Effects of length and unsaturation of the alkyl chain on the hydrophobic binding of curcumin with Tween micelles.

This work studies the effects of length and unsaturation of alkyl chain on the hydrophobic binding of curcumin with Tween 20, 60 and 80 micelles. While Tween 20 and 60 possess 12 and 18 saturated carbons, respectively, in their alkyl chains, the alkyl chain of Tween 80, with one double bond, has the same length as Tween 60. Tween 60 micelles are superior to Tween 20 and 80 micelles for improving curcumin stability. The fluorescence measurement suggests that Tween 60 micelles provide curcumin with the most hydrophobic microenvironment, owing to the long and saturated alkyl chain of Tween 60. The pKa1 and binding constants of curcumin have the same order of Tween 60 > Tween 20 > Tween 80. These results show that the length increase, and unsaturation, of the alkyl chain of Tween surfactants have opposite effects on the hydrophobic binding of curcumin with Tween micelles.