Biocompatible near-infrared quantum dots as ultrasensitive probes for long-term in vivo imaging applications

A facile synthesis method to produce monodisperse, biocompatible, lysine crosslinked mercaptoundecanoic acid (MUA) CdSe₀₂₅Te _0.75/CdS near-infrared (NIR) quantum dots and use them as probes to study their long term in vivo distribution, clearance, and toxicity is presented. Large signal enhancements are demonstrated by these quantum dots, which enables their use as efficient and sensitive probes for live-animal imaging. An important finding is that mice intravenously injected with ≈10.5mg kg ^-1 of NIR QDs survive for more than three months without any apparent adverse effect to their health. Furthermore, it is determined that there is a significant reduction in the number of the QDs in the liver and spleen three months post injection. In addition, histological analysis of heart, kidney, liver, spleen, and lung tissue indicates that there are no acute toxic effects from these lysine crosslinked MUA NIR QDs. This study suggests that these NIR QDs can be potentially used for long-term targeted imaging and therapy studies in vivo.