Construction, in vitro release and rheological behavior of apigenin-encapsulated hexagonal liquid crystal

- WCS increased the phase transition temperature of Api-H1 phase under the shear.
- The increase of WCS content can prolong the release time of apigenin effectively.
- The structure of Api-H1 phase was destroyed with increasing temperature.
- With increasing pH (5.6-7.4), Api-H1 phase with WCS showed better slow release.

For the purpose of encapsulating apigenin, hexagonal liquid crystal was constructed in Tween 80/water-souble chitosan (WCS)/ethyl oleate (EtOL)/H2O systems at different WCS content. After introducing WCS, the hexagonal liquid crystal underwent a transition from viscoelastic fluid to gel-like fluid as determined by rheological measurement. The WCS enhanced the stability of apigenin-encapsulated hexagonal liquid crystal as indicated by high elastic modulus and prolonged the release time of apigenin effectively. At relatively high WCS content, the elastic modulus of hexagonal phase decreased with an increase in temperature, showing different stability. While the release rate of apigenin increased and then decreased with increasing temperature. It was worth noting that after introducing WCS, the apigenin-encapsulated hexagonal phase showed pH-dependence, where the higher the pH, the slower the resulting apigenin release. These results suggested that the hexagonal liquid crystal is promising drug carrier to deliver apigenin.

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