An activatable water-soluble photoacoustic probe for real–time imaging of endogenous cysteine in the mouse tumor model

Cysteine (Cys), one of the most common cellular biothiols, is closely related with many diseases such as Alzheimer's disease, Parkinson's disease and cancer. However, photoacoustic (PA) probes for detecting Cys-associated complicated diseases are still rare, especially for deep imaging of Cys in tumor. Therefore, the development of a reliable approach for noninvasive imaging Cys in tumor to fully understand the physiological functions of Cys has great significance. Herein, a novel activatable water-soluble photoacoustic probe ( NCTy ) for accurately monitoring of Cys was developed. The probe NCTy could specifically respond to Cys and release a near-infrared absorbing dye, causing the PA signals at 695 nm to be turned on. Furthermore, the Cys-activated probe exhibited a 5.3-fold PA signal enhancement, while high-resolution PA images were obtained. In light of these outstanding features, the PA probe NCTy was utilized for PA imaging of exogenous and endogenous Cys in living cells and mice. Notably, the probe NCTy had been employed for real-time monitoring Cys level in vivo tumor through PA imaging technology, for the first time. We expect that the probe NCTy would provide a new method for the research and diagnosis of tumor-related pathological processes. • An activatable water-soluble new optoacoustic probe ( NCTy ) for monitoring of Cys was developed. • The probe has the advantages of high sensitivity, good selectivity, and deep penetration. • The probe exhibited low cytotoxicity, and can be used for PA imaging of Cys in cells and in mice. • The probe was used to realize the real-time imaging of Cys level in the tumor mice through PA imaging technology, for the first time.