Fine-Tuning NIR-Absorbing BODIPYs for Photoacoustic Detection of Hypochlorous Ion (OCl⁻).

Highly reactive oxygen and nitrogen species (ROS/RNS) play crucial roles in various pathological conditions. Among them, hypochlorous ion (OCl⁻), a potent ROS, is associated in numerous oxidative stress-related disorders. Elevated levels of OCl⁻ are thus recognized as a biomarker for diagnosing inflammatory conditions. To enable selective detection of OCl⁻ via photoacoustic (PA) imaging, we present development of a near infrared(NIR)-absorbing BODIPY-based acoustogenic probe. Four regioisomers of methoxyphenols-conjugated BODIPYs were synthesized to investigate the positional influence on OCl- selectivity over other ROS/RNS. Our study reveals that only one isomer, 4-methoxy phenol conjugation, exhibited exceptional selectivity for OCl- without any competitive reactions, making it suitable for PA imaging. This study highlights the importance of regioisomers characterization in achieving intricate selectivity among competing reactive species. The fine-tuning and development of a suitable dye now enable the optimization of physicochemical properties for in vivo OCl-  detection using PA imaging.