NIR-II fluorescent Ag₂Se polystyrene beads in a lateral flow immunoassay to detect biomarkers for breast cancer

Fluorescent lateral flow immunoassay (LFA), one tool in point of care testing (POCT) systems for breast cancer, has attracted attention because it is quick, simple, and convenient. However, samples and the constituent material exhibit autofluorescence in the visible region, which is a very large obstacle in the development of fluorescent LFAs. The autofluorescence of biological samples is scarcely found in the second near-infrared (NIR-II) range and samples scatter and absorb less NIR-II light than visible light. Here, we report an NIR-II QD-LFA platform using the NIR-II fluorescent Ag₂Se quantum dots (QDs) with 1020 nm emission encapsulated into polystyrene beads as fluorescent probes. The NIR-II LFA platform was established to detect breast cancer tumour markers (CEA and CA153) within 15 min with a low limit of detection (CEA: 0.768 ng mL^-1, CA153: 1.192 U mL^-1), high recoveries (93.7% ~ 108.8%), and relative standard deviations (RSDs) of less than 10%. This study demonstrated the potential of NIR-II Ag₂Se polystyrene beads as a fluorescent probe in LFA for rapid and accurate identification of biomarkers. They are suited for use in professional situations.