Tendências em modificação de eletrodos amperométricos para aplicações eletroanalíticas

The most relevant advances on the analytical applications of chemically modified electrodes (CME) are presented. CME have received great attention due to the possibility of electrode surface modification including chemisorption, composite generation and polymer coating. In recent years, the interest in CME has increased overall to improve the sensitivity and selectivity of the electroanalytical probes, considering the electron mediator incorporation and the new conducting polymers development. The general procedures employed for the electrode modification and the operational characteristics of some electrochemical sensors are discussed.

Nanocompósitos de matriz polimérica: estratégias de síntese de materiais híbridos

Associating the well known advantages of hybrid materials to the wide potential of nanomaterials, the new and featuring class of polymer nanocomposites turned into one of the most intensively researched areas. This review highlights recent developments in the field of the synthesis of polymer based nanocomposites. Important issues related to the surface modification of fillers, in order to promote the compatibility between the inorganic/organic components, are also reported. The enhancement of the physical properties and the potential applications of polymer nanocomposites are considered in typical examples, given for each synthetic method described.

Biomateriais: deposição de hidroxiapatita sobre superfície de Ti-cp modificada por aspersão térmica

The osseointegrated titanium implants are reliable and safe alternatives to treatments for long periods of time. For surface modification, thermal aspersion of TiO2 was used. The samples with and without TiO2 were treated with NaOH and SBF in order to obtain a layer of HA. Characterization was done by SEM and FTIR. The images of HA obtained by SEM show a uniform morphology and a porous structure with spherical particles. The IR spectra show that the surface of Ticp/ TiO2 is more favorable for the HA deposit, as can be seen by the increase of the crystalline structure and the very intense and defined bands of the OH group of HA that is verified about 3571 and 630 cm-1. Thus the Ticp/ TiO2 surface presents a satisfactory nucleation of HA when compared to Ticp.

Sinterabilidade de pós de precursor vitrocerâmico do sistema LZSA tratados por troca iônica

Ion exchange method was employed by means of surface modification of the glass powders of LZSA (Li2O-ZrO2-SiO2-Al2O3) system submitted to a 70wt% NaNO3/30wt% NaSO4 bath salt followed by a heat treatment. Chemical analysis by X-ray fluorescence was used to evaluate the efficiency of ion exchange, while optical dilatometry was employed to evaluate sintering of compacts. Evaluation of the structure of sintered bodies was made by scanning electron microscopy. Substitution of Li+ ions by Na+ ions on the surface of powders during heat treatments of 450 and 600 ºC for 2-10 h promoted an increase in densification of the sintered bodies.

Os nanomateriais e a descoberta de novos mundos na bancada do químico

In recent years there has been great progress in the field of nanotechnology largely driven by research into nanomaterials. Chemistry appears in this context for its relevant role in the synthesis and surface modification of nanomaterials. This review article discusses fundamental concepts related to the synthesis and properties of inorganic nanoparticles with diverse properties. Aspects related to unique size dependent optical and magnetic properties are discussed and the chemistry involved in the preparation of nanomaterials reviewed. Fundamental aspects of the chemical modification of nanoparticles envisaging potential applications for these materials are also addressed.

USO DE SÍLICAS MODIFICADAS PARA IMOBILIZAÇÃO DE LIPASES

Enzyme-support strategies are increasingly replacing conventional chemical methods in both laboratories and industries with attributes including efficiency, higher performance and multifarious use, where silica surfaces show potential due to the chemical bonds based on the presence of hydroxyl groups which can be modified with different additives. Surface-modified silica is a novel class of materials capable of improving enzyme stability and reusability that can be applied to support several immobilization techniques. This review describes the use of innovative modified supports to improve the state of enzyme immobilization and provide the industrial sector with new perspectives.

Evaluation of polymethylmethacrylate as ocular implant in rabbits subjected to evisceration

Spheres of different types of material are used for the replacement of lost volume after removal of the eye bulb or its content to prevent contraction of the orbital cavity. The aim of this study was to evaluate the scope of polymethylmethacrylate (PMMA) used as intraocular implant in eviscerated rabbit eye. Twelve New Zealand rabbits underwent unilateral evisceration of the left eye, with subsequent implantation of PMMA sphere 12 mm in diameter. Clinical evaluation was performed daily during the first 15 days after surgery and every 15 days until the end of the study period (180 days). For the histopathological analysis, three animals per trial underwent enucleation at 15, 45, 90 and 180 days after evisceration. There was no wound dehiscence, signs of infection or implant extrusion in any animal throughout the study period. Histological examination revealed the formation of fibrovascular tissue around the implants. The PMMA behaved as inert and non-integrable.

Acute Hepatitis B in a patient previously positive for antibody to surface antigen (anti-HBs) determined by radioimmunoassay: case report and review of the literature

The determination of anti-HBs as a screening test before vaccination has been advisable in order to encounter immune individuals that don't need to receive vaccine protection. A case-report is presented and three other cases are reviewed from the literature. Anti-HBs was positive in these health-care personnels that developped typical acute B hepatitis. Different subtyping involving the d/y determinants were found in the first case, but false-positive anti-HBs even with high titres, determined by RIA, were found in the other cases. Concomitant determination of anti-HBc or absence of screening tests seem to be more reasonable policies until a low-cost and risk-free vaccine is produced.

Growth curves of Leishmania braziliensis braziliensis Promastigotes and surface antigen expression before and after adaptation to Schneider's drosophila medium as assessed by anti-Leishmania human sera

Leishmania braziliensis braziliensis(MHOM/BR/75/M2903) was grown in Schneider's Drosophila medium. In one set of experiments promastigotes were already adapted to the medium by means of serial passages whereas in the second cells were grown in a biphasic medium and transfered to the liquid. Growth was more abundant for culture medium adapted cells; degenerate cells in small numbers as well as dead ones were present from day 5 for promastigotes adapted to liquid medium and from day 3 for newly adapted cells. Synthesis of surface antigens differed according to length of cell culture as assessed by the titer of five mucocutaneous leishmaniasis sera on subsequent days. Five days of culture for cells already adapted to the culture medium and 3 days for newly adapted ones were judged to be the best for the preparation of immunofluorescence antigens.