Immobilization of a Ce(IV)-substituted polyoxometalate on ethylenediamine-functionalized graphene oxide for selective extraction of phosphoproteins.

A sorbent for selective extraction of phosphoproteins was obtained by immobilization of a Ce(IV)-substituted polyoxometalate on ethylenediamine-functionalized graphene oxide (CeEGO). The resulting composites exhibit an adsorption capacity of 981 mg g-1 for β-casein due to the synergistic effect of metal-affinity interaction between Ce(IV) and phosphate groups and π-stacking interaction between the polyoxometalate framework and the phosphate groups. The results of LC-MS and SDS-PAGE analysis show that the CeEGO composites can be applied to the extraction of phosphoproteins from protein mixture, and as little as 50 μg mL-1 of the phosphoprotein β-casein can be detected by SDS-PAGE. It was also applied to the extraction of β-casein from spiked biological samples such as drinking milk, whole blood and swine heart tissue extract. Graphical abstract An efficient sorbent is obtained by immobilization of a Ce(IV)-substituted polyoxometalate on ethylenediamine-functionalized graphene oxide (CeEGO). The resulting composites exhibit highly selective capture capacity towards phosphoproteins due to the synergistic effect of metal-affinity interaction between Ce(IV) and phosphate groups and π-stacking interaction between the polyoxometalate framework and the phosphate groups.