Enzymatic reaction based biosensor for specific detection of organophosphate pesticides

Abstract

This research aims to design and develop two-biosensor platforms based on graphene quantum dots (GQDs) via enzymatic reaction for determining organophosphate pesticides (OPs). A first platform consisting of GQDs and active enzyme, GQDs/Enz platform, is simply fabricated in aqueous solution. Ongoing development of GQDs/Enz platform for effective OPs sensing by hybrid hydrogel (GQDs/Enz/Gels) was of great interest to improve the sensitivity and enzyme stability under the benefit of easy to be used for sensing approach.

The GQDs/Enz and GQDs/Enz/Gels were constructed and characterized by general methods such as FT-IR, SEM and TEM. Based on the concept, H2O2 generated in situ by the active enzymatic reaction of acetylcholinesterase and choline oxidase enables to react with GQDs resulting in photoluminescence (PL) quenching of GQDs at 467 nm. The PL recovery of GQDs was observed in the system with OPs due to enzymatic inhibition process by OPs. With a selectivity study of sensing platform toward OPs, GQDs/Enz platform exhibited a significant fluorescent change in case of dichlorvos and methyl-paraoxon. In quantitative analysis, the limits of detection (LOD) of GQDs/Enz platform for dichlovos and methyl paraoxon are 0.78 μMand 0.34 μM in linear range of 0.45-45 and 0.40-4 μM, respectively. Furthermore, novel incorporation of GQDs and enzyme in hydrogels (GQDs/Enz/Gels) based gelator 4b enables to significantly enhance the PL intensity of GQDs and effectively improve 10-100 folds in the limit of detection and in linearity range towards dichlorvos and methyl-paraoxon (26.10x10-3 and 6.79x10-3 μM in linear range of 12.5 x10-3-125 μM and 1.25 x10-3-62.5 μM, respectively). In this approach, the biosensors are expected to offer the promising selective and sensitive determination of the OPs and a benefit for easy checking of OPs in food, water and environment in future.