TRIS buffer in simulated body fluid distorts the assessment of glass–ceramic scaffold bioactivity

Dana Rohanová¹, Aldo Roberto Boccaccini^2,3, Darmawati Mohamad Yunos², Diana Horkavcová¹, Iva Březovská¹, Aleš Helebrant¹

¹Department of Glass and Ceramics, Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic, ²Department of Materials, Imperial College, London, Prince Consort Road, London SW7 2BP, UK,³Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen–Nuremberg, 91058 Erlangen, Germany

Acta Biomaterialia 7, (2011) 2623-2630, IF=5.093

The bioactive materials are often tested in simulated body fluid (SBF). This solution is mimicking the inorganic part of blood plasma and it is usually buffered with tris-(hydroxymethyl) aminomethane (TRIS). The presented study demonstrated the significant effect of the TRIS on interaction between the bioactive material and SBF which could influence the in vitro tests of bioactivity of biomaterials.

The glass-ceramic scaffold derived from Bioglass (containing 77 wt.% of crystalline phases Na₂O.2CaO.3SiO₂ and CaO.SiO₂ and 23 wt.% of residual glass phase) was leached in different solutions. The glass-ceramic scaffold was exposed to a series of in vitro tests using different media as follows: (i) a fresh liquid flow of SBF containing tris (hydroxy-methyl) aminomethane; (ii) SBF solution without TRIS buffer; (iii) TRIS buffer alone; and (iv) demineralised water. The original results of SBF-scaffold interaction were found. SBF buffered with TRIS dissolved both the crystalline and residual glass phases of the scaffold and a crystalline form of hydroxyapatite (HAp) developed on the scaffold surface. In contrast, when TRIS buffer was not present in the solutions only the residual glassy phase dissolved and an amorphous calcium phosphate (Ca-P) phase formed on the scaffold surface. It was confirmed that the TRIS buffer primarily dissolved the crystalline phase of the glass-ceramic, doubled the dissolving rate of the scaffold and moreover supported the formation of crystalline HAp. This significant effect of the buffer TRIS on bioactive glass-ceramic scaffold degradation in SBF has not been demonstrated previously and should be considered when analysing the results of SBF immersion bioactivity tests of such systems.

The tested material was prepared by co-authors at Imperial College. The interaction of this material with simulated body fluids was studied at Dept. of Glass and Ceramics ICT Prague. The interpretation of interaction between scaffold and different solutions was based on discussion of all authors.