Bioinspired pH-Sensitive Surface on Bioinert Substrate

Polydimethylsiloxane (PDMS) is a common biomaterial with excellent properties. However, its inherent hydrophobicity impedes cell growth and differentiation. PDMS is an intrinsically inert material, which limits its applications to specific scenarios where responsive materials are needed. Dopamine can easily adhere to various substrate surfaces through noncovalent and covalent interactions. In this work, a bioinert PDMS surface was modified into a bioactive surface by biocompatible and pH-sensitive polydopamine (PDA). The binding of PDA and PDMS in different forms was verified by the typical scanning electron microscopy (SEM) and atomic force microscope (AFM). By PDA film modification, the contact angle of PDMS was significantly reduced. Hydrophobicity was achieved by PDA nanosphere (PDA NS) modification. PDA-modified PDMS was also found to be pH-sensitive, as validated by contact angle measurement, macroscopic friction test, and protein adsorption. Compared to an unmodified surface, the PDA significantly improved cell adhesion, proliferation and spreading. We came to a conclusion that the surface roughness of PDA-modified PDMS had little effect on cell growth and the cytocompatibility of the materials was mainly determined by the surface chemical properties. Our results further validated that PDA/PDMS is pH-sensitive and can effectively promote cell growth and proliferation.