A 20-40 mum pellicular high density (similar to3.7 g cm(-3)) expanded bed material has been designed for the capture of DNA and other large macromolecules. Anion exchangers fashioned out of these supports exhibited dramatically enhanced DNA binding capacities over commercial anion exchange adsorbents (6 mg ml(-1), c.f. similar to 50 mug ml(-1) at 10% breakthrough), due to a combination of small particle and 'fuzzy' surface architecture created through the coupling of polyethylene imine chains.