In vitro and in vivo optical imaging using water-dispersible, noncytotoxic, luminescent, silica-coated quantum rods

A facile method for synthesis of monodisperse, biocompatible, silica coated CdSe/CdS/ZnS quantum rods (QRs) and their use as probes for in vitro and in vivo optical bioimaging is presented. The silica coating procedure involves condensation-polymerization of the precursor tetraethylorthosilicate (TEOS) over QRs encapsulated within the reverse micellar core of Igepal CO-520/cyclohexane microemulsion. The silica-coated QRs have been characterized by TEM, DLS, and photoluminescence spectroscopy. The silica shell thickness has also been shown to be tuned by varying the ratio of TEOS and QRs. Confocal bioimaging of different cell lines (Panc 1 and RAW), treated with silica coated QRs, has shown a robust uptake of the nanoparticles, without the need of specific targeting molecules. To evaluate the cytotoxicity of the nanoparticles, MTS assay has been carried out over a period of 48 h. In vivo imaging of subcutaneously xenografted tumor-bearing mice, following direct intratumoral injection of the nanoparticles, have shown fluorescence from the tumor within 10 min of injection. This study suggests that these silica-coated QRs can be potentially used for long-term targeted imaging studies in vitro and in vivo.