Large Scale Synthesis of Highly Stable Fluorescent Carbon Dots Using Silica Spheres as Carriers for Targeted Bioimaging of Cancer Cells

In this paper, fluorescent carbon dots (CDs) loaded on silica (SiO2) spheres are synthesized by the one -pot hydrothermal route, and then folic acids (FA) are covalently conjugated on the surface of SiO2 spheres. The formed SiO2@CDs-FA composites can target specific tissues, e.g., cancer. The key of this method is the employment of (3-aminopropyl)trimethoxysilane as bridge joint, which not only serves as surface passivation agents allowing the large scale synthesis of CDs with high quantum yield, but also enables SiO2@CDs composites further covalent conjugation of FA. The resultant SiO2@CDs composites have many advantages such as easy separation and purification, highly stable, well water-soluble, and biocompatible. Moreover, the SiO2@CDs-FA could be used as fluorescent probes for biological imaging in vitro. The uptake of the SiO2@CDs-FA into HeLa cells is receptor-mediated endocytosis, which is confirmed by a comparative study using FR-negative 293T cells. Findings from this study suggest that the SiO2@CDs-FA composites could be used as a platform for cancer diagnosis studies in various biological systems.