Nanopaper Integrated Smart Device: An Opto-Electrochemical Biosensor for Real-Time Dual On-Field Detection of Organophosphorus Pesticides

The frequent and excessive use of organophosphorus pesticides in the agriculture industry raises persistent concerns regarding their environmental protection and public health implications. Addressing these issues requires the development of affordable and reliable sensing platforms for on-field monitoring to mitigate their adverse impacts promptly. This study utilizes nanocellulose papers (bacterial and TEMPO-oxidized) combined with butyrylcholinesterase to create a novel reagent-free and orthogonal nanobioplatform featuring smart opto-electrochemical dual outputs. An integrated nano-PAD, preloaded with enzymes and enzymatic substrates, is fabricated using wax-printing and screen-printing technologies. The nano-PAD measures opto-electroactive products, specifically indoxyl and thiocholine, whose concentrations correlate directly with the enzymatic inhibition caused by paraoxon, used as the organophosphate model. To enhance user convenience and meet the requirements for smart real-time point-of-need detection, integration of the nano-PAD with a smartphone-operated miniaturized potentiostat and a self-developed portable smart optical reader is achieved. The developed bioanalytical platform, further supported by a self-developed Android application, enables accurate and efficient quantification of dual signals in real time. The system covers a wide detection range of paraoxon (20-100 ppb) and demonstrates reliable recovery levels (ranging from 98 to 107%) in a real matrix, specifically wastewater. Given these demonstrated capabilities, this innovative biosensing strategy holds substantial potential for practical application in environmental surveillance, facilitating timely and informed environmental management decisions, particularly in resource-limited settings where traditional analytical tools are inaccessible.