RT Journal Article SR Electronic T1 Three-dimensional printing of complex biological structures by freeform reversible embedding of suspended hydrogels JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP e1500758 DO 10.1126/sciadv.1500758 VO 1 IS 9 A1 Hinton, Thomas J. A1 Jallerat, Quentin A1 Palchesko, Rachelle N. A1 Park, Joon Hyung A1 Grodzicki, Martin S. A1 Shue, Hao-Jan A1 Ramadan, Mohamed H. A1 Hudson, Andrew R. A1 Feinberg, Adam W. YR 2015 UL http://advances.sciencemag.org/content/1/9/e1500758.abstract AB We demonstrate the additive manufacturing of complex three-dimensional (3D) biological structures using soft protein and polysaccharide hydrogels that are challenging or impossible to create using traditional fabrication approaches. These structures are built by embedding the printed hydrogel within a secondary hydrogel that serves as a temporary, thermoreversible, and biocompatible support. This process, termed freeform reversible embedding of suspended hydrogels, enables 3D printing of hydrated materials with an elastic modulus <500 kPa including alginate, collagen, and fibrin. Computer-aided design models of 3D optical, computed tomography, and magnetic resonance imaging data were 3D printed at a resolution of ~200 μm and at low cost by leveraging open-source hardware and software tools. Proof-of-concept structures based on femurs, branched coronary arteries, trabeculated embryonic hearts, and human brains were mechanically robust and recreated complex 3D internal and external anatomical architectures.