Norman L. Burns

Comparison of polysaccharide and poly(ethylene glycol) coatings for reduction of protein adsorption on polystyrene surfaces

Abstract There has been much recent interest in the use of poly(ethylene glycol)s (PEGs) for a variety of biotechnical applications. In the present work we have immobilized several cellulose derivatives and dextran on polystyrene surfaces and have measured the extent of fibrinogen adsorption onto the coated surfaces. Immobilization was achieved by adsorption onto clean polystyrene and by covalent linkage of oxidized polysaccharides to polyethylenimine which was ionically bound to polystyrene. Covalently bound polysaccharides, and adsorbed polysaccharides that are strongly held, compare well with poly(ethylene glycol) in preventing fibrinogen adsorption. The same polymers were coupled to polystyrene latex particles to permit examination by analytical microparticle electrophoresis. This investigation suggests that adsorbed polysaccharides form thicker layers than do covalently bound polysaccharides. Despite the polysaccharides being bound at many points along the polymer chain while PEG is bound only at the polymer terminus, the functional equivalence of polysaccharide and PEG coatings is of significance in interpreting the protein-rejecting ability of polymer-modified surfaces.

Electrokinetic characterization of hydrophilic polymer coatings of biotechnical significance

Abstract Analytical microparticle electrophoresis was used to characterize various polymer coatings known to control protein adsorption and related phenomena of biotechnical significance. The electrophoretic mobility of polystyrene latex microspheres and the electro-osmosis associated with quartz capillaries were characterized over the pH range 2–11. Such characterization provides information related to surface modification. Aminopropylsilane and mercaptopropylsilane were shown to be effective sublayers for covalent attachment of hydrophilic polymers to quartz glass surfaces. Poly(ethylenimine) was similarly verified as an effective sublayer for polystyrene latex. Polymer coatings based on poly(ethylene glycol) and three polysaccharides, dextran, ethyl(hydroxyethyl)cellulose, and hydroxypropylcellulose, were found to reduce capillary electro-osmosis and microsphere electrophoretic mobility significantly over a broad pH range. This reduction corresponds to the ability of these coatings to reduce protein adsorption and control surface wetting by aqueous polymer two-phase systems.

Modified pellicle formation and reduced in vitro bacterial adherence after surface treatment with different siloxane polymers

Formation of salivary pellicles is a prerequisite of bacterial colonization on the tooth and the aim of this study has been to further the understanding of the role of surface properties in formati ...

Automated Particle Electrophoresis: Modeling and Control of Adverse Chamber Surface Properties

Electrophoretic analysis of colloidal particles is adversely affected by a host of surface phenomena, including electroosmosis, phase wall wetting, and sample or air bubble adsorption. Neutral, hydrophilic polymer coatings control such phenomena on a variety of surfaces. Poly(ethylene glycol)-poly(ethylene imine) (PEG-PEI) conjugates significantly reduce electroosmosis and positively control adsorption and wetting in the glass sample chambers (5 mm × 3 mm × 1 mm i.d.) employed in a representative commercial electrophoresis apparatus (Coulter DELSA 440). The reduction in electroosmosis (e.g., 80% in 7.5 mM solution at pH 11) was similar to that exhibited by coated 2-mm-i.d. quartz capillaries in a Rank MK I manual apparatus. PEG-PEI coatings significantly reduce electroosmosis over a wide range of pH (2-11) and ionic strength (1-100 mM) and can be stable for weeks under normal laboratory conditions. They greatly enhance ease of operation and accuracy (sample mean electrophoretic mobility ± SD) of the DELSA 440. The latter results from reduced electroosmosis flow profile gradients near the chamber center-axis stationary levels, where particle mobility is typically measured. Such flow profiles may also be affected by chamber wall surface asymmetries. A hydrodynamic description of electroosmotic fluid flow in rectangular chambers was adapted in order to analyze the propagation of errors due to both nonideal focusing and chamber surface asymmetry. The analysis indicated that the accuracy of rectangular chambered devices may be improved by measuring particle mobility at stationary levels different than chamber center-axes. As a result, some rectangular chambers may confer accuracy advantages over cylindrical chambers.

Nernst-Hartley evaluation of the interdiffusion coefficient of aqueous nickel sulfamate using new measurements of the equivalent conductances of the ions

A diaphragm cell for measuring diffusion coefficients consists of two well stirred solution compartments on opposite sides of a membrane, which is usually a sintered glass disk [l-4]. Once the geometric cell constant for the device has been determined by calibration, the differential diffusion coefficient of a two-component system can be determined by following the time dependence of the concentration difference (of either solute or solvent) appearing across the sinter. Recent advances in theory have placed the diaphragm cell method on a sound mathematical basis [5,6]. Subject to question, however, is the accuracy of diaphragm cell measurements of interdiffusion coefficients of strong electrolytes at high dilution [7,8]. As this is the region where the diffusion coefficient depends steeply on concentration, it is important to check the experimental values against theoretical results involving the transport coefficients. The most useful of thes,e theoretical results is the NernstHartley equation,