Surface functionalization of keratin fibers with polyphenol-rich extracts from agri-food by-products for active wound dressing

Keratin is one of the main components of waste from the textile and slaughterhouse industries, thus representing an attractive candidate for the evaluation of its second use into high-value products, because by now this waste is considered an environmental pollutant and a threat to the ecosystem. Polyphenols are natural substances, primarily found in fruits, vegetables, and plants, well known for their health benefits, including antioxidant, antibacterial, vasculoprotective, bone-stimulating, anticancer, and immunomodulating properties, among others. Due to their peculiar properties, these molecules have been widely studied in traditional medicine, phytotherapy and nutriceutics. In the present research, for the first time, keratin, extracted from discarded wool, was converted in the form of patches composed of randomly oriented nanofibers, and natural polyphenols, extracted from selected agri-food by-products, were combined to obtain cytocompatible sustainable bioactive dressings with antioxidant and antibacterial properties able to meet clinical needs. The obtained dressings were firstly characterized for their physical-chemical properties in order to verify the keratin functionalization with polyphenols; then, a biological evaluation was performed to confirm dressings’ cytocompatibility, antioxidant and antibacterial properties. Results showed that dressings composed of keratin functionalized with pomegranate extracts seem to hold the required need, being cells-friendly with human fibroblasts, acting as a strong scavenger of toxic ROS active species and preventing the infection of the wound site from the skin pathogen Staphylococcus epidermidis. In this work, we demonstrate that a combination of keratin nanofibers extracted from discarded wool functionalized with polyphenols-rich solutions extracted from pomegranate and grape by-products represents an example of how to obtain green, low-cost and bioactive wound dressings matching the desired clinical needs.