Core-shell-typed selective-area ion doping wollastonite bioceramic fibers enhancing bone regeneration and repair in situ

Silicate-based bioceramics are being received great attention because of its potential osteostimulative properties in facilitating bone regeneration. Meanwhile, foreign ion doping in bioceramics is a versatile strategy for regulating the biological performances. Herein we developed the new core-shell-typed wollastonite bioceramic fibers (Zn8@Mg10) with 8% Zn and 10% Mg selective-area doping. It was found that the fibrous diameter of Zn-doped core layer could be finely tuned by the extrusion force through the coaxially aligned bi-nozzle system and thus the ultralong bioceramic fibers with different core-shell thickness ratios (2:4, 3:3; 4:2) could be fabricated after sintering treatment. The Zn8@Mg10 fibers exhibited tailorable Zn and Mg ion release and more controllable bio-dissolution in vitro in comparison with the mechanically mixed Zn8/Mg10 fibers. The osteogenic efficacy of core-shell fibers was validated in femoral bony defect in rabbits. The fibers with equal core/shell thickness (3:3) showed more appreciable osteogenic capability after 8 weeks and the new bone tissue could grow into the entire defected region, while the Zn8/Mg10 group only presented new bone at the boundary. Histological examination also indicated more appreciable bone formation in the core-shell fiber groups, whereas less new bone ingrowth was observed in the Zn8/Mg10 group. These findings indicate that bone repair can be enhanced by component distribution design to control bioactive ion release and osteostimulation in vivo. It is demonstrated that selective-area ions doping bioceramics can be translated to a core-shell-structuring strategy through layer thickness adjustment and fiber fabrication with strong clinical translation.