Gold nanorods as peroxidase mimetics and its application for colorimetric biosensing of malathion

Nanozymes have drawn lot of attention as they overcome the limitations of natural enzymes and present a more robust alternative. Herein, the potential of Gold nanorods (GNRs) as nanozyme or enzyme mimetics is investigated. The detailed catalytic parameters of GNRs are studied and compared with other gold nanostructures (+ve and −ve nanoparticles) and horseradish peroxidase (HRP). Gold nanorods of 2.8 aspect ratio were synthesized and demonstrated to have 2.5 times higher peroxidase activity than HRP and +ve gold nanoparticles. GNRs are found to be robust enzyme mimetics displaying stability over a wide range of pH and temperature. Proof of concept is demonstrated for developing a simple, colorimetric inhibition assay for malathion using GNRs as nanozyme. The assay shows an inverse relationship between GNRs catalytic activity and malathion concentration. The sensitivity of the assay is 1.78 μg/mL and the assay is specific with <0.01% cross-reaction with organosphosphates and metal salts. The study presents the intrinsic catalytic potential of GNRs for the first time and its subsequent use thereof for developing an assay for malathion.