A selective,sensitive and label-free visual assay of fructose using anti-aggregation of gold nanoparticles as a colorimetric probe

A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles (AuNPs) is presented. 4-Mercaptophenylboronic acid (MPBA) induces the aggregation of AuNPs, leading to a color change from red to blue. Fructose as a potent competitor has strong affinity for MPBA and a borate ester is formed between MPBA and fructose. There is an obvious color change from blue to red with increasing the concentration of fructose. The anti-aggregation effect of fructose on AuNPs was seen by the naked eye and monitored by UV-vis spectra. Our results showed that the absorbance ratio (A₅₁₉/A₆₄₀) was linear with fructose concentration in the range of 0.032-0.96 mmol/L (R₂ = 0.996), with a low detection limit of 0.01 mmol/L (S/N = 3). Notably, a highly selective recognition of fructose was shown against other monosaccharide and disaccharide (glucose, mannose, galactose, lactose and saccharose). With anti-aggregation assays higher selectivity is achievable. The results of this work provide a rapid method for evaluating the quantitative analysis of fructose in human plasma at physiologically meaningful concentrations and at neutral pH. The proposed procedure can be used as an efficient method for the precise and accurate determination of fructose.