Purification of virus particles for viral vaccines and applications of gene therapy is a major large scale separations challenge. Here adsorption of Aedes aegypti densonucleosis virus by anion and cation exchange membranes has been investigated. As the virus particles are viable at pH values above and below their isoelectric point, adsorption by anion and cation exchange membranes is feasible. The capacity of the membranes for virus particles is orders of magnitude less than the manufacturer's stated capacity for model proteins such as BSA and lysozyme indicating that binding patterns are very different for different sized solutes. In order to visualize solute binding confocal laser scanning microscopy (CLSM) has been used to observe binding of thyroglobulin, BSA and lysozyme to cation exchange membranes. The results are in qualitative agreement with the measured capacities for virus particles, BSA and lysozyme. However, the results also indicate that the binding patterns for thyroglobulin, BSA and lysozyme are very different. It appears that compared to lysozyme and BSA, only a few pores are available for thyroglobulin binding, in agreement with the much lower measured binding capacity for thyroglobulin compared to BSA and lysozyme. Therefore, CLSM could be a useful visualization technique when designing membranes with optimized pore structures. (c) 2006 Elsevier B.V. All rights reserved.