One step electrochemical synthesis of gold-nanoparticles–polypyrrole composite for application in catechin electrochemical biosensor

Abstract

An electrochemical biosensor has been fabricated for catechin detection using the nanoparticle–polymer composite as a matrix. The composite has been electrochemically synthesized and tyrosinase enzyme was entrapped during polymerization of the composite material. The composite has been characterized for its morphology, optical, structural, and electrochemical behavior. Studies revealed that the presence of gold nanoparticles (AuNPs) in the polymer matrix resulted in an increase in conductivity, enhanced current intensity and diffusion coefficient. The AuNPs–PPy composite provided large surface area for enzyme immobilization and facilitated electron transfer, evident from almost 10% enhancement in biosensor response in the presence of nanoparticles (NPs). For catechin detection, the biosensor showed well defined redox peaks at 0.24 V/0.14 V for the redox reaction of the hydroxyl group present in the catechol moiety of the catechin and a weak oxidation peak at 0.62 V corresponding to the oxidation of the hydroxyl group present in the central ring of catechin. The linearity was achieved from 1 × 10⁻⁹ M to 1 × 10⁻⁸ M, with a sensitivity of 6.8 × 10⁻⁵ A M⁻¹. The limit of detection (3 × SD/sensitivity) and K_m value are 1.2 × 10⁻⁹ M and 4.5 × 10⁻⁹ M respectively. The response time of the biosensor was about 10–12 s with an optimum pH at 7.0. The biosensor has been tested for catechin detection in water and apple juices and the response was within 10% error.