Investigation of interactions between biological thiols and gold nanoparticles by capillary electrophoresis with laser‐induced fluorescence

Abstract

Biological thiols spontaneously form a stable Au–S dative bond with gold nanoparticles (AuNP) that might be used for their selective extraction and enrichment in biological samples. In this work, interactions of selected biological thiols (glutathione, cysteine, homocysteine [Hcys], cysteamine [CA], and N‐acetylcysteine) with AuNP stabilized by different capping agents (citrate, Tween 20, Brij 35, CTAB, SDS) were investigated by UV–Vis spectroscopy and capillary electrophoresis with laser‐induced fluorescence. Spectrophotometric measurements showed aggregation of Hcys and CA with AuNP. In contrast, it was confirmed by CE‐LIF that biological thiols were adsorbed to all types of AuNP. Citrate‐capped AuNP were selected for AuNP‐based extraction of biological thiols from exhaled breath condensate (EBC). Dithiothreitol was utilized for desorption of biological thiols from the AuNP surface, which was followed by derivatization with eosin‐5‐maleimide and CE‐LIF analysis. AuNP‐based extraction increased the sensitivity of CE‐LIF analysis; however, further optimization of methodology is necessary for accurate quantification of biological thiols in EBC.