Ratiometric photoacoustic nanoprobes for monitoring and imaging of hydrogen sulfide in vivo

Abstract

Detection and visualization of hydrogen sulphide (H₂S) is crucial for understanding its physiological and pathological roles towards human health and diseases, but precisely tracking of H₂S in vivo remains challenging due to the limitations of available analytical methods. In this study, we developed a novel ratiometric photoacoustic (PA) nanoprobe for selective detection and imaging of H₂S in biological fluids, live cells, brain tissues and animals. The nanoprobe AzHD-LP was fabricated by encapsulation of a newly synthesized H₂S-responsive near-infrared (NIR) dye (AzHD) within a liposome (LP). The as-prepared AzHD-LP exhibits a dramatically red-shift response of its absorption peak after reduction reaction of AzHD with H₂S: the absorbance of AzHD-LP centered at 600 and 700 nm is decreased and increased, respectively, producing a turn-on ratiometric PA signal in the presence of H₂S. Typically, under the excitation of a 532 nm and 700 nm pulsed laser, the selective detection and imaging of H₂S was achieved in aqueous solution, living cells and brain tissues of Alzheimer's diseased mice. Moreover, after AzHD-LP conjugated with a tumor-targeting peptide – c(RGDyK) as RGD-AzHD-LP – ratiometric PA mapping of the intratumoral generated H₂S in the HCT116 colon tumor-bearing live mice was demonstrated.