Comparative analysis of the chemical treatments used in keratin extraction from red sheep’s hair and the cell viability evaluations of this keratin for tissue engineering applications

Keratin-based bioplastics extracted from chicken feathers: Effect of chitosan concentration on the structural, chemical bonding, and mechanical properties of bioplastics

Keratin was synthesized by alkaline hydrolysis from chicken feathers and then continue by casting method for producing bioplastics with additional various amounts of chitosan as a filler, polyvinyl alcohol (PVA) and glycerol as a plasticizer. The main purpose is analysis the effect of chitosan on the structural properties using quantitative analysis of X-ray diffraction (XRD) spectra, chemical bonding by Fourier transforms infrared (FTIR) spectra, and mechanical properties by texture analyser to the keratin-based bioplastics. Biodegradation of bioplastics was analysed from the loss of weight by burying in the soil. It's found that, the additional of chitosan (0 %, 2 %, 5 %, and 8 %) increased the crystallinity of bioplastics by 11.83 %, 11.12 %, 18.99 %, and 17.03 %, respectively, but decreasing tensile strength and elasticity of bioplastics. Degradation of bioplastic keratin-based shows that the addition of chitosan can reduce the degradation time which is directly proportional to the loss of CO bonds. The highest degradation rate is 89.29 % in 49 days for keratin-based bioplastics with 8 % chitosan, indicated that high potential for future production.

Natural polysaccharides and proteins-based films for potential food packaging and mulch applications: A review

Conventional nondegradable packaging and mulch films, after reaching the end of their use, become a major source of waste and are primarily disposed of in landfills. Accumulation of non-degradable film residues in the soil leads to diminished soil fertility, reduced crop yield, and can potentially affect humans. Application of degradable films is still limited due to the high cost, poor mechanical, and gas barrier properties of current biobased synthetic polymers. In this respect, natural polysaccharides and proteins can offer potential solutions. Having versatile functional groups, three-dimensional network structures, biodegradability, ease of processing, and the potential for surface modifications make polysaccharides and proteins excellent candidates for quality films. Besides, their low-cost availability as industrial waste/byproducts makes them cost-effective alternatives. This review paper covers the performance properties, cost assessment, and in-depth analysis of macromolecular structures of some natural polysaccharides and proteins-based films that have great potential for packaging and mulch applications. Proper dissolution of biopolymers to improve molecular interactions and entanglement, and establishment of crosslinkages to form an ordered and cohesive polymeric structure can help to obtain films with good properties. Simple aqueous-based film formulation techniques and utilization of waste/byproducts can stimulate the adoption of affordable biobased films on a large-scale.

The fabrication and evaluation of silver nanoparticle-based keratin scaffolds

The biotoxicity caused by focus releasing of Ag, which associated with the Ag loading mode, is a problematic issue that need to be solved for practical utilization of the keratin based wound dressing. In this study, keratin/AgNPs blend scaffolds (Ker/Ag) and keratin scaffolds with AgNPs attached on the scaffold's wall surface (Ag@Ker) were prepared. Structure and physical properties of the scaffolds were tested and investigated. In comparison to the Ag@Ker scaffolds, the Ker/Ag scaffolds with uniform dispersion of AgNPs have larger tensile strength and slower degradation rate. Both kind of scaffolds present excellent antibacterial property with 10 μg mL^-1 AgNPs addition, while the Ker/Ag displayed a linear Ag releasing ratio in the first 5-7 days, which is beneficial for obtaining a continuous antibacterial property and avoiding the biotoxicity caused by focus release of Ag. Correspondingly, cytotoxicity assay further reveals that the continuously slow release of Ag of the Ker/Ag scaffolds accelerated the proliferation of cell. Infectious animal models and histological studies showed that the Ker/Ag scaffolds can effectively inhibit the inflammatory response and accelerate epithelialization. Thus, it can be concluded that the Ker/Ag scaffolds with uniform dispersion of AgNPs are more attractive as wound repair materials.

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.

Preparation Methods and Functional Characteristics of Regenerated Keratin-Based Biofilms

The recycling, development, and application of keratin-containing waste (e.g., hair, wool, feather, and so on) provide an important means to address related environmental pollution and energy shortage issues. The extraction of keratin and the development of keratin-based functional materials are key to solving keratin-containing waste pollution. Keratin-based biofilms are gaining substantial interest due to their excellent characteristics, such as good biocompatibility, high biodegradability, appropriate adsorption, and rich renewable sources, among others. At present, keratin-based biofilms are a good option for various applications, and the development of keratin-based biofilms from keratin-containing waste is considered crucial for sustainable development. In this paper, in order to achieve clean production while maintaining the functional characteristics of natural keratin as much as possible, four important keratin extraction methods—thermal hydrolysis, ultrasonic technology, eco-friendly solvent system, and microbial decomposition—are described, and the characteristics of these four extraction methods are analysed. Next, methods for the preparation of keratin-based biofilms are introduced, including solvent casting, electrospinning, template self-assembly, freeze-drying, and soft lithography methods. Then, the functional properties and application prospects of keratin-based biofilms are discussed. Finally, future research directions related to keratin-based biofilms are proposed. Overall, it can be concluded that the high-value conversion of keratin-containing waste into regenerated keratin-based biofilms has great importance for sustainable development and is highly suggested due to their great potential for use in biomedical materials, optoelectronic devices, and metal ion detection applications. It is hoped that this paper can provide some basic information for the development and application of keratin-based biofilms.

Performance and Structure Evaluation of Gln-Lys Isopeptide Bond Crosslinked USYK-SPI Bioplastic Film Derived from Discarded Yak Hair

To reduce the waste from yak hair and introduce resource recycling into the yak-related industry, an eco-friendly yak keratin-based bioplastic film was developed. We employed yak keratin (USYK) from yak hair, soy protein isolate (SPI) from soybean meal as a film-forming agent, transglutaminase (EC 2.3.2.13, TGase) as a catalytic crosslinker, and glycerol as a plasticizer for USYK-SPI bioplastic film production. The structures of the USYK-SPI bioplastic film were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-Ray diffraction (XRD). The mechanical properties, the thermal behavior, light transmittance performance, and water vapor permeability (WVP) were measured. The results revealed that the added SPI possibly acted as a reinforcement. The formation of Gln-Lys isopeptide bonds and hydrophobic interactions led to a stable crosslinking structure of USYK-SPI bioplastic film. The thermal and the mechanical behaviors of the USYK-SPI bioplastic film were improved. The enhanced dispersion and formation of co-continuous protein matrices possibly produced denser networks that limited the diffusion of water vapor and volatile compounds in the USYK-SPI bioplastic films. Moreover, the introduction of SPI prompted the relocation of hydrophobic groups on USYK molecules, which gave the USYK-SPI bioplastic film stronger surface hydrophobicity. The SPI and USYK molecules possess aromatic amino residuals (tyrosine, phenylalanine, tryptophan), which can absorb ultraviolet radiation. Thus, the USYK-SPI bioplastic films were shown to have an excellent UV barrier. The synergy effect between USYK and SPI is not only able to improve rigidity and the application performance of keratin-based composite film but can also reduce the cost of the keratin-based composite film through the low-cost of the SPI alternative which partially replaces the high-cost of keratin. The data obtained from this research can provide basic information for further research and practical applications of USYK-SPI bioplastic films. There is an increasing demand for the novel USYK-SPI bioplastic film in exploit packaging material, biomedical materials, eco-friendly wearable electronics, and humidity sensors.

Protein by-products: Composition, extraction, and biomedical applications

Significant upsurge in animal by-products such as skin, bones, wool, hides, feathers, and fats has become a global challenge and, if not properly disposed of, can spread contamination and viral diseases. Animal by-products are rich in proteins, which can be used as nutritional, pharmacologically functional ingredients, and biomedical materials. Therefore, recycling these abundant and renewable by-products and extracting high value-added components from them is a sustainable approach to reclaim animal by-products while addressing scarce landfill resources. This article appraises the most recent studies conducted in the last five years on animal-derived proteins' separation and biomedical application. The effort encompasses an introduction about the composition, an overview of the extraction and purification methods, and the broad range of biomedical applications of these ensuing proteins.

Unhairing of bovine hide using wastewater from Merox unit of oil refinery: techno-environmental aspect

The effluent generated by Merox unit of oil refinery was used instead of freshwater for bovine hide unhairing because of its proper composition and alkalinity. The effect of temperature, treatment period, sodium sulfide (Na₂S), and calcium carbonate (CaCO₃) dosage was investigated on unhairing efficiency using lutrom (unhairing slurry) prepared from the Merox effluent (effluent-based lutrom). Under similar operating conditions and chemicals' dosage, the effluent-based lutrom resulted in a higher efficiency (98.6%) than water-based lutrom (67.3%) indicating faster unhairing kinetics for the former lutrom. Moreover, an acceptable swelling (48%) and suitable mechanical properties were also observed. The experimental strategy can save 50 to 67% toxic chemicals and 100% of water consumption in unhairing, which is equivalent to US$ 34 per ton of hide, leading to zero discharge from Merox unit. Recycling of effluent-based lutrom after 3 consecutive runs was associated with a significant reduction in COD (55.6 kg/t hide) and BOD₅ (11.6 kg/t hide) load. The effluent-based and conventional lutroms, before and after unhairing, were treated with ozone under moderate conditions. The FTIR results indicated a high-quality and low costly pelt benefits from the integration of wastewater treatment units of both industries in an environment-friendly manner.

Effective utilization of tannery hair waste to develop a high-performing re-tanning agent for cleaner leather manufacturing

Accumulation of hair waste is a major burden to the leather industry, causing a negative impact on the industry's sustainable development. The industry is already bogged down by the usage of synthetic re-tanning agents that are not only extremely challenging for biodegradation but also release free-form of formaldehyde in the final leather stage. This research work focuses on developing a formaldehyde-free bio-based re-tanning agent from hair waste. In order to do so, hair waste is subjected to alkali hydrolysis and subsequently graft-copolymerized with methacrylic acid (MAA). These treatments were optimal using 20 % (w/w) sodium hydroxide and thermal activity at 90 °C. This resulted in effective hydrolysis of red sheep hair, which was the ideal candidate in this study. The hydrolysate was subjected to monomer in situ polymerization (using MAA) with potassium per sulfate/sodium meta-bisulphite redox system, leading to the development of keratin hydrolysate-g-methacrylic acid (KH-g-MA) copolymer (this was noted both at a laboratory level and pilot scale). The obtained KH-g-MA copolymer exhibited ideal characteristics such as increased protein content (78.3 ± 1.2), appropriate particle size (1516 nm), suitable pH (5) and required viscosity of 512 cP. The developed KH-g-MA copolymer was then applied as a re-tanning agent in the leather manufacturing process. Significant improvement in leather's mechanical strength characteristics was observed. In addition, the organoleptic properties of leather such as fullness, softness and grain tightness showed much improvement. Scanning electron microscopy (SEM) showed an enhanced surface smoothness and filling of the voids in experimental leather in comparison to the control leather. This recycle and reuse strategy of hair waste not only helps resolve issues with handling of hair solid waste but also results in producing an eco-friendly re-tanning agent in leather manufacturing, thereby paving the way for cyclic economic utilization and cleaner environment.

Beneficial use of animal hides for abattoir and tannery waste management: a review of unconventional, innovative, and sustainable approaches

The art of using animal hides, an apparent waste from the meat processing industry, goes back to the dawn of humanity and was highly demanded for leather manufacturing. In Ontario (Canada), small- and medium-sized abattoirs process all together approximately 300,000 sheep and 100,000 cattle per year, and for decades, the collected hides and skins have been processed into leather. However, there has been a decline in the price as well as in the demand for animal hides in the last few years, mainly due to increased customer interest in synthetic materials. This has significantly impacted small- and medium-scale abattoirs as they are left with no other option but to landfill these hides, which is not a sustainable approach. This review discusses the alternative approaches available for the management of animal hides, including those also suitable for tannery residues, which can economically and environmentally benefit society. These benefits include the production or generation of energy, compost, yarn, and medicinal goods, among other beneficial uses.

Closing the Loop with Keratin-Rich Fibrous Materials

One of the agro-industry's side streams that is widely met is the-keratin rich fibrous material that is becoming a waste product without valorization. Its management as a waste is costly, as the incineration of this type of waste constitutes high environmental concern. Considering these facts, the keratin-rich waste can be considered as a treasure for the producers interested in the valorization of such slowly-biodegradable by-products. As keratin is a protein that needs harsh conditions for its degradation, and that in most of the cases its constitutive amino acids are destroyed, we review new extraction methods that are eco-friendly and cost-effective. The chemical and enzymatic extractions of keratin are compared and the optimization of the extraction conditions at the lab scale is considered. In this study, there are also considered the potential applications of the extracted keratin as well as the reuse of the by-products obtained during the extraction processes.

Detection of 6-monoacetylemorphine in hair sample of heroin addicts using gas chromatography–mass spectrometry and significance of rehabilitation program

Background

The analysis of hair samples for the detection of drugs has become one of the convincing strategies in the field of forensic toxicology. A large number of cases concerning heroin abuse or its byproducts have been documented under the Control of Narcotic Substances Act, 1997, over the past decade. The present study was carried out with an aim to evaluate the primary metabolite of heroin, i.e., 6-monoacetylemorphine (6-MAM), in hair samples of addicts and subjects undergoing rehabilitation, thereafter accessing the success rate of the rehabilitation program at the de-addiction center.

Results

Hair samples were randomly collected from 20 regular heroin addicts and 20 heroin addicts from their past, from the rehabilitation center, of different age groups. Samples were cleaned, digested, and extracted using an alkaline digestion mediator methyl tertiary butyl ether, followed by quantification of 6-MAM via gas chromatography–mass spectrometry (GC–MS). The mean concentration of 6-MAM in regular heroin addicts detected was 7.80 ng/mg and 2.34 ng/mg in samples of subjects undergoing rehabilitation at the de-addiction center, respectively.

Conclusion

Traces of 6-MAM in the hair sample of heroin addicts can be efficiently detected days after the last intake of heroin. In addition to that, our findings also give an idea for future evaluating the approximate timeframe for detection of 6-MAM and/or other metabolites of heroin in the hair sample. However, in the future, by carefully analyzing the hair samples that can be taken from rehabilitation centers from target subjects at different time intervals, the exact duration of traceable quantity of 6-MAM can be determined in the hair sample. Finally, it can be concluded that there is a significant success rate of the rehabilitation program at de-addiction centers in connection with dragging the 6-MAM level from the body.

Recent progress in the conversion of biomass wastes into functional materials for value-added applications

The amount of biomass wastes is rapidly increasing, which leads to numerous disposal problems and governance issues. Thus, the recycling and reuse of biomass wastes into value-added applications have attracted more and more attention. This paper reviews the research on biomass waste utilization and biomass wastes derived functional materials in last five years. The recent research interests mainly focus on the following three aspects: (1) extraction of natural polymers from biomass wastes, (2) reuse of biomass wastes, and (3) preparation of carbon-based materials as novel adsorbents, catalyst carriers, electrode materials, and functional composites. Various biomass wastes have been collected from agricultural and forestry wastes, animal wastes, industrial wastes and municipal solid wastes as raw materials with low cost; however, future studies are required to evaluate the quality and safety of biomass wastes derived products and develop highly feasible and cost-effective methods for the conversion of biomass wastes to enable the industrial scale production.

Novel versatile 3D bio-scaffold made of natural biocompatible hagfish exudate for tissue growth and organoid modeling

Hagfish exudate is a natural biological macromolecule made of keratin intermediate filament protein skeins and mucin vesicles. Here, we successfully examined this remarkable biomaterial as a substrate for three-dimensional (3D) cell culturing purposes. After the sterilization with chloroform vapor, Dulbecco's modified eagle medium was mixed with the exudate to rupture the vesicles and skeins; a highly soft, adherent, fibrous and biocompatible hydrogel was formed. A variety of cells, including Hela-FUCCI, NMuMG-FUCCI, 10T1/2 and C2C12, was cultured on the hagfish exudate. A remarkable 3D growth by ~2.5 folds after day 3, ~5 folds after day 5, ~10 folds after day 7 and ~15 folds after day 14 were seen compared to day one of culturing in the hagfish exudate scaffold. In addition, the phase contrast, fluorescent and confocal microscopy observations confirmed the organoid shape formation within the three-week culture. The viability of cells was almost 100% indicating the great in vitro and in vivo potential of this exceptional biomaterial with no cytotoxic effect.