Thermal analysis of chitosan based networks

In this work two kinds of material were studied: chitosan cross-linked with glutaraldehyde and in a blend with PEO. The resulting products as well as chitosan and PEO raw materials, were analyzed by TG/DTG, DSC and DMTA to determinate the in?uence of cross-linking and PEO addition on thermal properties of the resulting materials. It was observed by thermogravimetry that the water-polymer interaction will be different for the cross-linked material compared to the blend, according to the specific site availability. The in?uence of such modifications (cross-linking and PEO addition), on chitosan thermal stability was also studied. The DSC results showed a good agreement with the TG/DTG results, reinforcing the interpretation given for TG/DTG results. DMTA results indicate that glass transition temperature is around 50 degrees C for the polymer under study. (c) 2005 Elsevier Ltd. All rights reserved.

A layer-by-layer film of chitosan in a taste sensor application

Chitosan is alternated with sulfonated polystyrene (PSS) to build layer-by-layer (LBL) films that are used as sensing units in an electronic tongue. Using impedance spectroscopy as the principle method of detection, an array using chitosan/PSS LBL film and a bare gold electrode as the sensing units was capable of distinguishing the basic tastes - salty, sweet, bitter, and sour - to a concentration below the human threshold. The suitability of chitosan as a sensing material was confirmed by using this sensor to distinguish red wines according to their vintage, vineyard, and brands.

Alginate-chitosan systems: In vitro controlled release of triamcinolone and in vivo gastrointestinal transit

The aim of this study was to develop multiparticulate therapeutic systems of alginate (AL) and chitosan (CS) containing triamcinolone (TC) to colonic drug delivery. Multiparticulate systems of AL-CS, prepared by a complex coacervation/ionotropic gelation method, were characterized for morphological and size aspects, swelling degree, encapsulation content and efficiency, in vitro release profile in different environments simulating the gastrointestinal tract (GIT) and in vivo gastrointestinal transit. The systems showed suitable morphological characteristics with particle diameters of approximately 1.6 mm. In simulated gastric environment, at pH 1.2, the capsules presented low degree of swelling and in vitro release of drug. A higher swelling degree was observed in simulated enteric environment, pH 7.5, followed by erosion. Practically all the drug was released after 6 h of in vitro assay. The in vivo analysis of gastrointestinal transit, carried out in rats, showed that the systems passed practically intact through the stomach and did not show the same profile of swelling observed in the in vitro tests. It was possible to verify the presence of capsules in the colonic region of GIT. The results indicate that AL-CS multiparticulate systems can be used as an adjuvant for the preparation of therapeutic systems to colonic delivery of drugs. (C) 2010 Elsevier Ltd. All rights reserved.

In vitro drug permeation from chitosan pellets

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

In vitro characterization of coevaporates containing chitosan for colonic drug delivery

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Chitosan-pectin multiparticulate systems associated with enteric polymers for colonic drug delivery

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Histological evaluation of chitosan-based biomaterials used for the correction of critical size defects in rat's calvaria

Chitosan, a biopolymer obtained from chitin, and its derivates, such as chitosan hydrochloride, has been reported as wound healing accelerators and as possible bone substitutes for tissue engineering, and therefore these Substances could be relevant in dentistry and periodontology. The purpose of this investigation was to make a histological evaluation of chitosan and chitosan hydrochloride biomaterials (gels) used in the correction of critical size bone defects made in rat's calvaria. Bone defects of 8 mm in diameter were surgically created in the calviria of 50 Holtzman (Rattus norvegicus) rats and filled with blood clot (control), low molecular weight chitosan, high molecular weight chitosan, low molecular weight chitosan hydrochloride, and high molecular weight chitosan hydrochloride, numbering 10 animals, divided into two experimental periods (15 and 60 days), for each biomaterial. The histological evaluation was made based on the morphology of the new-formed tissues in defect's region, and the results indicated that there was no statistical difference between the groups when the new bone formation in the entire defect's area were compared (p > 0.05) and, except in the control groups, assorted degrees of inflammation Could be Seen. In Conclusion, chitosan and chitosan hydrochloride biomaterials used in this study were not able to promote new bone formation in critical size defects made in rat's calvaria. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 93A: 107-114, 2016

Evaluation of chitosan gel as antibiotic and photosensitizer delivery

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Different Molecular Weight Chitosan-Based Membranes for Tissue Regeneration

Natural polymers, such as chitosan, obtained from chitin, are been widely studied for use in the tissue regeneration field. This study established a protocol to attain membranes made from this biopolymer, consisting of high or low molecular weight chitosan. The biocompatibility of these membranes was histologically evaluated, comparing them to collagen membrane surgically implanted in rat subcutaneous tissue. Fifteen Holtzmann rats were divided in three experimental groups: High and Low Molecular Weight Chitosan membranes (HMWC and LMWC) and Collagen membranes (C-control group); each of them with three experimental periods: 7, 15 and 30 days. As a result, after the seven days evaluation, the membranes were present and associated with a variable degree of inflammation, and after the 15 and 30 days evaluations, the membranes were absent in all groups. It is concluded that the chitosan-based membranes were successfully attained and presented comparable resorption times to collagen membranes.

Evaluation of the beta-glucanolytic enzyme complex of Trichoderma harzianum Rifai for the production of gluco-oligosaccharide fragments by enzymatic hydrolysis of 1,3;1,6-beta-D-glucans

Botryosphaeran, a new exopolysaccharide from the endophytic fungus Botryosphaeria rhodina MAMB-05, and algal laminarin were hydrolyzed by partially-fractionated enzymes of the beta-glucanolytic complex from Trichoderma harzianum Rifai. beta-Glucanase fractions (F-I and F-II) separated by gel permeation chromatography presented different modes of attack on botryosphaeran and laminarin. Botryosphaeran was hydrolyzed to the extent of 66% (F-I) and 98% (F-II) within 30 min, and its main hydrolysis products were gluco-oligosaccharides of DP >= 4, with lesser amounts of glucose, di- and tri-saccharides. The action of enzyme fractions I and II on laminarin resulted in 15% conversion to glucose, while the percentage of saccharification was radically different (70% for F-I and 25% for F-II). The different product arrays within the polysaccharide hydrolysates can be explained by the difference in the enzymes' specificities within each enzyme fraction, and the molecular structures of the polysaccharides and their complexity.

Interaction of amphiphilic derivatives of chitosan with DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis of chitosan/hydroxyapatite membranes coated with hydroxycarbonate apatite for guided tissue regeneration purposes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Multifunctional antitumor magnetite/chitosan-l-glutamic acid (core/shell) nanocomposites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

New tetra-acetylated oligosaccharide diterpene from Cupania vernalis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Microspheres of alginate-chitosan containing isoniazid

Isoniazid was encapsulated into microspheres of alginate-chitosan by means of a complex coacervation method in an emulsion system. Since the encapsulation of isoniazid tends to be limited by its hydrophilic characteristics, this study proposes its microencapsulation by adsorption. The particles were prepared in three steps: (1) preparation of a W/O emulsion; (2) phase separation; and (3) adsorption of the drug. The isolated particles were placed in a solution of the drug under stirring to allow adsorption. The morphology and particle size were analysed by scanning electron microscopy (SEM). The isoniazid content was determined by extraction in 1 m phosphate buffer pH 7.5 under stirring for 4 h. Finally, the samples were filtered and analysed in an UV/VIS spectrophotometer at 260 nm. In vitro release tests were carried out in 0.05 m phosphate buffer pH 7.5. The results showed that microspheres of alginate-chitosan obtained were of spherical shape. The emulsion used for microparticle formation allows the preparation of particles with a narrow size distribution. The adsorption observed is probably of chemical nature, i.e. there is an ionic interaction between the drug and the surface of the particles.