Incorporation of a Designed Ruthenium Nitrosyl in PolyHEMA Hydrogel and Light-Activated Delivery of NO to Myoglobin

A ruthenium nitrosyl with 4-vinylpyridine (4-vpy) as one ligand, namely, [Ru(Me₂bpb)(NO)(4-vpy)](BF₄) (1), has been synthesized and structurally characterized. This diamagnetic {Ru−NO}⁶ nitrosyl is photoactive and readily releases NO upon exposure to low-intensity (5−10 mW) UV light (quantum yield at 300 nm = 0.18). Radical-induced copolymerization of 2-hydroxyethyl methacrylate (HEMA) and ethyleneglycol dimethacrylate (EGDMA) in the presence of 1 has afforded a 1-pHEMA, a transparent hydrogel in which 1 is covalently attached to the polymer backbone. Exposure of 1-pHEMA to UV light (5−10 mW) results in rapid release of NO (detected by NO electrode) that can be delivered to biological targets such as myoglobin. The photoactivity of 1-pHEMA is strictly dependent on exposure to UV light.