Redox State of PDA Directs Cellular Responses through Preadsorbed Protein

Polydopamine (PDA) is capable of adhering on nearly all kinds of surfaces and shows good biocompatibility. Moreover, its surface state could be switched between oxidation and reduction states under different electrical stimulation. In this work, the effects of PDA redox states on protein adsorption, as well as the subsequent effects on cellular responses were characterized and evaluated. It was found that the electrical treatment changed the redox states of PDA, which in turn changed the state of preadsorbed protein molecules and eventually affected the cellular responses. BSA preadsorbed PDA film was found to be beneficial for cell proliferation when PDA was changed into reduction state (RPDA), while BMP-2 preadsorbed PDA film showed promotion on cell differentiation when PDA was changed into oxidation state (OPDA). It was found that the transitions of PDA to RPDA and OPDA greatly changed the secondary structure of protein preadsorbed on it. This work provides a deeper insight on changes of protein molecules between cells and PDA surfaces with different redox states, which is important for both optimization of cell-material interactions and application of PDA as a functional coating for biomedical engineering.