Kátia Monteiro Novack

Synthesis and characterization of hydrogels from cellulose acetate by esterification crosslinking with EDTA dianhydride

Hydrogels were prepared from cellulose acetate with a degree substitution (DS) 2.5 dissolved in dimethylformamide by esterification crosslinking with Ethylenediaminetetraacetic dianhydride (EDTAD) catalyzed by triethylamine. Subsequent conversion of the unreacted carboxyl groups to sodium carboxylates by the addition of aqueous NaHCO3 was performed to enhance the water affinity of the gels. The absorbency of the products was strongly dependent on the amount of EDTAD that was esterified to cellulose acetate, and the highest absorbency was observed for the hydrogel composed of approximately 0.36 molecules of EDTAD per repeat unit of cellulose acetate. The hydrogels were synthesized with different degrees of crosslinking and were analyzed by IR spectral (FTIR), near infrared (NIR), thermogravimetry analysis (TG and DTG), and crosslink density evaluation by Flory-Rehner theory. The hydrogels have synthesized with molar ratios EDTAD/OH groups: [1/1], [1/2], and [0.1/1]. The capacity for water absorbency was studied and compared with the water absorbency of the CA.

Modulated dissolution rate from the inclusion complex of antichagasic benznidazole and cyclodextrin using hydrophilic polymer.

Benznidazole (BNZ) is the primary chemotherapeutic agent for treating Chagas’ disease; however, its poor water solubility and irregular oral absorption lead to the treatment failure in the chronic phase. The aim of this work was to investigate the utility of the polymer hydroxypropyl methylcellulose (HPMC) in controlling the release of BNZ from solid inclusion complexes with cyclodextrin to overcome the problem of its bioavailability. Preliminary studies of solubility were conducted in solution using selected β-cyclodextrin derivatives according to an experimental mixture design. The best cyclodextrin composition was used to produce solid-state systems by kneading in the presence or absence of HPMC. The formulations were characterized by different physico-chemical techniques, including the dissolution rate. Hydroxypropyl-β-cyclodextrin (HPβCD) produced the greatest improvement in drug solubility and was selected for the development of solid systems. Assays confirmed the production of true inclusion complexes between BNZ and HPβCD. The dissolution rate of the BNZ-HPβCD system was markedly increased, while the presence of HPMC retarded drug release. An optimal formulation obtained by the combination of kneading systems developed in appropriate ratios could be a promising drug delivery system with a prolonged therapeutic effect coupled with more balanced bioavailability. The produced systems present interesting perspectives for Chagas’ therapy.

Biological evaluation of crude and degummed oil from Moringa oleifera seeds

The aim of this work was to evaluate the oil extrac ted from Moringa oleifera (fam. Moringaceae) seeds from the nutritional standpoint. Nutritional evaluation of crude or degummed moring a oil or soybean oil (as a control) involved the determination of the Food Efficiency ( FE) in male Fisher rats and the fatty acid composit ion of the moringa oil. Hepatic and renal functions were asses sed by measuring serum transaminases activity and u rea and creatinine concentrations, respectively. Serum chol esterol and triglycerides, alkaline phosphatase, to tal proteins and albumine were also measured. Results showed tha t FE was slightly increased by the crude moringa oi l while no differences were found between the soybean and degu mmed moringa oil regarding this parameter. Renal or hepatic injures as well as major alterations in serum prote ins were not induced by the tested oils. These resu lts suggested that degummed M. oleifera oil possessed adequate biological quality as compa red to the crude oil.

Biodegradation of Moringa oleifera’s polymer blends

ABSTRACT Vegetable oils are used as a base for the synthesis of polymers and monomers with structures similar to that of petroleum, as plasticizers for conventional polymers and biodegrading additives. The Moringa oleifera oil was extracted from seeds and polymerized after being submitted to 16 h of microwave irradiation without catalysers. This polymer was characterized and the efficiency of the oil polymerization was verified by the reduction of double bonds and the increase of molecular weight up to 50,000 g mol−1. Films produced by a mixture of low-density polyethylene (LDPE) with poly(butylene adipate-co-terephthalate)/poly(lactic acid) (PBAT/PLA) present low tensile resistance and low biodegradation behaviour. In order to improve those properties, the Moringa polymer (PMO) was mixed with LDPE and PBAT/PLA in specific mass concentrations. The films produced with this mixture were characterized and submitted to biodegradation analysis. The PMO behaves as a compatibilizer by improving thermal properties, reducing the crystalline phase and improving the biodegradation behaviour. The biodegradation improved up to five times in comparison to conventional polymers and it restores the mechanical properties.

Influence of Moringa oleifera derivates in blends of PBAT/PLA with LDPE

1Programa de Pós-graduação em Engenharia de Materiais, Rede Temática em Engenharia de Materiais – REDEMAT, Escola de Minas, Universidade Federal de Ouro Preto – UFOP, Ouro Preto, MG, Brasil 2Departamento de Química, Universidade Federal de Ouro Preto – UFOP, Campus Morro do Cruzeiro, Ouro Preto, MG, Brasil 3Departamento de Química, Biotecnologia e Engenharia de Bioprocessos, Universidade Federal de São João del-Rei – UFSJ, Campus Alto Paraopeba, Ouro Branco, MG, Brasil

Moringa oleifera oil influence on biodegradation behaviour of polymers

ABSTRACT Vegetable oils (VOs) can be used as plasticizers or as biodegrading additives for commercial polymers. According to the literature, the use of concentrations higher than 5% of oils added to polymers or their mixtures indicated loss of mechanical properties on the final product. However, VOs can be used as a compatibilizer for the mixture of synthetic polymers with biopolymers (PM) under concentrations higher than 5%. Moringa oleifera oil (MO) was used as a compatibilizer to PM mixtures using oil concentrations higher than 5%, 10% and 15% in mass. PMs were analysed at first based on mechanical properties which indicated a better concentration at 15% of MO. This article presents a study of MO influence on biodegradation behaviour of PM, which was composed of low-density polyethylene obtained from food bags and biopolymers (PB) obtained in market plastic bags. PM doped with different concentrations of MO was submitted to studies of mechanical, chemical, morphological and thermal properties and their biodegradation behaviour was evaluated. The concentration of 15% of MO increased the thermal resistance of PM, improved the biodegradation behaviour according to controlled and free tests and reduced its stiffness without a loss of important mechanical properties. The results of this work showed that MO influenced positively the biodegradation of the PM mixture by improving 30% of the degrading speed. GRAPHICAL ABSTRACT

Bifunctionalized chitosan: A versatile adsorbent for removal of Cu(II) and Cr(VI) from aqueous solution

This study describes the chemical modification of chitosan to produce a novel bifunctionalized adsorbent material (C4) for the removal of Cu2+ and oxyanions of Cr6+ from a single aqueous solution. The chemical modifications allowed C4 to be insoluble under acidic conditions, improving the chemical properties of the modified chitosan in aqueous solution. C4 adsorbent was synthesized by reaction of the amino group of chitosan with 2-pyridinecarboxaldehyde, a reduction of imine group, followed by esterification with EDTA dianhydride (EDTAD). C4 was characterized by solid-state 13C nuclear magnetic resonance, infrared spectroscopy, and elemental analysis. The adsorption studies of Cu2+ and oxyanions of Cr6+ in a batch mode were evaluated as a function of the contact time (kinetics), solution pH, and initial metal ion concentration. The maximum adsorption capacities (Qmax) of C4 for the adsorption of Cu2+ (pH 5.5) and Cr6+ (pH 2.0) were 2.60 and 3.50 mmol/g, respectively. The reusability of the recovered C4 adsorbent was also evaluated.

Efeito compatibilizante de copolímeros contendo segmentos líquido-cristalinos em misturas com poli(tereftalato de etileno) e um poliéster líquido-cristalino termotrópico (TLCP)

Uma serie de copolimeros com segmentos liquido-cristalinos foram sintetizados por policondensacao em solucao a alta temperatura e misturados com poli(tereftalato de etileno) (PET) e um poliester liquido-cristalino termotropico (TLCP), previamente sintetizado. Os copolimeros foram utilizados com sucesso como compatibilizantes nas misturas PET/TLCP. As tecnicas de caloria diferencial de varredura, analises dinâmico-mecânicas, analises termicas e microscopia eletronica (SEM) foram utilizadas na caracterizacao dos polimeros. Foi verificada boa processabilidade e diminuicao da velocidade de cristalizacao das misturas. As micrografias das superficies fraturadas das amostras, obtidas das analises de SEM, mostraram melhor miscibilidade para as misturas com maior teor de copolimero.

Estudo cinético da cristalização dinâmica de um poliéster líquido-cristalino termotrópico com espaçadores flexíveis na cadeia principal

The study of dynamic crystallization kinetics of a thermotropic polyester with flexible spacers in the main chain was done. The aim of this study was to verify the crystallization kinetics mechanism of a thermotropic semi-flexible polyester by a dynamic method. The selected method (Ozawa method) has allowed to describe the crystallization kinetics and the values of n (Avrami exponent) correspond to sheaf-like aggregation without further growing into spherulites.