A Model of Using the Asymmetric Polydopamine Thin Film for Mimicking Epithelial Folding In Vitro

The basement membrane (BM) is a biointeractive ultrathin network with distinct composition and organization of its epithelial and stromal sides, which render BMs with asymmetric biofunctions and mechanical properties. There are difficulties in the recapitulation of the highly hierarchical structure and function of BM. Here, the interfacial assembly method for the generation of BM mimics is applied. Dopamine is the starting material for the polymerization and assembly of polydopamine (PDA) into asymmetric materials. Compared to the PDA coating formed at the solid/liquid interface (approximate to 20 nm), the PDA film formed at the air/liquid interface displays a thickness of approximate to 100 nm. Moreover, it possesses an asymmetric surface topography and an apparent Young's modulus of approximate to 1.0 MPa, which is structurally and mechanically similar to natural BMs. Of interest, the airside and the waterside of the PDA film exhibit differences in their adhesion affinity to the human skin keratinocytes. With stronger active mechanical processes between living cells and the waterside of PDA film, epithelial folding could be mimicked. Together, the PDA film is able to recapitulate the structural and mechanical complexity of natural BMs, indicating the prospective future of using PDA films for in vitro modeling cell-BM interaction and tissue formation.