Preparação, caracterização e aplicação de derivados de quitosana

Abstract

Chitosan is a polycationic polymer containing more than 5000 glucosamine units and is obtained commercially by alkaline deacetylation of chitin (a N-acetyl-glucosamine polymer) from shellfish exo-skeletons. Chitosan is inexpensive, non-toxic and possesses potentially reactive amino functional groups. It has been shown of potential use in many different fields: as an antifungal compound in agriculture, as a flocculating agent in wastewater treatment, as a food additive in food industry, as a hydrating agent in cosmetics, and more recently, as a pharmaceutical agent in medicine. In this work is reported the preparation, characterization and applications of several chitosan derivatives. These derivatives were prepared, after the deacetylation degree of the starting chitosan was determined by 13C MAR. The derivates were obtained by chitosan condensation with carboxylic acids using carbodiimides as acylating and chitosan reaction with aldehydes, obtained from essential oils, produced the respective Schiff bases which were reduced with NaBH4 to give the alkyl derivatives. All these compounds were obtained in high yields and were characterized by spectroscopy specially NMR CP/MAS 13C and IR. These chitosan derivatives were tested to check their capacity in adsorbing metallic ions such as Cu(ll), NO), and Pb(II) being the residual solutions of those metals analyzed by atomic absorption spectrophotometry. Two derivatives, N-3,7-dimethy1-2,6-octadien-chitosan and N-3,7-dimethy1-6- octaen-chitosan were selected for the adsorption isothermal using non linear regression to adjust the absorption data. The proposed model used in this studies was the Langmuir model. N-3,7-dimethy1-6-octaen-chitosan was also tested as vehicle for controlled drug liberation. Paracetamol and L-Dopa were microencapsulated with chitosan, by spray dry technique, and then submitted to the study of liberation "in vitro" using simulation of the gastrointestinal tract. The liberated drug was analysed by IR spectroscopy and shown that Paracetamol was liberated in good yield at pH 1,2 in two hours period. However L-Dopa did not show good results in the liberation due to oxidation of this substance under the conditions of the experiment. Another derivative was obtained by the reaction of chitosan with azelaic acid (nonanedienoic acid) and it was tested as chelating agent for iron. The study occurred through the impregnation of the beads of QTS-AZ with the iron(11), and soon after the liberation of the iron was tested in certain acid middle your concentration for atomic absorption. The results obtained were excellent because only 16% of iron(ll) was liberated. These results shown a great potential for the new chitosan derivatives prepared in this work. They shown potential in several applications such capacity of adsorbing metallic ions, in drug liberation and in chelating metals such iron (II).