Morphological, structural, and in vitro bioactivity of core-shell-structured bioactive glass by multitechnical spectroscopic approach

Abstract

The pioneeristic work of Hench led to the development of a calcium sodium phosphosilicate composition called 45S5 Bioglass®, which has been investigated extensively for applications in the field of bone repair and regeneration because of its bioactivity, i.e., ability to form a bond to living bone. The bioactivity of silicate glass is qualitatively associated with the development over time of the apatite layer on a bioactive glass, while quantitatively it would be related to how fast the formation of this crystalline phase occurs. In this work, (Camoltensaltbath2+|Naglass+) ion exchange in a molten salt bath (MSB) was employed for modifying the glass surface aiming to create a more reactive glass in a thin shell that surrounds the vitreous core, which preserves all the bioactivity characteristics of 45S5 Bioglass® composition. The 45S5@Ca45S5 core-shell-structured bioactive glass is characterized by a vitreous matrix enriched with calcium and a highly depolymerized silicate network. The presence of calcium-rich glass composition restricted to a thin shell acts as a catalyst, accelerating all the earlier events that occur at the glass/solution interface. The kinetics of deposition of the silica-gel and apatite layers was investigated by FTIR and 31P MAS NMR, respectively. The results suggest that the modification of the glass surface causes not only a reduction in the formation time of silica-gel and amorphous calcium phosphate on the glass surface but also induced the formation of the apatite phase with a higher degree of crystallinity.