Preparation and Characterization of Multi-shell Hollow Biphase Bioceramic Microsphere Composites

A series of hollow bioceramic microspheres with two or three shell layers were fabricated via alginate microsphere template and layer-by-layer coating techniques. The Na2SiO3–alginate mixture hydrosol beads were firstly injected into the Ca(NO3)2 aqueous solution under mild stirring to form calcium silicate hydrate-coated alginate microspheres. The composite microspheres were dispersed into the beta-tricalcium phosphate(β-TCP)-containing alginate hydrosol and wollastonite(CaSiO3)-containing alginate hydrosol in turn while gently stirring. The microspheres were filtered,dried in vacuum and finally calcined at 850℃ for 2 h to obtain the multi-shell hollow bi-phase ceramic microspheres. The microstructure and chemical composition of the microspheres were characterized by SEM,EDX,XRD and FTIR analysis. In vitro biodegradation behavior of the two-shell hollow microspheres was tested in weak acidic Tris buffer and confirmed a unique controlled release characteristic for the silicate and phosphate groups. These results suggest that the rational design of the two- or multi-shell layer allows the preparation of bioceramic composites composed of β-TCP and CaSiO3 with stage adjustable biodegradation and these biomaterials are potential candidates for improving bone regeneration and repair.