Bifunctional Au-Fe3O4 nanoparticles for protein separation.

In this article, we report the synthesis of bifunctional Au-Fe(3)O(4) nanoparticles that are formed by chemical bond linkage. Due to the introduction of Au nanoparticles, the resulting bifunctional Au-Fe(3)O(4) 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-Fe(3)O(4) 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 strategy paves the way for facile preparation of diverse bifunctional and even multifunctional nanomaterials.