Development of a temperature-responsive agarose-based ion-exchange chromatographic resin

A temperature-responsive ion-exchange resin (ItBA) has been prepared by grafting poly(N-isopropylacrylamide-co-acrylic acid-co-tert-butylacrylamide; ItBA) onto cross-linked agarose. A carboxymethylated ion exchanger (CM) of similar charge density was also prepared. Maximum adsorption capacities (B_max) for lactoferrin at 20 °C and 50 °C were determined for both resins by batch adsorption procedures. Dynamic adsorption and desorption characteristics of the CM and ItBA with lactoferrin were established, as well as the ability of ItBA to selectively adsorb and desorb lactoferrin in the presence of other proteins. With the CM-agarose resin there was no significant difference between the B_max values obtained at 20 °C and 50 °C. However, for the agarose-based ItBA resin the B_max value at 50 °C was almost three times higher than the B_max value at 20 °C. Dynamically, lactoferrin adsorbed to the ItBA packed column at 50 °C with a significant proportion of the adsorbed lactoferrin desorbed by reducing the temperature to 20 °C. In addition, anionic proteins did not adsorb to the ItBA packed column, and did not interfere with the dynamic adsorption/desorption behaviour of lactoferrin. These results indicate that this new temperature-responsive agarose-based ItBA resin has potential for the fractionation of whey proteins, with good selectivity for cationic proteins.