Bifunctional Au-Fe3O4 Nanoparticles for Protein Separation

In this article, we report the synthesis of bifunctional Au-Fe3O4 nanoparticles that are formed by chemical bond linkage. Due to the introduction of Au nanoparticles, the resulting bifunctional Au-Fe3O4 nanoparticles can be easily modified with other functional molecules to realize various nanobiotechnological separations and detections. Here, as an example, we demonstrate that as-prepared Au-Fe3O4 nanoparticles can be modified with nitrilotriacetic acid molecules through Au–S interaction and used to separate proteins simply with the assistance of a magnet. Bradford protein assay and sodium dodecyl sulfate–polyacrylamide gel electrophoresis were performed to examine the validity of the separation procedure, and the phosphate determination method suggested that the as-separated protein maintained catalytic activity. This result shows the efficiency of such a material in protein separation and suggests that its use can be extended to magnetic separation of other biosubstances. Moreover, this synthetic strat...