NALAWADE et al: LAYERED DOUBLE HYDROXIDES: A REVIEW 267 Journal of Scientific & Industrial Research Vol. 68, April 2009, pp.267-272 *Author for correspondence Tel: 9769244623 E-mail: rshirlekar@bvcop.com Layered double hydroxides: A review P Nalawade, B Aware, V J Kadam and R S Hirlekar* Bharati Vidyapeeth’s College of Pharmacy, Sec-8, C B D Belapur, Navi Mumbai 400 614, India Received 19 February 2008; revised 31 December 2008; accepted 15 January 2009 Combination of two-dimensional layered materials and intercalation technique offers a new area for developing nanohybrids with desired functionality. Layered double hydroxides (LDHs) are mineral and synthetic materials with positively charged brucite type layers of mixed metal hydroxides. Exchangeable anions located in interlayer spaces compensate for positive charge of brucite type layer. Since most biomolecules are negatively charged, can be incorporated between LDHs. A number of cardiovascular, anti-inflammatory agents are either carboxylic acids or carboxylic derivatives and could be ion exchanged with LDHs to have controlled release. LDHs have technological importance in catalysis, separation technology, medical science and nanocomposite material engineering. Keywords: Anticancer drugs, Intercalation, Layered double hydroxides (LDHs), Nanobiohybrides, Nanotechnology Introduction Since living matter is composed of biological nanomachines and nanostructures, biology and medicine could be prime field for application of nanotechnology 1 . In particular, combination of two- dimensional layered material and intercalation technique offers new area for developing nanohybrids with desired functionality. Nanohybrids have composites function and most biomolecules (nucleoside monophosphates and ATP) that are negatively charged can be incorporated between hydroxide layers as charge compensating anions through ion exchange. Layered double hydroxides [LDHs] are also called anionic clays; mineral of this family is Hydrotalcite (Mg-Al-CO 3 ). LDHs have technological importance in catalysis, separation technology, optics, medical science and nanocomposite material engineering 2 . Layered Double Hydroxides (LDHs) Chemical composition of LDH (Fig. 1) is generally expressed as M (II) 1-x M (III) x (OH) 2 (A n- ) x/n × yH 2 O, where, M (II) =divalent cation, M (III) =trivalent cation, A =interlayer anion, n- =charge on inerlayer ion, and x and y are fraction constants. Inorganic or organic anions can be introduced between hydroxide layer by ion exchange or precipitation 3 . LDHs containing magnesium and aluminum have already been used as an antacid and antipepsin agent; therefore, LDH is quite biocompatible. Novel biohybrids of LDH and biomolecules [ATP or nucleoside monophosphate] are designed and organized artificially on nanometer scale to provide opportunities for reservoir and delivery carriers of functional biomolecules in gene therapy and drug delivery. LDHs can act as soluble inorganic vectors for different genes and DNA biomolecules. Negatively charged biomolecules intercalated in gallery spaces would gain extra stabilization energy due to electrostatic interaction between cationic brucite like layers and anionic biomolecules. Such biomolecules incorporated between hydroxide layers can be intentionally dissolved in an acidic media, which offers a way of recovering encapsulated or intercalated biomolecules 5 . Hosting of biologically active molecules inside LDHs can act as a ‘chemical flask- jacket’, protecting host from degradation. Additionally,