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

Abstract

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 (Lα), cubic (space group of Ia3d, QG), and reverse hexagonal (HII), composed of GMO and water (and d-α-tocopherol, or tricaprylin in the case of HII 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 Lα and QG phases caused transformation of both structures to HII. The diffusion of GA out of the mesophases was found to be dependent on water content and PPIG2 concentration. Rapid release from Lα+PPIG2 and QG+PPIG2 mesophases was recorded. The release from both HII mixtures (with d-α-tocopherol and tricaprylin) was shown to be dependent on the type of oil.Release studies conducted for 72h 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.