Probing dispersion and re-agglomeration phenomena upon melt-mixing of polymer-functionalized graphite nanoplates.

A one-step melt-mixing method is proposed to study dispersion and re-agglomeration phenomena of the as-received and functionalized graphite nanoplates in polypropylene melts. Graphite nanoplates were chemically modified via 1,3-dipolar cycloaddition of an azomethine ylide and then grafted with polypropylene-graft-maleic anhydride. The effect of surface functionalization on the dispersion kinetics, nanoparticle re-agglomeration and interface bonding with the polymer is investigated. Nanocomposites with 2 or 10 wt% of as-received and functionalized graphite nanoplates were prepared in a small-scale prototype mixer coupled to a capillary rheometer. Samples were collected along the flow axis and characterized by optical microscopy, scanning electron microscopy and electrical conductivity measurements. The as-received graphite nanoplates tend to re-agglomerate upon stress relaxation of the polymer melt. The covalent attachment of a polymer to the nanoparticle surface enhances the stability of dispersion, delaying the re-agglomeration. Surface modification also improves interfacial interactions and the resulting composites presented improved electrical conductivity.

High performance free-standing films by layer-by-layer assembly of graphene flakes and ribbons with natural polymers.

In this work, novel free-standing (FS) films based on chitosan, alginate and graphene oxide (GO) were developed through layer-by-layer assembly. First, GO was synthesized from graphite and multi-walled carbon nanotubes using a modified Hummer's method, yielding oxidized graphene flakes (o-GFs) and oxidized graphene nanoribbons (o-GNRs), respectively, which were then characterized. Then FS films were produced and their morphological, thermal and mechanical properties, as well as the o-GF and o-GNR dispersion along the films were assessed. Their degradation and swelling profiles as well as their biological behavior were evaluated. Graphite and nanotubes were successfully oxidized and exfoliated forming stable suspensions that could be combined with chitosan (CHI) and alginate (ALG) solutions by layer-by-layer processing. The addition of o-GFs and o-GNRs resulted in rougher, hydrophilic FS films with significantly improved mechanical properties relative to CHI/ALG films. The presence of o-GFs or o-GNRs did not affect the thermal stability and the addition of o-GFs resulted in films with enhanced cytocompatibility. The results demonstrate the high potential of the GO reinforced films for biomedical applications, in particular o-GF films, for wound healing, and cardiac and bone engineering applications.

Diels-Alder functionalized carbon nanotubes for bone tissue engineering: in vitro/in vivo biocompatibility and biodegradability.

The risk-benefit balance for carbon nanotubes (CNTs) dictates their clinical fate. To take a step forward at this crossroad it is compulsory to modulate the CNT in vivo biocompatibility and biodegradability via e.g. chemical functionalization. CNT membranes were functionalised combining a Diels-Alder cycloaddition reaction to generate cyclohexene (-C6H10) followed by a mild oxidisation to yield carboxylic acid groups (-COOH). In vitro proliferation and osteogenic differentiation of human osteoblastic cells were maximized on functionalized CNT membranes (p,f-CNTs). The in vivo subcutaneously implanted materials showed a higher biological reactivity, thus inducing a slighter intense inflammatory response compared to non-functionalized CNT membranes (p-CNTs), but still showing a reduced cytotoxicity profile. Moreover, the in vivo biodegradation of CNTs was superior for p,f-CNT membranes, likely mediated by the oxidation-induced myeloperoxidase (MPO) in neutrophil and macrophage inflammatory milieus. This proves the biodegradability faculty of functionalized CNTs, which potentially avoids long-term tissue accumulation and triggering of acute toxicity. On the whole, the proposed Diels-Alder functionalization accounts for the improved CNT biological response in terms of the biocompatibility and biodegradability profiles. Therefore, CNTs can be considered for use in bone tissue engineering without notable toxicological threats.

Frequency of Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, Mycoplasma hominis and Ureaplasma species in cervical samples.

We investigated the relative frequencies of Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, Mycoplasma hominis and Ureaplasma sp. in cervical samples. PCR analyses were performed in ectocervical and endocervical samples from 224 patients attending public health services in Belo Horizonte and Contagem, Minas Gerais Brazil. A high prevalence of colonisation of the cervix (6.3% for C. trachomatis, 4.0% for N. gonorrhoeae, 0.9% for M. genitalium, 21.9% for M. hominis, 38.4% for Ureaplasma sp.) was demonstrated not only for pathogens classically associated to cervicitis (C. trachomatis and N. gonorrhoeae), but also for M. hominis and Ureaplasma sp. These findings may be useful to guide more adequate diagnosis to interrupt transmission and to avoid negative impacts on the female reproductive tract.

The 1,3-dipolar cycloaddition reaction in the functionalization of carbon nanofibers.

Carbon nanofibers were functionalized using a reaction scheme described in the literature for 1,3-dipolar cycloaddition of azomethine ylides generated in situ by the condensation of an alpha-amino acid and an aldehyde. The reagents used were Z-Gly-OH and paraformaldehyde. Their reaction with carbon nanofibers was studied as a solid mixture by controlled heating in the DSC. An oxazolidinone intermediate was formed as the major product. Z-Gly-OH and paraformaldehyde were also reacted with a model compound (anthracene) in DMF solution leading to the formation of a considerable amount of anthraquinone. These studies suggested that, under the conditions investigated, the 1,3-dipolar cycloaddition reaction was not favoured, and the main result of functionalization was the formation of quinone-type groups as a consequence of an oxidation process.

Functionalization of carbon nanofibers by a Diels-Alder addition reaction.

This paper reports functionalization of CNF via a Diels-Alder addition reaction and the characterization of the obtained materials. The functionalization was assessed by a calorimetric technique (DSC) and the morphology of CNF modified materials was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The functionalization was observed to be dependent on the preparative conditions. Detailed analysis of the CNF modified material surface using TEM, shows a deposited layer homogeneously distributed over the CNF structures with an average thickness of about 15 nm. Finally the chemical activity of the raw CNF and functionalized CNF was analyzed to determine the pH of the point of zero charge (pHpzc) values. The results obtained showed that the functionalized CNF materials presented enhanced acid activity comparatively with the modified carbonaceous materials reported in literature.

Kinetics of an experimental inflammatory reaction induced by Leishmania major during the implantation of paraffin tablets in mice.

In leishmaniasis, macrophages play important but potentially divergent roles. They act as the host cell in which the parasite may reside and replicate, and, at the same time, they act as an effector cell with the potential to eliminate the parasite. In this work, we experimentally induced an inflammatory model that provokes a continued recruitment of the monocytes to the site of inflammation. This model was carried out by means of implanting paraffin tablets under the skin of Balb/c or C57BL/6 mice. Mice were then infected with Leishmania major to determine how the monocyte inflammatory response to paraffin could influence the course of infection with L. major. Mice were sacrificed 15, 21, 30, and 45 days after infection, and skin and inflammatory capsule were collected for histopathology. At 15 days and 21 days, the lesions induced by L. major in combination with paraffin contained markedly increased numbers of parasites relative to lesions in parallel control animals infected with L. major (without paraffin). Both Balb/c and C57BL/6 mice exhibited high parasite numbers in their lesions. The intense parasite burden observed following paraffin implantation would suggest that the monocytes-macrophages that are recruited to the lesion are acting more as a host cell permitting parasite growth than as an effector cell capable of eliminating L. major. At later times, the two strains of mice stratified according to their genetic susceptibility/resistance profiles. Susceptible Balb/c mice continue to have large parasite burdens, whereas the resistant C56BL/6 mice begin to control parasite numbers. This later observation indicates that the genetic difference between susceptible and resistant strains is not due to differences in monocyte recruitment and cannot be reversed through the altering of monocyte inflammation.

Estudo das alteraçöes pulmonares em doentes com artrite reumatóide: correlaçäo clínico-radiológica funcional / Pulmonary changes in patients with rheumathoid arthritis: functional clinico-radiological correlation

Durante uma investigación de 21 pacientes consecutivos portadores de artrite reumatóide clássica (AR), foram encontradas anormalidades na funçäo pulmonar atribuíveis à AR em 52,4%, tendo a reduçäo da capacidade de difusäo e da queda da PaO2 após exercício sido as anormalidades mais comuns. Outras alteraçöes encontradas foram o shunt patológico, distúrbio espirográfico restritivo e hipoxemia em repouso. Os sintomas atribuíveis à AR foram infreqüentes, assim como as alteraçöes radiológicas. Em um caso, ocorreu alteraçäo radiológica com funçäo pulmonar normal. Desses 21 pacientes, seis estavam em tratamento com sais de ouro, droga esta que vem sendo descrita na literatura como capaz de desencadear doença intersticial pulmonar. No grupo estudado, näo houve correlaçäo entre a presença de deformidades e/ou erosäo óssea ou de títulos sorológicos elevados como alteraçöes pulmonares atribuíveis à AR

Um novo metodo para a purificacao do fator de von Willebrand. / A new method of purification of von Willebrand factor

O fracionamento do plasma humano para a obtencao de concentrado de fator de von Willebrand forneceu resultados superiores aos do esquema III quando se utilizou o aminoacido glicina. O esquema anteriormente empregado (esquema III) consistia em preparar um CRIO, precipita-lo com polietilenoglicol (PEG 1) e, depois, precipitar novamente com polietilenoglicol (PEG 2). Nas experiencias ora relatadas, o esquema de fracionamento (esquema IV) foi semelhante ao esquema III, exceto pela introducao da fase Glicina imediatamente apos a fase PEG 1. Com esta modificacao, o grau de purificacao da amostra final subiu de 130 para 550 vezes, embora a recuperacao da atividade do fator de von Willebrand tenha caido

Estudo da coagulacao em um caso de hepatite de Labrea. / Coagulation in a case of Labrea hepatitis

Um caso de hepatite de Labrea nos possibilitou um estudo do comportamento dos fatores da coagulao nessa doenca. O objetivo principal foi estudar a coagulacao do sangue, visando: 1. conhecer os niveis dos fatores da coagulacao na febre negra 2.contribuir para o melhor conhecimento da doenca, principalmente no que se refere as manifestacoes de hemorragia; 3. tentar correlacionar a gravidade do quadro clinico e prognostico a intensidade das alteracoes dos fatores da coagulacao.Os resultados evidenciaram uma alteracao acentuada da crase sanguinea, sugerindo que, alem do quadro infeccioso, o paciente desenvolveu, igualmente, uma sindrome de coagulacao intravascular disseminada

Purificacao do fator de von Willebrand. I - Fracionamento inicial do plasma. / Purification of the von Willebrand factor. I - Initial plasma fractionation

Este e o primeiro de uma serie de outros trabalhos sobre a purificacao do fator de von Willebrand. O objetivo deste primeiro trabalho e relatar a experiencia dos autores com o fracionamento do plasma a fim de obter um concentrado (PEG 2) altamente purificado, rico em atividade de vWF. Tres esquemas de fracionamento do plasma foram estudados. O Esquema I consistiu em precipitar o plasma a 22oC, por duas vezes, com uma solucao de polietilenoglicol (PEG) a 25g%. O Esquema II foi semelhante ao Esquema I, exceto que se utilizou a temperatura de 4oC para as precipitacoes com PEG.Para o Esquema III de fracionamento, acrescentou-se a fase de precipitacao pelo Crio ao Esquema II. A comparacao dos resultados revelou que o Esquema III de fracionamento foi o melhor, uma vez que o grau de purificacao (130 vezes) e a recuperacao da atividade do vWF (70%) aumentaram acentuadamente

Metabolismo do acido folico na malaria. / Folic acid metabolism in malaria

O estudo de 27 pacientes infectados pelo Plasmodium falciparum comparado com pessoas aparentemente sadias mostra: a) diminuicao do folato no soro dos pacientes infectados; b) diminuicao do folato serico nos primeiros 8 dias que seguiram ao tratamento, interpretados como sendo devido a mobilizacao pela eritropoiese compensadora; c) folato eritrocitico normal