Abstract
The international standard ISO 23317:2014 for the in vitro testing of inorganic biomaterials in simulated body fluid (SBF) uses TRIS buffer to maintain neutral pH. In our previous papers, we investigated the interaction of a glass–ceramic scaffold with TRIS and HEPES buffers. Both of them speeded up glass–ceramic dissolution and hydroxyapatite (HAp) precipitation, thereby demonstrating their unsuitability for the in vitro testing of highly reactive biomaterials. In this article, we tested MOPS buffer (3‐[N‐morpholino] propanesulfonic acid), another amino acid from the group of “Goods buffers”. A highly reactive glass–ceramic scaffold (derived from Bioglass®) was exposed to SBF under static–dynamic conditions for 13/15 days. The kinetics and morphology of the newly precipitated HAp were studied using two different concentrations of (PO4)3− ions in SBF. The pH value and the SiIV, Ca2+, and (PO4)3− concentrations in the SBF leachate samples were measured every day (AAS, spectrophotometry). The glass–ceramic scaffold was monitored by SEM/EDS, XRD, WD‐XRF, and BET before and after 1, 3, 7, 11, and 13/15 days of exposure. As in the case of TRIS and HEPES, the preferential dissolution of the glass–ceramic crystalline phase (Combeite) was observed, but less intensively. The lower concentration of (PO4)3− ions slowed down the kinetics of HAp precipitation, thereby causing the disintegration of the scaffold structure. This phenomenon shows that the HAp phase was predominately generated by the presence of (PO4)3− ions in the SBF, not in the glass–ceramic material. Irrespective of this, MOPS buffer is not suitable for the maintenance of pH in SBF.
Highlights
In accordance with ISO 23317:2014 (International Organization for Standardization, 2014), newly developed biomaterials intended for bone replacement must be tested in vitro with simulated body fluid (SBF)
We reported the use of TRIS and HEPES buffers for the in vitro testing of an inorganic glass–ceramic scaffold (Rohanová et al, 2011, 2018)
The interaction of the tested material with MOPS and influence of the kinetics of HAp formation were observed in two solutions: simulated body fluid (SBF + MOPS) and SBF with a reduced concentration of (PO4)3− ions (SBF 70P + MOPS)
Summary
In accordance with ISO 23317:2014 (International Organization for Standardization, 2014), newly developed biomaterials intended for bone replacement must be tested in vitro with simulated body fluid (SBF). Taha and Lee (2010) conclude that many experiments have failed because of the imperfections of the buffers employ They studied the ionic interaction from volumetric investigation, for example, MOPS in aqueous solutions of NaCl or KCl. ionic interactions in the biological system (de Carvalho Dias et al, 2016) and the kinetics of calcium phosphate precipitation (biomineralization) could be affected by a choice of the buffer system. Miyaji, Kokubo, Ohtsuki, and Nakamura (1995) studied the contribution of the P2O5 to the SBF supersaturation exposed in acellular SBF with the TRIS buffer They observed a little difference in the rates of ion dissolution and of apatite formation between Bioglass 45S5 and P2O5 free Na2O-CaO-SiO2 glass and confirmed bioactivity of P2O5 free glasses. The interaction of the tested material with MOPS and influence of the kinetics of HAp formation were observed in two solutions: simulated body fluid (SBF + MOPS) and SBF with a reduced concentration of (PO4)3− ions (SBF 70P + MOPS)
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More From: Journal of biomedical materials research. Part B, Applied biomaterials
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