The metastasis of breast cancer is mainly regulated by chemokine receptors such as CXCR4.As reported,neutralizing the interactions ofCXCL12/CXCR4 could significantly inhibit the metastasis of breast cancer cells to regional lymph nodes and lung[1].Herein,a nanogel system to deliver chemical drug and CXCR4 antagonist,as a tool for the development of a new therapy for metastatic breast cancer,is designed and explored in this study.