Three-dimensional (3D) bioprinting combines biomaterials, cells and functional components into complex living tissues. Herein, we assembled function-control modules into cell-laden scaffolds using 3D bioprinting. A customized 3D printer was able to tune the microstructure of printed bone mesenchymal stem cell (BMSC)-laden methacrylamide gelatin scaffolds at the micrometer scale. For example, the pore size was adjusted to 282 ± 32 μm and 363 ± 60 μm. To match the requirements of the printing nozzle, collagen microfibers with a length of 22 ± 13 μm were prepared with a high-speed crusher. Collagen microfibers bound bone morphogenetic protein 2 (BMP2) with a collagen binding domain (CBD) as differentiation-control module, from which BMP2 was able to be controllably released. The differentiation behaviors of BMSCs in the printed scaffolds were compared in three microenvironments: samples without CBD-BMP2-collagen microfibers in the growth medium, samples without microfibers in the osteogenic medium and samples with microfibers in the growth medium. The results indicated that BMSCs showed high cell viability (>90%) during printing; CBD-BMP2-collagen microfibers induced BMSC differentiation into osteocytes within 14 days more efficiently than the osteogenic medium. Our studies suggest that these function-control modules are attractive biomaterials and have potential applications in 3D bioprinting.

Hemoglobin‐based capsules for use as blood substitutes are successfully fabricated by covalent layer‐by‐layer assembly. Dialdehyde heparin (DHP) is used both as one of the wall components and a cross‐linker without employing other extraneous or toxic crosslinking agents. The biocompatibility of (Hb/DHP)6 microcapsules is evaluated through the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) (MTT) assay and cell experiments. The hemocompatibility of (Hb/DHP)6 microcapsules is characterized in terms of prothrombin time, thrombin time, activated partial thromboplastin time, and hemolysis rate. The oxygen‐carrying capacity of the microcapsules is demonstrated by converting the deoxy‐Hb state of the microcapsules into the oxy‐Hb state. All these results demonstrate that the hemoglobin‐based microcapsules exhibit oxygen‐carrying capacity as well as biocompatibility and hemocompatility, indicating that the as‐prepared capsules have great potential to function as blood substitutes.