Development of a novel amperometric biosensor utilising Chlorella sp. for determination of organophosphorus pesticides

Organophosphorus pesticides (OPs) are extensively used in agriculture and pose serious environmental and human health risks. This study presents a novel amperometric biosensor incorporating Chlorella sp., a photosynthetic microalga, to detect OPs based on their inhibitory interaction with Photosystem II (PS II). The biosensor was investigated in both suspended and immobilized configurations using chronoamperometric techniques. Optimization studies revealed maximum current response at 0.3 mL algal suspension and 25 μL immobilized cell volume, both at pH 7. The suspended biosensor exhibited opposite current trends for the two pesticides: a decrease in current for acephate and an increase for triazophos, both over a linear range of 10⁻⁸ to 10⁻² M. After immobilization via glutaraldehyde cross-linking on glassy carbon electrodes, both analytes showed consistent decreases in current, with linear detection ranges of 10⁻⁷ to 10⁻² M for acephate and 10⁻⁹ to 10⁻² M for triazophos. These differences underscore the impact of immobilization on analyte-specific response patterns. This work demonstrates the potential of Chlorella sp. as a sustainable, enzyme-free biosensing element for OP detection and highlights the value of PS II-based biosensing in environmental monitoring applications. The dual-configuration approach and analyte-dependent trends offer insights into algal-electrode interactions, providing a foundation for future research toward real-sample validation and portable sensor development.