A Simple and Robust Method to Prepare Polyelectrolyte Brushes on Polymer Surfaces

Abstract

A simple and robust method is presented to immobilize a heparin-analog polyelectrolyte on inert hydrophobic surfaces. It is demonstrated that an amphiphilic block copolymer consisting of linear polyglycerol sulfate (lPGS) and a benzophenone modified anchor block can be bound to polystyrene surfaces in a facile dip-coating procedure. The chaotropic salt guanidinium chloride is used to overcome the aggregation of the polymer as well as the repulsion between highly hydrated sulfate groups and the polystyrene surface. Irradiation with UV light tethers the polymer chains covalently to the surface. The resulting coating exhibits an aggregate morphology that resembles the aggregation behavior in solution, with a coating thickness of 8 nm. The behavior of the surfaces is dominated by the polyelectrolyte brush coating. They swell and collapse in response to different ionic strengths of the surrounding medium, and bind proteins via electrostatic interactions. The coating is stable toward physiological conditions over the course of several weeks. Coated surfaces bind to proteins of the complement cascade when in contact with dilute blood serum, which results in a decrease of complement activity to 78 ± 4%. The coating procedure can also be applied to other nonactivated polymer surfaces, as demonstrated on a polypropylene fleece.