3D printed concentrated alginate/GelMA hollow-fibers-packed scaffolds with nano apatite coatings for bone tissue engineering

Three-dimensional grafts/scaffolds with hierarchically biomimetic features from nano to macro scale and high porosity are required for bone tissue engineering. In this study, biomimetic organic/inorganic composite scaffolds with high porosity (78.7 ± 3.2%) and features from nano (nano apatite coatings) to macro (macro pores and hollow channels) scale were fabricated based on highly concentrated alginate/GelMA bioinks via co-axial 3D printing and in situ mineralization under mild conditions. Nano apatites were coated on both inner and outer surfaces of the hollow fiber scaffolds, homogeneously. Proteins were directly loaded in the bioinks achieving sustained release from the scaffolds over 28 days. The in vitro cell experiments showed that the scaffolds with good biocompatibility could support cells adhesion and proliferation. The nano apatite coatings presented remarkable osteogenic capability. The in vivo study indicated that the hollow fiber scaffolds with biomimetic nano apatite coatings showed the capability to enhance bone formation after 12 weeks of implantation. In conclusion, the prepared biomimetic organic/inorganic scaffolds with homogeneous nano apatite coatings and hollow channels structures might be potential candidates for bone tissue engineering.