Abstract:

To obtain a stable nano-carrier suitable for the encapsulation of active substances, an oil-in-water （O/W）microemulsion was prepared with PolyAquol LW as a non-ionic surfactant, butanediol as the cosurfactant, and jojoba oil as the oil phase. Pseudo-ternary phase diagram was plotted by the oil titration method, and the critical point of the as-obtained microemulsion was determined by the Tyndall effect. According to the pseudo-ternary phase diagram of the O/W microemulsion, the optimum preparation condition of the O/W microemulsion was determined. Then the oil-soluble cannabidiol （CBD） was selected as model active substance to prepare the cannabidiol microemulsion. The surface tension, particle size distribution and transmittance of the CBD microemulsion were measured. The effects of temperature and high-speed centrifugation on the stability of the CBD microemulsion were also investigated. The results showed that the maximum loading of jojoba oil was 9.09% when the mass ratio of PolyAquol LW/butanediol （ζ） was 2:1 and the mass fraction of PolyAquol LW was 1%; when such microemulsion was used as the carrier, the maximum loading of CBD could reach 1.62 mg/mL, and the minimum surface tension was 41.2 mN/m. The stability results showed that the CBD microemulsion could still remain stable without phase separation, and the light transmittance almost remained unchanged after centrifugation at 10 000 r/min for 20 min or being placed at -18 and 60 ℃ for 3 h, indicative of the excellent stability of CBD microemulsion. This work suggests that this microemulsion as a nano-carrier can realize the effective encapsulating of active substances in cosmetics, which has important value in the development and application of cosmetic products.

Key words: microemulsion, pseudo-ternary phase diagram, PolyAquol LW, jojoba oil, cannabidiol, nano-encapsulation