Electroconductive blends of poly(HEMA-co-PEGMA-co-HMMAco-SPMA) and poly(Py-co-PyBA): In vitro biocompatibility

Electroconductive hydrogels (ECHs) were prepared as blends of ultraviolet cross-linked poly(hydroxyethyl methacrylate) [poly(HEMA)]-based hydrogels and in situ electrochemically synthesized polypyrrole (PPy). ECH blends, with potential for neuronal prosthetic devices, implantable biosensors, and electro-stimulated release devices, were produced on surface functionalized microfabricated and planar gold electrodes. Hydrogels were synthesized from hydroxyethyl methacrylate (HEMA), poly(ethylene glycol) monomethacrylate (PEGMA), N-[tris(hydroxymethyl)methyl]-acrylamide (HMMA), and 3-sulfopropyl methacrylate potassium salt (SPMA) to produce p(HEMA-co-PEGMA-co-HMMA-co-SPMA). The electroconductive polymer component was electropolymerized from pyrrole and 4-(3'-pyrrolyl)butyric acid to form P(Py-co-PyBA) within the electrode-supported hydrogel. The dynamic electrochemical properties of Au*|Gel-P(Py-co-PyBA) were investigated using multiple scan rate cyclic voltammetry and electrical/electrochemical impedance spectroscopy (EIS) over the range 0.1-100 kHz and compared to Au*, Au*|Gel, and Au*|PPy. At 0.1 Hz, there was a three-fold decrease in the magnitude of the absolute impedance, subsequent to electropolymerization. The in vitro biocompatibility and cytotoxicity of the polymer-modified gold surfaces were investigated using murine pheochromocytoma (PC12) cells and human muscle fibroblasts (RMS13). For Au*|Gel-P(Py-co-PyBA) polymer films prepared with different electropolymerization times of 5, 25, and 50 s, there was an increase in cell proliferation of 49%, 61%, and 6% compared to initial cell seeding. These ECH blends have the desired characteristics of low interfacial impedance and noncytotoxicity that makes them good candidates for in vivo intramuscular and neural studies.