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Taylor dispersion is a microfluidic analytical technique with a high dynamic range and therefore is suited well to measuring the hydrodynamic radius of small molecules, proteins, supramolecular complexes, macromolecules, nanoparticles and their self-assembly. Here we calculate an unaddressed yet fundamental property: the limit of resolution, which is defined as the smallest change in the hydrodynamic radius that Taylor dispersion can resolve accurately and precisely. Using concepts of probability theory and inferential statistics, we present a comprehensive theoretical approach, addressing uniform and polydisperise particle systems, which involve either model-based or numerical analyses. We find a straightforward scaling relationship in which the resolution limit is linearly proportional to the optical-extinction-weighted average hydrodynamic radius of the particle systems.

S-Nitrosothiols (RSNOs) are carriers of nitric oxide (NO) and have important biological activities. We propose here the use of gold nanoparticles (AuNPs) and NO-selective amperometric microsensor for the detection and quantification of S-nitrosoglutathione (GSNO) as a step toward the determination of plasma RSNOs. AuNPs were used to decompose RSNOs with the quantitative release of free NO which was selectively detected with a NO microsensor. The optimal [GSNO]/[AuNPs] ratio was determined, corresponding to an excess of AuNP surface relative to the molar GSNO amount. Moreover, the influence of free plasma thiols on this method was investigated and a protocol based on the blocking of free thiols with iodoacetic acid, forming the carboxymethyl derivative of the cysteine residues, is proposed.

A major problem associated with nitric oxide (NO) donors is the release of the desired amount of NO at a specific site. A number of platforms have been developed for the regulation of NO dosage. We present the use of citrate-stabilized gold nanoparticles as a platform to regulate NO release. Because of the affinity between gold and thiols, the characteristic -S-NO bond of S-nitrosothiols (RSNOs) breaks in the presence of gold nanoparticles, thereby releasing NO and modifying the gold nanoparticle surface with the corresponding thiol. This system allows for surface-controlled NO release, where the amount of NO released is proportional to the number of thiols bound to the gold nanoparticle surface. Moreover, by employing an amperometric technique to detect the maximum NO release, we were able to estimate the stoichiometry of the reaction, that is, the number of adsorbed RSNO molecules per gold nanoparticle. A kinetic model for NO release and its subsequent decomposition is proposed and used to fit the experimental results. The reaction was found to be zeroth- and first-order with respect to RSNO and gold nanoparticles, respectively.