A reductively convertible nickel phthalocyanine precursor as a biological thiol-responsive turn-on photoacoustic contrast agent

A nickel phthalocyanine precursor bearing poly(ethylene glycol) as a turn-on contrast agent for photoacoustic imaging was prepared. The water-soluble polymeric chains were smoothly eliminated through thiol-mediated reductive aromatization in cancer cells, enabling the detection of endogenous biological thiols in vitro and in vivo. This manuscript describes the biological thiol-mediated reductive transformation of an MPc precursor under physiological conditions and its application to PA imaging.