Fabrication of Protein A-Functionalized Silica-Encapsulated Carbon Dot Bioconjugates for Cellular Fluorescence Imaging.

Fluorescent probes are widely employed in biofluorescence analysis and biomedical imaging. In this study, uniform spherical silica-encapsulated silicon-nitrogen co-doped carbon dots (Si-MPD-CDs@SiO2) with a particle size of 24 ± 15 nm were prepared via a modified Stöber method. The nanocomposites were further carboxylated and covalently conjugated with Protein A to construct Si-MPD-CDs@SiO2@PA bioconjugates. The resulting nanoprobe was successfully applied for specific immunofluorescence labeling and imaging of immortalized mouse thymic epithelial cells (iTECs). Compared with commercial fluorescent secondary antibodies, Si-MPD-CDs@SiO2@PA exhibit multiple superiorities including low cost, facile preparation and purification, favorable surface modifiability, strong fluorescence emission, and high photostability. These results indicate that Si-MPD-CDs@SiO2@PA can serve as a promising fluorescent nanoprobe for targeted cellular imaging and related biomedical applications.