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.

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.

Simultaneous identification of Trypanosoma cruzi surface and internal antigens reactive to different immunoglobulin classes (radio-immunoblotting)

A radioactive Western-blotting technique was developed by which the reactivity of Immunoglobulins (Igs) from different classes to both membrane radiolabelled and internal parasite antigens is simultaneously identified. The method includes radioiodination of parasites, polypeptide fractionation by SDS-PAGE, Western-blot transfer and autoradiography of the immunoblots developed with anti-Igs conjugates labelled with enzymes. The analysis is then performed by the comparison of common bands on the autoradiograms and the respective substrate stained nitrocellulose blots. This technique was used to analyse T. cruzi trypomastigote surface labelled antigens reactive to IgM, IgA and IgG specific antibodies. A different pattern of reactivity with acute Chagas' disease patients sera was thus obtained.

Trypanosoma cruzi: modification of alkaline phosphatase activity induced by trypomastigotes in cultured human placental villi

Human term placental villi cultured ''in vitro" were maintained with bloodstream forms of Trypanosoma cruzi during various periods of time. Two different concentrations of the parasite were employed. Controls contained no T. cruzi. The alkaline phosphatase activity was determined in placental villi by electron microscopy and its specific activity in the culture medium by biochemical methods. Results showed that the hemoflagellate produces a significant decrease in enzyme activity as shown by both ultracytochemical and specific activity studies and this activity was lower in cultures with high doses of parasites. The above results indicate that the reduction in enzyme activity coincides with the time of penetration and proliferation of T. cruzi in mammalian cells. These changes may represent an interaction between human trophoblast and T. cruzi.

Schistosoma mansoni: identification of a 46KDa antigen of the schistosomular surface by monoclonal antibody

An IgG2a subclass monoclonal antibody, C6G9, was obtained by immunization of BALB/c mice with Schistosoma mansoni egg antigens. With this monoclonal antibody, it was possible to identify a schistosomular antigen with a molecular weight of 46 kilodaltons (KDa), and its expression being evaluated by means of indirect immunofluorescence. The antigen persisted in the integument of the developing schistosomulum, for at least 96 hours post-transformation. The monoclonal antibody also reacted with the cercaria surface, but not with that of adult worm. The C6G9 was also able to mediate significant levels of cytotoxicity in the presence of complement for newly transformed schistosomula.

Human polyclonal anti-hepatitis B surface antigen immunoglobulin reduces the frequency of acute rejection after liver transplantation for chronic hepatitis B

BACKGROUND: Use of polyclonal anti-hepatitis B surface antigen immunoglobulin (HBIg) has been shown to reduce hepatitis B virus (HBV) recurrence after liver transplantation (LT) and to decrease the frequency of acute cellular rejection (ACR). However, the protective role of HBIg against ACR remains controversial, since HBV infection has been also associated with a lower incidence of ACR. AIM: To assess the relationship between HBIg immunoprophylaxis and the incidence of rejection after LT. METHODS: 260 patients (158 males, 43 ± 14 years old) submitted to LT were retrospectively evaluated and divided into three groups, according to the presence of HBsAg and the use of HBIg. Group I was comprised of HBsAg-positive patients (n = 12) that received HBIg for more than 6 months. Group II was comprised of HBsAg-positive patients that historically have not received HBIg or have been treated irregularly for less than 3 months (n = 10). Group III was composed of 238 HBsAg-negative subjects that have not received HBIg. RESULTS: HBIg-treated patients (group I) had significantly less ACR episodes, when compared to group II and III. No differences between groups II and III were observed. CONCLUSIONS: Long-term HBIg administration contributes independently to reduce the number of ACR episodes after LT.

Activity of Tri-N-Butyl Tin maleate in carpets against Staphylococcus aureus and Aspergillus niger, verified through two methodologies: Inhibition Halo (HZ) and Inhibition Surface (Print)

The aim of the present study was to verify the activity of the Tri-N-Butyl Tin maleate compound against Staphylococcus aureus and Aspergillus niger, after its industrial application in 40 samples of carpets of different materials (polypropylene, polyester, polyamide and wool). The qualitative assays were performed through two methodologies: Inhibition Halo (HZ) and Inhibition of Surface (Print). The carpet with the product inhibited 100% of bacterial (Staphylococcus aureus) and fungi (Aspergillus niger) growth, under the conditions of this study. The microbial inhibition was higher in upper portion of carpets. The methodologies employed appear to be adequate to test the bactericide and fungicide activities of the Tri-N-Butyl Tin maleate. The print methodology confirmed the results obtained by the inhibition zone assay. Further studies using the same methodologies are needed to confirm our results.

Cell surface hydrophobicity and adherence of a strain of group B streptococci during the post-antibiotic effect of penicillin

The minimum inhibitory concentration and post-antibiotic effects of an antimicrobial agent are parameters to be taken into consideration when determining its dosage schedules. The in vitro post-antibiotic effects on cell surface hydrophobicity and bacterial adherence were examined in one strain of group B streptococci. Exposure of the microorganism for 2 h at 37 °C to 1 x MIC of penicillin induced a PAE of 1.1 h. The cell surface charge of the Streptococcus was altered significantly during the post-antibiotic phase as shown by its ability to bind to xylene: hydrophobicity was decreased. Bacterial adherence to human buccal epithelial cells was also reduced. The results of the present investigation indicate that studies designed to determine therapeutic regimens should evaluate the clinical significance of aspects of bacterial physiology during the post-antibiotic period.

MOLECULAR CHARACTERIZATION AND SEQUENCE PHYLOGENETIC ANALYSIS OF SURFACE ANTIGEN 3 (SAG3) GENE OF LOCAL INDIAN ISOLATES (CHENNAI AND IZATNAGAR) OF Toxoplasma gondii

Context and objective:The molecular characterization of local isolates of Toxoplasma gondii is considered significant so as to assess the homologous variations between the different loci of various strains of parasites.Design and setting:The present communication deals with the molecular cloning and sequence analysis of the 1158 bp entire open reading frame (ORF) of surface antigen 3 (SAG3) of two Indian T. gondii isolates (Chennai and Izatnagar) being maintained as cryostock at the IVRI.Method:The surface antigen 3 (SAG3) of two local Indian isolates were cloned and sequenced before being compared with the available published sequences.Results:The sequence comparison analysis revealed 99.9% homology with the standard published RH strain sequence of T. gondii. The strains were also compared with other established published sequences and found to be most related to the P-Br strain and CEP strain (both 99.3%), and least with PRU strain (98.4%). However, the two Indian isolates had 100% homology between them.Conclusion:Finally, it was concluded that the Indian isolates were closer to the RH strain than to the P-Br strain (Brazilian strain), the CEP strain and the PRU strains (USA), with respect to nucleotide homology. The two Indian isolates used in the present study are known to vary between themselves, as far as homologies related to other genes are concerned, but they were found to be 100% homologous as far as SAG3 locus is concerned. This could be attributed to the fact that this SAG3 might be a conserved locus and thereby, further detailed studies are thereby warranted to exploit the use of this particular molecule in diagnostics and immunoprophylactics. The findings are important from the point of view of molecular phylogeny.