Sérgio P. Campana Filho

Caracterização de quitosanas comerciais de diferentes origens

Chitosan is a linear polysaccharide obtained from the deacetylation of chitin. The physico-chemical properties of chitosan dependent on the average degree of acetylation () and of the average molar mass (). Several applications of chitosan have been proposed in the literature, mainly in water treatment, cosmetic and drug manufacturing, food additives, semipermeable membranes and development of biomaterials. In this work, three commercial chitosan samples were characterized by proton nuclear magnetic resonance (1H NMR), infrared spectroscopy (IR), conductimetric titration and thermal analysis (TG and DSC) in order to compare commercial chitosans from different supplies. The average viscosimetric molecular weight Mv was estimated from the intrinsic viscosity. The results confirmed remarkable differences in relation to the mean degree of acetylation () (or desacetylation, ). The thermal analysis data permitted to follow the dehydration, decomposition, and glass transition temperature (Tg).

Quaternary Salts of Chitosan: History, Antimicrobial Features, and Prospects

Recently, increasing attention has been paid to water-soluble derivatives of chitosan at its applications. The chemical characteristics and the antimicrobial properties of these salts can play significant role in pharmacological and food areas mainly as carriers for drug delivery systems and as antimicrobial packaging materials. In the current paper, a historical sequence of the main preparative methods, physical chemistry aspects, and antimicrobial activity of chitosan quaternized derivatives are presented and briefly discussed. In general, the results indicated that the quaternary derivatives had better inhibitory effects than the unmodified chitosan.

Synergism Between Keratinocyte Growth Factor and Carboxymethyl Chitosan Reduces Pericardial Adhesions

BACKGROUND Mesothelial injury is the pivot in the development of adhesions. An increase in the proliferation of mesothelial cells was verified by in vitro studies with the use of keratinocyte growth factor (KGF). This study investigated the influence of KGF associated with thermo-sterilized carboxymethyl chitosan (NOCCts) in the reduction of pericardial adhesions. METHODS An induction model of pericardial adhesion was carried out in 24 pigs. Animals were randomly allocated to receive topical application of KGF, KGF + NOCCts, NOCCts, or saline (control). At 8 weeks, intrapericardial adhesions were evaluated and a severity score was established. The time spent to dissect the adhesions and the amount of sharp dissection used, were recorded. Histologic sections were stained with sirius red for a morphometric evaluation using a computer-assisted image analysis system. Cytokeratin AE1/AE3 immunostaining were employed to identify mesothelial cells. RESULTS The severity score expressed in median (minimum to maximum), in relation to the control group (17 [15 to 18]), was lower in the KGF + NOCCts group (7 [6 to 9], p < 0.01) followed by the KGF group (11.5 [9 to 12], 0.01 < p < 0.05) and the NOCCts group (12 [9 to 14], p > 0.05). The dissection time was significantly lower in the KGF + NOCCts group (7.1 + or - 0.6 vs 33.9 + or - 9.2 minutes, p < 0.001). A significantly less sharp dissection was also required in the KGF + NOCCts group. In the adhesion segment, a decreased collagen proportion was found in the KGF + NOCCts group (p < 0.05). Mesothelial cells were present more extensively in groups in which KGF was delivered (p = 0.01). CONCLUSIONS The use of KGF associated with NOCCts resulted in a synergic action that decreases postoperative pericardial adhesions in a highly significant way.

Formação de multicamadas de polissacarídeos e proteína

In this work the formation of multilayers composed by carboxymethylcellulose (CMC), chitosane and bovine serum albumin (BSA) was studied by ellipsometry. First, the adsorption behavior of carboxymethylcellulose onto amino-terminated surfaces was investigated as a function of molecular weight and average degree of substitution of CMC. The influence of these parameters on the adsorbed amount of CMC onto amino-terminated substrates was absent. However, the interaction of CMC covered surfaces with chitosane and BSA was favored when the average degree of substitution of CMC was increased. The adsorption of BSA onto the polysaccharide systems was studied as a function of pH. At the isoelectric point of BSA a maximum in the adsorbed amount was found.

Características e propriedades de quitosanas purificadas nas formas neutra, acetato e cloridrato

Commercial chitosan is purified in the neutral form and as chitosan acetate and chitosan hydrochloride. These samples were characterized and compared with respect to solubility, hydrophilicity, surfaces morphology and crystallinity. Commercial chitosan and its neutral purified form present similar characteristics and properties but the saline purified forms, mainly the chitosan hydrochlorides, are quite different from them. The surface morphologies of the former samples are similar but that of the lyophilized chitosan hydrochloride presents pores which are not observed in the other samples. Commercial chitosan and its neutral purified form are not soluble in pure water but chitosan acetate is partially soluble. These samples present similar hydrophylicities and crystallinities but in the cases of the chitosan hydrochlorides the presence of charges and of counter ions from a strong acid enhances the hydrophilicity, promotes solubility in water and significantly alters the interactions inter and intrachains, modifying the packing in the solid state and drastically reducing the crystallinity. In the case of chitosan acetate it is observed that the crystallites are smaller probably due to the partial protonation of amine groups and to the presence of acetate anions.

Purificação e caracterização de quitosana comercial

RESUMO: Procedimentos adequados para as purificacoes de quitosana comercial como cloridrato e na forma neutralizada sao descritos. As amostras obtidas apresentam elevado grau de pureza e baixo teor de cinzas conforme verificado atraves de termogravimetria. As determinacoes de graus de acetilacao por espectroscopia de ressonância magnetica nuclear (=23,6%) e por titulacoes (=23,0%) apresentam muito boa concordância. O cloridrato de quitosana e soluvel em agua, o que permite determinacoes de viscosidade intrinseca em solventes aquosos na ausencia de excesso de acido e facilita a comparacao de quitosana com outros polieletrolitos quanto a estimativas de rigidez/flexibilidade.

Carboximetilação de polpas de bagaço de cana-de-açúcar e caracterização dos materiais absorventes obtidos

Os processos soda/antraquinona e etanol/agua foram aplicados a producao de polpas de fibras e de medulas de bagaco de cana-de-acucar. Tais polpas foram carboximetiladas em suspensao de isopropanol/agua (8/1 m/m) por 4 horas a 800C, empregando a relacao molar 8,5/5,4/1 para acido monocloroacetico/hidroxido de sodio/celulose. Os graus medios de susbtituicao dos produtos carboximetilados foram determinados por espectroscopia 1H R.M.N. e variaram entre 0,44 e 1,27 em funcao da polpa empregada na derivatizacao. Os derivados mais substituidos foram os melhores absorventes, sugerindo que a capacidade de retencao de agua desses produtos esta diretamente associada a seus graus de substituicao.