Preparation of Mg2Al layered double hydroxide nanosheets from triton X-100 hexagonal lyotropic liquid crystal and their application as drug carriers

Abstract

A hexagonal lyotropic liquid crystal (LLC) was constructed with nonionic surfactant Triton X-100 and mixed magnesium chloride/aluminum chloride aqueous solutions. Layered double hydroxide (LDH) nanosheets (L-LDHs) were prepared using the LLC as a microreactor. A nanohybrid material of L-LDHs intercalated with a model anionic drug, diclofenac sodium (DS; DS/L-LDHs) was synthesized using an ionexchange method. The drug-release profile of DS/L-LDH was investigated under moderate conditions, i.e., 37.0 °C and pH 7.2. The results were compared with those for common LDH flaky particles (S-LDHs) synthesized using a traditional solution coprecipitation method. The crystalline structures, specific surface areas, and morphologies of these LDHs and DS/LDHs nanohybrids were characterized using powder X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and N2 adsorption-desorption. The results show that the L-LDH particles are less thick, and have larger specific surface areas and higher DS-loading capacities than the S-LDH particles. Drug release by the DS/L-LDH nanohybrid was clearly lower than that by the DS/S-LDH nanohybrid. This indicates that the L-LDH nanosheets are more suitable for use as drug carriers than the S-LDHs. Drug release by the DS/L-LDH nanohybrid can be described using a pesudo-second-order kinetic model, and drug diffusion through the LDH particles is the rate-limiting step. LLC can be used as a template for morphologycontrolled synthesis of LDHs.