Ana Adelina Winkler Hechenleitner

Microcrystalline cellulose from soybean husk: effects of solvent treatments on its properties as acetylsalicylic acid carrier.

Microcrystalline cellulose (MCC) is a very important product in pharmaceutic, food, cosmetic and other industries. In this work, MCC was prepared from soybean husk, produced in large quantities in soybean oil processing industries. It was characterized through various techniques (scanning electron microscopy (SEM), infrared spectroscopy (FTIR), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC)) and compared with a commercial MCC. The results obtained show that the prepared sample has similar crystallinity and lower particle size than the commercial MCC. Both MCC samples were treated with organic solvents (chloroform, acetone, ethanol and ethyl ether), for structural modifications to be introduced, and used as acetylsalicylic acid (ASA) carrier. Pretreated MCC and MCC/ASA 1:1 mixtures were analyzed through FTIR and thermal analysis. The drug release was evaluated in buffer solution of pH 4.5 and in pure water, at 37 degrees C. The MCC pretreated with different solvents show different thermal properties and ASA release rates, each MCC showing a particular behavior.

Lignin-poly (vinyl alcohol) blends studied by thermal analysis

Abstract Alkaline lignin was isolated from sugar cane bagasse for polyblends preparation with three poly (vinyl alcohol) (PVAl) samples (80, 87 and 98% hydrolyzed). Blends preparation was carried out by thorough manual grinding the solid polymer powders, and for one system a comparison was made with blends prepared without grinding. The resulting blends were studied by thermal analysis (TGA and DSC). Miscibility evaluation by T g determination was possible only in some extent because it was not clearly detected in all cases. These results suggest at least some miscibility of the lignin/PVAl80 and lignin/PVAl87 systems and immiscibility of the lignin/PVAl98 blend. Differences were observed in the properties of the blends prepared with and without grinding. Apparent activation energy of pyrolysis reaction ( E a ) were evaluated from TGA curves for pure polymers and blends. E a of PVAl increases with increasing acetate group content. E a of the blends suggest a dependence of thermal stability on the hydrolysis degree of the PVAl. Other parameters obtained from TGA and DSC curves were also analysed.

Nanometric particle size and phase controlled synthesis and characterization of γ-Fe2O3 or (α + γ)-Fe2O3 by a modified sol-gel method

Fe2O3 nanoparticles with sizes ranging from 15 to 53 nm were synthesized by a modified sol-gel method. Maghemite particles as well as particles with admixture of maghemite and hematite were obtained and characterized by XRD, FTIR, UV-Vis photoacoustic and Mossbauer spectroscopy, TEM, and magnetic measurements. The size and hematite/maghemite ratio of the nanoparticles were controlled by changing the Fe:PVA (poly (vinyl alcohol)) monomeric unit ratio used in the medium reaction (1:6, 1:12, 1:18, and 1:24). The average size of the nanoparticles decreases, and the maghemite content increases with increasing PVA amount until 1:18 ratio. The maghemite and hematite nanoparticles showed cubic and hexagonal morphology, respectively. Direct band gap energy were 1.77 and 1.91 eV for A6 and A18 samples. Zero-field-cooling–field-cooling curves show that samples present superparamagnetic behavior. Maghemite-hematite phase transition and hematite Neel transition were observed near 700 K and 1015 K, respectively. Magnet...

Optimization of maghemite-loaded PLGA nanospheres for biomedical applications

Magnetic nanoparticles have been proposed as interesting tools for biomedical purposes. One of their promising utilization is the MRI in which magnetic substances like maghemite are used in a nanometric size and encapsulated within locally biodegradable nanoparticles. In this work, maghemite has been obtained by a modified sol-gel method and encapsulated in polymer-based nanospheres. The nanospheres have been prepared by single emulsion evaporation method. The different parameters influencing the size, polydispersity index and zeta potential surface of nanospheres were investigated. The size of nanospheres was found to increase as the concentration of PLGA increases, but lower sizes were obtained for 3 min of sonication time and surfactant concentration of 1%. Zeta potential response of magnetic nanospheres towards pH variation was similar to that of maghemite-free nanospheres confirming the encapsulation of maghemite within PLGA nanospheres. The maghemite entrapment efficiency and maghemite content for nanospheres are 12% and 0.59% w/w respectively.

Cellophane and filter paper as cellulosic support for silver nanoparticles and its thermal decomposition catalysis.

Silver nanoparticles (AgNPs) have attracted great attention due to its optical, electrical and thermal properties. Cellulosic supports for these nanoparticles are of particular interest because of its availability, flexibility and biocompatibility. In this work, AgNPs were synthesized using two cellulosic materials, cellophane (CP) and filter paper (FP), as matrix support. Cellulosic materials were immersed in an aqueous solution of silver nitrate containing polyvinylpyrrolidone (PVP) and then reduced with hydroxylamine. The obtained nanocomposites (CP-AgNPs and FP-AgNPs) were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (DRX) and scanning electron microscopy (SEM). AgNPs of near 15nm anchored onto cellulosic surfaces were detected. The thermal properties of these materials were investigated through thermogravimetry (TG). Their kinetic of thermal decomposition was studied by the Vyasovkin method of dynamic isoconvertion, which indicated a catalytic effect of AgNPs in the cellulose thermal decomposition reaction.

Study of Thermal Degradation of PLGA, PLGA Nanospheres and PLGA/Maghemite Superparamagnetic Nanospheres

Poly(glycolide-co-lactide) (PLGA) nanospheres containing magnetic materials have been extensively studied because of its biomedical applications. Therefore, it is very important to know thermal properties of these materials in addition to other physical properties. Thermal degradation activation energy (Eα) of PLGA nanospheres with maghemite entrapment (PLGA-Mag), PLGA nanospheres (hollow spheres) (PLGA-H) obtained by an emulsion method and unprocessed PLGA (PLGA-R) were calculated by isoconversional Vyazovkin method based on data of TG analysis in order to evaluate modifications in thermal behavior caused by nanospheres obtainment process or by maghemite entrapment. Both hydrodynamic diameter in the range of 200-250 nm and polydispersity index lower than 0.3 are considered satisfactory. Thermal degradation of PLGA-R begins at higher temperatures than those of PLGA-H and PLGA-Mag, but processed samples presented increase in thermal stability, which was greater before processing by emulsion and in the presence of the magnetic materials. PLGA-Mag presents superparamagnetic behavior at room temperature.

ANÁLISES FÍSICO-QUÍMICAS DE BIOFILMES DE SULFATO DE CONDROITOINA MODIFICADO

Numerous investigations are dedicated to the research and development of new polymer materials destined for innovation in pharmaceutical forms. The application of these technological resources has allowed the commercialization of new therapeutic systems for modified drug release. This investigation aimed to evaluate the association of modified chondroitin sulfate with an insoluble polymer, Eudragit® RS 30 D, widely available in the pharmaceutical market. Isolated films were prepared by the evaporation process using a Teflon® plate. The aqueous dispersions (4% m/v) of synthetic polymer received the addition of modified chondroitin sulfate at different ratios. The interactions of the polymer chains in the blends were physicochemically characterized by means of Fourier transform infrared spectroscopy, thermal analyses, differential scanning calorimetry, thermogravimetry and scanning electron microscopy combined with hydration and assays in alkaline pH. The results showed appropriate properties of the coating materials for solid oral forms intended for drug deliver in specific environments.

Superparamagnetic maghemite loaded poly (ε- caprolactone) nanocapsules : characterization and synthesis optimization

Iron oxide nanoparticles (ION) have been studied for essential applications, like detection of biological constituents (virus, bacterials, cell, nucleic acids, protein, enzyme, etc.), magnetic bioseparation and clinic therapy and diagnosis (such as MRI magnetic fluid and hyperthermia). In this work, γ-Fe2O3 has been synthetized by a adapted sol-gel method and entraped in poly e-caprolactone (PCL) nanocapsules. The superparamagnetic nanocapsules have been formulated by double emulsion evaporation method. Some variables affecting the polydispersity index, zeta potential surface and size of nanocapsules were studied aiming optimize the formulation process of maghemite-loaded PCL nanocapsules. The following parameters were selected: sonication time, PCL concentration in organic phase, PVA concentration in external aqueous phase and maghemite/PCL weight ratio. Under these experimental conditions, the resulting nanocapsules displayed a mean size of about 346 nm and a maghemite content of about 7.5 µg/mg of nanocapsules and superparamagnetic behaviour at room temperature.

The Effects and Role of Polyvinylpyrrolidone on the Size and Phase Composition of Iron Oxide Nanoparticles Prepared by a Modified Sol-Gel Method

Fe2O3 nanoparticles (as maghemite and hematite mixtures) were prepared using adapted sol-gel method from a polyvinylpyrrolidone (PVP) aqueous solution in various Fe3

Ferroic behavior induced by oxygen vacancies in Mn-doped ZnO compounds

Abstract Mn-doped ZnO nanoparticles were successfully synthesized through the sol–gel technique. X-ray diffraction results showed that Mn doping did not disturb the hexagonal wurtzite structure of ZnO and no secondary phases were identified. Raman studies indicated the presence of defects in the form of oxygen vacancy clusters created due to Mn doping. Ferromagnetic-like curves were determined at room temperature for the sample with low doping (2% Mn). The results indicate that the observed ferromagnetism at room temperature can essentially be attributed to interactions mediated by magnetic impurities throughout the large number of oxygen vacancies created by Mn ions.