Abstract: Naproxen (Nap), a non-steroidal anti-inflammatory drug (NSAIDs), was intercalated into the gallery of Mg-Al layered double hydroxides (LDHs) by ion exchange and co-precipitation with different location of magnesium ion and aluminum ion solutions, respectively. The product was characterized with powder X-ray diffraction (XRD), Fourier Transform Infrared spectral (FT-IR) and Thermogravimetry (TG). The results showed an expanded LDH structure, indicating that the drug was successfully intercalated into LDH with the monolayer perpendicular to (along the short axis orientation in proper angle) Nap anion. As compared to the pure form of Nap, the thermal stability of the intercalated Nap was significantly enhanced due to the host-guest interaction involving hydrogen bond and electrostatic attraction. We further investigated the drug release characteristics of the pillared LDH materials by a dissolution test in simulation gastrointestinal and intestinal fluids under different pH values. The results indicated that the release percentages decrease upon increasing pH from 4.60 to 7.43, likely due to the dependence of release mechanism on pH. We have carried out a kinetic simulation to the release data and found that the dissolution mechanism was mainly responsible for the release behavior of Nap-LDHs at pH 4.60, while the ion-exchange mechanism was responsible for that at pH 7.43. In addition, the initial release rates and equilibrium percent releases of the nanohybrids depended significantly on the synthesis methods, from which we have proposed a schematic model. The current study clearly showed that this drug-inorganic layered material has prospective applications in drug delivery system.

Key words: LDH, Naproxen, Intercalation, Drug delivery system