In Vivo Tumor-Targeted Fluorescence Imaging Using Near-Infrared Non-Cadmium Quantum Dots

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Abstract
This article reported the high tumor targeting efficacy of RGD peptide labeled near-infrared (NIR) non-cadmium quantum dots (QDs). After using poly(ethylene glycol) to encapsulate InAs/InP/ZnSe QDs (emission maximum at about 800 nm), QD800-PEG dispersed well in PBS buffer with the hydrodynamic diameter (HD) of 15.9 nm and the circulation half-life of ∼29 min. After coupling QD800-PEG with arginine−glycine−aspartic acid (RGD) or arginine−alanine−aspartic acid (RAD) peptides, we used nude mice bearing subcutaneous U87MG tumor as models to test tumor-targeted fluorescence imaging. The results indicated that the tumor uptake of QD800-RGD is much higher than those of QD800-PEG and QD800-RAD. The semiquantitative analysis of the region of interest (ROI) showed a high tumor uptake of 10.7 ± 1.5%ID/g in mice injected with QD800-RGD, while the tumor uptakes of QD800-PEG and QD800-RAD were 2.9 ± 0.3%ID/g and 4.0 ± 0.5%ID/g, respectively, indicating the specific tumor targeting of QD800-RGD. The high reproducibility of bioconjunction between QDs and the RGD peptide and the feasibility of QD-RGD bioconjugates as tumor-targeted fluorescence probes warrant the successful application of QDs for in vivo molecular imaging.