Red-emitting ratiometric fluorescent metal-free CO-releasing molecule triggered by visible light for controllable and trackable CO delivery and efficient treatment of cutaneous wounds

CO is a highly toxic gas but also an important gasotransmitter in the human body that regulates cell functions and shows great therapeutic effects in clinical trials. Due to the unsafe nature of directly inhaling CO gas, the controllable and trackable release and delivery of CO are currently the key and main challenges in achieving CO therapy. In this work, we developed a novel red-emitting fluorescent metal-free CO-releasing molecule (CORM) named COR-FC that can be used to release CO under visible light irradiation and deliver CO in cells safely, accompanied by ratiometric fluorescence changes. COR-FC combines coumarin and 3-hydroxy flavonoid fluorophores and shows low cytotoxicity. Under the light irradiation of 460 nm, COR-FC undergoes rapid photolysis to release CO, accompanied by a decrease in fluorescence at 630 nm and a significant enhancement in fluorescence at 520 nm. More importantly, COR-FC can release CO in cells and tissues under visible light illumination, which provides a new metal-free CORM achieving precise control with self-fluorescence tracking. The released CO showed good anti-inflammatory effects and was successfully used to promote wound healing, indicating that COR-FC has the potential to be further applied in the biomedical field. [Display omitted] •A novel red-emitting fluorescent metal-free CO-releasing molecule (CORM) named COR-FC was developed.•COR-FC can release CO under visible light irradiation with ratiometric fluorescence changes.•COR-FC can deliver CO in cells and tissues with precise control and self-fluorescence tracking.•COR-FC can effectively promote wound healing, showing potential applications in the biomedical field.