1. Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Winston Salem, NC, USA
2. Section on Gastroenterology, Wake Forest School of Medicine, Winston Salem, NC, USA
3. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA
4. Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
5. Virginia Tech-Wake Forest School of Biomedical Engineering Sciences, Winston-Salem, NC, USA