Magnesium-aluminum Layered Double Hydroxide Research Articles

Studies of the Intercalation and " In Vitro " Liberation of Amino Acids in Magnesium Aluminium Layered Double Hydroxides

Layered double hydroxides (LDHs) can be structurally described as the stacking of positively charged layers with hydrated anions intercalated in the interlamellar domain. LDHs are a class of materials represented by the general formula: [{\\rm M}_{1-{\\rm x}}^{2+} {\\rm M}_{\\rm x}^{3+} ({\\rm OH}){}_2] {\\rm A}_{{\\rm x/m}}^{{\\rm m}-} \\cdot {\\rm nH}_2 {\\rm O} where: M 2+ is a bivalent cation; M 3+ is a trivalent cation; A is an anion with m m charge. We have studied the intercalation and "in vitro" liberation of aspartic and glutamic amino acids in Mg-Al-LDHs. LDHs intercalated with this type of anions could combine both the compound and the LDH properties. The materials were prepared by the coprecipitation method under constant pH, followed by a hydrothermal treatment for 18 hours, and subsequent characterisation of intercalated materials using PXRD, ATG/DTA and FT-IR. Studies of "in vitro" liberation were made by determination of amino acid concentrations in solution through UV-VIS (nynhydrin methods). Moreover, simultaneous pH monitoring was conducted during the experiment.

Organic Anions of Pharmaceutical Interest Intercalated in Magnesium Aluminum LDHs by Two Different Methods

Layered double hydroxides (LDHs) are a class of materials with increasing interest due to their singular properties, which make possible their application in a wide variety of fields. Because LDHs can intercalate anions within their interlayer region, they can be used in medicine as drug supports or matrices. Once encapsulated, the drug could be released at a rate dependent on the pH value. The aim of the present work was to intercalate a variety of anions of pharmaceutical interest, such as salicylate, citrate, glutamate and aspartate, using two different synthesis methods, a direct one (coprecipitation) and an indirect one (anion exchange of dodecylsulfate). The materials obtained were characterised by PXRD, simultaneous TG-DTA, chemical analysis and FT-IR spectroscopy. Furthermore, the buffer effect of the intercalated LDHs was evaluated.

Molecular Inclusion Properties of Hydrophobic Organic Compounds by a Modified β-Cyclodextrin Intercalated within a Layered Double Hydroxide

A study was conducted to evaluate the inclusion properties of various nonionic hydrophobic organic compounds by a novel intercalate derived from magnesium-aluminum layered double hydroxide (Mg/Al LDH) and carboxymethyl-β-cyclodextrin with a degree of substitution of 3 [CMCD(3)]. The isotherm sorption results at 25 °C showed that the CMCD(3)-Mg/Al LDH intercalate could retain all the organic compounds (trichloroethylene, tetrachloroethylene, benzene, toluene, p-, o-, m-xylene, ethylbenzene, 1,2,3-trichlorobenzene, naphthalene) studied and its sorption affinity for organic compounds was positively related to their hydrophobicities. The host-guest interaction was attributed to a partition process of the organic compounds into cyclodextrin cavities as well as intermolecular pores. A stereoselective interaction might also be involved due to the intercalation of CMCD(3) within Mg/Al LDH interlayers.