Visible photolysis and amperometric detection of S-nitrosothiols.

The concentration of S-nitrosothiols (RSNOs), endogenous transporters of the signaling molecule nitric oxide (NO), fluctuate greatly in physiology often as a function of disease state. RSNOs may be measured indirectly by cleaving the S-N bond and monitoring the liberated NO. While ultraviolet photolysis and reductive-based cleavage both decompose RSNOs to NO, poor selectivity and the need for additional reagents preclude their utility clinically. Herein, we report the coupling of visible photolysis (i.e., 500-550 nm) and amperometric NO detection to quantify RSNOs with greater selectivity and sensitivity. Enhanced sensitivity (up to 1.56 nA µM(-1)) and lowered theoretical detection limits (down to 30 nM) were achieved for low molecular weight RSNOs (i.e., S-nitrosoglutathione, S-nitrosocysteine) by tuning the irradiation exposure. Detection of nitrosated proteins (i.e., S-nitrosoalbumin) was also possible, albeit at a decreased sensitivity (0.11 nA µM(-1)). This detection scheme was used to measure RSNOs in plasma and illustrate the potential of this method for future physiological studies.

Efficacy of surface-generated nitric oxide against Candida albicans adhesion and biofilm formation.

This report details the efficacy of nitric oxide (NO)-releasing xerogel surfaces composed of N-(6-aminohexyl)aminopropyl trimethoxysilane (AHAP3) and isobutyltrimethoxysilane (BTMOS) against Candida albicans adhesion, viability, and biofilm formation. A parallel plate flow cell assay was used to examine the effect of NO on planktonic fungal cells. Nitric oxide fluxes as low as 14 pmol cm(-2) s(-1) were sufficient to reduce fungal adhesion by ∼49% over the controls after 90 min. By utilizing a fluorescence live/dead assay and replicate plating, NO flux was determined to reduce fungal viability in a dose-dependent manner. The formation of C. albicans biofilms on NO-releasing xerogel-coated silicon rubber (SiR) coupons was impeded when compared to control (non-NO-releasing) and bare SiR surfaces. The synergistic efficacy of NO and silver sulfadiazine against adhered fungal cells and biofilms is reported with increased killing and biofilm inhibition over NO alone.