Fluorometric detection of cholesterol based on β-cyclodextrin functionalized carbon quantum dots via competitive host-guest recognition

A sensitive and selective fluorescent method for detection of cholesterol based on beta-cyclodextrin functionalized carbon quantum dots (beta-CD-CQD) nanoprobe through competitive host guest recognition has been developed. The bright fluorescence of beta-CD-CQD nanoprobe can be effectively quenched by the introduction of a very small amount of p-nitrophenol, and strong quenching ability of p-nitrophenol to the probe was identified. This efficient fluorescence quenching as a static quenching is due to the formation of nonfluorescent complex between beta-CD-CQD and p-nitrophenol induced by host-guest interaction between them. Cholesterol, as a more suited guest molecule of beta-cyclodextrin, can form an inclusion complex with beta-cyclodextrin with a much greater binding constant than p-nitrophenol. As a result, the presence of cholesterol causes a replacement of guest molecule of beta-CD moiety in the probe through a competitive way, and the inclusion of cholesterol in the probe as the removal of p-nitropheonl induces significant fluorescence enhancement. The fluorescence recovery can be achieved by continuous addition of cholesterol. In terms of this relationship between enhanced fluorescence and concentration of cholesterol, a quantitative measurement for cholesterol based on beta-CD-CQD nanoprobe has been established. Under the optimized detection conditions, this method shows good analytical performance in detection of cholesterol with lowest detection limit of 0.7 +/- 0.1 mu M and a relatively wide linear scope of 110 mu M. Specificity test and complex matrix test show that this method possesses excellent selectivity to cholesterol, and complex matrix such as serum does not exert apparent influence on the analytical performance, which enables its use in practical serum samples.