The effect of surface modifications on protein microfiltration properties of Anopore™ membranes

The synthesis, characterization, and protein microfiltration behavior of a series of organic–inorganic nanocomposite membranes are reported. It is shown that by modifying the surface of an Anopore™ alumina membrane with a variety of chemistries that membrane fouling can be significantly reduced. The work presented here shows that electrostatic repulsion between the surface and protein can be used to reduce fouling, as can making the surface more hydrophilic. Two methods were used to make hydrophilic nanocomposite membranes: adsorption of Pluronic F108 onto Anopore™ membranes with an octadecylsilane overlayer, and the grafting of poly(ethylene glycol) (PEG) to either amine-functionalized surfaces or dendrons with amines on their outer periphery. Both approaches led to a significant reduction in membrane fouling with the PEG grafted materials displaying superior performance to the F108 functionalized samples. IR, XPS, and TGA were used to characterize the composite membranes, and the results of these methods correlate with the microfiltration data presented. Mathematical modeling of the microfiltration data indicates that the pore constriction model best describes the change in protein flux over time. The current work presents an alternative approach to membrane design for microfiltration, which has historically been dominated by polymeric membranes.