Cross-linked enzyme crystals of organophosphate hydrolase for electrochemical detection of organophosphorus compounds

Abstract

Cross-linked enzyme crystals of organophosphate hydrolase (CLEC-OPH) prepared from crude recombinant E. coli cell lysate was used for the development of an electrochemical biosensor for the detection of organophosphate pesticides. CLEC-OPH showed an increased V max of 0.721 U mg protein−1 and a slightly lower K m of 0.083 mM on paraoxon compared to the crude enzyme, resulting in an improved catalytic efficiency (k cat/K m = 4.17 × 105 M−1 min−1) with a remarkable increase on thermostability. An amperometric biosensor was constructed based on glutaraldehyde and albumin cross-linkage of CLEC-OPH with carbon nanotubes. The sensor exhibited greater sensitivity and operational stability with a lower limit of detection when compared with a sensor using an equivalent loading of crude OPH in a non-crystal form. The application of crude enzyme-based CLEC would offer a simple and economical approach for the fabrication of efficient electrochemical biosensors.