Gold nanoclusters as novel optical probes for in vitro and in vivo fluorescence imaging

Fluorescent probes play an important role in the development of fluorescence-based imaging techniques for life sciences research. Gold nanoclusters (AuNCs) are a novel type of fluorescent nanomaterials which have attracted great interest in recent years. Composed of only a few atoms, these ultrasmall AuNCs exhibit quantum confinement effects and molecule-like properties. Fluorescent AuNCs have an attractive set of features including ultrasmall size, good biocompatibility and photostability, and tunable emission in the red to near-infrared spectral region, which make them promising as fluorescent labels for biological imaging. Examples of their application include live cell labeling, cancer cell targeting, cellular apoptosis monitoring, and in vivo tumor imaging. Here, we present a brief overview of recent advances in utilizing these emissive ultrasmall AuNCs as optical probes for in vitro and in vivo fluorescence imaging.