Lateral flow aptamer assay integrated smartphone-based portable device for simultaneous detection of multiple targets using upconversion nanoparticles

Simultaneous detection of multiple targets with different analyte-recognition reactions in the same sample in a rapid, low-cost and reliable way has immense potential with widespread applications in food safety, medical diagnostics and environmental monitoring. Herein, we developed a lateral flow aptamer assay (LFAA) integrated smartphone-based portable device for highly sensitive and precise detection of multiple targets, using aptamers functionalized multi-colored upconversion nanoparticles as probes. The developed LFAA can provide rapid and sensitive analysis of three different kinds of targets (i.e., small molecules, ions and bacteria) without significant cross-reaction by using separate color channels. By using the competitive format, the concentration of each target can be determined from the color intensity of the corresponding colored band. With the LFAA, we have achieved detection ranges of 10-104 ppb, 0.01-50 μg/mL and 150-2000 CFU/mL and detection limits of 5 ppb, 3 ng/mL and 85 CFU/mL for mercury ions, ochratoxin A and Salmonella (as template analytes), respectively. The LFAA was further used for detection in real water samples (i.e., tap water) within 30 min. Subsequently, a smartphone-based device was used instead of a CCD camera to read the results, which could make the detection process rapid and portable. Therefore, the developed LFAA holds great potential as a sensitive, specific, convenient and stable platform for point-of-care detection of multiple targets in various fields.