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This work introduces results on a new drug delivery system (DDS) based on the use of chitosan/layered double hydroxide (LDH) biohybrid beads coated with pectin for controlled release in the treatment of colon diseases. Thus, the 5-aminosalicylic acid (5ASA), the most used non-steroid-anti-inflammatory drug (NSAID) in the treatment of ulcerative colitis and Crohn's disease, was chosen as model drug aiming to a controlled and selective delivery in the colon. The pure 5ASA drug and the hybrid material prepared by intercalation in a layered double hydroxide of Mg2Al using the co-precipitation method, were incorporated in a chitosan matrix in order to profit from its mucoadhesiveness. These compounds processed as beads were further treated with the polysaccharide pectin to create a protective coating that ensures the stability of both chitosan and layered double hydroxide at the acid pH of the gastric fluid. The resulting composite beads presenting the pectin coating are stable to water swelling and procure a controlled release of the drug along their passage through the simulated gastrointestinal tract in in vitro experiments, due to their resistance to pH changes. Based on these results, the pectin@chitosan/LDH-5ASA bionanocomposite beads could be proposed as promising candidates for the colon-targeted delivery of 5ASA, with the aim of acting only in the focus of the disease and minimizing side effects., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Biopolymers such as chitosan, pectin, alginate, ı-carrageenan and gelatin, can be assembled to layered solids by direct intercalation via ion exchange in the case of smectites or a 'co-organised assembly' method in the case of layered double hydroxides (LDHs). Layered perovskites can be delaminated and combined with the biopolymers following a delamination/restacking procedure. The starting cationic exchange ability of smectites such as montmorillonite is turned into an anionic exchange capacity due to the intercalated chitosan excess, while an opposite effect is observed in the case of the LDHs after incorporation of alginate, pectin or ı-carrageenan. This fact, combined with the good mechanical properties of these bionanocomposites, allows their use as the sensing phase of potentiometric sensors applied to the recognition of cationic or anionic species in aqueous solution. Besides, perovskite–gelatin bionanocomposites can be processed as robust translucent films with highly oriented two-dimensional particles exhibiting elevated dielectric permittivity values. [ABSTRACT FROM AUTHOR]

Abstract: Nanoporous Al2O3 membranes are employed in the development of amperometric biosensors for the immobilization of the biologically active elements. Anodized alumina membranes with the desired dimensions were prepared by controlled anodization of high purity aluminium in an acidic solution that slowly dissolves the formed aluminium oxide. The anodizing voltage controls the pore size and pore density, whereas the thickness is determined by the amount of transferred charge. This technique originates in the membrane an asymmetric structure of cylindrical pores of uniform diameter arranged in a hexagonal array perpendicular to the membrane surface. Such structure allows the uptake of relatively higher amounts of glucose oxidase (GOx) enzyme in a thin film. The preparation of the active phase of the biosensors is completed by procuring an external coating to the membrane surface with a natural polysaccharide, chitosan, which avoids the GOx leaching and provides a cage of high surface area inside the pores where the entrapped enzyme remains active. The aim of this study is to evaluate the influence of membrane dimensions on the biosensor response. [Copyright &y& Elsevier]