Gold nanoparticle based colorimetric sensing strategy for the determination of reducing sugars

The colorimetric sensors for reducing sugars based on a redox reaction between AuCl₄^- ions and fructose, glucose, lactose, or mannose are presented. Gold nanoparticles (AuNPs) that formed at room temperature as a product of this reaction were registered using a spectrophotometer. Lengthening reaction time had a positive effect on the sensitivity of the developed sensors. Different reducing sugars exhibited distinct reaction rates for AuNP formation, with the rate decreasing in the order fructose > glucose > lactose > mannose. LOD values after 60 min of the reaction for different sugars followed the same trend of 0.067, 0.081, 0.087, and 0.106 mM, while LOQ was 0.223, 0.270, 0.289, and 0.353 mM, respectively. The linear range 60 min since the start of the reaction varied from 0.3 up to 5.0 mM for different sugars. The colorimetric sensor was evaluated for use in real samples of beverages, milk, and saliva.