Nitric Oxide, Singlet Oxygen, and Peroxynitrite Release from Anthraquinone Photodonor Liposomes with Colorimetric and Fluorescent Readout for Anticancer Applications

Nitric oxide (NO) exhibits diverse therapeutic effects in biological systems. Recently, light-activated N-nitrosated NO donors with fluorescence and colorimetric responses have attracted considerable attention. Anthraquinones, known for their strong colorimetric and emissive properties as well as singlet oxygen (¹O₂) generation under light irradiation, remain largely unexplored as NO photodonors. Herein, we report the synthesis of an amphiphilic anthraquinone-based NO photodonor (Ant-NO) by incorporating an N-nitroso moiety. Upon light irradiation, Ant-NO efficiently releases NO, accompanied by distinct fluorescence and color changes. Embedding Ant-NO into the phospholipid DOPC yielded biocompatible, water-dispersible liposomal nanoassemblies (Ant-NO.Ves). The NO release behavior of Ant-NO and Ant-NO.Ves was investigated by time-dependent UV-vis absorption, fluorescence spectroscopy and the Griess assay. The photoinduced NO release rate constants were 0.15445 min^-1 (t_1/2 = 4.5 min) in acetonitrile and 0.36187 min^-1 (t_1/2 = 1.9 min) for the liposomal formulation. Notably, Ant-NO.Ves generated both NO and singlet oxygen upon light exposure. In vitro anticancer studies on HCT cells revealed significant light-induced cytotoxicity due to the synergistic production of NO and ¹O₂. Furthermore, Ant-NO.Ves enabled real-time fluorescent bioimaging in HCT cells, showing red emission during NO release and allowing visualization of intracellular NO dynamics.