Temperature induced phase transformation and in vitro release kinetic study of dihydromyricetin-encapsulated lyotropic liquid crystal

Abstract

In this paper, several lyotropic liquid crystals (LLCs) formed by AEO20-Tween80 (1:1, wt:wt)/isoamyl acetate/H2O with different mass ratios of 45/5/50 (S1), 45/10/45 (S2), 45/15/40 (S3), 35/20/45 (S4), 35/15/50 (S5),35/10/55 (S6) were prepared to encapsulate dihydromyricetin (DMY). The effect of temperature on the rheological properties of LLCs loaded DMY were further studied. Interestingly, S1 with a high AEO20-Tween80/isoamyl acetate ratio of 45/5 showed the same viscoelastic liquid-like properties at temperature range from 25 °C to 45 °C, corresponded to the stable hexagonal phase (H1) structure confirmed by small angle X-ray scattering (SAXS). While in vitro release results of S1 showed that the drug cumulative release percentage and release rate gradually increased as temperature rose, indicating that the release behaviors were dominated by temperature. As a contrast, by decreasing AEO20-Tween80/isoamyl acetate ratio to 35/15 (S5), an obvious transition from elastic gel-like properties to viscoelastic liquid-like properties appeared with the increase of temperature, corresponded to the mixed cubic phase changing to the lamellar phase (Pn3m + Fd3m at 25 °C → H1 + Fd3m at 31 °C → H1 + Lα at 37 °C → Lα at 45 °C). In vitro release results of S5 showed that the drug cumulative release rate dramatically increased with temperature increased, implying that the release behaviors were simultaneously dominated by structure and temperature. This provides a possibility for exploring controlled release liquid crystal carriers of dihydromyricetin.