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Cryogel bodies were modified to obtain epoxy groups by graft-copolymerization using both chemical and gamma irradiation initiation techniques. The free epoxy adsorbents were reacted further to introduce diethylaminoethanol (DEAE) functionalities. The resulting weak anion-exchange cryogel adsorbents showed dynamic binding capacities of ca. 27±3mg/mL, which was significantly higher than previously reported for this type of adsorbent material. Gamma irradiated grafting initiation showed a 4-fold higher capacity for proteins than chemical grafting initiation procedures. The phosphate capacity for these DEAE cryogels was 119mmol/L and also showed similar column efficiency as compared to commercial adsorbents. The large pores in the cryogel structure ensure convective transport of the molecules to active binding sites located on the polymer-grafted surface of cryogels. However, as cryogels have relatively large pores (10-100μm), the BET area available for surface activation is low, and consequently, the capacity of the cryogels is relatively low for biomolecules, especially when compared to commercial beaded adsorbents. Nevertheless, we have shown that gamma ray mediated surface grafting of cryogel matrices greatly enhance their functional and adsorptive properties.

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BACKGROUND: 'Expanded' composite materials are of interest as an alternative, or as a supplement, to packed-bed chromatography during bioproduct recovery and purification. Functionalized non-woven fabrics and mega-porous bodies are examples of systems that showed promise. However, there is scarce information on their suitability to capture and release plasmid DNA (pDNA), an important type of product employed in gene therapy. RESULTS: Composite adsorbents were prepared using either chemical (CG-DEAE-NW) or gamma-irradiated graft-polymerization (GIR-DEAE-MP), and subsequently modified to have diethylamino ethanol (DEAE) functionality. Capture experiments showed that pDNA can actually reversibly bind to the two mentioned adsorbents, with capacity values of 2.4 and 1.3 mg per mL, respectively. These values are in the range of what can be expected from commercial beaded adsorbents but lower that the values expected from monoliths. CONCLUSIONS: Expanded materials, due to their high voidage, may present limited capacity for pDNA. However, such materials are able to bind proteins and other contaminants from bacterial lysate, opening the way for their utilization in the 'negative' mode.