In this paper,we prepared a dual functional system based on dextrin-coated silver nanoparticles which were further attached with iron oxide nanoparticles and cell penetrating peptide (Tat),producing Tat-modified Ag-Fe3O4 nanocomposites (Tat-FeAgNPs).To load drugs,an-SH containing linker,3-mercaptopropanohydrazide,was designed and synthesized.It enabled the silver carriers to load and release doxorubicin (Dox) in a pH-sensitive patte.The delivery efficiency of this system was assessed in vitro using MCF-7 cells,and in vivo using null BalB/c mice bearing MCF-7 xenograft tumors.Our results demonstrated that both Tat and exteally applied magnetic field could promote cellular uptake and consequently the cytotoxicity of doxorubicin-loaded nanoparticles,with the IC50 of Tat-FeAgNP-Dox to be 0.63 μmol/L.The in vivo delivery efficiency of Tat-FeAgNP carrying Cy5 to the mouse tumor was analyzed using the in vivo optical imaging tests,in which TatFeAgNP-Cy5 yielded the most efficient accumulation in the tumor (6.7± 2.4％ ID of Tat-FeAgNPs).Anti-tumor assessment also demonstrated that Tat-FeAgNP-Dox displayed the most significant tumor-inhibiting effects and reduced the specific growth rate of tumor by 29.6％ (P =0.009),which could be attributed to its superior performance in tumor drug delivery in comparison with the control nanovehicles.