Structural characterization of lyotropic liquid crystals containing a dendrimer for solubilization and release of gallic acid

The role of 2nd generation polypropyleneimine (PPIG2) dendrimer in controlling the release of gallic acid (GA) as a model drug from lyotropic liquid crystal was explored. GA (0.2wt%) was solubilized in three types of mesophases: lamellar (L_α), cubic (space group of Ia3d, Q^G), and reverse hexagonal (H_II), composed of GMO and water (and d-α-tocopherol, or tricaprylin in the case of H_II mesophases).Small angle X-ray scattering (SAXS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) along with UV spectrophotometry were utilized to elucidate the structure modifications and release resulting from the cosolubilization of GA and PPIG2.Solubilization of PPIG2 into L_α and Q^G phases caused transformation of both structures to H_II. The diffusion of GA out of the mesophases was found to be dependent on water content and PPIG2 concentration. Rapid release from L_α+PPIG2 and Q^G+PPIG2 mesophases was recorded. The release from both H_II mixtures (with d-α-tocopherol and tricaprylin) was shown to be dependent on the type of oil.Release studies conducted for 72. h showed that GA release can be modulated and sustained by the presence of PPIG2, supposedly due to the electrostatic interactions between the dendrimer and the drug molecule.