In Vitro and In Vivo Evaluation of 3D Borosilicate Scaffolds

Bone grafts each have their limitations, prompting ongoing efforts to develop superior materials. Bioactive glasses (BAGs) are particularly promising due to their ability to form a hydroxyapatite (HA) layer in the body, enhancing compatibility with natural bone while releasing ions triggering signaling pathways leading to superior bone regeneration. The limitations of commercially available silicate bioactive glasses are, i.e., incomplete dissolution and conversion to HA, in vivo and the difficulties in processing porous scaffolds, without adverse crystallization. This study focuses on the development of 3D porous borosilicate glass scaffolds. Borosilicate glasses offer advantages over traditional silicate-based BAGs, such as reduced crystallization and enhanced HA conversion. However, challenges arise from their high boron content and rapid dissolution, potentially leading to cytotoxicity. To overcome these challenges, borosilicate compositions (B12.5, B12.5MgSr, and 1393B20) were synthesized and evaluated for in vitro and in vivo performance. The study aimed to achieve optimal degradation rates supporting favorable cell responses and bone regeneration. It has been shown that 2-3 days of preincubation are effective to decrease the burst release of ions, during cells culture consequently supporting their viability. Moreover, the addition of Mg and Sr has been shown to stabilize the B12.5MgSr BAG network, resulting in slower dissolution rate compared to B12.5 BAG, consequently allowing better cytocompatibility. Furthermore, it has been shown that addition of B into silicate 1393 scaffolds improves their angiogenic properties in vitro. In vivo, addition of B allowed higher bone mineralization and collagen formation with 1393B20 compared to 1393 scaffolds. Finally, it was demonstrated that cells exhibit less sensitivity to B concentrations release from scaffolds compared to the findings documented in existing literature. Summarizing, this study helps to understand how ion release from silicate (1393) and borosilicate (B12.5, B12.5MgSr and 1393B20) scaffolds can be control and altered to enhance their performance in vitro and consequently allowing better translation into in vivo studies.