Recent advances of molecular optical probes for imaging of β-galactosidase.

β-galactosidase (β-Gal), as a lysosomal hydrolytic enzyme, plays an important physiological role in catalyzing the hydrolysis of glycosidic bonds which convert lactose into galactose. Moreover, upregulation of β-Gal is often correlated with occurrence of primary ovarian cancers and cell senescence. Thereby, detection of β-Gal activity is relevant to cancer diagnosis. Optical imaging possesses high spatial and temporal resolution, high sensitivity, and real-time imaging capability. These properties are beneficial for the detection of β-Gal in living systems. This review summarizes the recent progress in development of molecular optical probes for near-infrared fluorescence (NIRF), bioluminescence (BL), chemiluminescence (CL), or photoacoustic (PA) imaging of β-Gal in biological systems. The challenges and opportunities in the probe design for detection of β-Gal are also discussed.