Electropolymerized Self-Assembled Layer on Gold Nanoparticles: Detection of Inducible Nitric Oxide Synthase in Neuronal Cell Culture

Novel nanostructures of gold nanoparticle (AuNP) encapsulated-conductive polymer have been developed to study biosensor probe materials and utilized to detect the concentration of inducible nitric oxide synthase (iNOS). A 2,2':5',5 ''-terthiophene-3'-benzoic acid (TTBA) monomer was synthesized and self-assembled on gold nanoparticles (AuNPs). The size effects of the AuNPs and TTBA monomer film thickness on the electrode conductivity were examined. Anti-iNOS antibody was covalently bound on an encapsulated-AuNPs polymer layer with self-assembled TTBA. The immunocomplex formation between iNOS and anti-iNOS was directly observed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This study looked at the applicability of the self-assembled TTBA layer where the results indicated an efficient electrochemical response toward iNOS. The calibration plot of the current response vs. iNOS concentration exhibited a linear relationship in the range of 0.001-0.02 mu g/mL. The calibration sensitivity of iNOS was 59.4 +/- 0.3 mV/mu g mL(-1). The detection limit of iNOS was determined to be 0.20 +/- 0.04 ng/mL based on five time measurements (95% confidence level, k = 3, n = 5). Further results show that AuNP-encapsulated conductive polymers are good nanostructured materials as biosensor probes and have a potential application in cell biosensors.