Chemical
Engineering

Faculty: J. L. Brash

Dr. Brash University Professor
Department of Chemical Engineering

Brockhouse Institute Member

McMaster University
1280 Main Street West, Hamilton
Ontario, Canada L8S 4L7
office: CRL-230
email: brashjl@mcmaster.ca
voice: (905) 525-9140 ext.24946

B.Sc. Glasgow University (1958), Ph.D. Glasgow University (1961), D. Hon.
Caus. University of Paris (Nord) (1996), P. Eng.

Research Projects

1. Biotechnology and Biomaterials

A major theme of our studies is the interfacial behavior of proteins which is of great
importance in biotechnology, diagnostics, and medical devices. Many of the products of
biotechnology are genetically engineered proteins - e.g. insulin and growth factors.
Processing presents unique problems due to the instability of these complex macro-
molecules. For example, chromatography involving interaction of the proteins with solid
surfaces is often used in final purification but can lead to molecular distortion and a
biologically inactive, even though pure, product. An example in the medical devices field
is blood compatible materials for arterial grafts, blood pumps and heart valves. A major
unsolved problem here is blood coagulation/thrombosis believed to be initiated by the
adsorption of plasma proteins to the surface of the implant. In these contexts we are
studying the adsorption of a range of proteins using tube flow, serum replacement
(equivalent to CSTR), and packed column experiments in conjunction with radiolabelled
proteins. Media range from buffered solutions to blood. Specific interests are the kinetics,
equilibria and reversibility of adsorption and changes in the structure and biologic function
of adsorbed proteins. A prime objective is to correlate specific interactions with surface
properties, e.g. wettability, electric charge, chemical composition. Materials for study, mostly
polymers, are synthesized in the laboratory or are acquired from collaborating
research groups around the world.

2. Polymerization and Polymer Characterization

This work is on condensation polymerization and is mainly concerned with segmented
polyurethanes, a versatile class of thermoplastic elastomers. Objectives are to improve
understanding of structure-property relationships, to develop methods for "tailoring"
surface properties, and to develop "bioactive" polyurethanes having specific biological activity
. An example of the latter are surfaces which will activate the fibrinolytic (clot dissolving system)
in blood.

3. Modification of Surfaces for Biotechnology Applications

Surface modification of materials is of considerable current interest in biotechnology
applications such as biosensors and diagnostic devices. In general one wants to
keep the bulk properties of the material intact while tailoring the surface to impart
properties such as resistance to fouling or binding of a specific molecule from a
contacting biofluid. We are developing a program in this area based on two
approaches: (a) gas plasma treatment of polymer surfaces, (b) chemical
grafting (c) modification of surfaces via exploitation of gold-thiol chemistry.
In the latter, the surface is coated with a thin film of gold which is then treated with
appropriate thiolates to give the desired properties. In some cases the resulting layers
have unique properties through ordering and self assembly.

Selected Publications

Hitchcock, AP, Morin, C, Zhang, X, Araki, T, Dynes, J, Stöver, H, Brash, JL, Lawrence, JR, Leppard, GG. “Soft X-ray spectromicroscopy of biological and synthetic polymer systems”, J. Electron Spectroscopy, 144-147, 259-269 (2005).

Unsworth LD, Sheardown H, Brash JL. “Protein resistance of surfaces prepared by sorption of end-thiolated poly(ethylene glycol) to gold: effect of surface chain density”, Langmuir, 21, 1036-1041 (2005).

Archambault, J.G., and Brash, J.L., “Protein repellent polyurethane surfaces by chemical grafting of PEO: amino-terminated PEO as grafting reagent” Colloids Surfaces B: Biointerfaces, 39, 9-16 (2004).

Feng, W., Brash, J.L., and Zhu, S. “Atom-Transfer Radical Grafting Polymerization of 2-Methacryloyloxyethyl Phosphorylcholine from Silicon Wafer Surfaces”. J Polymer Sci Polymer Chem, 42, 2931-2942 (2004).

Cornelius, R.M., Sanchez, J., Olsson, P., and Brash, J.L. Interactions of antithrombin and proteins in the plasma contact activation system adsorbed on immobilized functional heparin. J. Biomed Mater. Res., 67A, 475-83 (2003).