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.