pH-responsive casein-based films and their application as functional coatings in solid dosage formulations

Over the past few years, there has been increasing attention to the design of new drug delivery systems based on milk proteins due to their excellent functional properties. In this study, we report a new approach for preparing protein-based coating films using highly methacrylated casein as a macro-crosslinker. The films exhibited a smooth surface and an even casein distribution as evidenced by both scanning electron and atomic force microscopy, respectively. The mechanical behavior of the casein-based films could be easily tuned by controlling the degree of methacrylation of the bio-based crosslinker. The as-prepared films showed pH-dependent swelling, in which the swelling ability in alkaline medium was stronger than that at acid pH. The mechanical, swelling, rheological and release performance of the casein- based films suggest that these materials have a high potential as enteric coatings for intestinal drug delivery.