Keratin Fibers Research Articles

Thermal Characteristic of Keratin Fibres from Poultry Feathers and their Suitability to Conversion into Thermoset Biobased Composites

The possibility of using animal wastes in the form of feathers for the production of various types of composites is an extremely original concept, opening to researchers a wide field for experiments and interdisciplinary scientific research. This article presents the results of studies on the thermal stability of keratin from feathers originating from various poultry slaughterhouses, as well as an example of the use of feathers for the production of thermosetting composites. The keratin protein contained in feathers, like any protein, is very sensitive to various external factors, e.g. high temperature. The scientific goal of the research presented in the article was a deep analysis of changes occurring in the structure of keratin protein in feathers during heating. The technological goal was to develop new thermosetting composites based on spun-bonded nonwovens with the addition of keratin fibres from poultry feather wastes.

Nanoindentation of Hair Cortex and Medulla Regions

Reports related to cuticle damage and hair’s mechanical properties are of interest to dermatologists in treatment of hair disorders. Apart from tensile test, few studies were reported on mechanical properties of hair, especially nanomechanical properties of cortex and medulla regions. Inner diameter of hair fiber (8–12 µm) is considered as medulla and it exists in hair at the beginning of the anagen phase. This study is aimed for quantitative comparison of nanomechanical properties between cortex and medulla and also with respect to donor age by performing nanoindentation on fiber cross sections using two different instruments. The medulla and cortex regions revealed hardness values of 70–170 MPa and 200–312 MPa, respectively. Similarly lower values of indentation modulus were observed for medulla compared to cortex because medulla has poorer orientation of microfibrils compared to the surrounding cortex. This study also found a linear correlation between hardness and indentation modulus especially for medulla region. This could be due to the fact that organization of the microfibrils increases from the medulla center to medulla periphery. It is also found that donor age has no influence on cortex modulus and hardness. The findings of this study will be useful for dermatologists in estimating the hair disorders and for estimating dye uptake of keratin fibers in textiles.

Relevance and Evaluation of Hydrogen and Disulfide Bond Contribution to the Mechanics of Hard α-Keratin Fibers.

We propose a simple mechano-chemical model for the dependence of Young's modulus of α-keratin fibers on the hydrogen and disulfide bonds existing in the matrix and evaluate the relative change in bonding following an oxidative chemical treatment. Atomic force microscopy nanoindentation of longitudinal and cross sections of the fiber showed that, although the oxidative treatment breaks a significant amount of disulfide bonds, it introduces compensatory hydrogen bonds that maintain fiber elasticity at values comparable with those of the untreated fiber under dry conditions. The striking influence of humidity on the hydrogen bonding in keratin fibers is also evaluated. The hydrogen bonds are labeled as "type 1" and "type 2" hydrogen bonds; newly formed hydrogen bonds, type 2, are more labile than those native (type 1) to the matrix. Examining their contribution to Young's modulus of the matrix allowed for quantifying the loss of disulfide bonds, and the result matched the decrease in cystine, measured by amino-acid analysis, caused by the oxidative treatment.

Thermal insulation design bioinspired by microstructure study of penguin feather and polar bear hair

Nature is an amazing source of inspiration for the design of thermal insulation strategies, which are key for saving energy. In nature, thermal insulation structures, such as penguin feather and polar bear hair, are well developed; enabling the animals’ survival in frigid waters. The detailed microscopy investigations conducted in this study, allowed us to perform microstructural analysis of these thermally insulating materials, including statistical measurements of keratin fiber and pore dimensions directly from high resolution Scanning Electron Microscope (SEM) images. The microscopy study revealed many similarities in both materials, and showed the importance of their hierarchically-organized porous structure. Finally, we propose the schematic configuration of a thermally-insulating structure, based on the penguin feather and polar bear hair. These optimized thermal-insulator systems indicate the road maps for future development, and new approaches in the design of material properties. Statement of significanceWe present the first detailed comparison of microstructures of penguin feather and polar bear hair for designing optimum thermal insulation properties. This unique study involves the measurement of the sizes of pores and fibers of these two keratin-based materials, including the investigation of their 3D arrangements. We revealed porosity interconnection, especially in polar bear hair, which is one of the key designs exhibited by thermal insulation materials.

Effect of modified keratin from renewable sources on composites properties of synthetic isoprene rubber

The present conducted research focused on elastomeric materials containing reinforcing modified keratin fibers in their composition. The applied keratin was modified by solvolysis reaction to obtain the product in the form of a hydrolysate. Then, the hydrolysate was modified by the addition reaction of keratin adduct with a plasticizer—technical stearin is commonly used in processing elastomers. The keratin hydrolysate adducts were used in a different weight proportion in the composites in which the carrier was isoprene rubber (IR; Cariflex 305). The obtained composites (rubber Cariflex composites (RC)) were subjected to a series of tests aimed at understanding the structure and interactions between biopolymers and other components of elastomeric mixtures. Mechanical properties, including hardness, the cross-linking density, and thermo-oxidative aging were investigated. Microbiological tests were carried out, which in turn allowed to determine the effect of introduced keratin in a modified hybrid form, to the elastomeric matrix. The test results indicate a significant improvement of some properties, especially when using 10 parts by weight of keratin adducts introduced into 100 parts by weight of IR rubber.

Helical twist direction in the macrofibrils of keratin fibres is left handed

Macrofibrils, the main structural features within the cortical cells of mammalian hair shafts, are long composite bundles of keratin intermediate filaments (KIFs) embedded in a matrix of keratin-associated proteins. The KIFs can be helically arranged around the macrofibril central axis, making a cylinder within which KIF helical angle relative to macrofibril axis increases approximately linearly from macrofibril centre to edge. Mesophase-based self-assembly has been implicated in the early formation of macrofibrils, which first appear as liquid-crystal tactoids in the bulb of hair follicles. Formation appears to be driven initially by interactions between pre-keratinized KIFs. Differences in the nature of these KIF-KIF interactions could result in all macrofibrils being internally twisted in a single handedness, or a 50:50 mixture of handedness within each cortical cell. We data-mined 41 electron tomograms containing three-dimensional macrofibril data from previously published studies of hair and wool. In all 644 macrofibrils examined we found that within each tomogram all macrofibrils had the same handedness. We concluded that earlier reports of left- and right-handed macrofibrils were due to artefacts of imaging or data processing. A handedness marker was used to confirm (using re-imaged sections from earlier studies) that, in both human and sheep, all macrofibrils are left-handed around the macrofibril axis. We conclude that this state is universal within mammalian hair. This also supports the conclusion that the origin of macrofibril twist is the expression of chiral twisting forces between adjacent KIFs, rather than mesophase splay and bending forces relaxing to twisting forces acting within a confined space.

Influence of keratin and DNA coating on fire retardant magnesium hydroxide dispersion and flammability characteristics of PE/EVA blends

For the first time the combination of keratin fibers (KF), obtained from poultry feathers, with deoxyribose nucleic acid (DNA) are employed in low-density polyethylene-ethylene vinyl acetate (LDPE/EVA) blends in order to reduce the conventional hydroxide content and enhance the blend flame retardant properties. The combined effect of each filler and the use of maleated polyethylene (PEgMA) as compatibilizer on PE/EVA flame retardant properties was analyzed. DNA by its chemical structure can be considered as an intumescing agent and when it is combined with keratin the char formation is promoted and the flame retardant properties are enhanced. DNA was distributed in specific layers forming a segregated film which resulted in better PE/EVA blend flame retardant properties compared with either DNA deposited simply by compression molding on the material surface or with melt compounding in the bulk. The flame retardant behavior was compared with a reference PE/EVA sample with 55 wt% of Magnesium Hydroxide currently used for wire coatings in the wire and cable industry. The additives combination with DNA deposited as a segregated structure significantly increases the LOI up to 24.5% and reduces the heat release rate by 82% during cone calorimetry tests with very similar flame behavior as the reference sample with 55 wt% magnesium hydroxide loadings. The mechanical properties indicated that DNA has a marked increase in elongation as well as a marked reduction in torque and viscosity indicating that the combination of these additives can improve the mechanical performance, as well as facilitate the melt processing. Most important, the results indicated that the combination of these additives makes it possible to reduce the total Magnesium hydroxide filler content from 55 to 20 wt% to achieve the flame retardant requirements and with enhanced mechanical performance. Thus, this additives combination and this coating methodology provides a promising way to meet the growing demand and stringent requirements for high performance materials with high flame retardant standards using high efficient and green fire retardant coatings.

Structural Analysis of Cross-Sections of Hair Keratin Fibers Using Raman Spectroscopy

Structural Analysis of Cross-Sections of Hair Keratin Fibers Using Raman Spectroscopy

Possible beneficiation of waste chicken feathers via conversion into biomedical applications

Keratin-based waste materials such as wool and waste chicken feathers are driving investigations to beneficiate them. The poultry industry in South Africa generates about 230 million kg of waste chicken feathers per annum, which makes them the abundant keratin source. most of which is disposed of by landfilling or combustion. The current disposal techniques through landfilling or combustion are not environmentally friendly. Thus, methods for beneficiation of the waste are needed. Considering that chicken feathers are comprised of mainly keratin, it is plausible that the keratin can be exploited for application in biomedical applications. However, keratin biomaterials have not found a breakthrough in clinical applications. The keratin can be recovered in the form of fibres or dissolved from feathers in suitable solvents. Regenerated keratin biomaterials can take the form of hydrogels, membranes, films, sponges, scaffolds, and nanofibres. These materials possess excellent properties that can be applied to different fields, including the health sector. Currently, there is no review paper that puts together all possible beneficiations of waste chicken feathers keratin in biomedicine. Therefore, this work exposes the chemistry and characteristics of keratin from different sources including chicken feather keratin in relation to their potential use in the biomedical applications. This review also highlights the properties of regenerated keratin and corresponding biomaterials, including electrospun regenerated keratin fibres for biomedical applications. Keratin nanofibres, also possess advanced properties for biomedical applications due to nanofibres reception in medical applications. Keratin is one biopolymer that can function as an acceptable biopolymer. The review indicates that there is a need for biopolymers as many fields rely on petroleum-based polymers which tend to have biocompatibility limits and are unsustainably resourced.

Fabrication and performance of wool keratin–functionalized graphene oxide composite fibers

The objective of this study is to reduce environmental pollution caused by waste wool and to enable it to be recycled. L-Cysteine was used to dissolve wool in an aqueous solution for the extraction of keratin. Furthermore, the reconstruction of keratin was attempted by dissolving wool keratin in Na2CO3/NaHCO3 buffer with various contents of polyethylene glycol (PEG)–functionalized graphene oxide (PEG-g-GO). Then, the regenerated keratin/PEG-g-GO composite fibers were wet-spun to form a series of composite fibers. Fourier-transform infrared spectroscopy, XPS analysis, Raman spectroscopy, and thermogravimetric analysis were used to characterize the structure and properties of the composite. The results show that PEG was successfully grafted onto the GO. PEG-g-GO had a good interfacial effect with the keratin matrix in composite fibers without any agglomeration, apart from dispersing evenly. With the addition of PEG-g-GO, the crystallinity and the tensile strength and elongation at break of the composite fiber increased, and it induced more β-sheet secondary conformation within the keratin matrix. When the quality fraction of PEG-g-GO was 0.20%, the tensile strength of the composite fibers reached a maximum (157 ± 40 MPa) and the breaking elongation reached a maximum of 3.9%, which was approximately 168% and 89% higher than that of the pure keratin fibers, respectively. More importantly, the entire process is green and of low cost, which not only reduces environmental pollution but also improves resource utilization.

EBS generalized severe is an inflammatory disease

Epidermolysis bullosa (EB) is a group of genetic disorders in which the skin is abnormally fragile. In EB simplex, the skin cells tend to fall apart because their internal scaffolding of keratin fibres is defective, due to mutations in the genes encoding keratins type 5 or 14 (KRT5 and KRT14). But people with the generalised, severe type of EB simplex (EBS‐GS) are sometimes more ill than would be expected just from a mechanical problem with the skin; some even die in infancy, usually from infection. This group from France and Scotland explored the possibility that EBS‐GS patients also have a faulty immune system. They re‐examined skin specimens taken previously for diagnostic purposes from 17 patients with EBS‐GS and also tested fresh skin biopsies and blister fluid from a further 10 patients. They consistently found more inflammatory cells and higher levels of chemicals which promote inflammation (cytokines) than normal. The findings were the same regardless of whether the sample was from blistered or normal‐looking skin and whether the fault was in KRT5 or KRT14. Markers for the cytokine Th17 were particularly high, encouraging them to treat three EBS‐GS patients with the anti‐Th17 drug Apremilast as used in psoriasis. All three reported a dramatic reduction in blisters within the first month, which lasted throughout treatment for up to 10 months, with minimal side‐effects. One patient stopped the Apremilast after 7 months because of nausea and the blistering came back 2 days later. This appears to be a promising new approach to treating EBS‐GS.

Natural Keratin and Coconut Fibres from Industrial Wastes in Flame Retarded Thermoplastic Starch Biocomposites.

Natural keratin fibres derived from Mexican tannery waste and coconut fibres from coconut processing waste were used as fillers in commercially available, biodegradable thermoplastic starch-polyester blend to obtain sustainable biocomposites. The morphology, rheological and mechanical properties as well as pyrolysis, flammability and forced flaming combustion behaviour of those biocomposites were investigated. In order to open up new application areas for these kinds of biocomposites, ammonium polyphosphate (APP) was added as a flame retardant. Extensive flammability and cone calorimeter studies revealed a good flame retardance effect with natural fibres alone and improved effectiveness with the addition of APP. In fact, it was shown that replacing 20 of 30 wt. % of APP with keratin fibres achieved the same effectiveness. In the case of coconut fibres, a synergistic effect led to an even lower heat release rate and total heat evolved due to reinforced char residue. This was confirmed via scanning electron microscopy of the char structure. All in all, these results constitute a good approach towards sustainable and biodegradable fibre reinforced biocomposites with improved flame retardant properties.

Aqueous MEA and Ammonia Sorption-Induced Damage in Keratin Fibers.

The sorption of aqueous monoethanolamine (MEA) and ammonia solutions in keratin fibers and its subsequent effect on their mechanical performance has been investigated. The diffusion kinetics of MEA into keratin fibers for 0.1, 1.0, and 5 v/v % MEA in water at 30 and 50 °C were found to exhibit two clear regimes of absorption behavior: a linear Fickian diffusion regime for initial times up to 100 min, after which a second slower uptake process was observed. Single fiber tensile tests showed that the Young's modulus and the tensile failure stress for 5% MEA-treated fibers, compared to untreated fibers, were 25% lower after 1 h of treatment and 50% lower after 9 h of treatment. Aqueous treatments of 0.1 and 1% MEA, as well as 0.6 and 3% aqueous ammonia, had no measurable effect on either Young’s modulus or tensile failure stress for the fibers. Scanning electron microscopy images and protein content analysis confirmed that keratin fibers exposed to 5% MEA solution exhibited significant surface damage as well as high levels of protein loss. This study confirms for the first time the important damage hair treatments containing 5% aqueous MEA can cause on keratin fibers.

Spectrophotometry, Physiochemical Properties, and Histological Staining Potential of Aqueous and Ethanol Extracts of Beetroot on Various Tissues of an Albino Rat

Background and Aims: Natural dyes and pigments are nontoxic, ecofriendly alternatives to synthetic counterparts and beetroot is one such natural dye. The red color of beetroot derived from betalain pigments confers great advantage to this plant. In this study, the physiochemical and spectrophotometric characteristics of beetroot as well as the histological staining potential of various tissues were carried out to determine its tissue specificity. Methods: The aqueous and ethanol extracts of beetroot were prepared using distilled water and 95% ethanol, respectively. Spectrophotometry, pH, and concentration of both extracts were determined before histological staining with 10% neutral-buffered formalin-fixed, paraffin-wax-embedded tissue sections. Stained sections were viewed with a photomicroscope. Results: The aqueous and ethanol extracts of beetroot were slightly acidic and soluble at concentrations of 381.5 mg/100 g and 253.7 mg/100 g fresh beetroot sample, respectively. Both extracts consist of three betalain pigments with absorbances at different spectrophotometric wavelengths, namely betaxanthins (475 nm), betanin (525 nm), and betanidin (575 nm). The maximum absorbance was 0.925 and 0.615 for the aqueous and ethanol extracts, respectively, at a peak wavelength of 525 nm for each extract. Both extracts stained various tissue structures such as muscles, mucins, red blood cells, keratin, and nerve fibers. Conclusion: Thus, beetroot stain is slightly acidic, contains betalain pigments, stains basic histological tissue structures, and can be used as an ecofriendly alternative to hematoxylin and eosin.

Flexible Biocomposites with Enhanced Interfacial Compatibility Based on Keratin Fibers and Sulfur-Containing Poly(urea-urethane)s.

Feathers are made of keratin, a fibrous protein with high content of disulfide-crosslinks and hydrogen-bonds. Feathers have been mainly used as reinforcing fiber in the preparation of biocomposites with a wide variety of polymers, also poly(urea-urethane)s. Surface compatibility between the keratin fiber and the matrix is crucial for having homogenous, high quality composites with superior mechanical properties. Poly(urea-urethane) type polymers are convenient for this purpose due to the presence of polar functionalities capable of forming hydrogen-bonds with keratin. Here, we demonstrate that the interfacial compatibility can be further enhanced by incorporating sulfur moieties in the polymer backbone that lead to new fiber-matrix interactions. We comparatively studied two analogous thermoplastic poly(urea-urethane) elastomers prepared starting from the same isocyanate-functionalized polyurethane prepolymer and two aromatic diamine chain extenders, bis(4-aminophenyl) disulfide (TPUU-SS) and the sulfur-free counterpart bis(4-aminophenyl) methane (TPUU). Then, biocomposites with high feather loadings (40, 50, 60 and 75 wt %) were prepared in a torque rheometer and hot-compressed into flexible sheets. Mechanical characterization showed that TPUU-SS based materials underwent higher improvement in mechanical properties than biocomposites made of the reference TPUU (up to 7.5-fold higher tensile strength compared to neat polymer versus 2.3-fold). Field Emission Scanning Electron Microscope (FESEM) images also provided evidence that fibers were completely embedded in the TPUU-SS matrix. Additionally, density, thermal stability, and water absorption of the biocomposites were thoroughly characterized.

A novel "trifunctional protease" with reducibility, hydrolysis, and localization used for wool anti-felting treatment.

Proteases can cause unacceptable fiber damage when they are singly applied to wool anti-felting treatment which can make wool textiles machine-washable. Even if protease is attached by synthetic polymers, the modified protease plays a limited role in the degradation of keratin with dense structure consisting of disulfide bonds in the scales. Here, to obtain "machine-washable" wool textiles, a novel "trifunctional protease" with reducibility, hydrolysis, and localization is developed by means of covalent bonding of protease molecules with poly (ethylene glycol) bis (carboxymethyl) ether (HOOC-PEG-COOH) and L-cysteine using carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling, aiming at selectively degrading the scales on the surface of wool. The formation of polymer is confirmed with size exclusion chromatography (SEC) and Fourier transform infrared spectroscopy (FT-IR). Ellman's test and fluorescence microscopy reveal that the modified protease can reduce disulfide bonds and restrict hydrolysis of peptide bonds on the wool scales. Furthermore, when applied to wool fabrics, the modified protease reach better treatment effects considering dimensional stability to felting (6.12%), strength loss (11.7%) and scale dislodgement proved by scanning electron microscopy (SEM), alkali solubility, wettability, and dyeability. This multifunctional enzyme is well-designed according to the requirement of the modification of wool surface, showing great potential for eco-friendly functionalization of keratin fibers rich in disulfide linkage.

Aligned keratin submicrometric-fibers for fibroblasts guidance onto nanogrooved titanium surfaces for transmucosal implants

Biomaterials surface modification represents a very attractive tool to modulate host tissue response. Surface modifications of titanium for bone contact applications have been widely investigated, while only few papers can be found regarding modifications aimed at soft tissue contact. However, soft tissue healing represents a crucial step for percutaneous/transmucosal titanium implants success. Fibroblasts, the soft tissues most representative cells, are known to be sensitive to surface topography. Anyhow, fibroblasts adhesion and spread can be more influenced by the presence of attractive macromolecules; so, within a grooved and keratin-coated Ti surface, cells will align following the strongest biochemical guide provided by keratin submicrometric-fibers. In order to obtain the most effective cell stimulation/guidance keratin submicrometric-fibers should be aligned to substrate nanogrooves. Despite the very promising cells guidance provided by keratin submicrometric-fibers, the strong limitation to their synthesis is related to the macromolecules high sensitivity to environmental parameters (temperature/humidity/pH) which can seriously compromise the feasibility and reproducibility of the final submicrometric-fibers layer. Accordingly, this work has the aim to obtain, for the first time, a coating of submicrometric keratin fibers aligned to the nanogrooves of a Ti substrate, in order to validate the attitude of the coated surface to impart additive topographical plus biochemical signals in the same direction for the stimulation of fibroblasts repopulation.

HIF stabilization inhibits renal epithelial cell migration and is associated with cytoskeletal alterations

Acute kidney injury (AKI) is a common and potentially lethal complication in the hospitalized patients, with hypoxic injury being as a major cause. The loss of renal tubular epithelial cells (TEC), one of the AKI hallmarks, is potentially followed by tubular regeneration process orchestrated by the remaining uninjured TECs that undergo proliferation and migration. In this study, we used human primary TEC to investigate the initiation of tubular cell migration and associated cytoskeletal alterations in response to pharmacological HIF stabilization which resembles the pathophysiology of hypoxia. Tubular cells have been shown to migrate as cohorts in a wound healing assay. Importantly, cells of distal tubular origin moved faster than those of proximal origin. HIF stabilization impaired TEC migration, which was confirmed by live single cell tracking. HIF stabilization significantly reduced tubular cell migration velocity and promoted cell spreading. In contrast to the control conditions, HIF stabilization induced actin filaments rearrangement and cell adhesion molecules including paxillin and focal adhesion kinase. Condensed bundling of keratin fibers was also observed, while the expression of different types of keratins, phosphorylation of keratin 18, and the microtubule structure were not altered. In summary, HIF stabilization reduced the ability of renal tubular cells to migrate and led to cytoskeleton reorganization. Our data suggested an important involvement of HIF stabilization during the epithelial migration underlying the mechanism of renal regeneration in response to AKI.

Valorisation of chicken feathers: Characterisation of thermal, mechanical and electrical properties

Increasing consumption of chicken results in generation of large amounts of wastes that need to be disposed of properly. Chicken feathers constitute about 5–10% of the weight of the chicken and thus they comprise a significant portion of the poultry wastes. Disposal of waste chicken feathers is problematic in that they do not readily degrade after landfilling, there is increasing shortage of landfill space, and they are contaminated with microbial biomass that makes them hazardous waste. Feathers contain ~91% keratin protein and thus, potentially, feathers can be beneficiated into high-value compounds or products comprised of keratin proteins or keratin fibres. Thus, valorisation of feathers could be a viable option for sustainable disposal of the waste. Characterisation of physicochemical properties of the chicken feather is an essential step to identifying possible avenues for valorisation of this waste biomass. While chemical, physical and morphological properties of chicken feathers and related potential valorisation routes have described by the authors, identification of their mechanical, thermal and electrical properties have not been reported and this information is necessary to have a complete and comprehensive characterisation of waste chicken feathers. Hence, in this research, the mechanical, thermal and electrical properties of feathers were determined and evaluated to ascertain suitability of the feathers for production of high-value materials. The feathers and fractions thereof were characterised by TGA/DSC, Instron (material and structural testing), Dynamic Mechanical Analyser, and a two-probe measurement of resistivity instrument. Under heated conditions, the TGA of chicken feathers confirmed the occurrence of three zones of weight loss. The TGA/DSC results revealed a glass transition temperature around 67 °C and a melting temperature ~230 °C in the crystalline phase. The tenacity of chicken feather barbs at maximum load was ~16.93 cN/tex. The results from electrical properties indicated that chicken feather fractions have low conductivity. Overall, the results indicate that chicken feathers have potential to be used in a variety of applications such as electrical insulator materials, yarn production for use in textiles, nonwoven fabric production, filler for winter clothing, geotextile and construction materials.

Hydrogels from feather keratin show higher viscoelastic properties and cell proliferation than those from hair and wool keratins

Hydrogel prepared from keratin shows potential applications in tissue engineering. However, the importance of the keratin sources has not been considered. The objectives of this study were to characterize and compare the rheological (storage modulus), physical (porosity, pore size, swelling capacity, and water contact angle) and in vitro cell compatibility of hydrogel scaffolds prepared from various keratin sources. Keratins were characterized by means of their molecular weight, amino acid composition, thermal and conformational properties. Hydrogels from chicken feather keratins demonstrated substantially higher storage modulus (G′) than hair and wool keratin hydrogels. However, higher swelling capacity (>3000%) was determined in hair and wool over feather keratin (1500%) hydrogels. Our results suggest that small molecular weight and β-sheet conformation of feather keratin (~10 kDa) facilitated the self-assembly of rigid hydrogels through disulfide bond re-oxidation. Whereas, high molecular weight (10–75 kDa) stretchable α-helix conformation in hair and wool keratins resulted in weaker hydrogels. The cell cultures using fibroblasts showed the highest proliferation rate on chicken feather keratin hydrogel scaffolds. After 15 days of culture, partial breakdown of keratin fibers was observed. Results indicate that stiffer avian keratins can be used to fabricate more mechanically robust biomaterials than mammalian keratins.