Effect of Alkyl Chain Structure on the Encapsulation of Curcumin by Tween Surfactants

The order of the stability and binding constant of curcumin encapsulated by three Tween aggregates is: Tween-85 vesicles > Tween-60 vesicles > Tween-80 micelles. Upon UV and fluorescence measurements, it is found that curcumin is encapsulated in the hydrophobic region of the alkyl chains of Tween aggregates driven by hydrophobic interaction. The ¹H-NMR data confirm that the encapsulation position and force of curcumin are closely related to the alkyl chain structure of Tween surfactants. Compared with Tween-60 vesicles with a particle size of about 92 nm, the micelles formed by Tween-80 containing double bonds in the alkyl chain have loosely arranged hydrophobic region. Therefore, curcumin encapsulated by Tween-80 micelles exhibits lower stability, binding constant, UV absorption and fluorescence emission intensities. Tween-85 with three unsaturated alkyl chains can generate vesicles with a particle size of about 150 nm, and its bilayer has the highest hydrophobicity which shows the best encapsulation effect on curcumin.