NITRIC OXIDE RELEASE BY VISIBLE LIGHT IRRADIATION OF AN AQUEOUS SOLUTION OF A NITROSYL RUTHENIUM COMPLEX IN THE PRESENCE OF QDs

TF17

Vermeulen, DM; de Santana, DCAS; da Silva, RS; Biazzotto, JC; Lopez, RFV; de Oliveira, FM

Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences of Ribeirão Preto – University of São Paulo

Introduction: Nitric oxide (NO) is a radical molecule which presents fundamental roles in biochemical processes, including cardiovascular control, neuronal signaling and as an agent for defense mechanisms against microorganisms and tumors. Therefore efforts have been employed in the development of metallic complexes, such as [Ru(terpy)(Bdq)NO](PF₆)₃, which are able to release NO after light irradiation. Quantum Dots (QDs) have recently garnered the spotlight as imaging agents and diagnostics. But, knowing that QDs are nanocristals which present energy-transfer properties, papers have reported their potential therapeutic effect mainly as cytotoxic agents mediated by UV irradiation. Therefore, as energy donors, QDs could even improve the nitrosyl ruthenium NO release after light stimuli. Objectives: The objective of this work was to assess the release of NO by visible light irradiation of an [Ru(terpy)(Bdq)NO](PF₆)₃ aqueous_.solution in the presence of QDs. Materials and Methods: 20 mL of [Ru(terpy)(Bdq)NO](PF₆)₃ aqueous solutions at 40ug/ml containing or not QD (CdS-cadmium sulfide) at the same concentration were irradiated in a glass flask using mercury lamp for 180 minutes. NO release was assessed by a NO sensor electrode (Nometer) immersed in the solutions. In addition, samples were withdrawn and submitted to HPLC analysis in order to determine [Ru(terpy)(Bdq)NO](PF₆)₃ content. Results: It was observed that the light irradiation did lead to NO release from the Nitrosyl Ruthenium complex alone or associated with QDs during the assessment by NOmeter. In the HPLC analysis, in both experiments it was observed a gradual decrease in the [Ru(terpy)(Bdq)NO](PF₆)₃ content, inferring the NO release, since the NO release from this ruthenium complex leads to the formation of another complex. In the absence of QDs, it was observed that after 60 and 180 min of light irradiation, the Nitrosyl Ruthenium complex released around 6,413 mmols and 43,857 mmol of NO, respectively. In contrast, when QDs were present, the Nitrosyl Ruthenium complex had already released around 28,217 mmol already in the first 60 min of irradiation and 53,332 mmol of NO after the 180 min. Therefore, the QDs presence, induced a burst of NO release from the Nitrosyl Ruthenium complex of around 5-fold after 60 min of light irradiation. However, after 180 min the increase in NO release was around 1.5-fold. Conclusion: The presence of QDs in an aqueous solution of [Ru(terpy)(Bdq)NO](PF₆)₃ did  improved the NO release after light irradiation, inferring that this system may be suitably employed in pharmacological therapies, such as in the Photodynamic Therapy (PDT).