The exceptional properties of graphene enable applications in electronics, optoelectronics, energy storage, and structural composites. Here we demonstrate a 3D printable graphene (3DG) composite consisting of majority graphene and minority polylactide-co-glycolide, a biocompatible elastomer, 3D-printed from a liquid ink. This ink can be utilized under ambient conditions via extrusion-based 3D printing to create graphene structures with features as small as 100 μm composed of as few as two layers (<300 μm thick object) or many hundreds of layers (>10 cm thick object). The resulting 3DG material is mechanically robust and flexible while retaining electrical conductivities greater than 800 S/m, an order of magnitude increase over previously reported 3D-printed carbon materials. In vitro experiments in simple growth medium, in the absence of neurogenic stimuli, reveal that 3DG supports human mesenchymal stem cell (hMSC) adhesion, viability, proliferation, and neurogenic differentiation with significant upregulation of glial and neuronal genes. This coincides with hMSCs adopting highly elongated morphologies with features similar to axons and presynaptic terminals. In vivo experiments indicate that 3DG has promising biocompatibility over the course of at least 30 days. Surgical tests using a human cadaver nerve model also illustrate that 3DG has exceptional handling characteristics and can be intraoperatively manipulated and applied to fine surgical procedures. With this unique set of properties, combined with ease of fabrication, 3DG could be applied toward the design and fabrication of a wide range of functional electronic, biological, and bioelectronic medical and nonmedical devices.

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Despite substantial attention given to the development of osteoregenerative biomaterials, severe deficiencies remain in current products. These limitations include an inability to adequately, rapidly, and reproducibly regenerate new bone; high costs and limited manufacturing capacity; and lack of surgical ease of handling. To address these shortcomings, we generated a new, synthetic osteoregenerative biomaterial, hyperelastic "bone" (HB). HB, which is composed of 90 weight % (wt %) hydroxyapatite and 10 wt % polycaprolactone or poly(lactic-co-glycolic acid), could be rapidly three-dimensionally (3D) printed (up to 275 cm(3)/hour) from room temperature extruded liquid inks. The resulting 3D-printed HB exhibited elastic mechanical properties (~32 to 67% strain to failure, ~4 to 11 MPa elastic modulus), was highly absorbent (50% material porosity), supported cell viability and proliferation, and induced osteogenic differentiation of bone marrow-derived human mesenchymal stem cells cultured in vitro over 4 weeks without any osteo-inducing factors in the medium. We evaluated HB in vivo in a mouse subcutaneous implant model for material biocompatibility (7 and 35 days), in a rat posterolateral spinal fusion model for new bone formation (8 weeks), and in a large, non-human primate calvarial defect case study (4 weeks). HB did not elicit a negative immune response, became vascularized, quickly integrated with surrounding tissues, and rapidly ossified and supported new bone growth without the need for added biological factors.

Clinical interventions to preserve fertility and restore hormone levels in female patients with therapy-induced ovarian failure are insufficient, particularly for pediatric cancer patients. Laproscopic isolation of cortical ovarian tissue followed by cryopreservation with subsequent autotransplantation has temporarily restored fertility in at least 27 women who survived cancer, and aided in pubertal transition for one pediatric patient. However, reintroducing cancer cells through ovarian transplantation has been a major concern. Decellularization is a process of removing cellular material, while maintaining the organ skeleton of extracellular matrices (ECM). The ECM that remains could be stripped of cancer cells and reseeded with healthy ovarian cells. We tested whether a decellularized ovarian scaffold could be created, recellularized and transplanted to initiate puberty in mice. Bovine and human ovaries were decellularized, and the ovarian skeleton microstructures were characterized. Primary ovarian cells seeded onto decellularized scaffolds produced estradiol in vitro. Moreover, the recellularized grafts initiated puberty in mice that had been ovariectomized, providing data that could be used to drive future human transplants and have broader implications on the bioengineering of other organs with endocrine function.

A new method for complex metallic architecture fabrication is presented, through synthesis and 3D‐printing of a new class of 3D‐inks into green‐body structures followed by thermochemical transformation into sintered metallic counterparts. Small and large volumes of metal‐oxide, metal, and metal compound 3D‐printable inks are synthesized through simple mixing of solvent, powder, and the biomedical elastomer, polylactic‐co‐glycolic acid (PLGA). These inks can be 3D‐printed under ambient conditions via simple extrusion at speeds upwards of 150 mm s–1 into millimeter‐ and centimeter‐scale thin, thick, high aspect ratio, hollow and enclosed, and multi‐material architectures. The resulting 3D‐printed green‐bodies can be handled immediately, are remarkably robust, and may be further manipulated prior to metallic transformation. Green‐bodies are transformed into metallic counterparts without warping or cracking through reduction and sintering in a H2 atmosphere at elevated temperatures. It is shown that primary metal and binary alloy structures can be created from inks comprised of single and mixed oxide powders, and the versatility of the process is illustrated through its extension to more than two dozen additional metal‐based materials. A potential application of this new system is briefly demonstrated through cyclic reduction and oxidation of 3D‐printed iron oxide constructs, which remain intact through numerous redox cycles.