Folate–PEG functionalized silica CdTe quantum dots as fluorescent probes for cancer cell imaging

Fluorescent probes based on quantum dots (QDs) are emerging as ideal tools for sensing and imaging in biological applications owing to their great advantages such as high sensitivity and unique optical properties. Using QDs as potential effective toots for tumor optical imaging would allow early diagnosis, monitoring of tumor progression and treatment efficiency. We prepared a novel folate receptor-targeted, PEG-modified fluorescent probe based on silica-coated CdTe QDs. In the study, the hydrophilic thioglycolic acid stabilized CdTe QDs were directly synthesized in the water phase; the water-in-oil (W/O) reverse microemulsion method was applied to prepare the highly fluorescent amino-functionalized core-shell CdTe@SiO2 particles; subsequently, polyethylene glycol (PEG) and folate molecules were successfully bio-conjugated with the CdTec@SiO2 particles through the amino groups. The as-prepared particles were characterized by UV-Vis absorption, fluorescence measurements, particle size, zeta potential and high-resolution transmission electron microscopy (HR-TEM). The bioimaging efficiency and specificity of the prepared fluorescent probes were further evaluated on KB cells. Results indicate that the silica film encapsulated and PEGylated CdTe QDs can significantly reduce the cytotoxicity of CdTe QDs. In conclusion, folate receptor-targeted, PEG-modified and silica-coated CdTe quantum dot fluorescent probes are highly promising for tumor imaging in the near future.