Phase behaviors and curcumin encapsulation performance of Gemini surfactant microemulsion

Protection of environment-sensitive bioactive component is an important issue in biological and pharmaceutical applications. The aim of this study is to provide an alternative for the solubility enhancement and the controlled release of curcumin by encapsulation with the microemulsion formed with Gemini surfactant. Pseudo-ternary phase diagrams for the surfactant/cosurfactant/oil/water (S/C/O/W) systems are obtained and the phase behaviors are systematically investigated. Less amount of water can be solubilized in the microemulsion containing alcohol with a longer carbon chain or surfactant with a longer spacer. A lower mass ratio of S/C or a higher temperature also leads to a smaller microemulsion area. As a representative, the oil-in-water microemulsion of the 14-4-14/1-propanol/n-heptane/water system is applied to encapsulate curcumin. High drug loading capacity and encapsulation efficiency are achieved higher than 7 mg.g(-1) and 99%, respectively. Moreover, the in vitro release data are adequately described by the first-order reaction rate equation at both fast and mild release stages. A higher content of oil causes a slower release and a lower stable concentration for the packaged curcumin. The free radical scavenging activity is somewhat reduced when compared with that of free curcumin in ethanol due to gradual release. (C) 2020 Elsevier B.V. All rights reserved.