Photochemical Studies on Chromium(III) Cyclam Complexes: Photosensitization with Semiconductor Quantum Dots and Nitric Oxide Release.

摘要

The small molecule nitric oxide (NO) is involved in a variety of biological processes including blood pressure regulation, neural transmission, immune response, and cell apoptosis. In this context, the goal of the described research is to detail the development of systems for photochemical NO release that could be used in a new type of photodynamic therapy (PDT), where site-specific irradiation leads to photochemical NO release.;The metal complex trans-Cr(cyclam)(ONO)2 + (CrONO) is a NO precursor, where visible light irradiation of aqueous solutions at muM and lower concentrations, leads to sufficient NO release to activate the enzyme soluble guanylyl cyclase (sGC). In addition, photolysis of solutions 100 nM CrONO and greater leads to significant vasorelaxation of porcine coronary arteries. Irradiation of CrONO in aerated aqueous solutions the presence of the biological reductant glutathione (GSH) also leads to a greater net NO release.;The investigation of systems using semi-conductor quantum dots (QDs) as photosensitzers for CrONO is also described. We have demonstrated that water-soluble CdSe/ZnS core/shell QDs form electrostatic assemblies with the CrONO complexes and act as antenna for photosensitized release of nitric oxide (NO). Energy transfer is consistent with a Forster resonance energy transfer (FRET) mechanism, as the rate of energy transfer is a function of the overlap between the QD (donor) emission and the Cr(III) complex (acceptor) absorbance. These results provide a guideline for the design of other QD-based materials and devices that rely on photosensitized energy transfer.