Nanoporous membranes offering selectivity at the molecular level with a MWCO from 0 to 500 kDa were investigated with respect to permeability of key molecular constituents of an osmotic glucose sensor. The membrane should facilitate the passage of glucose (180 Da) with minimal delay, yet retain the larger molecular components of the concanavalin A-dextran affinity assay (60-102 kDa), using albumin (66 kDa) as a model. The results show that the membrane architecture plays just as an important factor as the pore size when it comes to determining the most functional membrane for the application. Further the viscous matrix of the affinity assay prevented the efflux of assay components that was observed using individual molecules such as albumin. It was found that the ceramic membrane from anodic aluminium oxide (AAO) with 4-6 nm pores within a membrane thickness of 1 mu m constituted the best compromise with respect to glucose permeability, retention of assay components and response time. (C) 2011 Elsevier B.V. All rights reserved.