Regulation of probe density on upconversion nanoparticles enabling high-performance lateral flow assays

Upconversion nanoparticles (UCNPs)-based fluorescence probes have shown great potential in point-of-care testing (POCT) applications, due to UCNPs' features of high photostability and background-free fluorescence. Ceaseless improvements of UCNPs-probes have been carried out to increase detection sensitivity and to broaden detection range of UCNPs-based POCT. In this paper, we optimized UCNPs-probes by regulating probe density. The optimization was verified by a traditional lateral flow assay (LFA) platform for C-reactive protein (CRP) detection. Further, the optimized UCNPs-LFA integrating with a home-made benchtop fluorescence analyzer holds the capability to achieve high-performance POCT. Finally, nearly a 20 times sensitivity enhancement with a limit of detection of 0.046 ng/mL and a broad detection range of 0.2-300 ng/mL for CRP detection was ob-tained. Moreover, the optimized UCNPs-LFA was applied to detecting CRP in clinical serum samples and the detection results were consistent with the clinical test, validating its clinical practicability. The proposed opti-mization method is also expected to optimize other nanoparticles-based bio-probes for wider POCT application.