1. School
of Materials Science and Engineering and Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
2. Departments of Medicine, Division of Gastroenterology and Hepatology, and Microbiology & Immunology, Stanford University School of Medicine, Stanford, California 94305, United States
3. Howard
Hughes Medical Institute, Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California 94158-2280, United States
4. Palo Alto Veterans Administration Medical Center, Palo Alto, California 94304, United States