CdTe/Silica Nanospheres in a Lateral Flow Immunoassay for Prostate-Specific Antigen

Fluorescent labeling via quantum dot (QD)-based nanospheres is intended to improve the detection performance for the lateral flow immunoassay (LFIA). In this thematic issue, current synthetic strategies for fluorescent nanospheres are rigorous, which might even cause the breaking of the photophysical properties of QDs. Here, a facile method was tailored to bright ultrastable QDs/silica nanospheres (UQSNs) via self-controlled sequential growth, used for sensitive LFIA. Specifically, in dendritic mesoporous silica nanoparticles (DMSNs) modified with a thiol compound beforehand, the in situ growth of highly fluorescent CdTe QDs is achieved; accompanying QD growth, under alkaline and high-temperature conditions, the -Si-O- bonds on the surface of DMSN will break and rapidly remodel to form a dense SiO2 outer layer (protecting the QDs from leakage and improving their stability). UQSN exhibits uniform size and high colloidal/optical stability, even under strong acid/base conditions; meanwhile, the size, fluorescence peak, and ligand of UQSN can also be controlled well. Importantly, it was found that the UQSN-115 has an optimal particle size, compared with the other three DMSNs with various diameters (80, 220, and 340 nm), for LFIA detection of the prostate-specific antigen (PSA, a valuable biomarker for prostate cancer diagnosis), reaching a detection limit of 0.138 ng/mL, besides the routine C-reaction protein (CRP) detection. This self-controlled sequential growth strategy provides new insights into producing promising fluorescent materials and developing the next sensitive bioassay.