COLL 336 |
| Paul R. Van Tassel and A. Pascal Ngankam. Department of Chemical Engineering, Yale University, P. O. Box 208286, New Haven, CT 06520 |
| The Layer-by-Layer deposition of positively and negatively charged macromolecular species is an ideal method for constructing thin films incorporating biological molecules. We investigate the control of adsorbed protein (fibronectin) layer structure through polyelectrolyte multilayer (PEM) films using optical waveguide lightmode spectroscopy (OWLS) and atomic force microscopy (AFM). PEM films are formed by adsorption onto Si(Ti)O2 from alternately introduced flowing solutions of anionic polystyrenesulfonate (PSS) and cationic polyallylamine hydrochloride (PAH). Using OWLS, we find the initial rate and overall extent of fibronectin adsorption to be greatest on PEM films terminated with a PAH layer. The optical density of the adsorbed protein layer, as measured by its refractive index, is virtually identical on both PAH and PSS terminated films; the higher adsorbed density on the PAH terminated film is due to an adsorbed layer of roughly twice the thickness. The binding of monoclonal antibodies specific to the protein’s cell binding site bind is considerably enhanced to fibronectin adsorbed to the PSS layer, indicating a more accessible adsorbed layer. With increased salt concentration, we find thicker PEM films but considerably thinner adsorbed fibronectin layers, owing to increased electrostatic screening. Using AFM, we find adsorbed fibronectin layers to contain clusters; these are more numerous and symmetrical on the PSS-terminated film. The picture emerging from these data is one of fibronectin adsorbed end-on (side-on) onto PAH (PSS) terminated PEM films, consistent with predictions based on the purely electrostatic binding of a segmental model fibronectin. |
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Bio-Colloids
2:00 PM-4:40 PM, Tuesday, March 30, 2004 Marriott -- Orange County 3, Oral
Division of Colloid and Surface Chemistry |