Novel tetrazole-functionalized ion exchanger for weak cation-exchange chromatography of proteins

A new type of weak cation exchanger, tetrazole-functionalized silica, was developed for bioseparation. It was prepared conveniently by modifying silica gel initially with γ-glycidoxypropyltrimethoxysilane, then with 3-hydroxypropionitrile and finally with ammonium-catalyzed (3 + 2) azide–nitrile cycloaddition, which is an element of click chemistry. The prepared stationary phase was characterized and evaluated for its separation performance, protein retention behavior, loading capacity, protein recovery and chemical stability. The results show that the stationary phase developed has excellent performance for protein separations with high mass recoveries, and has long-term stability. Some remarkable differences were observed between this new exchanger and a carboxylic methyl-functionalized ion exchanger, which is typically used in weak cation-exchange chromatography of proteins. The obtained column was also used for the purification of lysozyme from chicken egg white, and the purity and specific bioactivity of the obtained lysozyme were about 90% and 67 IU/mg, respectively.