Surface-confined enzymatic method for scalable thin film generation

Thin-film coatings enhance the physical and chemical properties of materials. Despite various application methods, the functionalization of all surfaces without pre-treatment, control of thickness, and scalability remains challenging. In this paper, a surface-confined enzymatic approach for film formation to overcome these limitations is presented. To investigate the broad applicability of the reported coating strategy, two metals and six synthetic polymers were selected as substrates for coating with the conducting polymer polypyrrole (PPy). This approach employs an enzyme, a copper efflux oxidase (CueO), fused to Macaque Histatin (MacHis), a universal adhesion-promoting peptide, for pyrrole polymerization. Immobilized CueO-MacHis generates a homogenous PPy-coating on materials from an aqueous solution at ambient temperature. The reaction stops ‘automatically’ when pyrrole monomers can no longer reach or be oxidized by CueO. To demonstrate scalability, a metal plate measuring 30 × 100 cm was functionalized with CueO-MacHis via spraying, and coated with PPy by immersion. The durability of the PPy-coated metal surfaces was characterized according to DIN EN 60068–2–52 and acid exposure. The sheet resistance of the PPy-coated synthetic polymers was in the range of 109 to 8250 kΩ/sq, showing a change in surface conductivity from non-conductive to conductive. Our results demonstrate a universal and scalable surface-confined strategy for enzymatic thin film formation at ambient conditions, consisting of enzyme immobilization on untreated material surfaces, followed by polymerization and coating formation. This resource-efficient strategy allows the coating of high surface areas with a defined thickness and can be used as a platform for numerous other coatings and materials.