Near-Infrared Lanthanide-Doped Nanoparticles for a Low Interference Lateral Flow Immunoassay Test

The lateral flow immunoassay test (LFT), as a method of a point of care test, is widely used in disease diagnosis, food security, and environment observation due to its portability and testing rapidity. A fluorescence lateral flow immunoassay was developed recently to enhance the sensitivity and accuracy of the LFT. However, for most fluorescence reporters, their emission and excitation wavelengths are located in the ultraviolet or visible region. Serum or whole blood significantly absorbs and scatters light of this region, and this will result in background signal interference. In this study, we replace traditional fluorescence reporters with near-infrared lanthanide-doped nanoparticles (NIR-RENPs) to establish a NIR-LFT platform. Blood and other biological samples scatter and absorb less near-infrared light than visible light, and the autofluorescence of biological samples is rarely located in this region. Therefore, using NIR light as a signal can diminish the interference of background noise and suffer from less signal attenuation. In addition, compared with commonly used NIR organic dye, NIR-RENPs have better stability. It is promising that lateral flow immunoassays based on NIR lanthanide-doped nanoparticles are able to acquire a lower detection limit and better accuracy, and they are more suitable for application in commercial settings.