Carboxyl-functionalized and bio-conjugated silica-coated quantum dots as targeting probes for cell imaging

We report the synthesis of carboxyl-functionalized silica-coated CdSe/ZnS quantum dots (QDs) via a reverse microemulsion approach. This facile method does not need to change the solvent phase of the nanoparticles during the synthesis process, and requires no other reaction condition such as high temperature or inertia atmosphere. The synthesized nanoparticles have many advantages, such as mono-dispersed and stable in aqueous solution, minimal non-specific targeting, and more direct and cost-effective for bio-conjugation. The carboxyl functionalized nanoparticles were further conjugated with apo-transferrin for receptor-mediated targeting in cancer cell lines. In vitro experiments have revealed that the cellular uptake of Tf-conjugated nanoparticles was significantly higher than that of (only-)carboxyl functionalized nanoparticles in HeLa cells, which are well known to overexpress the transferrin-receptor. The bio-conjugated nanoparticles are potentially useful as efficient probes for bio-diagnosis, both in vitro and in vivo.