Visualizing Human Prostate Cancer Cells in Mouse Skeleton Using Bioconjugated Near-infrared Fluorescent Quantum Dots

Objectives: To visualize human prostate cancer cells in mouse bone with bioconjugated near-infrared quantum dot (QD) probes. Near-infrared fluorescent probes using QDs can visualize tumors in deep tissues in vivo. Methods: Human prostate cancer C4-2B xenografts grown in mouse tibia were detected by prostate-specific membrane antigen antibody conjugated with QDs emitting light at the near-infrared range of 800 nm (QD800). Images in culture and in vivo were acquired using the IVIS Imaging System. Results: As few as 5000 cells can be detected subcutaneously when tagged with QD800 conjugate and injected directly into mice. QD800 conjugate injected intravenously in mice harboring C4-2B tumors in tibia detected signals from a minimum of 500 000 cells. The maximal light emission was detected 30 minutes after intravenous injection of QD800 conjugate in mice with established C4-2B tumors. Conclusions: Bioconjugated near-infrared QD probes are highly sensitive molecular imaging tools for human prostate cancer micrometastases in mice.