Photoacoustic nanoprobe for β-galactosidase activity detection and imaging in vivo

Abstract

Detection and visualization of [Formula: see text]-galactosidase ([Formula: see text]-gal) is essential to reflect its physiological and pathological effects on human health and disease, but it is still challenging to precisely track [Formula: see text]-gal in vivo owing to the limitation of current analytical methods. In our work, we reported a photoacoustic (PA) nanoprobe for selective imaging of the endogenous [Formula: see text]-gal in vivo. Our nanoprobe Cy7-[Formula: see text]-gal-LP was constructed by encapsulation of a near-infra red (NIR) dye Cy7-[Formula: see text]-gal within a liposome (LP, DSPE-PEG2000-COOH). The dye Cy7-[Formula: see text]-gal was synthesized based on a dye Cy-OH where the hydroxyl group was replaced by a [Formula: see text]-D-galactopyranoside residue, which can be recognized by [Formula: see text]-gal as an enzyme hydrolytic site. With the addition of [Formula: see text]-gal, the absorbance of Cy7-[Formula: see text]-gal exhibited a significant red shift with the absorption peak moved from 600[Formula: see text]nm to 680[Formula: see text]nm, which should generate a switch-on PA signal at 680[Formula: see text]nm in the presence of [Formula: see text]-gal. In addition, as the fluorescence of the dye was totally quenched due to aggregation within the liposome, Cy7-[Formula: see text]-gal-LP exhibited high PA conversion efficiency. With the nanoprobe, we achieved the selective PA detection and imaging of [Formula: see text]-gal in the tumor-bearing mice.