PubMed · 7983107
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P Ducheyne. 1994. Bioactive ceramics.. https://pubmed.ncbi.nlm.nih.gov/7983107/
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The objective of this study was to explore the potential use of self-assembled monolayers (SAMs) of alkylamine and arylalkyamine as well-defined, homogeneous, tailored in vitro model surfaces for exploring the effect of hydrodynamic flow on morphology and strength of adhesion of human umbilical vein endothelial cells. The cell surface area, shape, f-actin distribution, and adhesion strength of human umbilical vein endothelial cells cultured on self-assembled monolayers of organosilanes were found to be dependent on the chemical composition of the organosilane film and the magnitude of wall shear stress. The direct effects of the differences in chemistry between the two silanes, in modulating cellular response, are probably only secondary to the modulation of cellular functions mediated by differential protein adsorption and conformation on the two silanes. For short seeding times (30 min), prior to application of flow, both substrate chemistry and shear stress modulated the cellular morphology and cytoskeletal organization. For longer seeding times (24 h), prior to application of flow, the chemistry of the underlying surface was the dominant variable in modulating cellular morphology, while the hydrodynamic shear stress modulated the cytoskeleton organization. Cells on N-(2-aminoethyl)-3-aminopropyl trimethoxysilane (EDA) were pleomorphic, while cells on ((((aminoethyl)amino)methyl)phenylethyl)trimethoxysilane (PEDA) expressed a rounded morphology. Application of an incrementally loaded flow regime (0.07-1.25 ml/s) resulted in a time- and shear stress-dependent (10-180 dyn/cm2) detachment of cells, with the cells on EDA depicting higher resistance to wall shear stress. Cellular morphology correlated with the strength of adhesion; cells with rounded morphology on a hydrophobic silane, PEDA, were less tightly bound to the silane, while spread cells on a hydrophilic silane, EDA, were more tightly bound. The higher surface free energy of EDA is speculated to influence the increased cell spreading and strength of adhesion observed in these studies. The presence of the phenyl group in PEDA reduces the surface free energy and may account for the reduced spreading and lower strength of adhesion. The use of well-defined systems, such as monolayer organosilanes, with tunable surface physicochemical properties may serve to deconstruct the complex interaction of cells with extracellular matrix components: surface charge, surface hydrophobicity, and other short- and long-range forces can be individually controlled and correlated with cellular functions. The organosilane monolayers could serve as the building blocks for sequential addition of proteins or cell adhesive/cell repulsive cues to stepwise engineering and construction of more complex systems resembling ECM matrices.
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To develop a dual-curing monomer system for the photopultrusion of reformable (soft) composites, a microhardness assay showed that in a blend with 2,2-Bis[4-2-hydroxy-3-methacryloxypropoxy)phenyl] propane (Bis-GMA), the substitution of methyl methacrylate (MMA) for triethylene glycol dimethacrylate (TEGDMA) delayed the onset of gelation during photopolymerization. Adding lauroyl peroxide permitted the completion of polymerization thermally. This system was used to form silicate-glass-fiber-reinforced composites, with varying degrees of conversion, by photopultruding over a range of pulling speeds. Sol-gel extractions demonstrated both fully soluble and insoluble matrices. For the soluble material, gel permeation chromatography elucidated a trimodal distribution of molecular weights that corresponded to MMA, Bis-GMA, and polymeric molecules with molecular weights in the tens of thousands. Composites with matrix solubilities above about 10% wt could be swaged after photopultrusion to change the cross section from circular to rectangular before thermal processing. The effect on the final elastic modulus was small (-44GPa, as measured in flexure for 57% vol-reinforced composites); but the final flexure strength was reduced by approximately 25% to a constant of about 1.2 GPa. Morphological characteristics that were seen in the circular-sectioned precursors were observed in the swaged rectangular products as well, including flaws when swaging was conducted at matrix solubilities above about 75%.