Spectrometric study on the binding of curcumin with AOT: effect of micelle-to-vesicle transition

In this work, the role of micelle-to-vesicle transition of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in the binding, stability and antioxidant activity of curcumin has been studied using absorption and fluorescence measurements. As AOT molecules aggregate into micelles and vesicles, curcumin bound with AOT often gives higher intensities of absorption and fluorescence than that of free curcumin. The most enhanced absorption and fluorescence of curcumin induced by AOT vesicles, are attributed to the location of curcumin in their lipid bilayer. The measurement of curcumin anisotropy suggests that the bilayer of AOT vesicles provides curcumin with a more hydrophobic microenvironment than the palisade layer of AOT micelles. The binding constant (Kb) of curcumin with AOT vesicles is three times that of curcumin with AOT micelles. Moreover, AOT vesicles are found to be superior to AOT micelles for enhancing the stability and radical scavenging ability of curcumin.