Synthesis and characterization of layered double hydroxides (LDH) intercalated with non-steroidal anti-inflammatory drugs (NSAID)

Layered double hydroxides (LDHs) with the hydrotalcite type structure and a Mg:Al ratio of two have been prepared, with salicylate or naproxen in the interlayer. Two synthetic routes have been used: reconstruction from a mildly calcined hydrotalcite-CO3 precursor, and a coprecipitation method with chlorides of the metals. The solids have been characterized using several physicochemical techniques, i.e., powder X-ray diffraction, FTIR and C-13 CP/MAS NMR spectroscopies and thermal analysis (therrnogravimetric and differential thermal analyses). The gallery height determined is in all cases larger than the size of the drug, 11.5 Angstrom for salicylate and 15.8 and 16.6 Angstrom for naproxen, depending on the specific synthesis route followed. Experimental data suggest the anion molecules form a tilted bilayer, with the carboxylate groups pointing towards the brucite-like layers. The solids are stable up to 230degreesC and their evolution from 350degreesC upwards is very similar to that observed for a carbonatc-containing hydrotalcite, forming mostly amorphous solids with a large specific surface area. (C) 2004 Elsevier Inc. All rights reserved.