Development of glass-related biomaterials for enhanced bone regeneration via stimulation of cell function

Glasses can be systematically designed according to their composition, and their potential to release ions can also be manipulated by tailoring their structures. Notably, phosphate invert glasses (PIG) can contain various elements that are comparable with silicate glasses due to their acidity. In this review article, novel PIGs containing therapeutic ions for bone regeneration, and anisotropic scaffolds for reconstructing bone quality were reviewed. PIGs have been structurally designed to utilize intermediate oxides, such as TiO2, Nb2O5, ZnO, and MgO. As a result, PIGs with excellent chemical durability are expected to sustain their ion-relesability for bone regeneration and exhibit antibacterial activities. In contrast, PIGs have been designed with improved ion-releasing rates, with some releasing 20 times more ions compared to conventional PIGs. This was accomplished by manipulating the glass structure to contain only orthophosphates and orthosilicates. In other words, these glasses have no long-chain structures. Therefore, such glasses can be carriers of therapeutic ions for composite biomaterials, and are expected to enhance bone regeneration. Fibrous anisotropic scaffolds containing the designed glass have also been developed for the simultaneous reconstruction of bone quantity and quality. These scaffolds were enhanced to encourage bone formation by releasing ions from the glass, which controlled bone quality by direction of the calcified tissue in a single direction. Therefore, PIGs are expected to expand into various biomedical fields, as they can be tailored to have different properties according to their glass network structure.