S-Nitrosothiol Analysis via Photolysis and Amperometric Nitric Oxide Detection in a Microfluidic Device

Abstract

A 530 nm light emitting diode was coupled to a microfluidic sensor to facilitate photolysis of nitrosothiols (i.e., S-nitrosoglutathione, S-nitrosocysteine, and S-nitrosoalbumin) and amperometric detection of the resulting nitric oxide (NO). This configuration allowed for maximum sensitivity and versatility while limiting potential interference from nitrate decomposition caused by ultraviolet light. Compared to similar measurements of total S-nitrosothiol content in bulk solution, use of the microfluidic platform permitted significantly enhanced analytical performance in both phosphate buffered saline and plasma (6–20× improvement in sensitivity depending on nitrosothiol type). Additionally, the ability to reduce sample volumes from milliliters to microliters provides increased clinical utility. To demonstrate its potential for biological analysis, this device was used to measure basal nitrosothiol levels in the vasculature of a healthy porcine model.

Colorimetric analysis of the decomposition of S-nitrosothiols on paper-based microfluidic devices

“…4). These results are in accordance with those reported by Hunter et al 53 who observed the same trend when RSNO was decomposed inside a microchannel using Vis green light (λ = 530 nm) and amperometric detection to quantify NO. Riccio et al 35 reported low efficiency for the decomposition of RSNOs into NO in bulk solution using visible green light (λ = 500-550 nm).…”

“…5b), while no decomposition was obtained using light sources. Based on these results and those reported by Hunter et al 53 a correlation between the size of the RSNO and its sensitivity through the decomposition by light can be suggested. LMW-RSNOs are more prone to decompose than HMW-RSNO.…”

Electrochemical detection of nitric oxide and S-nitrosothiols in biological systems: Past, present & future

“…NO from nitrite and NONOate in less than 1 min. To the best of our knowledge, only one study analyzed total RSNOs in microfluidic devices with electrochemical detection ** [84]. No separation step was performed and the decomposition duration was quite long (100 s).…”

Integrated microfluidic device for the separation, decomposition and detection of low molecular weight S-nitrosothiols

“…This system allowed to perform analysis of total RSNOs in plasma samples without any separation step. Other approaches were proposed by Hunter et al for NO 23 and total RSNO detection 24 (after light decomposition) using a single PDMS microfluidic channel with amperometric detection. In all cases no separation of RSNOs occurred before detection in these miniaturized devices.…”

“…After 5 min, more than 90% of cysteine was converted into CysNO. The solution was neutralized by 0.1 M PBS buffer (pH 7.4) containing 0.5 mM EDTA to prevent decomposition by trace metal cation contaminants.Final concentrations of RSNOs were determined spectrophotometrically in aqueous solution at 335 nm (ε = 586 and 503 M −1 cm −1 for GSNO and CysNO, respectively)29 .InstrumentationElectrophoretic experiments were performed using a SU-8/Pyrex microchips with integrated micro band platinum electrodes at the outlet end of the separation channel from Micrux Technologies (Oviedo, Spain) (MCE-SU8-Pt001T) (Figure 1). Only working (WE) and reference (RE) electrodes were used, with widths of 50 μm and 250 μm, respectively.…”