Porous star-star polyelectrolyte multilayers for protein binding

Abstract

This work employs layer-by-layer adsorption of star-poly[2-(dimethylamino)ethyl methacrylate] (star-PDMAEMA) and star-poly(acrylic acid) (star-PAA) to create porous coatings that bind the equivalent of many monolayers of lysozyme. AFM images of (star-PDMAEMA/star-PAA)n films on gold-coated wafers reveal pore diameters ranging from 100–550 nm, depending on the number of arms in the polymer and the number of bilayers, n, in the films. (Star-PDMAEMA/star-PAA)n coatings on Au-coated wafers bind the equivalent of up to 150 nm of lysozyme, and binding is greater for films containing star-PAA with 3, rather than 4, arms. Deposition of star-PAA/star-PDMAEMA films in porous hydroxylated nylon gives membranes that bind proteins via ion-exchange interactions. Such membranes capture as much as 120 mg of lysozyme per cm3 of membrane (equilibrium binding capacity), which is more than twice the capacity of commercial ion-exchange membranes, but films are unstable at neutral and high pH.