Design of Asymmetric Nanofibers-Membranes Based on Polyvinyl Alcohol and Wool-Keratin for Wound Healing Applications

The development of asymmetric membranes—i.e., matching two fibrous layers with selected composition and morphological properties to mimic both the epidermis and dermis—currently represents one of the most promising strategies to support skin regeneration during the wound healing process. Herein, a new asymmetric platform fabricated by a sequential electrospinning process was investigated. The top layer comprises cross-linked polyvinylalcohol (PVA) nanofibers (NFs)—from water solution—to replicate the epidermis’s chemical stability and wettability features. Otherwise, the bottom layer is fabricated by integrating PVA with wool-keratin extracted via sulfitolysis. This protein is a biocompatibility polymer with excellent properties for dermis-like structures. Morphological characterization via SEM supported by image analysis showed that the asymmetric membrane exhibited average fiber size—max frequency diameter 450 nm, range 1.40 μm—and porosity suitable for the healing process. FTIR-spectrums confirmed the presence of keratin in the bottom layer and variations of keratin-secondary structures. Compared with pure PVA-NFs, keratin/PVA-NFs showed a significant improvement in cell adhesion in in vitro tests. In perspective, these asymmetric membranes could be promisingly used to confine active species (i.e., antioxidants, antimicrobials) to the bottom layer to support specific cell activities (i.e., proliferation, differentiation) in wound healing applications.

Wool Keratin-Based Nanofibres—In Vitro Validation

Protein-based nanofibres are commonly used in the biomedical field to support cell growth. For this study, the cell viability of wool keratin-based nanofibres was tested. Membranes were obtained by electrospinning using formic acid, hexafluoroisopropanol, and water as solvents. For aqueous solutions, polyethylene oxide blended with keratin was employed, and their use to support in vitro cell interactions was also validated. Morphological characterization and secondary structure quantification were carried out by SEM and FTIR analyses. Although formic acid produced the best nanofibres from a morphological point of view, the results showed a better response to cell proliferation after 14 days in the case of fibres from hexafluoroisopropanol solution. Polyethylene oxide in keratin nanofibres was demonstrated, over time, to influence in vitro cell interactions, modifying membranes-wettability and reducing the contact between keratin chains and water molecules, respectively.

Palladium nanoparticles/wool keratin-assisted carbon composite-modified flexible and disposable electrochemical solid-state pH sensor

Several pH-dependent processes and reactions take place in the human body; hence, the pH of body fluids is the best indicator of disturbed health conditions. However, accurate and real-time diagnosis of the pH of body fluids is complicated because of limited commercially available pH sensors. Hence, we aimed to prepare a flexible, transparent, disposable, user-friendly, and economic strip-based solid-state pH sensor using palladium nanoparticles (PdNPs)/N-doped carbon (NC) composite material. The PdNPs/NC composite material was synthesized using wool keratin (WK) as a precursor. The in-situ prepared PdNPs played a key role in the controlled switching of protein structure to the N-doped carbon skeleton with π-π arrangement at the mesoscale level, which mimics the A-B type polymeric structure, and hence, highly susceptible to H+ ions. The optimized carbonization condition in the presence of PdNPs showed that the material obtained using a modified Ag/AgCl reference electrode had the highest pH sensitivity with excellent stability and durability. The optimized pH sensor showed high specificity and selectivity with a sensitivity of 55 mV/pH unit and a relative standard deviation of 0.79%. This study is the first to synthesize PdNPs using WK as a stabilizing and reducing agent. The applicability of the sensor was investigated for biological samples, namely saliva and gastric juices. The proposed protocol and material have implications in solid-state chemistry, where biological material will be the best choice for the synthesis of materials with anticipated performance.

Photocatalytic Properties of a Novel Keratin char-TiO2Composite Films Made through the Calcination of Wool Keratin Coatings Containing TiO2 Precursors

In this study, the photocatalytic properties of novel keratin char-TiO2 composite films, made through the calcination of wool keratin coatings containing TiO2 precursors at 400 °C, were investigated for the photodegradation of organic contaminants under visible light irradiation. Its structural characteristics and photocatalytic performance were systematically examined. It was shown that a self-cleaning hydrophobic keratin char-TiO2 composite film containing meso- and micro-pores was formed after the keratin—TiO2 precursors coating was calcined. In comparison with calcinated TiO2 films, the keratin char-TiO2 composite films doped with the elements of C, N, and S from keratins resulted in decreased crystallinity and a larger water contact angle. The bandgap of the char-TiO2 composite films increased slightly from 3.26 to 3.32 eV, and its separation of photogenerated charge carriers was inhibited to a certain degree. However, it exhibited higher photodegradation efficiency to methyl blue (MB) effluents than the pure calcinated TiO2 films. This was mainly because of its special porous structure, large water contact angle, and high adsorption energy towards organic pollutants, confirmed by the density functional theory calculations. The main active species were 1O2 radicals in the MB photodegradation process.

Vibrational Study on Structure and Bioactivity of Protein Fibers Grafted with Phosphorylated Methacrylates

In the last decades, silk fibroin and wool keratin have been considered functional materials for biomedical applications. In this study, fabrics containing silk fibers from Bombyx mori and Tussah silk fibers from Antheraea pernyi, as well as wool keratin fabrics, were grafted with phosmer CL and phosmer M (commercial names, i.e., methacrylate monomers containing phosphate groups in the molecular side chain) with different weight gains. Both phosmers were recently proposed as flame retarding agents, and their chemical composition suggested a possible application in bone tissue engineering. IR and Raman spectroscopy were used to disclose the possible structural changes induced by grafting and identify the most reactive amino acids towards the phosmers. The same techniques were used to investigate the nucleation of a calcium phosphate phase on the surface of the samples (i.e., bioactivity) after ageing in simulated body fluid (SBF). The phosmers were found to polymerize onto the biopolymers efficiently, and tyrosine and serine underwent phosphorylation (monitored through the strengthening of the Raman band at 1600 cm−1 and the weakening of the Raman band at 1400 cm−1, respectively). In grafted wool keratin, cysteic acid and other oxidation products of disulphide bridges were detected together with sulphated residues. Only slight conformational changes were observed upon grafting, generally towards an enrichment in ordered domains, suggesting that the amorphous regions were more prone to react (and, sometimes, degrade). All samples were shown to be bioactive, with a weight gain of up to 8%. The most bioactive samples contained the highest phosmers amounts, i.e., the highest amounts of phosphate nucleating sites. The sulphate/sulphonate groups present in grafted wool samples appeared to increase bioactivity, as shown by the five-fold increase of the IR phosphate band at 1040 cm−1.