Abstract: The mechanisms underlying fluorescence enhancement of aflatoxin B1 (AFB1) by β-cyclodextrin (β-CD) and its derivatives were explored using spectroscopy, Benesi-Hidebrand analysis and thermodynamics. Moreover the effects of methanol volume percentage, M-β-CD concentration, reaction time and interfering ions on fluorescence enhancement were analyzed. β-CD and its six derivatives showed an inclusion ratio to AFB1 of 1:1 at low concentrations and 2:1 at high concentrations. The thermodynamic parameters entropy change (ΔS), enthalpy change (ΔH) and free energy change (ΔG) for maximum inclusion constant between M-β-CD and AFB1 were negative, suggesting that the inclusion reaction is exothermic and can occur spontaneously. Enthalpy change was the dominant force during the formation of inclusion complexes. UV absorption spectra and KI quenching experiments showed that AFB1 could enter M-β-CD cavity to protect fluorescence. Therefore, β-cyclodextrin and its derivatives can allow considerable enhancement in the fluorescence emission intensity of AFB1 by the formation of supramolecular inclusion complexes, resulting in increased sensitivity of AFB1 fluorescence analysis.

Key words: β-cyclodextrin, aflatoxin B1, fluorescence enhancement, supramolecular inclusion