Fiat Lux: selective delivery of high flux of nitric oxide (NO) to biological targets using photoactive metal nitrosyls

In addition to its beneficial roles in blood pressure regulation, immune response, neurotransmission, and redox balance, nitric oxide (NO) can induce cellular apoptosis at relatively high concentrations. Since photoactive metal nitrosyls can deliver NO under the control of light, they are uniquely suited as NO drugs in photodynamic therapy (PDT) to destroy cancer cells. Stable and photoactive metal nitrosyls can first be placed in close proximity of a malignant site and then triggered via pulses of light to deliver high flux of NO. During the past few years, a number of such metal-based ‘NO carriers’ have been synthesized and tuned for rapid release of NO upon exposure to UV or visible light. Using various chromophore conjugation strategies, attempts are now being made to photosensitize the M–NO bond to infrared light. Progress has also been made in incorporating metal nitrosyls into biocompatible matrices for site-specific delivery of NO to tumors. A combination of light and NO could offer a viable treatment modality for cancer.