Interactive Response Of Mussel-Inspired Polydopamine On Titanium Surface For Regulation Of Cells Behaviors

Titanium and its alloys have been widely prepared similar to human bone over the past few decades as implants for healing bone defects. Nevertheless, the bioinert property of titanium alloy limits its clinical application due to lack of contact with cells. Moreover, surface modification method can only improve the cell growth without regulation of cell function, and the cell life activities can not be efficiently and orderly operated. Therefore, titanium implants was coated with the mussel-inspired polydopamine (PDA) film with chelation of calcium ions, pH response and electrical response for regulation of cell function. Thus, an ideal titanium implant surface should favor responsive while concomitantly regulating osteoblast adhesion and growth behavior.In this paper, calcium ions chelation platform was successfully obtained on a titanium surface by modification with PDA. The chelation mechanism of PDA with Ca2+was studied in this paper. The results showed that the functional groups of PDA chelated Ca2+were changed from phenolic hydroxyl to benzoquinone. It had been found that the surface of Ca2+ chelated with PDA could induce the nucleation and growth of hydroxyapatite in SBF, indicating its good bioactivity. Meanwhile, cytotoxicity assay demonstrated that low concentration of Ca2+chelation possessed a good cytocompatibility.Secondly, PDA films were deposited on titanium surface by electropolymerization method. The experimental results showed that the interface resistance of PDA films increased with the increase in pH, and the protonation of PDA exhibited higher charge storage capacity at pH=3.0. The surface potential of PDA was switched from 349±3.8 mV to 601±13.9mV after protonation/deprotonation cycles, resulting the reversible change of surface potential under acidic (pH=3.0) or alkaline (pH=11.0) conditions. Moreover, the cells experiments showed that the protonation of PDA also accelerated the cell spreading response manifested by extensive flattening and an increase in mean cellular area. The surface protonation process increased in the cell adhesion activity were correlated with previously demonstrated the positive charge of polydopamine films at pH=3.0.Lastly, a strategy for on demand electrochemically controlled phenolic hydroxyl/benzoquinone transformation of PDA layer is described, which combines electrochemical redox reactions of 2e- and H+. This strategy utilizes PDA containing phenolic hydroxyl moieties that can be reversible electrochemically converted into benzoquinone moieties, and the generated benzoquinone moieties can rarely reduce Cu2+and mainly attach BSA protein. By using this strategy, we can easily regulate cell adhesion and spreading, and even control of cell proliferation.