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

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 x 10(5) 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.