Keratin in drug delivery: A narrative review of sources, processing techniques, formulation strategies, and biomedical applications

Abstract

Keratin is a naturally occurring fibrous structural protein that has attracted considerable attention as a biomaterial due to its excellent biocompatibility, biodegradability, low immunogenicity, and intrinsic cell-binding properties. These characteristics designate keratin as a promising candidate for biomedical and pharmaceutical applications, particularly in drug delivery systems. This study investigated keratin molecule, physicochemical properties suitable for drug delivery, some keratin-based formulations from 2015 to 2025, and applications of keratin. The study also presented an array of extraction methods comparing their yield, feasibility, and disadvantages. Furthermore, future perspectives and research opportunities for safer methods, hybrid systems for targeted therapy, stimuli-responsive systems, gene delivery systems, bioinks, and personalized medicine were also hypothesized. The review also presented some challenges and limitations, including breaking the extensive disulfide linkages using toxic, non-eco-friendly chemicals; variability in amino acid composition among different keratin sources, resulting in difficulty in standardization and reproducibility; and limited in vivo studies, which have limited the clinical application of the developed systems. Future research should focus on developing greener extraction technologies, standardizing keratin-based formulations, and conducting comprehensive preclinical and clinical evaluations to facilitate its successful integration into pharmaceutical and biomedical practice.