy, and inexpensive hair evaluation and has potential as a gold standard in hair care research/medical fields.

Recent Progress in Hair Science and Trichology

Hair is important to our appearance as well as to protect our heads. Human hair mainly consists of proteins (80-85%), melanin pigments (0-5%), water (10-13%), and lipids (1-6%). The physicochemical properties of hair have been studied for over 100 years. However, they are not yet thoroughly understood. In this review, recent progress and the latest findings are summarized from the following three perspectives: structural characteristics, delivery and distribution of active ingredients, and hair as a template. The structural characteristics of hair have been mainly investigated by microscopic and/or spectroscopic techniques such as atomic force microscopy integrated with infrared spectroscopy (AFM-IR) and rheological measurements. The distribution of active ingredients has been generally evaluated through techniques such as nanoscale secondary ion mass spectrometry (NanoSIMS). And finally, attempts to explore the potential of hair to be used as a substrate for flexible device fabrication will be introduced.

Recent omics advances in hair aging biology and hair biomarkers analysis

Aging is a complex natural process that leads to a decline in physiological functions, which is visible in signs such as hair graying, thinning, and loss. Although hair graying is characterized by a loss of pigment in the hair shaft, the underlying mechanism of age-associated hair graying is not fully understood. Hair graying and loss can have a significant impact on an individual's self-esteem and self-confidence, potentially leading to mental health problems such as depression and anxiety. Omics technologies, which have applications beyond clinical medicine, have led to the discovery of candidate hair biomarkers and may provide insight into the complex biology of hair aging and identify targets for effective therapies. This review provides an up-to-date overview of recent omics discoveries, including age-associated alterations of proteins and metabolites in the hair shaft and follicle, and highlights the significance of hair aging and graying biomarker discoveries. The decline in hair follicle stem cell activity with aging decreased the regeneration capacity of hair follicles. Cellular senescence, oxidative damage and altered extracellular matrix of hair follicle constituents characterized hair follicle and hair shaft aging and graying. The review attempts to correlate the impact of endogenous and exogenous factors on hair aging. We close by discussing the main challenges and limitations of the field, defining major open questions and offering an outlook for future research.

Physico-Chemical Characterization of Keratin from Wool and Chicken Feathers Extracted Using Refined Chemical Methods

In this work, the characteristic structure of keratin extracted from two different kinds of industrial waste, namely sheep wool and chicken feathers, using the sulfitolysis method to allow film deposition, has been investigated. The structural and microscopic properties have been studied by means of scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), and infrared (IR) spectroscopy. Following this, small-angle X-ray scattering (SAXS) analysis for intermediate filaments has been performed. The results indicate that the assembly character of the fiber can be obtained by using the most suitable extraction method, to respond to hydration, thermal, and redox agents. The amorphous part of the fiber and medium range structure is variously affected by the competition between polar bonds (reversible hydrogen bonds) and disulfide bonds (DB), the covalent irreversible ones, and has been investigated by using fine structural methods such as Raman and SAXS, which have depicted in detail the intermediate filaments of keratin from the two different animal origins. The preservation of the secondary structure of the protein obtained does offer a potential for further application of the waste-obtained keratin in polymer films and, possibly, biocomposites.

Integration Analysis of Transcriptome and Proteome Reveal the Mechanisms of Goat Wool Bending

Zhongwei goat is a unique Chinese native goat breed for excellent lamb fur. The pattern of flower spikes of the lamb fur was significantly reduced due to the reduction of the bending of the hair strands with growth. In order to explore the molecular mechanism underlying hair bending with growth, we performed the comprehensive analysis of transcriptome and proteome of skins from 45-days, 108-days and 365-days goat based on TMT-based quantitative proteomics and RNA-seq methods. In the three comparison groups, 356, 592 and 282 differentially expressed proteins (DEPs) were screened, respectively. KEGG pathway analysis indicated that DEPs were significantly enriched in a set of signaling pathways related to wool growth and bending, such as ECM-receptor interaction, PI3K-Akt signaling pathway, PPAR signaling pathway, protein digestion and absorption, and metabolic pathways. In addition, 20 DEPs abundance of goat skin at three development stages were examined by PRM method, which validated the reliability of proteomic data. Among them, KRT and collagen alpha family may play an important role in the development of goat hair follicle and wool bending. COL6A1, COL6A2, CRNN, TNC and LOC102178129 were identified as candidate genes based on combined analysis of transcriptome and proteome data and PRM quantification. Our results identify the differential expressed proteins as well as pathways related to the wool bending of Zhongwei goats and provide a theoretical basis for further revealing the molecular mechanism underlying wool bending of goats.