Keratin biomaterials with high molecular weights were intensively investigated but few are marketed due to complex methods of extraction and preparation and limited understanding of their influence on cells behavior. In this context the aim of this research was to elucidate decisive molecular factors for skin homeostasis restoration induced by two low molecular weight keratin hydrolysates extracted and conditioned through a simple and green method. Two keratin hydrolysates with molecular weights of 3758 and 12,400 Da were physico-chemically characterized and their structure was assessed by circular dichroism (CD) and FTIR spectroscopy in view of bioactive potential identification. Other investigations were focused on several molecular factors: α1, α2 and β1 integrin mediated signals, cell cycle progression in pro-inflammatory conditions (TNFα/LPS stimulated keratinocytes and fibroblasts) and ICAM-1/VCAM-1 inhibition in human vascular endothelial cells. Flow cytometry techniques demonstrated a distinctive pattern of efficacy: keratin hydrolysates over-expressed α1 and α2 subunits, responsible for tight bounds between fibroblasts and collagen or laminin 1; both actives stimulated the epidermal turn-over and inhibited VCAM over-expression in pro-inflammatory conditions associated with bacterial infections. Our results offer mechanistic insights in wound healing signaling factors modulated by the two low molecular weight keratin hydrolysates which still preserve bioactive secondary structure.

Essential oils are valuable alternatives to synthetic antibiotics that have the potential to avoid the pathogen resistance side effects generated by leather. Helichrysum italicum and Lavandula latifolia essential oils combined with fish scale gelatin were electrospun using a coaxial technique to design new bioactive materials for skin wound dressings fabrication. Fish scale gelatins were extracted from carp fish scales using two variants of the same method, with and without ethylenediaminetetraacetic acid (EDTA). Both variants showed very good electrospinning properties when dissolved in acetic acid solvent. Fish scale gelatin nanofibers with Helichrysum italicum and Lavandula latifolia essential oil emulsions ensured low microbial load (under 100 CFU/g of total number of aerobic microorganisms and total number of yeasts and filamentous fungi) and the absence of Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 10536, and Candida albicans ATCC 1023 as compared to fish scale gelatin without essential oils, which recommends them for pharmaceutical or topical applications. A scratch-test performed on human dermal fibroblasts proved that the biomaterials contributing to the wound healing process included fish scale gelatin nanofibers without EDTA (0.5% and 1%), fish scale gelatin nanofibers without EDTA and Lavandula latifolia essential oil emulsion (1%), fish scale gelatin nanofibers with EDTA (0.6%), and fish scale gelatin nanofibers with EDTA with Helichrysum italicum essential oil emulsion (1% and 2%).

Xerosis cutis represents one of the most common dermatological diagnoses, which, when untreated, can be the trigger for open wounds, infections, and other skin diseases. Plant extracts are a valuable option for long-term treatments for xerosis due to their phytocompounds, especially polyphenols, flavonoids, triterpenes, and polysaccharides, with antioxidant, anti-inflammatory, antimicrobial, moisturizing, and reparatory effects. Active substances have different mechanisms; therefore, evaluating the effects on the cells can be a key indicator, providing valuable information in terms of both cytotoxicity and efficacy. The in vitro and in vivo toxicity tests performed for Betulae extractum, Liquiritiae extractum, and Avenae extractum highlighted potential toxic effects at higher concentrations in a dose-dependent relationship, but at lower levels they can be considered safe (12.5 µg/mL for birch and licorice extracts, 50 µg/mL for oat extract). Concerning the re-epithelialization process, the results revealed that all three dry extracts effectively stimulate skin cell migration, highlighting a potential anti-inflammatory effect by increasing the cell migration rate in conditions of induced inflammation associated with oxidative stress. Among the tested concentrations with a potential contribution to wound healing, the following standout: are birch bark extract 3 μg/mL, licorice root extract 7.5 µg/mL, and oat herb (harvested before flowering) extract 7.5 µg/mL.