Fabrication of Cluster/Shell Fe3O4/Au Nanoparticles and Application in Protein Detection via a SERS Method

We have successfully synthesized cluster/shell Fe 3 O 4 /Au nanoparticles using a pH-sensitive polyethyleneimine (PEI) linker. We propose that PEI binds gold seeds, prevents the formation of large aggregates, and changes the spatial structure in an alkaline environment to bundle several Fe 3 O 4 /Au seed nanoparticles together through a bridging flocculation function, thereby producing cluster/shell Fe 3 O 4 /Au nanoparticles. We successfully applied the synthesized cluster/shell Fe 3 O 4 /Au nanoparticles to free-PSA detection via a surface-enhanced Raman scattering (SERS) method, presenting a convenient way for preconcentrating, purifying, and detecting target proteins in complex biosamples. The synthesis strategy demonstrated here can be extended to the fabrication of a wide range of cluster/shell nanocomposites for biomedical applications.