Bacterial cellulose/poly(3-hydroxybutyrate) composite membranes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Kinetic parameters for thermal decomposition of microcrystalline, vegetal, and bacterial cellulose

Cellulose can be obtained from innumerable sources such as cotton, trees, sugar cane bagasse, wood, bacteria, and others. The bacterial cellulose (BC) produced by the Gram-negative acetic-acid bacterium Acetobacter xylinum has several unique properties. This BC is produced as highly hydrated membranes free of lignin and hemicelluloses and has a higher molecular weight and higher crystallinity. Here, the thermal behavior of BC, was compared with those of microcrystalline (MMC) and vegetal cellulose (VC). The kinetic parameters for the thermal decomposition step of the celluloses were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and at heating rates of 5, 10, and 20 A degrees C/min, the E(alpha) and B(alpha) terms could be determined and consequently the pre-exponential factor A(alpha) as well as the kinetic model g(alpha). The pyrolysis of celluloses followed kinetic model g(alpha) = [-ln(1 - alpha)](1.63) on average, characteristic for Avrami-Erofeev with only small differences in activation energy. The fractional value of n may be related to diffusion-controlled growth, or may arise from the distributions of sizes or shapes of the reactant particles.

Preparation and antibacterial activity of silver nanoparticles impregnated in bacterial cellulose

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

Synthesis and characterization of microcrystalline cellulose produced from bacterial cellulose

In this study, microcrystalline cellulose (MCC) was prepared from the acid hydrolysis of bacterial cellulose (BC) produced in culture medium of static Acetobacter xylinum. The MCC-BC produced an average particle size between 70 and 90 mu m and a degree of polymerization (DP) of 250. The characterization of samples was performed by thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy (SEM). The MCC shows a lower thermal stability than the pristine cellulose, which was expected due to the decrease in the DP during the hydrolysis process. In addition, from X-ray diffractograms, we observed a change in the crystalline structure. The images of SEM for the BC and MCC show clear differences with modifications of BC fiber structure and production of particles with characteristics similar to commercial MCC.

Self-supported silver nanoparticles containing bacterial cellulose membranes

Hydrated bacterial cellulose (BC) membranes obtained from cultures of Acetobacter xylinum were used in the preparation of silver nanoparticles containing cellulose membranes. In situ preparation of Ag nanoparticles was achieved from the hydrolytic decomposition of silver triethanolamine (TEA) complexes. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns both lead to the observation of spherical metallic silver particles with mean diameter of 8 nm well adsorbed onto the BC fibriles. (c) 2007 Elsevier B.V. All rights reserved.

Bacterial cellulose-laponite clay nanocomposites

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

Synthesis and characterization of silver nanoparticles impregnated into bacterial cellulose

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

Antimicrobial Bacterial Cellulose-Silver Nanoparticles Composite Membranes

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

Alchornea glandulosa Ethyl Acetate Fraction Exhibits Antiangiogenic Activity: Preliminary Findings from In Vitro Assays Using Human Umbilical Vein Endothelial Cells

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Anti-inflammatory activity of Alchornea triplinervia ethyl acetate fraction: Inhibition of H2O2, NO and TNF-alpha

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

Effect of cyproterone acetate on alpha1-adrenoceptor subtypes in rat vas deferens

Gonadal hormones regulate the expression of alpha1-adrenoceptor subtypes in several tissues. The present study was carried out to determine whether or not cyproterone acetate, an anti-androgenic agent, regulates the alpha1-adrenoceptor subtypes that mediate contractions of the rat vas deferens in response to noradrenaline. The actions of subtype selective alpha1-antagonists were investigated in vas deferens from control and cyproterone acetate-treated rats (10 mg/day, sc, for 7 days). Prazosin (pA2 ~9.5), phentolamine (pA2 ~8.3) and yohimbine (pA2 ~6.7) presented competitive antagonism consistent with activation of alpha1-adrenoceptors in vas deferens from both control and treated rats. The pA2 values estimated for WB 4101 (~9.5), benoxathian (~9.7), 5-methylurapidil (~8.5), indoramin (~8.7) and BMY 7378 (~6.8) indicate that alpha1A-adrenoceptors are involved in the contractions of the vas deferens from control and cyproterone acetate-treated rats. Treatment of the vas deferens from control rats with the alpha1B/alpha1D-adrenoceptor alkylating agent chloroethylclonidine had no effect on noradrenaline contractions, supporting the involvement of the alpha1A-subtype. However, this agent partially inhibited the contractions of vas deferens from cyproterone acetate-treated rats, suggesting involvement of multiple receptor subtypes. To further investigate this, the actions of WB 4101 and chloroethylclonidine were reevaluated in the vas deferens from rats treated with cyproterone acetate for 14 days. In these organs WB 4101 presented complex antagonism characterized by a Schild plot with a slope different from unity (0.65 ± 0.05). After treatment with chloroethylclonidine, the complex antagonism presented by WB 4101 was converted into classical competitive antagonism, consistent with participation of alpha1A-adrenoceptors as well as alpha1B-adrenoceptors. These results suggest that cyproterone acetate induces plasticity in the alpha1-adrenoceptor subtypes involved in the contractions of the vas deferens.

Experimental lamellar keratoplasty in rabbits using microfibrilar cellulose membrane: clinical, morphological and immunohistochemical findings

Avaliaram-se aspectos clínicos, histopatógicos e imunoistoquímicos da córnes de coelhos da raça Nova Zelândia adultos e machos em ceratoplastias lamelares com membrana de celulose microfibrilar. Trinta animais distribuídos em cinco grupos (n=6) foram estudados por até 60 dias de pós-operatório. A avaliação clínica revelou manifestações moderadas de edema, blefaroespasmo e fotofobia ao segundo dia, evoluindo para formas discretas ou ausentes a partir do sétimo dia, período em que se observou, clinicamente, reparo do defeito corneal. A histopatologia revelou uma fina camada de células escamosas, recobrindo a área lesada já aos sete dias, com discreto infiltrado de células polimorfonucleares. Observaram-se vasos no epitélio a partir do 15o dia, com regressão ao 48o dia. A marcação com o anticorpo Ki67 mostrou aumento de células em proliferação aos 15 dias no epitélio e aos 30 dias no estroma. Nesse período, ocorreram remodelamento e adesão epitealial. Considerando a boa integração do implante, admite-se a membrana de celulose como um bom material a ser utilizado em ceratoplastia lamellar.

Determination of solubility product of mercurous acetate at various ionic strengths in aqueous medium

The conditionals (K-ps) and thermodynamics (K-ps(o)) solubility products of mercurous acetate have been determined, in aqueous solution, at 25 degrees C and ionic strength (I) comprised between 0.300 and 3.000 mol/L (NaClO4). The investigation was carried out potentiometrically by using a second class electrodes which responds to acetate ions. The values obtained for [pK(ps) (I)] were: 9.49+/-0.08 (0.000); 9.51+/-0.08 (0.300); 9.53+/-0.08 (0.500); 9.54+/-0.08 (0.700); 9.55+/-0.09 (0.900), 9.57+/-0.09 (1.200); 9.59+/-0.10(1.500); 9.61+/-0.10 (1.800); 9.63+/-0.10 (2.100); 9.65+/-0.11 (2.400); 9.67+/-0.11 (2.700) e 9.69+/-0.12 (3.000).

REACTIONS OF MERCURIC ACETATE WITH PENTACARBONYLIRON IN ALCOHOLS - CRYSTAL AND MOLECULAR-STRUCTURES OF HG[FE(COOR)(CO)(4)](2) (R=CH3, C2H5)

Reactions of Hg(CH3COO)(2) with [Fe(CO)(5)] in MeOH and EtOH lead to the compounds Hg[Fe(COOR)(CO)(4)](2) (I for R = CH3 and II for R = C2H5). Crystals of I are triclinic, P (1) over bar, with a = 6.272(2), b = 6.441(3), c = 11.703(4) Angstrom, a = 92.94(3)degrees, beta = 103.77(3)degrees, gamma = 96.10(2)degrees, and Z = 1. Crystals of II are tetragonal, I4(1)/a, with a = 17.906(3) Angstrom, c = 12.756(2) Angstrom, and Z = 8. The geometry around Hg is linear for compound I and approximately linear for compound II. The Hg-Fe distances are 2.5716(8) and 2.575(4) Angstrom for compounds I and II, respectively. The geometry around the Fe in both compounds is approximately octahedral. The carboalkoxy group is cis to Hg in both compounds with Fe-C distances equal to 2.034(6) and 2.05(4) Angstrom for compounds I and II, respectively.