Visual and spectrophotometric detection of metformin based on the host-guest molecular recognition of cucurbit[6]uril-modified silver nanoparticles

A simple, sensitive, and naked-eye assay of metformin (MET), based on the host–guest molecular recognition of cucurbit[6]uril (CB[6])-modified silver nanoparticles, has been developed for the first time. The molecular recognition between CB[6] and MET is initially demonstrated and the related recognition mechanism is further discussed. CB[6]-modified AgNPs were first synthesized and then characterized by UV–vis spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. The solution behavior of CB[6] in the presence of AgNO3 was also studied, and the correlative result revealed that AgNPs could combine with the carbonyl portals of CB[6]. On the basis of the molecular recognition of CB[6] and the surface plasmon resonance effect of AgNPs, CB[6]-modified AgNPs were used as visual probes to detect MET. In CB[6]-modified AgNP solution, the aggregation of CB[6]-modified AgNPs induced by MET triggered changes of color and the UV–vis absorption spectrum, which laid the foundation for the visual identification and spectrophotometric determination of MET. Under the optimized detection conditions, the UV–vis spectral assay had a good linear relationship in the range from 3 to 750 μM, and the limit of detection was 1 μM. According to the color changes, the minimum concentration recognized by the naked eye was about 75 μM. Furthermore, this assay has high selectivity for coexisting interferents and was also applied to MET detection in human urine samples. This strategy provides a novel and facile tool for highly selective and sensitive detection of MET.