On demand, wireless electrochemical release of brain derived neurotrophic factor

Organic conductive polymers are prime candidates for the on demand or controlled release of neurotrophic proteins which can enhance the electrode-neural interface. In this study, bipolar electrochemistry (BPE) is employed to provide a wireless electrical stimulation that avoids the need for the direct physical connection necessary for conventional approaches. Brain-derived neurotrophic factor (BDNF) was incorporated into polypyrrole (PPy) with poly (2-methoxy-5 aniline sulfonic acid) (PMAS) as a dopant during the course of electrochemical synthesis. The synthetic PPy-PMAS-BDNF material acts as the bipolar electrode and is placed within an electric field generated by two driving electrodes. Controlled release of BDNF is demonstrated, which is wireless powered by BPE. This is likely due to the wirelessly activated redox reactions which induce gaps/channels within the structure. Quantification of the BDNF reveals significant differences in the controlled-release properties of the films driven by BPE compared to conventional wired electrochemistry. Human neuroblastoma cells (SH-SY5Y) cultured on the PPy-PMAS-BDNF electrode were subjected to one-week of wireless electrostimulation. Neurite outgrowth was significantly improved when the polymer containing BDNF and the film BPE stimulation. The data suggest that when the BPE is applied, the cells simultaneously respond to the wirelessly released BDNF and the wireless electrical stimulation through the bipolar electroactive polymer electrode. This synergistic effect promotes enhanced neurite outgrowth across the electrodes.