A broad spectrum amperometric pesticide biosensor based on glutathione S-transferase immobilized on graphene oxide-gelatin matrix

In this work we have fabricated a glutathione-S-transferase based amperometric biosensor for pesticides by immobilizing the enzyme on platinum electrode using graphene oxide-gelatin matrix, evaluated various biosensor parameters, applied the same for detection and quantification of four different classes of pesticides and validated the biosensor results with GC–MS analysis. The enzyme immobilization was confirmed through scanning electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometry. The apparent Michaelis-Menten constant for the immobilized glutathione-S-transferase in the said matrix was found to be 0.083 mmol L−1 and 0.15 mmol L−1 respectively for glutathione and 1-Chloro-2,4-dinitrobenzene. Substrate specificity found to be 2.56 × 107 s−1 M−1 for glutathione and 2.15 × 107 s−1 M−1 for 1-Chloro-2,4-dinitrobenzene. Pesticide analysis was done in 25% methanol solution. The biosensor is a promising new tool for pesticide analysis as it can be applied for analysis of a broad spectrum of pesticides covering at least six different classes namely - benzamidazole, organochlorine, organothiophosphate, organocarbamate, polyphenol and pyrethroid.