Objectives: Wnt/β-catenin signalling plays important roles in regeneration, particularly in hard tissues such as bone and teeth, and can be regulated by small molecule antagonists of glycogen synthase kinase 3 (GSK3); however, small molecules can be difficult to deliver clinically. Lithium (Li)is also a GSK3 antagonist and can be incorporated into bioactive glasses (BG), which can be used clinically in dental and bone repair applications and tuned to quickly release their constituent ions. Methods: Here, we created phosphate (P)- and borate (B)-based BG that also contained Li (LiPBG and LiBBG)and examined their ion release kinetics and the toxicity of their dissolution ions on mouse 17IA4 dental pulp cells. Results: We found that although LiPBG and LiBBG can both quickly release Li at concentrations known to regulate Wnt/β-catenin signalling, the P and B ions they concomitantly release are highly toxic to cells. Only when relatively low concentrations of LiPBG and LiBBG were placed in cell culture medium were their dissolution products non-toxic. However, at these concentrations, LiPBG and LiBBG's ability to regulate Wnt/β-catenin signalling was limited. Significance: These data suggest that identifying a BG composition that can both quickly deliver high concentrations of Li and is non-toxic remains a challenge.
Zhang, K., Alaohali, A., Sawangboon, N., Sharpe, P. T., Brauer, D. S., & Gentleman, E. (2019). A comparison of lithium-substituted phosphate and borate bioactive glasses for mineralised tissue repair. Dental Materials, 35(6), 919–927. https://doi.org/10.1016/j.dental.2019.03.008