Calcium silicate scaffolds promoting bone regeneration via the doping of Mg2+ or Mn2+ ion

Biodegradation and bioinductivity are important factors to decide scaffold efficiency in inducing tissue regeneration. For bone regeneration, calcium silicate (CS) is attractive for its degradation to release Ca2+ and Si4+ ions, which are inductive for osteogenesis and angiogenesis. The doping of Mg2+ or Mn2+ can further strengthen the capacity of CS bioceramic in promoting osteogenesis and angiogenesis. Therefore, CS scaffolds were made by soaking polymeric foam in precursor sol-gels containing different amounts of doping elements and subsequent calcination. Mechanical properties of the scaffolds were improved by gelatin coating. In comparison with the un-doped scaffold, the Mg-doped scaffolds demonstrated lower compression strengths, while the Mn-doped scaffolds displayed higher compression strengths. The ion doping would decrease the degradation and the ion release rates, showing negative dependence on the doping amounts of Mg2+ or Mn2+. The Mg-doped scaffolds promoted the osteogenic and angiogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) more efficiently than the Mn-doped scaffolds, and both of them had stronger promotion effects on cell activities than the CS scaffold. In vivo evaluations were conducted using the rat calvarial defect model, from which, significant vascularization and new bone formation were identified with the Mg-doped CS scaffolds being implanted for 12 weeks, and the Mn-doped CS scaffolds displayed slightly inferior results. Both the Mg- and Mn-doped CS scaffolds could enhance bone regeneration more efficiently than the CS scaffold. CS scaffolds doped with bioactive elements were deemed as good candidates for bone tissue engineering benefiting from their adjustable biodegradation and bioinductivity.