• Brückner, Raika
• Brauer, Delia S.
• Hupa, Leena
• Tylkowski, Maxi

Abstract

Partially substituting one alkali oxide for another reduces thecrystallisation tendency and improves the processing of bioactiveglasses. Here, we investigate how we can use alkali ions of varyingionic radii to control glass degradation and ion release from Bioglass45S5. Partially replacing sodium by lithium reduced ion release instatic and dynamic dissolution studies in Tris buffer, while ion releaseincreased with increasing potassium for sodium substitution. While themixed alkali effect is known to reduce ion release from conventionalsilicate glasses (compared to compositions containing one alkali oxideonly), in the glasses studied here ion release was controlled by thepacking of the silicate network, described by glass molar volume andoxygen density. Incorporating an alkali ion of smaller ionic radius (Lifor Na or Na for K) resulted in a more compact network of higher oxygendensity, which reduced ion release. On the other hand, an alkali ion oflarger ionic radius (K for Na or Na for Li) expanded the silicatenetwork, allowing for faster ion release. This can be explained by watermolecules penetrating an expanded silicate network more easily than amore compact one, thereby directly influencing the ion exchange betweenmodifier ions and protons from the dissolution medium. This shows thatthe use of modifier ions of varying ionic radii allows for tailoringbioactive glass ion release and degradation while maintaining silicatenetwork polymerisation and network connectivity. And, indeed, recentliterature suggests that this concept can be extended to other modifiersbesides alkali metal ions, making it possible to design bioactiveglasses of tailored solubility.

Topics

• density
• impedance spectroscopy
• glass
• glass
• Sodium
• Potassium
• Lithium
• molar volume