Poly(vinyl alcohols) (PVA) of a molecular weight of about 50 000 were applied to the modification of fused silica surfaces for the separation of large charged molecules such as proteins. Basic and acidic proteins could be separated in PVA-modified capillaries at highly optimized and analytically suitable performance with regard to efficiency, zone symmetry, and resolution. PVA can be used in the dynamic mode as an additive to the buffer medium or as a water-insoluble permanent coating on the fused silica surfaces which can be achieved by a simple procedure of thermal immobilization

Capillary Zone Electrophoresis Separations of Basic and Acidic Proteins Using Poly(vinyl alcohol) Coatings in Fused Silica Capillaries

A procedure for obtaining highly stable coated capillaries for use in capillary electrophoresis (CE) is described. Reaction of surface-chlorinated fused silica capillaries with the Grignard reagent, vinyl magnesium bromide, followed by reaction of the vinyl group with acrylamide, results in an immobilized layer of polyacrylamide attached through hydrolytically stable Si-C bonds. This method is an extension of the capillary coating procedure described previously by Hjerten, differing in the means by which the polyacrylamide layer is bonded to the capillary walls. Capillaries treated in the manner described here can be used over a pH range of 2-10.5, without noticeable decomposition of the coating. In comparison to uncoated capillaries, separations of proteins using such coated capillaries are improved due to a reduction in protein adsorption to the capillary walls, although interaction is still present to some degree as evidenced by an inability to obtain plate counts as high as those predicted by theory. Electroosmotic flow is virtually eliminated in the coated capillaries, resulting in improved reproducibilities of protein migration times in comparison to uncoated capillaries. Additionally, peak skew is evaluated for model proteins and improvements are noted for the coated capillaries. Results are presented for separations of model protein mixtures, comparing the performance of the vinyl-bound polyacrylamide coated capillaries and uncoated capillaries at both high and low pH extremes.

Electrophoretic separations of proteins in capillaries with hydrolytically stable surface structures.

There is much interest in attaching polyethylene glycol (PEG) and other hydrophilic, neutral polymers to surfaces to reduce the extent of protein and cell adsorption. Interestingly, these same surface-bound polymers are effective in masking surface charge and reducing electrokinetic effects such as particle electrophoretic mobility, streaming potential, and electroosmosis. It is apparent that similar molecular properties are responsible for both protein and cell rejection and reduction of electrokinetic effects. In this work we compared the fibrinogen-rejecting ability and the effect on electrophoretic mobility of three polymer coatings bound to polystyrene. The three polymers were side-bound dextran, end-bound dextran, and end-bound PEG. The results of these measurements were used to elucidate the importance of polymer packing density and polymer layer thickness on protein adsorption and reduction of electrokinetic effects. Protein adsorption appears not to be sensitive to polymer layer thickness or the presence of dilute polymer tails in a surface coating, while electrokinetic effects are. Protein adsorption is, however, very sensitive to the availability of exposed surface. Finally, the unique effectiveness of PEG is apparent in this research as in previous studies. © 1995 John Wiley & Sons, Inc.

Protein-rejecting ability of surface-bound dextran in end-on and side-on configurations: comparison to PEG.

Hydrophilic protein adsorption resistant coatings for microfluidic devices are provided. Additionally, microfluidic devices and methods of manufacturing microfluidic devices that include the coatings are provided.

J.P. Chang

Papers

Capillary zone electrophoretic separations of proteins in polyethylene glycol-modified capillaries