Effects of the Blending Ratio on the Design of Keratin/Poly(butylene succinate) Nanofibers for Drug Delivery Applications

Electrospun Poly-ε-Caprolactone Nanofibers Incorporating Keratin Hydrolysates as Innovative Antioxidant Scaffolds

This manuscript describes the development and characterization of electrospun nanofibers incorporating bioactive hydrolysates obtained from the microbial bioconversion of feathers, a highly available agro-industrial byproduct. The electrospun nanofibers were characterized using different instrumental methods, and their antioxidant properties and toxicological potential were evaluated. Keratin hydrolysates (KHs) produced by Bacillus velezensis P45 were incorporated at 1, 2.5, and 5% (w/w) into poly-ε-caprolactone (PCL; 10 and 15%, w/v solutions) before electrospinning. The obtained nanofibers were between 296 and 363 nm in diameter, showing a string-like morphology and adequate structural continuity. Thermogravimetric analysis showed three weight loss events, with 5% of the mass lost up to 330 °C and 90% from 350 to 450 °C. Infrared spectroscopy showed typical peaks of PCL and amide bands corresponding to keratin peptides. The biological activity was preserved after electrospinning and the hemolytic activity was below 1% as expected for biocompatible materials. In addition, the antioxidant capacity released from the nanofibers was confirmed by DPPH and ABTS radical scavenging activities. The DPPH scavenging activity observed for the nanofibers was greater than 30% after 24 h of incubation, ranging from 845 to 1080 µM TEAC (Trolox equivalent antioxidant capacity). The antioxidant activity for the ABTS radical assay was 44.19, 49.61, and 56.21% (corresponding to 972.0, 1153.3, and 1228.7 µM TEAC) for nanofibers made using 15% PCL with 1, 2.5, and 5% KH, respectively. These nanostructures may represent interesting antioxidant biocompatible materials for various pharmaceutical applications, including wound dressings, topical drug delivery, cosmetics, and packaging.

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.

A scientific version of understanding "Why did the chickens cross the road"? - A guided journey through Bacillus spp. towards sustainable agriculture, circular economy and biofortification

The world, a famished planet with an overgrowing population, requires enormous food crops. This scenario compelled the farmers to use a high quantity of synthetic fertilizers for high food crop productivity. However, prolonged usage of chemical fertilizers results in severe adverse effects on soil and water quality. On the other hand, the growing population significantly consumes large quantities of poultry meats. Eventually, this produces a mammoth amount of poultry waste, chicken feathers. Owing to the protein value of the chicken feathers, these wastes are converted into protein hydrolysate and further extend their application as biostimulants for sustained agriculture. The protein profile of chicken feather protein hydrolysate (CFPH) produced through Bacillus spp. was the maximum compared to physical and chemical protein extraction methods. Several studies proved that the application of CFPH and active Bacillus spp. culture to soil and plants results in enhanced plant growth, phytochemical constituents, crop yield, soil nutrients, fertility, microbiome and resistance against diverse abiotic and biotic stresses. Overall, "CFPH - Jack of all trades" and "Bacillus spp. - an active camouflage to the surroundings where they applied showed profound and significant benefits to the plant growth under the most adverse conditions. In addition, Bacillus spp. coheres the biofortification process in plants through the breakdown of metals into metal ions that eventually increase the nutrient value of the food crops. However, detailed information on them is missing. This can be overcome by further real-world studies on rhizoengineering through a multi-omics approach and their interaction with plants. This review has explored the best possible and efficient strategy for managing chicken feather wastes into protein-rich CFPH through Bacillus spp. bioconversion and utilizing the CFPH and Bacillus spp. as biostimulants, biofertilizers, biopesticides and biofortificants. This paper is an excellent report on organic waste management, circular economy and sustainable agriculture research frontier.

Antibacterial aroma compounds as property modifiers for electrospun biopolymer nanofibers of proteins and polysaccharides: A review

Electrospinning is one of the most promising techniques for producing biopolymer nanofibers for various applications. Proteins and polysaccharides, among other biopolymers, are attractive substrates for electrospinning due to their favorable biocompatibility and biodegradability. However, there are still challenges to improve the mechanical properties, water sensitivity and biological activity of biopolymer nanofibers. Therefore, these strategies such as polymer blending, application of cross-linking agents, the addition of nanoparticles and bioactive components, and modification of biopolymer have been developed to enhance the properties of biopolymer nanofibers. Among them, antibacterial aroma compounds (AACs) from essential oils are widely used as bioactive components and property modifiers in various biopolymer nanofibers to enhance the functionality, hydrophobicity, thermal properties, and mechanical properties of nanofibers, which depends on the electrospun strategy of AACs. This review summarizes the recently reported antimicrobial activities and applications of AACs, and compares the effects of four electrospinning strategies for encapsulating AACs on the properties and applications of nanofibers. The authors focus on the correlation of the main characteristics of these biopolymer electrospun nanofibers with the encapsulation strategy of AACs in the nanofibers. Moreover, this review also particularly emphasizes the impact of the characteristics of these nanofibers on their application field of antimicrobial materials.

Carboxymethylcellulose hydrogels crosslinked with keratin nanoparticles for efficient prednisolone delivery

Carboxymethylcellulose (CMC) and keratin nanoparticle (KNP) hydrogels were obtained, characterized, and applied as drug delivery systems (DDSs) for the first time. Lyophilized CMC/KNP mixtures containing 10, 25, and 50 wt% of KNPs were kept at 170 °C for 90 min to crosslink CMC chains through a solid-state reaction with the KNPs. The hydrogels were characterized by infrared spectroscopy, thermal analyses, X-ray diffraction, mechanical measurements, and scanning electron microscopy. The infrared spectra indicated the formation of ester and amide linkages between crosslinked CMC and KNPs. The elastic modulus of the hydrogel containing 10 wt% KNPs was 2-fold higher than that of the hydrogel containing 50 wt% KNPs. The mechanical properties influenced the hydrogel stability and water uptake. The anti-inflammatory prednisolone (PRED) drug was incorporated into the hydrogels, and the release mechanism was investigated. The hydrogels supported PRED release by drug desorption for approximately 360 h. A sustained release mechanism was achieved. The CMC/KNP and CMC/KNP/PRED hydrogels were cytocompatible toward mammalian cells. The CMC/KNP/PRED set imparted the highest cell viability after 7 days of incubation. This study showed a straightforward procedure to create DDSs (chemically crosslinked) based on polysaccharides and proteins for efficient PRED delivery.

Wool Keratin Nanofibers for Bioinspired and Sustainable Use in Biomedical Field

Keratin is a biocompatible and biodegradable protein as the main component of wool and animal hair fibers. Keratin-based materials support fibroblasts and osteoblasts growth. Keratin has been extracted by sulphitolysis, a green method (no harmful chemicals) with a yield of 38-45%. Keratin has been processed into nanofibers from its solutions by electrospinning. Electrospinning is a versatile and easy-to-use technique to generate nanofibers. It is an eco-friendly and economical method for the production of randomly and uniaxially oriented polymeric nanofibers. Thanks to their high specific surface area, nanofibers have great potential in the biomedical field. Keratin nanofibers have received significant attention in biomedical applications, such as tissue engineering and cell growth scaffolds, for their biocompatibility and bio-functionality. Accordingly, we propose an extensive overview of recent studies focused on the optimization of keratinbased nanofibers, emphasizing their peculiar functions for cell interactions and the role of additive phases in blends or composite systems to particularize them as a function of specific applications (i.e., antibacterial).

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.

Advances in the Application of Electrospun Drug-Loaded Nanofibers in the Treatment of Oral Ulcers

Oral ulcers affect oral and systemic health and have high prevalence in the population. There are significant individual differences in the etiology and extent of the disease among patients. In the treatment of oral ulcers, nanofiber films can control the drug-release rate and enable long-term local administration. Compared to other drug-delivery methods, nanofiber films avoid the disadvantages of frequent administration and certain side effects. Electrospinning is a simple and effective method for preparing nanofiber films. Currently, electrospinning technology has made significant breakthroughs in energy-saving and large-scale production. This paper summarizes the polymers that enable oral mucosal adhesion and the active pharmaceutical ingredients used for oral ulcers. Moreover, the therapeutic effects of currently available electrospun nanofiber films on oral ulcers in animal experiments and clinical trials are investigated. In addition, solvent casting and cross-linking methods can be used in conjunction with electrospinning techniques. Based on the literature, more administration systems with different polymers and loading components can be inspired. These administration systems are expected to have synergistic effects and achieve better therapeutic effects. This not only provides new possibilities for drug-loaded nanofibers but also brings new hope for the treatment of oral ulcers.

Electrospun Nanofiber Composites for Drug Delivery: A Review on Current Progresses

A medication’s approximate release profile should be sustained in order to generate the desired therapeutic effect. The drug’s release site, duration, and rate must all be adjusted to the drug’s therapeutic aim. However, when designing drug delivery systems, this may be a considerable hurdle. Electrospinning is a promising method of creating a nanofibrous membrane since it enables drugs to be placed in the nanofiber composite and released over time. Nanofiber composites designed through electrospinning for drug release purposes are commonly constructed of simple structures. This nanofiber composite produces matrices with nanoscale fiber structure, large surface area to volume ratio, and a high porosity with small pore size. The nanofiber composite’s large surface area to volume ratio can aid with cell binding and multiplication, drug loading, and mass transfer processes. The nanofiber composite acts as a container for drugs that can be customized to a wide range of drug release kinetics. Drugs may be electrospun after being dissolved or dispersed in the polymer solution, or they can be physically or chemically bound to the nanofiber surface. The composition and internal structure of the nanofibers are crucial for medicine release patterns.

Electrospun Zein/Polyoxyethylene Core-Sheath Ultrathin Fibers and Their Antibacterial Food Packaging Applications

The purpose of this work is to develop a novel ultrathin fibrous membrane with a core-sheath structure as antibacterial food packaging film. Coaxial electrospinning was exploited to create the core-sheath structure, by which the delivery regulation of the active substance was achieved. Resveratrol (RE) and silver nanoparticles (AgNPs) were loaded into electrospun zein/polyethylene oxide ultrathin fibers to ensure a synergistic antibacterial performance. Under the assessments of a scanning electron microscope and transmission electron microscope, the ultrathin fiber was demonstrated to have a fine linear morphology, smooth surface and obvious core-sheath structure. X-ray diffraction and Fourier transform infrared analyses showed that RE and AgNPs coexisted in the ultrathin fibers and had good compatibility with the polymeric matrices. The water contact angle experiments were conducted to evaluate the hydrophilicity and hygroscopicity of the fibers. In vitro dissolution tests revealed that RE was released in a sustained manner. In the antibacterial experiments against Staphylococcus aureus and Escherichia coli, the diameters of the inhibition zone of the fiber were 8.89 ± 0.09 mm and 7.26 ± 0.10 mm, respectively. Finally, cherry tomatoes were selected as the packaging object and packed with fiber films. In a practical application, the fiber films effectively reduced the bacteria and decreased the quality loss of cherry tomatoes, thereby prolonging the fresh-keeping period of cherry tomatoes to 12 days. Following the protocols reported here, many new food packaging films can be similarly developed in the future.

Electrospun Core–Sheath Nanofibers with Variable Shell Thickness for Modifying Curcumin Release to Achieve a Better Antibacterial Performance

The inefficient use of water-insoluble drugs is a major challenge in drug delivery systems. Core–sheath fibers with various shell thicknesses based on cellulose acetate (CA) were prepared by the modified triaxial electrospinning for the controlled and sustained release of the water-insoluble Chinese herbal active ingredient curcumin. The superficial morphology and internal structure of core–sheath fibers were optimized by increasing the flow rate of the middle working fluid. Although the prepared fibers were hydrophobic initially, the core–sheath structure endowed fibers with better water retention property than monolithic fibers. Core–sheath fibers had flatter sustained-release profiles than monolithic fibers, especially for thick shell layers, which had almost zero-order release for almost 60 h. The shell thickness and sustained release of drugs brought about a good antibacterial effect to materials. The control of flow rate during fiber preparation is directly related to the shell thickness of core–sheath fibers, and the shell thickness directly affects the controlled release of drugs. The fiber preparation strategy for the precise control of core–sheath structure in this work has remarkable potential for modifying water-insoluble drug release and improving its antibacterial performance.

Keratin-based wound dressings: From waste to wealth

Keratin is a natural protein with a high content of cysteine residues (7-13%) and is widely found in hair, wool, horns, hooves, and nails. Keratin possesses abundant cell-binding motifs such as leucine-aspartate-valine (LDV), glutamate-aspartate-serine (EDS), and arginine-glycine-aspartate (RGD), which benefit cell attachment and proliferation. It has been confirmed that keratin plays important roles in every stage of wound healing, including hemostasis, inflammation, proliferation, and remodeling, making keratin-based materials good candidates for wound dressings. In combination with synthetic and natural polymers, keratin-based wound dressings in the forms of films, hydrogels, and nanofibers can be achieved with improved mechanical properties. This review focuses on the recent development of keratin-based wound dressings. Firstly, the physicochemical and biological properties of keratin, are systematically discussed. Secondly, the role of keratin in wound healing is proposed. Thirdly, the applications of keratin-based wound dressings are summarized, in terms of the forms and functionalization. Finally, the current challenges and future development of keratin-based wound dressings are presented.

Keratin/Polylactic acid/graphene oxide composite nanofibers for drug delivery

In this work keratin/poly(lactic acid) (PLA) 50/50 wt blend nanofibers with different loadings of graphene-oxide (GO) were prepared by electrospinning and tested as delivery systems of Rhodamine Blue (RhB), selected as a model of a drug. The effect of GO on the electrospinnability and drug release mechanism and kinetics was investigated. Rheological measurements carried out on the blend solutions revealed unsatisfactory compatibility between keratin and PLA under quiet condition. Accordingly, poor interfacial adhesion between the two phases was observed by SEM analysis of a film prepared by solution casting. On the contrary, keratin chains seem to rearrange under the flux conditions of the electrospinning process thus promoting better interfacial interactions between the two polymers, thereby enhancing their miscibility, which resulted in homogeneous and defect-free nanofibers. The loading of GO into the keratin/PLA solution contributes to increase its viscosity, its shear thinning behavior, and its conductivity. Accordingly, thinner and more homogeneous nanofibers resulted from solutions with a relatively high conductivity coupled with a pronounced shear thinning behavior. FTIR and DSC analyses have underlined, that while the PLA/GO interfacial interactions significantly compete with the PLA/keratin ones, there are no significant effects of GO on the structural organization of keratin in blend with the PLA. However, GO offers several advantages from the application point of view by slightly improving the mechanical properties of the electrospun mats and by slowing down the release of the model drug through the reduction of the matrix swelling.

A Review on Electrospun Poly(amino acid) Nanofibers and Their Applications of Hemostasis and Wound Healing

The timely and effective control and repair of wound bleeding is a key research issue all over the world. From traditional compression hemostasis to a variety of new hemostatic methods, people have a more comprehensive understanding of the hemostatic mechanism and the structure and function of different types of wound dressings. Electrospun nanofibers stand out with nano size, high specific surface area, higher porosity, and a variety of complex structures. They are high-quality materials that can effectively promote wound hemostasis and wound healing because they can imitate the structural characteristics of the skin extracellular matrix (ECM) and support cell adhesion and angiogenesis. At the same time, combined with amino acid polymers with good biocompatibility not only has high compatibility with the human body but can also be combined with a variety of drugs to further improve the effect of wound hemostatic dressing. This paper summarizes the application of different amino acid electrospun wound dressings, analyzes the characteristics of different materials in preparation and application, and looks forward to the development of directions of poly(amino acid) electrospun dressings in hemostasis.

Electrospun Coaxial Fibers to Optimize the Release of Poorly Water-Soluble Drug

In a drug delivery system, the physicochemical properties of the polymeric matrix have a positive impact on the bioavailability of poorly water-soluble drugs. In this work, monolithic F1 fibers and coaxial F2 fibers were successfully prepared using polyvinylpyrrolidone as the main polymer matrix for drug loading and the poorly water-soluble curcumin (Cur) as a model drug. The hydrophobic poly (3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) was designed as a blank layer to change the hydrophilicity of the fiber and restrain the drug dissolution rate. The curved linear morphology without beads of F1 fibers and the straight linear morphology with few spindles of F2 fibers were characterized using field-emission environmental scanning electron microscopy. The amorphous forms of the drug and its good compatibility with polymeric matrix were verified by X-ray diffraction and attenuated total reflectance Fourier transformed infrared spectroscopy. Surface wettability and drug dissolution data showed that the weaker hydrophilicity F2 fibers (31.42° ± 3.07°) had 24 h for Cur dissolution, which was much longer than the better hydrophilic F1 fibers (15.31° ± 2.79°) that dissolved the drug in 4 h.