Light-triggered and cysteine-mediated nitric oxide release from a biodegradable starch-based film

A new nitric oxide-releasing material produced with cassava starch is described. The ruthenium nitrosyl complex trans-{[}Ru(NH3)(4)(isn)NO](BF4)(3) (RuNOisn; isn = isonicotinamide) is able to release NO upon either photolysis or chemical reduction. Impregnating this complex under mild conditions into cassava starch (CS) films produced a NO-delivery platform (CSx-RuNOisn). Spectroscopic analysis of CSx-RuNOisn indicates that the coordination sphere of RuNOisn remains intact during film production. Exposure of CSx-RuNOisn to long wave UV-light (lambda(irr) = 355 nm) leads to NO release and formation of the paramagnetic photoproduct trans-{[}RuIII(NH3)(4)isn(H2O)](3+) in the CS film. Reaction of this aquaruthenium(III) complex with aqueous nitrite regenerates RuNOisn in the film. Delivery of NO upon photolysis of CSx-RuNOisn was verified by trapping with oxymyoglobin. Moreover, NO release upon chemical reduction was carried out using L-cysteine as a reductant. Cysteine-mediated NO delivery from CSx-RuNOisn persisted for more than 7 h, during which physiologically relevant NO concentrations were liberated. These results suggest that CSx-RuNOisn is a promising candidate for use in biological applications. (AU)