Dumbbell-like Au-Fe(3)O(4) nanoparticles (NPs) were made and coupled with Herceptin and a platin complex. The platin-Au-Fe(3)O(4)-Herceptin NPs act as a target-specific nanocarriers for delivery of platin into Her2-positive breast cancer cells (Sk-Br3) with strong therapeutic effects. The conjugate has a half-maximal inhibitory concentration (IC(50)) toward Sk-Br3 cells of 1.76 microg of Pt/mL, which is lower than that needed for cisplatin (3.5 microg/mL). The work demonstrates that the dumbbell-like Au-Fe(3)O(4) NPs are promising nanocarriers for highly sensitive diagnostic and therapeutic applications.