Formation, drug-release kinetics and solution-stability of N-acetyl-N-carboxymethyl chitosan nanoparticles as potential drug carriers

Nano-aggregates of N-acetyl-N-carboxymethyl chitosan (NCac) were studied at 0.5 mg.mL-1 using pyrene fluorimetry analysis in 0.1 mol.L-1 phosphate buffer (pH 7.4). The size and morphology of the aggregates were determined by dynamic light scattering and atomic force microscopy. The stability of the particles for periods up to 20 h in buffer was determined. Camptothecin was entrapped in the particles using various methods and the rate constant for drug release (k) was determined. Lower k values indicate strong interactions between the drug and the hydrophobic core of the polymeric micelles

Echogenicity enhancement by end-fluorinated polylactide perfluorohexane nanocapsules: Towards ultrasound-activable nanosystems

International audienc

Time-dependent viscometry study of endoglucanase action on xyloglucan: A real-time approach

AbstractHydrolysis of xyloglucan from Tamarindus indica and Hymenaea courbaril seeds with endoglucanase (EGII), which randomly breaks the (1→4)-linked β-glycosidic bonds of the polymer chain, was monitored in real time using time-dependent viscometry analysis (TDV). For both samples there was a decrease in the intrinsic viscosity ([η]), viscosity average molar mass (Mv), radius de gyration (Rg) and persistence length (Lp) immediately after the addition of the enzyme. It was observed the formation of oligosaccharides and oligomers composed of ∼2 units, up to 140min. Galactose-containing side chains two positions away from the non-substituted glucose, modulated the action of EGII, and the complete hydrolysis of the XG oligomers occurred after 24h. The results demonstrate for the first time the real-time degradation of xyloglucan as well the macromolecular and oligosaccharide composition during the EGII hydrolysis process

Estrutura e interaçoes entre galactoxiloglucanas e amidos

AnexosOrientadora: Maria Rita SierakowskiTese(doutorado) - Universidade Federal do Paraná. Setor de Ciencias Biológicas. Curso de Pós-graduaçao em BioquímicaInclui biliografiaResumo: As galactoxiloglucanas (XG) são polissacarídeos com potenciais aplicações industriais e, neste estudo, foram analisadas em termos de composição química, estrutura e algumas propriedades físico-químicas. As XG extraídas de sementes de H. courbaril (Jatobá), colhidas em diferentes regiões do Brasil, a saber: da reserva de Foz do Chopin, Estado do Paraná (HC-I), Cuiabá (HC-II) e Sinop/Estado do Mato Grosso (HC-III), Natal/Estado do Rio Grande do Norte (HC-IV), Fortaleza/Estado do Ceará (HC-V) e de T. indica (TM) de Conceição de Almeida/Estado da Bahia. Através das análises por HPSEC-MALLS e de viscosidade intrínseca observamos que as amostras aquecidas a 85°C por 2h apresentam redução da agregação molecular. O valor de razão característica (Co") para a XG de Tamarindo menor que o das amostras de Jatobá, provavelmente, é devido à presença de uma série única de oligossacarídeos em XG de sementes de jatobá (XX XXG ), que gera, possivelmente, uma molécula mais rígida quando comparada com a de Tamarindo. A oxidação seletiva da HC-I com o radical TEMPO (2,2,6,6- tetrametilpiperidinil-1-oxil) gerou produtos com 3,0; 5,4 e 9,5% de grupos carboxila em C-6, como determinado colorimetricamente e por titulação com NaOH. As análises de Mw dos polieletrólitos mostraram uma redução do seu valor, e o aumento do ângulo de inclinação entre o Rg e a Mw, mostrou que o processo de oxidação gera uma molécula mais rígida, partindo de uma conformação mais ao acaso (polímero nativo) para uma molécula com conformação em bastão (polímero oxidado), o que pode ser explicado pela presença e repulsão de cargas sobre a superfície da molécula. Nas cinéticas termogravimétricas, utilizando a equação de Arrhenius, foi observado um aumento na Ea do processo de degradação dos polímeros oxidados, o qual é diretamente proporcional ao grau de oxidação e coerente com o mecanismo de degradação. O teor de amilose para diferentes amidos foram determinados colorimetricamente, como sendo 27% para o amido de milho comum, 80% para o amido de milho com altos teores de amilose, traços para o amido de milho com altos teores de amilopectina, 36% para o amido de cará, e 24% para o amido de mandioca. Nas análises por DSC utilizando diferentes taxas de aquecimento (2,5; 3,0; 4,0 e 5,0ºC/min), através da equação de Arrhenius, observou-se que o amido de cará tem uma maior E a de gelatinização, quando comparado aos outros amidos e, também, uma menor constante de velocidade (s-1), mostrando um processo de gelatinização relativamente lento a altas temperaturas e dependente do teor de amilose. As misturas galactoxiloglucanas-amidos, avaliadas por medidas reológicas em sistema dinâmico oscilatório, mostraram uma interação sinérgica positiva quando em presença de amidos ricos em amilose (amido de cará e de milho rico em amilose), e negativa quando em presença de amidos com altos teores de amilopectina (amido de milho rico em amilopectina e de mandioca). As melhores propriedades das misturas foram comprovadas por análises reológicas dinâmicas e por digestão com (alfa)-amilase.Abstract: Galactoxyloglucan (XG) is a polysaccharide with potential industrial applications, which in this study was extracted from the seeds of H. courbaril (Jatobá) harvested from trees growing at different locations in Brazil. They were from Foz do Chopin Forest Reserve, State of Paraná (HC-I), Cuiaba (HC-II) and Sinop/State of Mato Grosso (HC-III), Natal/State of Rio Grande do Norte (HC-IV), Fortaleza/State of Ceará (HC-V) and T. indica (TM) from Conceição de Almeida/State of Bahia - Brazil. We observed by HPSEC-MALLS and intrinsic viscosities results that when samples were heated at 85°C for 2 h there was a reduction of aggregation. The Tamarind XG showed a lower value of C (infinite) in relation of that from Jatobá, probably due the presence of an unique oligossacharide series in the H. courbaril samples (XX XXG ), that possibly generates a more rigid molecule when compared with that of T. indica. Selective TEMPO radical oxidation (2,2,6,6-tetramethylpiperidine-1 -oxyl) at C-6 of HCI galactoxyloglucan gave products with 3.0, 5.1 and 9.5% of carboxyl groups, as determined colorimetrically. Molecular mass analyses showed a decrease in the Mw of the oxidized galactoxyloglucans and an increase in angular fit from the RMS ratio versus molar mass plot. This indicated that the oxidation process generated a more rigid structure, going from a random coil in the native polymer to a rod conformation in the oxidized samples, probably due to the polyanionic structure. Thermogravimetric kinetics of degradation was obtained using the Arrhenius equation and an increase in the degradation rate, was apparently directly dependent on the oxidation level. The amylose level in the starch samples were, 27% for corn starch; 80% for corn starch rich in amylose; traces of amylose for corn starch rich in amylopectin, 36% for yam starch and 24% for cassava starches. A gelatinization study were carried out from starch samples by DSC using different heating rates (2.5, 3.0, 4.0 and 5.0ºC/min), to obtain, by the Arrhenius equation, the activation Energy (Ea) of this process. Yam starch show a more energetic process of gelatinization when compared to others starches and have also a lower rate constant (s-1), indicating a relative slow process of gelatinization at higher temperatures. The mixtures galactoxyloglucan-starches showed a positive synergic interaction dependent of the amylose content (cara and amilose corn starch). These interactions were observed by dynamic rheological analysis and by digestion with (alfa)-amylose

Rheological properties of low-density polyethylene filled with hydrophobic Co(Ni)-Al layered double hydroxides

Abstract Cobalt/aluminum and nickel/aluminum layered double hydroxide (LDH - M+2:Al molar ratio of 3:1) were intercalated with dodecylsulphate (DDS), laurate (LAU), stearate (STE) and palmitate (PAL) and used as filler in low-density polyethylene (LDPE) in percentages between 0.2 and 7.0wt%. After injection molding, the samples were submitted to morphological characterization by scanning electron microscopy (SEM), analysis of thermal behavior by differential scanning calorimetry (DSC) and investigation of rheological properties. All Co/Al-LDPE samples showed the formation of a high temperature polymer crystal domain, induced by the LDH filler. The rheological properties indicated in general a reduction of shear modulus due to incompatibility between some regions of LDH and LDPE, which promoted phase separation. However, interaction with the LDH surface indicated higher affinity of the Ni/Al-LDH for the LDPE compared to Co/Al-LDH, forming permanent networks

Toxicity acute study at limit-dose of N-Carboxymethylchitosan

O objetivo deste trabalho foi obter e analisar a N-Carboximetilquitosana (N-CMQ) a partir da Quitosana comercial (QTS) quanto ao potencial de toxicidade aguda (via oral). A N-CMQ obtida apresentou características adequadas quanto ao grau de substituição (26%), possuindo vantagens em relação ao polímero de origem, como a solubilidade em água, viabilizando inúmeras aplicações farmacêuticas. Neste estudo foram empregados ratos fêmeas, realizando-se um ensaio limite, a partir do qual foi concluído que a N-CMQ pode ser classificado como "sem classificar" quando administrado em uma dose de 2 g/kg, via oral, em ratos.The aim of this work was to analyze the possible oral acute toxicity of the N-carboxymethylchitosan (N-CMC) obtained from commercial chitosan. The N-CMC presented suitable characteristics (degree of substitution of 26%) and represent an alternative to pharmaceutical applications due to they aqueous solubility. In the present study were used females rats, in a limit dose assay and the product was classified into unclassified category when being administrated in one dose of 2 g/kg (p.o.) in rats.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Toxicity acute study at limit-dose of N-Carboxymethylchitosan

O objetivo deste trabalho foi obter e analisar a N-Carboximetilquitosana (N-CMQ) a partir da Quitosana comercial (QTS) quanto ao potencial de toxicidade aguda (via oral). A N-CMQ obtida apresentou características adequadas quanto ao grau de substituição (26%), possuindo vantagens em relação ao polímero de origem, como a solubilidade em água, viabilizando inúmeras aplicações farmacêuticas. Neste estudo foram empregados ratos fêmeas, realizando-se um ensaio limite, a partir do qual foi concluído que a N-CMQ pode ser classificado como "sem classificar" quando administrado em uma dose de 2 g/kg, via oral, em ratos.The aim of this work was to analyze the possible oral acute toxicity of the N-carboxymethylchitosan (N-CMC) obtained from commercial chitosan. The N-CMC presented suitable characteristics (degree of substitution of 26%) and represent an alternative to pharmaceutical applications due to they aqueous solubility. In the present study were used females rats, in a limit dose assay and the product was classified into unclassified category when being administrated in one dose of 2 g/kg (p.o.) in rats.Colegio de Farmacéuticos de la Provincia de Buenos Aire