Polysaccharide films built by simultaneous or alternate spray: a rapid way to engineer biomaterial surfaces.

We investigated polysaccharide films obtained by simultaneous and alternate spraying of a chitosan (CHI) solution as polycation and hyaluronic acid (HA), alginate (ALG), and chondroitin sulfate (CS) solutions as polyanions. For simultaneous spraying, the film thickness increases linearly with the cumulative spraying time and passes through a maximum for polyanion/CHI molar charge ratios lying between 0.6 and 1.2. The size of polyanion/CHI complexes formed in solution was compared with the simultaneously sprayed film growth rate as a function of the polyanion/CHI molar charge ratio. A good correlation was found. This suggests the importance of polyanion/polycation complexation in the simultaneous spraying process. Depending on the system, the film topography is either liquid-like or granular. Film biocompatibility was evaluated using human gingival fibroblasts. A small or no difference is observed in cell viability and adhesion between the two deposition processes. The CHI/HA system appears to be the best for cell adhesion inducing the clustering of CD44, a cell surface HA receptor, at the membrane of cells. Simultaneous or alternate spraying of CHI/HA appears thus to be a convenient and fast procedure for biomaterial surface modifications.journal articleresearch support, non-u.s. gov't2012 Jun 052012 05 23importe

Comparative Study of Hematopoietic Differentiation between Human Embryonic Stem Cell Lines

Directed differentiation of human embryonic stem cells (hESCs) into any desired cell type has been hailed as a therapeutic promise to cure many human diseases. However, substantial roadblocks still exist for in vitro differentiation of hESCs into distinct cell types, including T lymphocytes. Here we examined the hematopoietic differentiation potential of six different hESC lines. We compare their ability to develop into CD34+ or CD34+CD45+ hematopoietic precursor populations under several differentiation conditions. Comparison of lymphoid potential of hESC derived- and fetal tissue derived-hematopoietic precursors was also made. We found diverse hematopoietic potential between hESC lines depending on the culture or passage conditions. In contrast to fetal-derived hematopoietic precursors, none of the CD34+ precursors differentiated from hESCs were able to develop further into T cells. These data underscore the difficulties in the current strategy of hESC forward differentiation and highlight distinct differences between CD34+ hematopoietic precursors generated in vitro versus in vivo

Os compostos fenólicos são mais influenciados pelos fatores clima e cultivar quando comparados aos perfis metabólicos de aminoácidos e RMN 1H.

o HPLC é um método analítico com excelente sensibilidade que permite analisar diferentes metabólitos a partir de extratos vegetais ou animais. Ele é usado com sucesso para a determinação de compostos fenólicos e aminoácidos de uvas e vinhos. Estes dois grupos de compostos são importantes para os padrões de qualidade no meio enológico. A concentração dos compostos relacionados pode variar fortemente em relação às condições do meio

Direct Assessment of MHC Class I Binding by Seven Ly49 Inhibitory NK Cell Receptors

Mouse NK cells express at least seven inhibitory Ly49 receptors. Here we employ a semiquantitative cell–cell adhesion assay as well as class I/peptide tetramers to provide a comprehensive analysis of specificities of Ly49 receptors for class I MHC molecules in eight MHC haplotypes. Different Ly49 receptors exhibited diverse binding properties. The degree of class I binding was related to the extent of functional inhibition. The tetramer studies demonstrated that neither glycosylation nor coreceptors were necessary for class I binding to Ly49 receptors and uncovered peptide-specific recognition by a Ly49 receptor. The results provide a foundation for interpreting and integrating many existing functional studies as well as for designing tests of NK cell development and self-tolerance

Polysaccharide Films Built by Simultaneous or Alternate Spray: A Rapid Way to Engineer Biomaterial Surfaces

We investigated polysaccharide films obtained by simultaneous and alternate spraying of a chitosan (CHI) solution as polycation and hyaluronic acid (HA), alginate (ALG), and chondroitin sulfate (CS) solutions as polyanions. For simultaneous spraying, the film thickness increases linearly with the cumulative spraying time and passes through a maximum for polyanion/CHI molar charge ratios lying between 0.6 and 1.2. The size of polyanion/CHI complexes formed in solution was compared with the simultaneously sprayed film growth rate as a function of the polyanion/CHI molar charge ratio. A good correlation was found. This suggests the importance of polyanion/polycation complexation in the simultaneous spraying process. Depending on the system, the film topography is either liquid-like or granular. Film biocompatibility was evaluated using human gingival fibroblasts. A small or no difference is observed in cell viability and adhesion between the two deposition processes. The CHI/HA system appears to be the best for cell adhesion inducing the clustering of CD44, a cell surface HA receptor, at the membrane of cells. Simultaneous or alternate spraying of CHI/HA appears thus to be a convenient and fast procedure for biomaterial surface modifications