The applications of superparamagnetic iron oxide nanoparticles (SPIONs), especially in the biomedical field, is rapidly increasing for tumor diagnosis and therapy.However, two problems are common confronted when applying these particles in vivo: (1) conventional SPIONs have severely nonspecific uptake by non-target cells under the action of an external magnetic field, which weakens the targeting efficiency of SPIONs;(2) at size less than 15 nm, the particles have very limited drug-loading capacity which undermines the curative effect severely.