José María Meseguer Dueñas

Analysis of the Biological Response of Endothelial and Fibroblast Cells Cultured on Synthetic Scaffolds with Various Hydrophilic/Hydrophobic Ratios: Influence of Fibronectin Adsorption and Conformation

In this study we developed polymer scaffolds intended as anchorage rings for cornea prostheses among other applications, and examined their cell compatibility. In particular, a series of interconnected porous polymer scaffolds with pore sizes from 80 to 110 microns were manufactured varying the ratio of hydrophobic to hydrophilic monomeric units along the polymer chains. Further, the effects of fibronectin precoating, a physiological adhesion molecule, were tested. The interactions between the normal human fibroblast cell line MRC-5 and primary human umbilical vein endothelial cells (HUVECs) with the scaffold surfaces were evaluated. Adhesion and growth of the cells was examined by confocal laser scanning microscopy. Whereas MRC-5 fibroblasts showed adhesion and spreading to the scaffolds without any precoating, HUVECs required a fibronectin precoating for adhesion and spreading. Although both cell types attached and spread on scaffold surfaces with a content of up to a 20% hydrophilic monomers, cell adhesion, spreading, and proliferation increased with increasing hydrophobicity of the substrate. This effect is likely due to better adsorption of serum proteins to hydrophobic substrates, which then facilitate cell adhesion. In fact, atomic force microscopy measurements of fibronectin on surfaces representative of our scaffolds revealed that the amount of fibronectin adsorption correlated directly with the hydrophobicity of the surface. Besides cell adhesion we also examined the inflammatory state of HUVECs in contact with the scaffolds. Typical patterns of platelet/endothelial cell adhesion molecule-1 expression were observed at intercellular boarders. HUVECs adhering on the scaffolds retained their proinflammatory response potential as shown by E-selectin mRNA expression after stimulation with lipopolyssacharide (LPS). The proinflammatory activation occurred in most of the cells, thus confirming the presence of a functionally intact endothelium. Little or no expression of the proinflammatory activation markers in the absence of LPS stimulation was observed for HUVECs growing on scaffolds with up to a 20% of hydrophilic component, whereas activation of these markers was observed after stimulation. In conclusion, scaffolds containing up to 20% hydrophilic monomers exhibited excellent cell compatibility toward human fibroblast cell line MRC-5 and human endothelial cells. Atomic force microscopy confirmed that adsorbed serum proteins such as fibronectin probably accounted for the positive correlation of HUVEC adhesion and surface hydrophobicity.

Dielectric and dynamic mechanical studies on homogeneous PBA/PBMA interpenetrating polymer networks

Broadband dielectric relaxation spectroscopy (DRS, 10 -2 - 10 9 Hz), thermally stimulated depolarization currents (TSDC) techniques and dynamic mechanical analysis (DMA) were employed to investigate the dynamic glass transition and, thus, phase morphology in sequential IPNs of poly(butyl acrylate) (PBA) and poly(butyl methacrylate) (PBMA) with 10 weight % of ethyleneglycol dimethacrylate (EGDMA) as branching agent. In a parallel investigation, similar IPNs with only 0.1 % branching agent showed clearly phase separation. In the highly branched IPNs, forced compatibilization induces miscibility of the two components. The results are discussed in terms of suppression of cooperativity and dynamic heterogeneity in the IPNs.

Avaluació entre companys i treball en equip

La evaluacion entre companeros es una forma de aprendizaje colaborativo en el que los estudiantes valoran el producto de aprendizaje de otros estudiantes. En nuestro caso, realizan dos tipos de evaluaciones relacionadas con la comunicacion efectiva: evaluan cualitativamente presentaciones orales de ejercicios, y en equipo evaluan cuantitativamente documentos con la resolucion de problemas de otros equipos. Se les han dado pautas sobre como llevar a cabo la evaluacion. El resultado ha sido comparado con la evaluacion hecha por los profesores. En la evaluacion cualitativa, la ordenacion por cualidad de los alumnos coincide con la de los profesores, i en la cuantitativa, las diferencias entran dentro de lo razonable entre profesores expertos. Ademas, la argumentacion que hacen a las calificaciones demuestra un trabajo de evaluacion riguroso y un aprendizaje a traves del trabajo hecho por los companeros.