New Mg/Sr phosphate bioresorbable glass system with enhanced sintering properties

Phosphate glasses are ideal candidates to substitute traditional silicate bioactive glasses as they can exhibit controlled ion release. Furthermore, phosphate glasses possess congruent dissolution and also resistance to crystallization, two properties that are favorable for the processing of 3D porous scaffolds. However, most of the phosphate glasses also exhibit a fast dissolution rate, which is inappropriate for bone tissue regeneration. In this context, a new bioresorbable phosphate glass within the 45P₂O₅- 2.5B₂O₃- 2.5SiO₂- 10Na₂O- 20CaO- (20-x) SrO- (x)MgO (in %mol) composition was developed. Magnesium is substituted for strontium in order to promote bone formation but in the present study, its role is mainly to favor sintering at lower temperatures without crystallization. The in vitro dissolution in simulated body fluid was assessed for glass particles <38 μm (pH, ICP, SEM-EDS). All glasses were found bioresorbable, rather than bioactive. The newly developed phosphate glasses containing Sr and Mg were found to have a slower dissolution rate when compared to traditional metaphosphate glasses while maintaining their congruent dissolution and hot forming ability. All glasses were 3D printed into scaffolds with controlled pore size and without apparent crystallization. The substitution of SrO for MgO was shown to be highly effective in enhancing the sintering ability of the material by enabling sintering at lower temperatures while avoiding the risk of crystallization leading to the processing of scaffolds with mechanical properties, in compression, above that of the cancellous bone.