Fluorescence-Based Detection of Cholesterol Using Inclusion Complex of Hydroxypropyl-β-Cyclodextrin and l-Tryptophan as the Fluorescence Probe

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The study is inspired by the fact that intravenous administration of 2-hydroxypropyl-beta-cyclodextrins (HP-β-CD) in rats leads to a rapid decrease in plasma cholesterol levels. Further, HP-β-CD being more water soluble than native β-CD, HP-β-CD forms soluble complex with cholesterol and higher affinity of cholesterol towards HP-β-CD than native β-CD leads to increase sensitivity. Hence, present work reports potential use of HP-β-CD as a chemosensor to detect cholesterol aided with l-tryptophan (l-Trp) as a fluorescence probe. The purpose of the study is to develop fast, cost-effective, and high throughput fluorescence-based chemosensor as convenient point-of-care diagnostic method for cholesterol detection. The host-guest interaction of l-Trp with HP-β-CD was elaborately studied using characterization techniques such as FT-IR, NMR, and DSC. Time and concentration dependent interactions were studied to determine the stoichiometry of molecular inclusion complexes of HP-β-CD with l-Trp. Further, the inclusion complex of HP-β-CD with l-tryptophan is explored to detect cholesterol based on the competitive displacement phenomenon and further explored for detecting different concentrations of cholesterol. Fluorescence spectroscopic data revealed that HP-β-CD served as a quencher for l-Trp. Also, promising results of the displacement assay proved that the fluorescence of l-Trp was quenched by HP-β-CD followed by increase in fluorescence signals in quantitative relation with cholesterol as it replaces l-Trp from the HP-β-CD host. The present investigation is a proof-of-concept that proves the potential of HP-β-CD with l-Trp as a novel fluorescence–based technique for cholesterol detection which is developed using competitive host–guest interaction.