Water-Dispersed Near-Infrared-Emitting Quantum Dots of Ultrasmall Sizes for In Vitro and In Vivo Imaging

摘要

Near-infrared (NIR)-fluorescence imaging is widely recognized as an effective method for high-resolution and high-sensitivity bioimaging because of its minimized biological autofluorescence background and the increased penetration of excitation and emission light through tissues in the NIR wavelength window (700-900 nm). There have been tremendous efforts to develop high-efficiency fluorescent biological probes for NIR-fluorescence imaging. Semiconductor quantum dots (QDs) have attracted much recent attention as a new generation of fluorescent probes because of their unique optical properties such as strong luminescence, high photostability, and size-tunable emission wavelength. While QDs emitting in the range of 450-650 nm have been well developed, NIR-emitting QDs have been much less explored because of their relatively complicated synthesis and post-treatment manipulations. Furthermore, NIR-emitting QDs are usually prepared in organic phase, and additional surface modification is employed to render them water-dispersible for biological applications. The relatively com- plicated surface modification often results in an increase in size of the QDs. Only recently, water-dispersed NIR-emitting CdTe/CdS QDs with tetrahedral structure were directly prepared in aqueous phase through the epitaxial-shell-growth method. Despite these advances, much work is still needed to obtain NIR-emitting QDs that can be facilely synthesized in aqueous phase for high-sensitivity and specific bioimaging.