It is significant to use functional biomaterials to rationally engineer microenvironments for in situ bone regeneration in the field of bone tissue engineering. To this end, we constructed the gypsum-coated β-tricalcium phosphate (G-TCP) scaffolds by combing a three-dimensional printing technique and an epitaxial gypsum growth method. In vitro simulation experiments showed that the as-prepared scaffolds could establish a dynamic and weakly acidic microenvironment in a simulated body liquid, in which the pH and the calcium ion concentration always changed due to the gypsum degradation and growth of bone-like apatite nanoplates on the scaffold surfaces. The cell experiments confirmed that the microenvironment established by the G-TCP surfaces promoted rapid osteogenic differentiation and proliferation of bone marrow mesenchymal stem cells (BM-MSCs). In vivo experiments confirmed that the G-TCP scaffolds had high bioactivity in modulating in situ regeneration of bone, and the bioactivity of the G-TCP scaffolds was endowed by correct pore structures, degradation of gypsum, and growth of a bone-like apatite layer. The microenvironment established by the gypsum degradation could stimulate tissue inflammation and recruit white blood cells and BM-MSCs and thus accelerating native healing cascades of the bone defects via a bone growth/remodeling-absorption cycle process. Furthermore, in vivo experiments demonstrated that after the bone defects had healed completely, the as-prepared scaffolds also degraded completely within 24 weeks.
Keywords: 3D printing; bone tissue engineering; gypsum; in situ bone regeneration; scaffolds; tricalcium phosphate.