Multifunctional quantum dots for cellular and molecular imaging

Multifunctional nanoparticle probes based on semiconductor quantum dots (QDs) have been developed for cancer targeting and imaging in living animals. The structural design involves encapsulating luminescent QDs with block copolymer, and linking this amphiphilic polymer to tumor-targeting ligands. In vivo targeting studies of human prostate cancer growing in nude mice indicate that the QD probes can be delivered to tumor sites by both enhanced permeation and retention and by antibody binding to cancer-specific cell surface biomarkers. Using both subcutaneous injection of QD-tagged cancer cells and systemic injection of multifunctional QD probes, we have achieved sensitive and multicolor fluorescence imaging of cancer cells under in vivo conditions. We have also integrated a whole-body macro-illumination system with wavelength-resolved spectral imaging for efficient background removal and precise delineation of weak spectral signatures. These results raise new possibilities for ultrasensitive and multiplexed imaging of molecular targets in vivo.