Doping functional ions in phase-stabilizing core–shell biphasic granules readily tunes bone regeneration in situ

Some silicate- and phosphate-based bioactive ceramics exhibit excellent biocompatibility and undergo biodegradation to different extents, thereby attracting extensive attention and showing application in the field of bone tissue engineering. Moreover, functional ion doping is a versatile strategy for optimizing the performance of bioceramics. Herein, we developed a series of core–shell bio-ceramic granules, with zinc-doped wollastonite (CSi–Zn) as the core and tricalcium phosphate (TCP) or sodium-doped tricalcium phosphate (TCP–Na) as the shell, using a coaxial dual-nozzle system. The thickness ratio of the core and shell layers was finely controlled as 2 : 1 or 1 : 1. An in vitro immersion test demonstrated that the core–shell structure and functional ion doping could tailor the ion release behavior and granule dissolution in tris buffer, and the CSi component readily induced biomimetic re-mineralization in simulated body fluids. Critical size femoral bone defect repair experiments indicated that when the core–shell thickness ratio was 1 : 1, CSi–Zn@TCP granules exhibited superior bone repair performance at 18 weeks of post-implantation. This advantage was also particularly significant in the early stages (8 weeks) of post-implantation. Altogether, the tunable composition and structure of granule biomaterials offer excellent flexibility and feasibility, with the potential for the development of a series of derivative and variant products to address various clinical requirements.