Enzymatically controlled material design with casein—From defined films to localized deposition of particles

•A novel concept for material design of biological coatings is presented.•Deposition of colloidal particles is induced by an enzymatic reaction.•Cleavage of casein micelles with chymosin is the model system.•Film formation is highly site-specific.•The concept allows the formation of very sophisticated biological coatings.

A new concept for deposition and material design of coatings from biological compounds is presented. An enzymatic reaction triggers the specific coagulation of particles on a support surface. The first examined model system is casein and is based on the natural rennet reaction as applied in the process of cheese-making. The aspartic protease chymosin is immobilized on a support surface and cleaves the hydrophilic parts of the casein micelles, inducing deposition. The concept allows for a high level of control over film characteristics and enables the formation of site-specific film structures. The variability rages from formation of casein films with several micrometers film thickness to the targeted deposition of casein micelles.