ABSTRACT
Folate receptor ( FR )-targeted fluorescent nanoprobes ( RSiNPs-Folate ) were constructed by modifying Rubpy-doped silica nanoparticles ( RSiNPs) with folic acid ( FA) based on click chemistry coupling method, which was successfully used for cancer cell imaging. Firstly, RSiNPs were prepared by St?ber method and modified with azide groups through the hydrolysis of silane coupling agents ( Az-PTES ) , then propargyl folate were conjugated onto the nanoparticle surfaces via click reaction. It was demonstrated that the FA-functionalized nanoprobes were successfully prepared by monitoring the characteristic peak of the azide group at 2105 cm-1 before and after coupling. In the condition of physiological pH, the nanoprobes exhibited strong red emission at 601 nm when excited at the 458 nm excitation wavelength. The cell imaging results showed that RSiNPs-Folate could effectively target FR-positive HeLa cells, while no obvious fluorescence was observed for FR-negative A549 cells. The receptor-mediated imaging mechanism was confirmed by free FA competition experiments. More importantly, HeLa cells could be selectively recognized and imaged in the mixing cell system. Compared with the carbodiimide conjugation protocols, the click-functionalized nanoprobes had many advantages such as simple synthesis procedures, mild reaction conditions and high yields, which could be potentially used for fluorescent labeling and imaging of different cancer cells.