Rheological behaviors of Brij 97 based liquid crystals containing sodium deoxycholate and curcumin

Curcumin encapsulated hexagonal (H1-Cur) and cubic (I1-Cur) liquid crystals, which were characterized by small angel X-ray scattering (SAXS), were formed in the mixture of Brij 97 and sodium deoxycholate (NaDC). Rheological experiments showed that at constant surfactants concentration (56.2%), with increasing oil/water ratio, the elastic and viscous moduli of H1-Cur phases decreased in sequence M2Cur3 → M3Curs → M4Curs → M6Curs → M5Curs, M2Cur3 → M3Cur3 ≈ M4Cur3 → M5Cur → M6Cur3 at high frequency region. While the moduli of H1 phase without curcumin increased and then decreased. Moreover, for a H1-Cur phase (M3Curn), with increasing curcumin content, the elastic modulus decreased from 4.2 × 104 to 2.3 × 104 Pa and then increased to 5.5 × 104 Pa, while the values of as increased from 213.4 to 218.4 Å2 and then decreased to 210.4 Å2. For an I1-Cur phase (M7Curn), with increase in curcumin content, the elastic modulus changed from 1.5 × 105 to 1.2 × 105 Pa, while the values of as increased from 214.7 to 217.6 Å2. These results indicated different stability of the liquid crystals containing curcumin. For H1-Cur phase, the amount of oil, surfactant, curcumin to obtain stable crystal were 6.3%, 56.2%, 0.018 mg/g, while for I1-Cur phase, these were 4.5%, 40.5%, 0.013 mg/g, which may give guidance for release behavior of curcumin encapsulated liquid crystals.

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