Surface modification of colloidal CdX-based quantum dots for biomedical applications

Colloidal CdX (X = Se, S, and Te) and their core/shell quantum dots (QDs) have narrow and size-dependent emission spectra, multicolor excitation with large extinction coefficients, and excellent photostability against photobleaching. Because of these unique photoluminescence properties of QDs over conventional fluorescent organic dyes and fluorescent proteins, QDs are useful for various applications such as biological labeling, biosensing and detection, light emitting diodes (LED), and solar cells (photovoltaics). Toward successful biological applications, control of the surface chemistry of QDs is required, enabling the preparation of QDs with water-solubility (or colloidal stability), biocompatibility, nonspecific adsorption to cells, efficient fluorescence, and active targeting. This highlight describes recent strategies developed for the modification of the surface of CdX-based QDs for biological applications.