ABSTRACT
Nanocomposites of Ethylene Vinyl Acetate (EVA 260) with Cloisite 20A organo clay and Cloisite 20A organo clay impregnated with Fe(CO)(5) were produced in a twin-screw extruder. Dynamic mechanical analysis (DMA) measurements indicated that the moduli increased monotonically for the Cloisite, up to a concentration of 10%, after which the modulus decreased. Adult human dermal fibroblasts (AHDF) were plated on these surfaces and the cell growth was found to be maximal on the nanocomposites containing 10% Cloisite. AHDFs cultured on substrates with higher Cloisite content had low surface area, poor growth curves, and misshaped actin fibers. Compounding EVA with Fe(CO)(5) soaked Cloisite did not enhance the modulus even at a loading of 10%. TEM images indicate nanoparticles form and coat the Cloisite platelet surfaces, possibly interfering with the exfoliation process. On the other hand, cell culture of MC3T3 osteoblasts proliferated on the Fe containing nanocomposites, the largest effect being observed when cultured in a constant magnetic field. These results indicate how the chemical nature of the Cloisite 20A organo clay can also play a major role. Finally, since natural ECM is fibrillar, these EVA nanocomposites were also electrospun into micron thick fibers. MC3T3s proliferated well on these fibers and the MC3T3 proliferation was maximized by culture on electrospun aligned fibers in a constant magnetic field.
Subject(s)
Bentonite/pharmacology , Ferric Compounds/pharmacology , Fibroblasts/cytology , Nanoparticles/chemistry , Osteoblasts/cytology , Polyvinyls/pharmacology , Quaternary Ammonium Compounds/pharmacology , Adsorption , Adult , Animals , Cell Adhesion/drug effects , Cell Proliferation/drug effects , Cells, Cultured , Dermis/cytology , Fibroblasts/drug effects , Humans , Magnetics , Mechanical Phenomena/drug effects , Mice , Nanocomposites/chemistry , Osteoblasts/drug effects , Polymethyl Methacrylate/pharmacology , TemperatureABSTRACT
We have demonstrated that monolayer films of randomly charged polystyrene sulfonated acid (PSSA) can be produced by the Langmuir technique, and observed the micro-domain structures, produced by the phase separation of electrostatically charged moieties and the hydrophobic moieties. Using atomic force microscopy and Langmuir isotherm, we found three specific regimes for the polyelectrolytes with various degrees of sulfonation (4-35%); very low charged PSSA (4-5%) in the hydrophobic regime, moderately charged PSSA (6-16%) which possessed a well-balanced nature between electrostatic and the hydrophobic interactions, and strongly amphiphilic nature of PSSA (6-16%) in the ionomer regime. Finally, we could categorize PSSA 35% in the polyelectrolyte regime, due to the dominance of the electrostatic interactions over the hydrophobic interactions.
