Fluorescence Biosensor for the Determination of Organophosphorus Pesticides

Abstract

A whole cell based fluorescence biosensor was developed for the determination of organophosphorus pesticides (OPs) based on the measurements of PSII in Chlorella vulgaris cells. PSII is the enzymatic complex supporting photosynthetic electron transport, the splitting of water and the production of ATP and NADPH in photosynthetic organisms and was very sensitive to pesticides that affect the photosynthesis process. C. vulgaris was cultivated in laboratory in BG-11 media. For optimal response of algal biosensor, parameters such as cell density, pH and response time was optimized. Organopesticides acephate, chloropyrifos, triazophos and malathion were selected for the study. The algal fluorescence biosensor was excited at 482 nm and the emission was recorded at 683 nm, which reflects their photosynthetic activity. It was found that the fluorescence response was different for each pesticide. Acephate decreased the fluorescence intensity upto 10-9 M, however, malathion increasesd the fluorescence intensity upto 10-8 M. The study was carried out in both free and immobilized states. Algal cells were immobilized using calcium alginate method. Fluorescence intensity decreased in case of immobilized algae due to the entrapment of the cells, but the trends remained same as were obtained for free algal-biosensor.