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.

The self-assembly of molecules into desired architectures is currently a challenging subject for the development of supramolecular chemistry. Here we present a facile "breath figure" assembly process through the use of the self-assembled peptide building block diphenylalanine (L-Phe-L-Phe, FF). Macroporous honeycomb scaffolds were fabricated, and average pore size could be regulated, from (1.00±0.18) μm to (2.12±0.47) μm, through the use of different air speeds. It is indicated that the honeycomb formation is humidity-, solvent-, concentration-, and substrate-dependent. Moreover, water molecules introduced from "breath figure" intervene in the formation of hydrogen bonds during FF molecular self-assembly, which results in a hydrogen bond configuration transition from antiparallel β sheet to parallel β sheet. Meanwhile, as a result of the higher polarity of water molecules, the FF molecular array is transformed from laminar stacking into a hexagonal structure. These findings not only elucidate the FF molecule self-assembly process, but also strongly support the mechanism of breath figure array formation. Finally, human embryo skin fibroblast (ESF) culture experiments suggest that FF honeycomb scaffolds are an attractive biomaterial for growth of adherent cells with great potential applications in tissue engineering.

We have fabricated tubular hydrogel scaffolds of nano-hydroxyapatite (nHA)/alginate (ALG) via a layer-by-layer (LbL) technique. Using Ca 2+ as a crosslinker, nHA was assembled with ALG to form a hydrogel network. The inner diameter of scaffolds could be controlled from 0.5 mm to 7 mm by varying the assembled layer numbers of nHA/ALG pairs. By changing the nHA concentration, we can also control the crosslinking degree of the hydrogel network, and further change the mechanical properties, swelling behavior, permeability and diffusivity of the scaffolds. The elastic modulus of the hydrogel scaffolds was regulated from 0.98 AE 0.05 MPa to 2.78 AE 0.08 MPa as the concentration of nHA was changed from 50 mg mL À1 to 300 mg mL À1 , which reached the requirements of avascular soft tissue. The diffusion coefficient was tuned from 23.84 Â 10 À7 cm 2 s À1 to 9.92 Â 10 À7 cm 2 s À1 for controlled mass transport in the hydrogel network. Moreover, human embryo skin fibroblast (ESF) culture experiments prove that nHA can improve cellular adhesion on the hydrogel surface. These results thus suggest that the assembled nHA/ALG hydrogel scaffolds are an attractive biomaterial for great potential application in soft tissue engineering.

This study describes a facile breath-figure method for the preparation of honeycomb-like porous TiO2 films with an organometallic small-molecule precursor. Multiple characterization techniques have been used to investigate the porous films and a mechanism for the formation process of porous TiO2 films through the breath-figure method is proposed. The pore size of the TiO2 films could be modulated by varying the experimental parameters, such as the concentration of titanium n-butoxide (TBT) solution, the content of cosolvent, and the air flow rate. In vitro cell-culture experiments indicate that NIH 3T3 fibroblast cells seeded on the honeycomb-like porous TiO2 films show good adhesion, spreading, and proliferation behaviors, which suggests that honeycomb-like porous TiO2 films are an attractive biomaterial for surface modification of titanium and its alloys implants in tissue engineering to enhance their biocompatibility and bioactivity.

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