A novel layer-by-layer assembled multi-enzyme/CNT biosensor for discriminative detection between organophosphorus and non-organophosphrus pesticides

Abstract

Organophosphate compounds are heavily used in agriculture and military activities, while non-organophosphate pesticides are mostly used in agriculture and home defense. Discriminative detection of such toxic compounds is very challenging and requires sophisticated and bulky instrumentation. Meanwhile, multi-enzyme biosensors may offer an effective solution to the problem and may become a versatile analytical tool for discriminative detection of different neurotoxins. In this study, we report for the first time a novel bi-enzyme biosensing system incorporating electrostatically interacted enzyme-armored MWCNT-OPH and MWCNT-AChE along with a set of cushioning bilayers consisting of MWCNT-polyethyleneimine and MWCNT-DNA on glassy carbon electrode for discriminative detection of organophosphorus (OP) and non-organophosphorus (non-OP) pesticides. LbL interfaces were characterized by surface plasmon resonance and electrochemical impedance spectroscopy, demonstrating stepwise assembly and electron conductivity studies. The detection limit was found to be ~0.5 for OP pesticide paraoxon and 1 μM for non-OP pesticide carbaryl, in a wide linear range. The biosensor performance was also validated using apple samples. Remarkable discriminative and straightforward detection between OP and non-OP neurotoxins was successfully achieved with cyclic voltammetry (CV) and UV-vis methods on the MWCNT-(PEI/DNA)2/OPH/AChE biosensor, showing great potential in large screening of OP and non-OP pesticides in practical applications.

Keywords: Carbaryl; Discriminative detection; Layer-by-layer self-assembly; Multi-enzyme; Multi-walled carbon nanotube (MWCNT); Paraoxon.