The development of hybrid organic-inorganic membranes with a low propensity for protein adsorption and highly uniform nanometre size pores is described. Poly(ethylene glycol) (PEG) monolayers were grafted to nanoporous alumina membranes using covalent silane and physical adsorption poly(ethyleneimine) (PEI) immobilization chemistries. X-ray photoelectron spectroscopy (XPS) and electron microscopy were used to investigate the chemical and physical surface properties of the membranes. The adsorption behaviour of a serum albumin on the membranes was characterized with fluorescence spectroscopy and it was determined that the PEG coating reduced nonspecific protein adsorption to a level too small to be measured. The gas and liquid permeabilities of membranes were measured to determine if the surface chemistries changed the functional behaviour of the membranes. Surprisingly, the silane chemistry produced little change in the permeabilities while polymer adsorption resulted in a total loss of water permeability. The diffusion of ovalbumin through the membranes was also measured and compared with a theoretical value. Diffusion of ovalbumin through the silane-PEG-modified membranes was found to be 50% slower than the unmodified membranes, which suggests that the pores are coated with a dense film of PEG. These results suggest that hybrid organic-inorganic membranes can provide significantly improved functional behaviour over existing organic or inorganic membranes.
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