In vivo behavior of near infrared-emitting quantum dots.

Near-infrared (NIR, 700-900 nm) fluorescent nanomaterials-based probes have shown major impacts on high-resolution and high-sensitivity bioimaging applications. Typically, NIR-emitting quantum dots (QDs) are highly promising as NIR bioprobes due to their unique optical properties. However, NIR-emitting QDs-related in vivo behavior remains unknown at present, severely limiting their wide-ranging bioapplications. Herein, we investigate short- and long-term in vivo biodistribution, pharmacokinetics, and toxicity of the NIR-emitting QDs. Particularly, we reveal that the NIR-emitting QDs are initially accumulated in liver, spleen, and lung for short-time (0.5-4 h) post-injection, and then increasingly absorbed by kidney during long-time (4-94 days) blood circulation. Obviously time-dependent biodistribution is observed: with time continues, most of NIR-emitting QDs are finally accumulated in liver and kidney; comparatively, less NIR-emitting QDs are observed in spleen, lung, and bone marrow. Furthermore, histological and biochemical analyses, and body weight measurements demonstrate that there is no overt toxicity of NIR-emitting QDs in mice even at long-time (94 days) exposure time. Our studies provide invaluable information for the design and development of NIR-emitting QDs-based nanoprobes for biological and biomedical applications.