Aptasensor based on fluorophore-quencher nano-pair and smartphone spectrum reader for on-site quantification of multi-pesticides

Current techniques for the detection of multi-pesticides are limited by technical complexity, sensitivity and cost. There is an urgent demand of developing new specific recognition elements and sensitive signal readouts for on site monitoring. In this work, we developed a fluorescent aptamer-based lateral flow biosensor (apta-LFB) integrated with fluorophore-quencher nano-pairs and a smartphone spectrum reader to accomplish triple-target detection of chlorpyrifos, diazinon, and malathion. Aptamers serve as alternative recognition elements instead of antibodies in LFB, offering better specificity and stability. A novel fluorophore-quencher nano-pair (quantum dots nanobeads and gold nanostars) was implemented to perform "signal-on" instead of "signal-off". After optimization, detection limit of chlorpyrifos, diazinon, and malathion were determined to be 0.73 ng/mL, 6.7 ng/mL, and 0.74 ng/mL, respectively. Greatly increased sensitivity may come from the combination of improved signal and zero background. This innovative cascade strategy allowed to lower the detection limit of pesticides residue level in food, which is largely considered satisfactory. The accuracy and practicality of this design for effective on-site quantification of multi-pesticides were further confirmed using 12 vegetable and fruit samples. The estimated recoveries were between 82.4% and 112.8% in spiked vegetable samples, which indicated that the developed method is capable for detecting multi-pesticides in food samples. This sensitive handheld-system is promising to become a powerful tool for practical on-site application of multi-pesticide quantification procedures.