Poly(vinylidene fluoride-trifluoroethylene) porous films: tailoring microstructure and physical properties by solvent casting strategies

A systematic study for the production of porous poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), films using solvent evaporation and non-solvent induced phase separation techniques is presented. Processing parameters such as copolymer volume fraction, solvent, preset exposure time to air before immersion, and non-solvent and temperature of the coagulation bath were varied and the corresponding sample morphology, hydrophobicity, thermal and mechanical properties were determined. Film morphologies including homogeneous pore distributions, micropores, microvoids, spherulites and non-porous films were obtained. The morphology variations strongly influence sample hydrophobicity and mechanical properties. All samples crystallize in the electroactive β-phase with a degree of crystallinity around 30 %.

Produção de bioplásticos a partir de agro-resíduos

Dissertação de mestrado integrado em Engenharia de Materiais

A convenient method for the determination of moisture in aromatic plants

A method is proposed for the determination of the moisture content of aromatic plants. This method is based on the co-distillation of the starting material in a modified Clevenger apparatus with four organic solvents (toluene, cyclohexane, dichloromethane and carbon tetrachloride). The results were compared with those obtained by oven drying at 105 ºC and steam distillation of the essential oil. The efficiencies of the methods were shown to be equivalent. The solvent distillation method was more practical, especially with respect to operating time (2 h).

A low-cost ultrasonic spray dryer to produce spherical microparticles from polymeric matrices

The spray-drying technique has been widely used for drying heat-sensitive foods, pharmaceuticals, and other substances, because it leads to rapid solvent evaporation from droplets. This method involves the transformation of a feed from a fluid state into a dried particulate, by spraying the feed into a hot medium. Despite being most often considered a dehydration process, spray drying can also be used as an encapsulation method. Therefore, this work proposes the use of a simple and low-cost ultrasonic spray dryer system to produce spherical microparticles. This equipment was successfully applied to the preparation of dextrin microspheres on a laboratory scale and for academic purposes.

Encapsulation of naproxen in nanostructured system: structural characterization and in vitro release studies

Nanoparticles were produced by solvent emulsification evaporation method with the following characteristics: nanometric size (238 ± 3 nm), narrow polydispersity index (0.11), negative zeta potential (-15.1 mV), good yield of the process (73 ± 1.5%), excellent encapsulation efficiency (81.3 ± 4.2%) and spherical shape. X-rays diffraction demonstrated the loss of drug crystallinity after encapsulation; however, the profile of the diffractograms of the poly-ε-caprolactone (PCL) nanoparticles was kept. Differential scanning calorimetry thermograms, correspondingly, exhibited the loss of drug melting peak and the increasing of the melting point of the PCL nanoparticles, evidencing an interaction drug-polymer. Naproxen release was low and sustained obeying the Higuchi´s kinetic. The results show that nanoparticles are promising sustained release system to the naproxen.

Gemifloxacin mesylate: UV spectrophotometric method for quantitative determination using experimental design for robustness

This study describes the validation of UV spectrophotometric method for quantitative determination of gemifloxacin mesylate (GFM) in tablets using methanol as solvent. The method was specific, linear, precise, exact and robust at 272 and 343 nm. The results confirmed that the method in both wavelengths is valid and useful to the routine quality control of GFM in coated tablets. The validate method was compared to liquid chromatography (HPLC), microbiological assay and visible (VIS) spectrophotometry, which were previously developed and validated to the same drug. There was not significative difference between the methods for GFM quantitation.

PET-SWNT nanocomposites through ultrasound assisted dissolution-evaporation

Poly(ethylene terephthalate) (PET) based nanocomposites have been prepared with single walled carbon nanotubes (SWNTs) through an ultrasound assisted dissolution-evaporation method. Differential scanning calorimetry studies showed that SWNTs nucleate crystallization in PET at weight fractions as low as 0.3%, as the nanocomposite melt crystallized during cooling at temperature 24 °C higher than neat PET of identical molecular weight. Isothermal crystallization studies also revealed that SWNTs significantly accelerate the crystallization process. Mechanical properties of the PETSWNT nanocomposites improved as compared to neat PET indicating the effective reinforcement provided by nanotubes in the polymer matrix. Electrical conductivity measurements on the nanocomposite films showed that SWNTs at concentrations exceeding 1 wt% in the PET matrix result in electrical percolation. Comparison of crystallization, conductivity and transmission electron microscopy studies revealed that ultrasound assisted dissolution-evaporation method enables more effective dispersion of SWNTs in the PET matrix as compared to the melt compounding method

Mechanisms of burst release from pH-responsive polymeric microparticles.

Microencapsulation of drugs into preformed polymers is commonly achieved through solvent evaporation techniques or spray drying. We compared these encapsulation methods in terms of controlled drug release properties of the prepared microparticles and investigated the underlying mechanisms responsible for the “burst release” effect. Using two different pH-responsive polymers with a dissolution threshold of pH 6 (Eudragit L100 and AQOAT AS-MG), hydrocortisone, a model hydrophobic drug, was incorporated into microparticles below and above its solubility within the polymer matrix. Although, spray drying is an attractive approach due to rapid particle production and relatively low solvent waste, the oil-in-oil microencapsulation method is superior in terms of controlled drug release properties from the microparticles. Slow solvent evaporation during the oil-in-oil emulsification process allows adequate time for drug and polymer redistribution in the microparticles and reduces uncontrolled drug burst release. Electron microscopy showed that this slower manufacturing procedure generated non-porous particles whereas thermal analysis and X-ray diffractometry showed that drug loading above the solubility limit of the drug in the polymer generated excess crystalline drug on the surface of the particles. Raman spectral mapping illustrated that drug was homogeneously distributed as a solid solution in the particles when loaded below saturation in the polymer with consequently minimal burst release.

Synthesis and Characterization of Magnetic Composites Based on Cis-Polyisoprene and CoFe(2)O(4) Nanoparticles

CoFe(2)O(4) nanoparticles were obtained by the co-precipitation method. They were further modified by the adsorption of ricinoleic acid (RA). The non-modified and modified CoFe(2)O(4)/RA nanoparticles were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman, and Fourier transform infrared (FTIR) spectroscopy. The modified particles present a mean diameter < 20 nm. The adsorption of RA on the CoFe(2)O(4) surface is characterized by the IR absorptions of the RA while in the Raman spectrum the predominant signals are those from the CoFe(2)O(4). The cis-polyisoprene (PI) composite was prepared by dissolving PI in cyclohexane followed by the addition of a magnetic fluid based on CoFe(2)O(4)/RA nanoparticles dispersed in cyclohexane. After solvent evaporation a magnetic composite was obtained and characterized by AFM, Raman, and FTIR measurements. AFM images show uniformly CoFe(2)O(4)/RA particles distributed in the PI matrix. Raman spectra obtained for the composites reveal the characteristic Raman peaks of PI and CoFe(2)O(4) nanoparticles.

Biobased films prepared from NaOH/thiourea aqueous solution of chitosan and linter cellulose

In the present study, films based on linter cellulose and chitosan were prepared using an aqueous solution of sodium hydroxide (NaOH)/thiourea as the solvent system. The dissolution process of cellulose and chitosan in NaOH/thiourea aqueous solution was followed by the partial chain depolymerization of both biopolymers, which facilitates their solubilization. Biobased films with different chitosan/cellulose ratios were then elaborated by a casting method and subsequent solvent evaporation. They were characterized by X-ray analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal analysis, and tests related to tensile strength and biodegradation properties. The SEM images of the biofilms with 50/50 and 60/40 ratio of chitosan/cellulose showed surfaces more wrinkled than the others. The AFM images indicated that higher the content of chitosan in the biobased composite film, higher is the average roughness value. It was inferred through thermal analysis that the thermal stability was affected by the presence of chitosan in the films; the initial temperature of decomposition was shifted to lower levels in the presence of chitosan. Results from the tests for tensile strength indicated that the blending of cellulose and chitosan improved the mechanical properties of the films and that an increase in chitosan content led to production of films with higher tensile strength and percentage of elongation. The degradation study in a simulated soil showed that the higher the crystallinity, the lower is the biodegradation rate.

(-)-Hinokinin-loaded poly(d,l-lactide-co-glycolide) microparticles for Chagas disease

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of nanoparticles loaded with benzopsoralen in rat peritoneal exudate cells

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sistemas biodegradáveis contendo acetato de prednisolona para administração orbitária

Purpose: The present study aimed to evaluate an injectable extended-release formulation of prednisolone acetate (PA) for orbital administration. Methods: Microspheres (MEs) of poly-ε-caprolactone (PCL) containing PA were developed by the method of solvent evaporation. The MEs obtained were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), encapsulation efficiency and in vitro release profile. The in vivo release profile was evaluated in rabbits after periocular injection of an aqueous suspension of MEs. The local biocompatibility of the system was verified by histopathologic analysis of the deployment region. Results: After MEs preparation, morphological analysis by SEM showed the feasibility of the employed method. The content of PA encapsulated was 43 ± 7% and can be considered as satisfactory. The system characterization by DSC technique, in addition to confirm the system stability, did not indicate the existence of interaction between the drug and the polymer. The in vitro release study showed the prolonged-release features of the developed system. Preliminary in vivo study showed the absence of local toxicity and confirmed the prolonged release profile of PA from MEs, suggesting the viability of the developed system for the treatment of orbital inflammatory diseases. Conclusion: The results obtained in this work are relevant and accredit the system developed as a possible alternative to the treatment of inflammatory orbitopathy.

Development and evaluation of praziquantel solid dispersions in sodium starch glycolate

Purpose: To develop and characterize solid dispersions of praziquantel (PZQ) with sodium starch glycolate (SSG) for enhanced drug solubility. Methods: PZQ solid dispersion (SD) was prepared using co-precipitation method by solvent evaporation. The ratios of PZQ to SSG were 2:1, 1:1, 1:2, 1:3 (w/w). PZQ solubility was evaluated in purified water, and PZQ dissolution test was carried out in 0.1N HCl. Structural characterization of the dispersions was accomplished by x-ray diffraction (XRD) and infrared spectroscopy (FTIR) while the external morphology of the SDs, SSG and PZQ were studied by scanning electron microscopy (SEM). Mucoadhesion properties of the SD (1:3) and SSG, on mucin disks were examined using texture profile analysis. Results: The highest solubility was obtained with 1:3 solid dispersion, with PZQ solubility of 97.31 %, which is 3.65-fold greater than the solubility of pure PZQ and physical misture (PM, 1:3). XRD results indicate a reduction in PZQ crystallinity while infrared spectra showed that the functional groups of PZQ and SSG were preserved. SEM showed that the physical structure of PZQ was modified from crystalline to amorphous. The amount of PZQ in PM and SD (1:3) that dissolved in 60 min was 70 and 88 %, respectively, and these values increased to 76 and 96 %, respectively. The solid dispersion reduced the mucoadhesive property of the glycolate. Conclusion: Solid dispersion formulation using SSG is a good alternative approach for increasing the dissolution rate of PZQ. © Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria. All rights reserved.

Análise da interação funcional entre as proteínas elF5A e Yptl em S. cerevisiae

Pós-graduação em Biotecnologia - IQ