Quantitative characterization of pore structure of cellulose gels with or without bound protein ligand.

Structural properties of cellulose gels Perloza MT, materials designed for the preparation of chromatographic adsorbents and immobilized biocatalysts, having a different content of polymer were investigated using a batch solute exclusion method. A homologous set of dextrans with a wide range of molecular weights was used to probe the pore accessibility of the gel particles. It was found that all gels possessed a bimodal pore structure where macropores were fully accessible to all dextrans whereas the solute partitioning depending on the molecule size occurred in the micropores of the swollen polymer network. The macropore and micropore fractions of the gels were estimated from the masses of total water and water accessible to the largest solute. The macropore fraction decreased with the gel polymer content. It was 0.57 at the gel containing 8% of polymer but only 0.22 at the gel with 38% of polymer. The micropore fraction varied from 0.38 to 0.47. The mass of accessible water for each solute was used to calculate the particle and gel-phase partition coefficients. The dependence of the latter quantity on the solute hydrodynamic radius was successfully fitted with the Ogston model. Bovine serum albumin that was used as a model protein ligand blocked almost all gel-phase pores of the gel with the highest polymer content whereas it little affected the accessibility of other materials.