Dynamic Electrophoretic Assembly of Metal–Phenolic Films: Accelerated Formation and Cytocompatible Detachment

Material-independent coating has emerged as an advanced tool for interface engineering in numerous applications, including drug delivery, single-cell nanoencapsulation, catalysis, and agrotechnology. Despite remarkable progress made in controlled film formation on solid substrates, the high adhesion of coating species, exemplified by metal–phenolic materials, hinders the film detachment and subsequent formation of freestanding films. In particular, there have been no reports on cytocompatible fabrication of biofriendly freestanding films of metal–phenolic materials and polyphenols, which is required in biomedical engineering and nanomedicine. Considering the high demand for cytocompatible protocols for cytocompatible freestanding films, in this work, we have developed an electrophoresis-based, biocompatible method called dynamic electrophoretic assembly (dEPA) for dynamically and locally regulating the cohesion and adhesion processes of metal–phenolic materials under mild conditions. The locally concentrated cohesive process in dEPA increases the film growth rate by 2–3 orders of magnitude, and, importantly, simple current switching weakens only film adhesiveness and yields durable freestanding films under cytocompatible conditions. Cytocompatibility of the materials and processes in dEPA leads to the fabrication of freestanding cell sheets as well as enabling the incorporation of various functional entities, including enzymes, into the metal–phenolic films.