Biothiol modulated growth and aggregation of gold nanoparticles and their determination in biological fluids using digital photometry

Abstract

This work describes a novel and easy to use method for the determination of biologically important thiols that relies on their ability to inhibit the catalytic enlargement of AuNP seeds in the presence of ACl4− ions and trigger their aggregation. UV–vis spectroscopic monitoring of the plasmon resonance bands of the formed AuNPs showed that the spectral and color transitions depend both on the concentration and the structure of biothiols. The colorimetric changes induced by biothiols were quantified in the concentration range from 5 to 300 μM in the RGB color system with digital photometry using a commercially available flatbed scanner as detector. On the basis of these results, the applicability of the method was tested to the determination of glutathione in red blood cells and cysteine in blood plasma with satisfactory recoveries (88.7–96.5%), low detection limits (1.0 μM), good selectivity against major biomolecules under physiologically relevant conditions and satisfactory reproducibility (<8%). The method requires minimum technical expertise, is easy to use and is performed without scientific equipment, holding promise as a simple assay of biothiol testing even by non-experts.