Direct ink writing core-shell Wollastonite@Diopside scaffolds with tailorable shell micropores favorable for optimizing physicochemical and biodegradation properties

Additive manufacture has recently been proposed as a versatile process for fabricating porous bioceramic scaffolds for bone repair and tissue engineering; however, to control or tailor the biodegradation of the porous biomaterials is still a challenge. Here, the core-shell-structured biphasic bioceramic porous scaffolds with tailorable ion release and biodegradation were prepared by direct ink writing technique with coaxially aligned binozzle system. Our method employed rapidly gelling filaments of wollastonite (CSi) and diopside without and with Zn or Sr doping (Dio, ZnDio, SrDio) derived from bi-flow of sodium alginate-loaded bioceramic slurries, and varying the powder slurry design made it easy to create core-shell struts (e.g. CSi@Dio, CSi@ZnDio, CSi@SrDio) with adjustable bioceramic-phase distribution. It was found that the Zn- or Sr-doping could readily adjust the mechanical strength and biodegradation rate in the early stage. Furthermore, when 30% organic microspheres were pre-mixed into the powder slurry, the controllable high-density micropores could be introduced into the shell layer after sintering (e.g. CSi@Dio-p, CSi@ZnDio-p, CSi@SrDio-p), and thus permeability is maximally tuned and favorable for ion release through the porous shell layer. This new core-shell direct ink writing strategy can be used to fabricate a variety of biphasic bioceramic scaffolds with adjustable physicochemical properties which could be potentially beneficial for improving biological performance and bone repair in situ.