An aza-BODIPY-based NIR-II luminogen enables efficient phototheranostics.

The fabrication of a high-performance second near-infrared (NIR-II) biological window fluorophore is in urgent need for precise diagnosis and treatment of cancer. Nevertheless, the construction of phototherapeutic agents in the NIR-II region with excellent imaging performance and minimal side effects remains a big challenge due to the limited availability of core fluorophore candidates. In this study, a new NIR-II fluorescent probe, CB1, which is an aza-BODIPY core conjugated with bulky donors, was designed and synthesized. CB1 was further encapsulated in DSPE-PEG2000 to impart water solubility, which shows brighter NIR-II fluorescence and higher photostability than the clinically used indocyanine green (ICG). CB1 nanoparticles show deep tissue penetration and high imaging contrast in vivo . In addition, molecular conformation enables CB1 nanoparticles to exhibit good photothermal properties. Both in vitro and in vivo assessments confirm that CB1 nanoparticles could be utilized as distinguished theranostic agents for NIR-II fluorescence imaging and tumor growth inhibition with negligible side effects. Collectively, this work provides a promising approach for constructing a new platform for cancer diagnosis and therapy.