Anionic Long-Circulating Quantum Dots for Long-Term Intravital Vascular Imaging.

A major impediment to the long-term in vivo vascular imaging is a lack of suitable probes and contrast agents. Our developed mercaptosuccinic acid (MSA) capped cadmium telluride/cadmium sulfide (CdTe/CdS) ultrasmall quantum dots (QDs) have high fluorescent quantum yield, long fluorescence lifetime and long half-life in blood, allowing high resolution long-term intravital vascular imaging. In this study, we showed that these QDs can be used to visualize the in vivo the vasculature in normal and cancerous livers in mice using multiphoton microscopy (MPM) coupled with fluorescence lifetime imaging (FLIM), with cellular resolution (~1 µm) up to 36 h after intravenous injection. Compared to highly regulated and controlled sinusoids in normal liver tissue, disordered, tortuous, and immature neovessels were observed in tumors. The utilized imaging methods have great potential as emerging tools in diagnosis and monitoring of treatment response in cancer.