1. Huaxi MR Research Center (HMRRC) Department of Radiology Functional and Molecular Imaging Key Laboratory of Sichuan Province West China Hospital Sichuan University Chengdu 610041 China
2. School of Chemistry and Chemical Engineering Mianyang Normal University Mianyang 621000 China
3. Department of Applied Chemistry Faculty of Science Sichuan Agricultural University Yaan 625014 China
4. Amgen Bioprocessing Centre Keck Graduate Institute Claremont CA 91711 USA