Electrical Potential Specified Release of BSA/Hep/Polypyrrole Composite Film and Its Cellular Responses.

A facile strategy is needed for accurate time-space supply of suitable growth factors or drugs. Polypyrrole (PPy) was able to carry almost all kinds of negatively charged biomolecules through anodizing method, which made it an appropriate way for codeposition of multiple molecules. The difference in the conjugation between different molecules and PPy makes it possible for selective release when the redox state of PPy changes. In this work, bovine serum albumin (BSA) and heparin (Hep) were chosen to be the model molecules in view of their differences in the level of electronegativity and molecular weight. Double-layer deposition method was used to improve the biocompatibility of PPy/BSA/Hep film. It was found the content of BSA and Hep in the film can be controlled by regulating deposition current and time. BSA release was facilitated under positive voltage and then promote the proliferation of preosteoblasts, while Hep release was promoted under negative voltage and enhance cell differentiation. Our work provides a dual-molecule model in PPy for selective release and further explores the mechanism of release selectivity, this discovery has potential applications in tissue engineering and regenerative medicine.