Strong mineralization ability of strontium zinc silicate: Formation of a continuous biomorphic mineralized layer with enhanced osteogenic activity.

Silica gel plays an important role in the formation of some biomorphic minerals (e.g. silica-carbonates) with morphologically complex micro/nanostructures in a pure inorganic system. Herein, we demonstrate the potential of strontium zinc silicate (Sr2 ZnSi2 O7 , SZnS) bioceramics as a biomorphic mineral "garden" due to its incongruent dissolution behavior. Briefly, the preferential release of Sr ions from SZnS leaves behind a silica-rich gel on the ceramic surface and leads to an alkaline pH in the localized area close to the silica-rich gel, providing a growth condition similar to that for the conventional synthesis of biomorphic minerals. Based on this unique characteristic of SZnS, a continuous and integrated carbonated calcium-phosphate mineralized layer was formed on 3D porous SZnS scaffolds with the purpose of enhancing scaffold's bioactivity. The mineralized layer not only provides numerous nanotopographic cues for guiding cell behavior, but also avoids burst ion release, thus overcoming side effects caused by the overdose of bioactive ions and the over-high pH. In vitro cell culture experiments and in vivo animal studies demonstrate that the scaffold with nanostructured mineralized layers promotes osteogenic differentiation of osteoblasts and induce more new bone tissues compared to the non-mineralized scaffold.