An orthoformate-bridged bis-diazeniumdiolates: Enhanced nitric oxide loading and released NO under physiological conditions

Diazeniumdiolates are highly valued as NO donors in biomedical applications because of their exceptional NO-loading efficiency. Typically, the NO-releasing properties of these compounds can be tailored by incorporating various substitutes at the O²-position of N-diazeniumdiolates. In this study, we report a novel class of bis-diazeniumdiolates, which are covalently linked through an orthoformate-bridge between two diazeniumdiolate groups. Under physiological conditions (pH = 7.4, 37 ^°C), these orthoformate-bridged bis-diazeniumdiolates were found to release four equivalents of NO. The half-lives of NO release varied between 1.3 and 17.9 min. Furthermore, these bis-diazeniumdiolates exhibited superior bactericidal activity against Escherichia coli (MIC = 1–8 mM, MBC = 8–32 mM) and Staphylococcus aureus (MIC = 2–8 mM, MBC = 16–32 mM) compared to the commercial 2-(N, N-diethylamino)-diazenolate-2-oxide, which only releases two equivalents of NO per molecular (MIC _{(E. coli)} = 32 mM, MIC _(S.aureus) = 64 mM, MBC = 128 mM). These bis-diazeniumdiolates enhance NO loading and release NO independently of enzymes or chemical additives, indicating their potential benefits for further biomedical applications.