Tereza Přívracká is a PhD student at the University of Chemistry and Technology, Prague (Department of Glass and Ceramics). Her research focuses on glass corrosion, bioactive glasses, and glass–solution interactions, including the effects of solution composition on glass dissolution and in vitro bioactivity.

Simulated body fluid (SBF) is commonly used for in vitro testing of bioactive materials, and its preparation is described in ISO 23317:2025. Previous studies have shown that TRIS buffer, used to maintain the pH of SBF, is not inert but accelerates the dissolution of bioactive glass and glass-ceramics and promotes the precipitation of hydroxyapatite (HAp)1,2.

This work aimed to study the effects of TRIS and HEPES buffers on the dissolution of Bioglass 45S5 and the formation of HAp. Bulk samples were tested in unbuffered SBF, TRIS-buffered SBF (ISO 23317:2025), and HEPES-buffered SBF. Glass dissolution and HAp formation were evaluated using ICP-OES, SEM/EDS, XRD, and FTIR. Both buffers significantly accelerated glass dissolution and Ca–P layer formation. Approximately 30 mg of Ca–P phase was formed in TRIS-buffered SBF and 10–13 mg in HEPES-buffered SBF (Fig.1), compared with only 1–3 mg in unbuffered SBF. Crystalline HAp was detected only in buffered solutions.

These results demonstrate that TRIS and HEPES are not inert components of SBF but actively interact with Bioglass 45S5. These buffers can affect in vitro bioactivity tests, leading to false-positive results. Therefore, the current approach to in vitro bioactivity testing of reactive biomaterials needs to be reconsidered, with more attention to interactions between the material and the testing solution.

1. D. Rohanová et al., Acta Biomaterialia. 7, 2623(2011) DOI: 10.1016/j.actbio.2011.02.028
2. D. Rohanová et al., J. Biomed. Mater. Res. B Appl. Biomater. 106, 143(2018) DOI: 10.1002/jbm.b.33818