Fabrication of polypyrrole/proteins composite film and their electro-controlled release for axons outgrowth

The potential applications of growth factor-electrocontrolled release in nerve tissue regeneration need to be studied. An electrochemically controlled release system with proteins was developed based on glutamate (Glu)-doped polypyrrole (PPy) films with good electrical conductivity (10.1 S/cm) and redox activity. Glu-doped PPy films were synthesized via electrochemical oxidation at constant current of 2 mA, then proteins of nerve growth factor (NGF) and neurotrophin-3 (NT-3) were conjugated onto doped PPy film via carbodiimide chemistry, and the amounts of conjugated NGF and NT-3 on PPy film reached to 458.2 ng/cm–2 and 415.3 ng/cm–2, respectively. Subsequently, these linked proteins could be released under electro-stimulus of 0.5 mA, and they were still kept good bio-activity. Analyses of neurites outgrowth on NGF/NT-3-conjugated PPy film under electro-stimulus of 0.5 mA show that, the conjugated NGF/NT-3 and electro-stimulus could form synergistic effect through the conductive PPy film to promote the axon elongation. These results provide good foundation on the electro controlled release of growth factors from conductive PPy for nerve tissue engineering.