Electroactive MnO2-poly(3,4-ethylenedioxythiophene) composite nanocoatings enhance osteoblastic electrical stimulation

Electroactive biointerfaces on metallic implants can transduce electrical into ionic signals under exogenous electrical stimulation (ES), which have been proposed to compensate the mislaid bioelectricity signals in bone defects. However, unsatisfied electrical properties and long-term stability are the major issues that hinder their clinical applications. Herein, based on the merits of birnessite-type MnO 2 (the large capacitance and effective surface area) and poly(3,4-ethylenedioxythiophene) (PEDOT, the high conductivity and physicochemical stability), MnO 2 -PEDOT composite nanocoatings (MnO 2 -P1 and MnO 2 -P2) were prepared by coating trace amounts of PEDOT onto the MnO 2 nanocoating surfaces via an in-situ polymerization method. The composite nanocoatings exhibited decreased charge transfer resistance and concurrently enhanced charge storage capacity. More importantly, the MnO 2 -P2 nanocoating with thicker PEDOT layer withstood higher voltages with minor loss of mass and charge injection capacity, thus enhancing mechanical and electrochemical stability. The composite nanocoatings were further applied to MC3T3-E1 osteoblastic cells to enhance their adhesion, proliferation and differentiation with the MnO 2 -P2 showing the greatest enhancement. Enhanced cellular proliferation on the MnO 2 -P2 nanocoating under ES could be ascribed to the combination of the ES-induced Ca 2+ -fibronectin interactions and the limited Mn 2+ release prevented by PEDOT protective layer.