Research Equipment Development Program of the Chinese Academy of Sciences [YZ201351]
; National High Technology Research and Development Program of China (863 Program) [2012AA020501]
; National Natural Science Foundation of China 
; Ministry of Science and Technology of China (973 Program) [2011CB965001]
; 'Strategic Priority Research Program' of the Chinese Academy of Sciences [XDA01030000]
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 mu m and 363 +/- 60 mu m. To match the requirements of the printing nozzle, collagen microfibers with a length of 22 +/- 13 mu m were prepared with a highspeed 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.