Salt-Induced Aggregation of Polyallylamine-Coated Gold Nanoparticles(PAH-AuNP) for Rapid Detection of Methyl Parathion

Abstract

Several approaches for the detection of methyl parathion (MPT) have been reported. However, concern about the complexity and complicated instrumentation hampers its application for rapid analysis. Hence, colorimetric mode of detection for rapid analysis of MPT utilizing the unique property of an aggregated gold nanoparticles is reported herein. Polyallylamine-coated gold nanoparticles (PAH-AuNP) were prepared, and recombinant methyl parathion hydrolase (MPH) was used to specifically hydrolyze MPT into paranitrophoneol (PNP). Different experimental conditions, such as the pH of the salt-induced aggregation of AuNP, condition for the immobilization of MPH, the concentration of the MPH enzyme, the duration of incubation, among others were evaluated. Results showed that the prepared AuNP readily recognized the product (PNP) upon salt-induced aggregation when PNP is all converted to its ionic form. Rapid detection was obtained within 5 minutes at a pH greater than 7 at concentrations ranging from 0.1-14 ppm of MPT. The minimum MPT concentration that can be detected using this technique is 0.1 ppm. An ongoing experiment is currently being undertaken to demonstrate the applicability of the method for the detection of similar structure pesticides. Likewise, mechanistic study to further explain the obtained results is also being considered and will be incorporated in the subsequent report.