Toxicant Isomers Characteized Using Fluorescence Emission of Coumarin Attached to Beta-Cyclodextrin

Abstract

Chapter 1 reports a highly sensitive and selective array-based sensing strategy for classifying isomeric and analogous analytes based on their differential interactions with three supramolecular cyclodextrin-fluorophore sensors. Each analyte-sensor interaction results in a distinct fluorescence modulation response, and these variable responses are then statistically classified via linear discriminant analyses (LDA) into clusters of maximum separation. Three classes of isomeric analytes (aromatic alcohols, aliphatic alcohols, and hexanes) and two classes of analogous analytes (analogues of dichlorodiphenyltrichloroethane (DDT) and congeners of polychlorinated biphenyls (PCBs)) have been successfully classified with 100% accuracy. High sensitivity of this sensor is demonstrated as well, with limits of detection approaching or surpassing known levels of concern, and preliminary efforts at successfully classifying binary analyte mixtures using this sensor system are also reported. Chapter 2 discusses the extensive literature reported on the properties of pyrene in β-cyclodextrin and γ-cyclodextrin. Despite this literature, little has been published on the interactions of pyrene with β-cyclodextrin derivatives (methyl-β- cyclodextrin and 2-hydroxypropyl-β-cyclodextrin) or mixtures of different cyclodextrins. These experiments focused on characterizing pyrene’s interactions, as well as those of perdeuterated pyrene-d10 and benzo[a]pyrene, within different cyclodextrin solutions using fluorescence spectroscopy. The vibronic bands within the fluorescence emission spectrum of pyrene reflected the polarity of the microenvironment around pyrene (characterized by Py values). Little change in the Py values was observed when pyrene was introduced to different concentrations of methyl-β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin. Benzo[a]pyrene had a large excimer peak when doped into γ- or β:γ solutions, which suggested that benzo[a]pyrene may be forming 2:1 complexes with the cyclodextrins. Deuterated pyrene (pyrene-d10) had a lower binding constant in β-cyclodextrin (compared to pyrene-h10), but a higher binding constant in γ-cyclodextrin (compared to pyreneh10). Further studies should be conducted to determine why deuterium incorporation would produce a higher binding constant in the γ-cyclodextrin solutions.