Upconversion fluorescence-based paper disc for multiplex point-of-care testing in water quality monitoring

Water quality monitoring is of great significance for human health, which involves a large number of distinct targets detection, such as pathogens, heavy metal ions, and toxins. Traditional detection methods usually carried out in well-equipped central labs are subjected to time, labor, and expense consumption, thus not suitable for implementing water quality monitoring at point of care, where the detection implemented on a multiplexed, miniaturized, and simplified device with rapid and sensitive answer out is desired. To this end, we developed a paper disc relying on upconversion fluorescence signal and aptamer recognition probes for multiplex detection of water contaminants with high sensitivity and specificity. Finally, several different typical kinds of water contaminants have been successfully detected on our paper disc with limit of detection of 115 cfu/mL for Salmonella, 3 ng/mL for Ochratoxin A and Microcystin-LR, 20 nM for Hg²⁺ and 4 nM for Pb²⁺, respectively. Additionally, we designed a compact smartphone-based reading device to enable water quality monitoring at point-of-care. Furthermore, this paper disc-based detection platform can be extended to apply to multiplex detection for disease diagnosis and food safety monitoring.