Gold nanoparticle shape dependence of colloidal stability domains.

Controlling the spatial arrangement of plasmonic nanoparticles is of particular interest to utilize inter-particle plasmonic coupling, which allows changing their optical properties. For bottom-up approaches, colloidal nanoparticles are interesting building blocks to generate more complex structures via controlled self-assembly using the destabilization of colloidal particles. For plasmonic noble metal nanoparticles, cationic surfactants, such as CTAB, are widely used in synthesis, both as shaping and stabilizing agents. In such a context, understanding and predicting the colloidal stability of a system solely composed of AuNPs and CTAB is fundamentally crucial. Here, we tried to rationalize the particle behavior by reporting the stability diagrams of colloidal gold nanostructures taking into account parameters such as the size, shape, and CTAB/AuNP concentration. We found that the overall stability was dependent on the shape of the nanoparticles, with the presence of sharp tips being the source of instability. For all morphologies evaluated here, a metastable area was systematically observed, in which the system aggregated in a controlled way while maintaining the colloidal stability. Combining different strategies with the help of transmission electron microscopy, the behavior of the system in the different zones of the diagrams was addressed. Finally, by controlling the experimental conditions with the previously obtained diagrams, we were able to obtain linear structures with a rather good control over the number of particles participating in the assembly while maintaining good colloidal stability.

Insight on Chirality Encoding from Small Thiolated Molecule to Plasmonic Au@Ag and Au@Au Nanoparticles.

Chiral plasmonic nanomaterials exhibiting intense optical activity are promising for numerous applications. In order to prepare those nanostructures, one strategy is to grow metallic nanoparticles in the presence of chiral molecules. However, in such approach the origin of the observed chirality remains uncertain. In this work, we expand the range of available chiral plasmonic nanostructures and we propose another vision of the origin of chirality in such colloidal systems. For that purpose, we investigated the synthesis of two core-shell Au@Ag and Au@Au systems built from gold nanobipyramid cores, in the presence of cysteine. The obtained nanoparticles possess uniform shape and size and show plasmonic circular dichroism in the visible range, and were characterized by electron microscopy, circular dichroism, and UV-vis-NIR spectroscopy. Opto-chiral responses were found to be highly dependent on the morphology and the plasmon resonance. It revealed (i) the importance of the anisotropy for Au@Au nanoparticles and (ii) the role of the multipolar modes for Au@Ag nanoparticles on the way to achieve intense plasmonic circular dichroism. The role of cysteine as shaping agent and as chiral encoder was particularly evaluated. Our experimental results, supported by theoretical simulations, contrast the hypothesis that chiral molecules entrapped in the nanoparticles determine the chiral properties, highlighting the key role of the outmost part of the nanoparticles shell on the plasmonic circular dichroism. Along with these results, the impact of enantiomeric ratio of cysteine on the final shape suggested that the presence of a chiral shape or chiral patterns should be considered.

Acute effects of whole-body vibration on the motor function of patients with stroke: a randomized clinical trial.

OBJECTIVE: The aim of this study was to investigate the acute effects of whole-body vibration on the motor function of patients with stroke. DESIGN: The present investigation was a randomized clinical trial studying 43 individuals with hemiparesis after stroke, with 33 subjects allocated to the intervention group and 10 subjects allocated to the control group. The intervention group was subjected to one session of vibration therapy (frequency of 50 Hz and amplitude of 2 mm) comprising four 1-min series with 1-min rest intervals between series in three body positions: bipedal stances with the knees flexed to 30 degrees and 90 degrees and a unipedal stance on the paretic limb. The analytical tests were as follows: simultaneous electromyography of the affected and unaffected tibialis anterior and rectus femoris muscles bilaterally in voluntary isometric contraction; the Six-Minute Walk Test; the Stair-Climb Test; and the Timed Get-Up-and-Go Test. The data were analyzed by independent and paired t tests and by analysis of covariance. RESULTS: There was no evidence of effects on the group and time interaction relative to variables affected side rectus femoris, unaffected side rectus femoris, affected side tibialis anterior, unaffected side tibialis anterior, and the Stair-Climb Test (P > 0.05). There was evidence of effects on the group interaction relative to variables Six-Minute Walk Test and Timed Get-Up-and-Go Test (P < 0.05). CONCLUSIONS: Whole-body vibration contributed little to improve the functional levels of stroke patients.

Viability of nerve grafts preseved in different storage medium

We compared the structural features of nerve segments stored in two different solutions previous and after autologous transplantation. Male Wistar rats were divided into groups to obtain normal tibial nerves, freshly transplanted nerves, and nerves stored in Wisconsin/Belzer or Collins solution for 24 or 72 h at 4ºC and transplanted. Stored and transplanted segments were processed for morphologic and morphometric analysis. The cross-sections of segments stored in Wisconsin/Belzer and Collins solution presented aspects similar to that of normal nerves. The density of large-caliber myelinated axons was higher in grafts stored in Wisconsin/Belzer solution than in those preserved in Collins solution. But the density of myelinated axons regenerated through these grafts was around 80% to that registered in the fresh and Wisconsin/Belzer preserved grafts. Moreover, no significant differences in the morphometric parameters were observed between groups. Our data confirm the efficacy of Wisconsin/Belzer to nerve graft preservation and stimulate more detailed physiological, biochemical and molecular studies to rationalize the employment of less expensive and handful storage solutions for short term preservation of peripheral nerve grafts.

Estudo da viabilidade de enxertos de nervos mantidos em soluções conservadoras / Study of viability of grafts of nerves maintained in conservative solutions

As lesoes tramaticas que incidem com grande frequencia sobre o sistema nervoso periferico, apresentando prognostico reservado principalmente quando ocorre transeccao completa do nervo. Todavia, com o melhor conhecimento dos fenomenos celulares e moleculares envolvidos na regeneracao axonal e das tecnicas microcirurgicas, tem-se buscado melhorar esse quadro. Neste sentido, tem sido objeto de investigacao nos ultimos anos a criacao de um banco de nervos que viria facilitar o reparo de lesoes nervosas com extensa perda de substancia. Assim, diversos metodos vem sendo testados para a conservacao dos segmentos de nervos para posterior transplante. Neste estudo foram analisados os aspectos morfologicos e quantitativos de enxertos autologos previamente mantidos em dois tipos de solucao conservadora. Foram utilizados quarenta ratos machos da linhagem Wistar, sendo que 16 deles foram subdivididos em grupos de 4 animais, que tiveram os nervos tibial esquerdo e direito removidos e mantidos em solucao conservadora de Wisconsisin/Belzer (4ºC), por 24 ou 72 horas, ou em solucao conservadora de Collins (4ºC) por 24 ou 72 horas, respectivamente. Apos os periodos de conservacao previstos, estes nervos foram precessados para analise histologica, conforme descrito a seguir. Outros 4 animais, controles, tiveram os nervos tibial direito e esquerdo removidos e imediatamente processados para histologia. Por sua vez, um grupo de 15 animais teve o nervo tibial esquerdo removido e conservado por 24 horas ou 72 horas em solucao de Wisconsin/Belzer (4ºC ou solucao de Collins (4ºC), e posteriormente transplantado no mesmo animal para o lado direito. Outros 5 animais, tiveram o nervo tibial esquerdo retirado e imediatamente transplantado para o lado direito. A conduta cirurgica foi precedida sempre de anestesia profunda com pentobarbital sodico (50mg/Kg/peso) para todos os animais. Apos 50 dias do transplante, os animais que receberam os enxertos nervosos foram anestesiados exposicao do respect...