Amperometric Biosensor for Dopamine Determination Based on Over-Oxidized Polypyrrole-Plant Tissue Composite

Abstract An amperometric biosensor based on over-oxidized polypyrrole (OPPy) coated on a sol-gel bioelectrode was developed by entrapment of plant tissue into sol-gel matrix. Polymer film was electrochemically synthesized by electro-oxidation of 0.1 M pyrrole in aqueous solution onto the sol-gel biosensor. PPY was then over-oxidized by scanning potential from − 0.2 to 1.1 V versus SCE at a scan rate of 20 mVs−1 in 0.5 M NaOH. The OPPy-modified sol-gel bioelectrode showed a high catalytic activity toward the electro-oxidation of dopamine (DA). The effects of pH, pyrrole concentration, and potential range of polypyrrole over-oxidation on the response of the electrode were investigated. The modified bioelectrode presented a linear response range for DA from 9.99 × 10−6 M up to 1.1 × 10−3 M by amperometry. Amperometric measurements were performed at a constant potential of 0.4 V versus SCE. The diffusion coefficient of 6.86 × 10−8 cm 2  s−1 for DA was also obtained using chronoamperometry study. The responses...