Lithium-silicate sol\u2013gel bioactive glass and the effect of lithium precursor on structure\u2013property relationships

Anthony L B Maçon,Sergio Bertazzo,Julian R Jones,John V Hanna,Molly M Stevens,Samuel J Page,Siwei Li,Manon Jacquemin

doi:10.1007/s10971-016-4097-x

Abstract

This work reports the synthesis of lithium-silicate glass, containing 10 mol% of Li_2O by the sol–gel process, intended for the regeneration of cartilage. Lithium citrate and lithium nitrate were selected as lithium precursors. The effects of the lithium precursor on the sol–gel process, and the resulting glass structure, morphology, dissolution behaviour, chondrocyte viability and proliferation, were investigated. When lithium citrate was used, mesoporous glass containing lithium as a network modifier was obtained, whereas the use of lithium nitrate produced relatively dense glass-ceramic with the presence of lithium metasilicate, as shown by X-ray diffraction, ^{29}Si and ^7Li MAS NMR and nitrogen sorption data. Nitrate has a better affinity for lithium than citrate, leading to heterogeneous crystallisation from the mesopores, where lithium salts precipitated during drying. Citrate decomposed at a lower temperature, where the crystallisation of lithium-silicate crystal is not thermodynamically favourable. Upon decomposition of the citrate, a solid-state salt metathesis reaction between citrate and silanol occurred, followed by the diffusion of lithium within the structure of the glass. Both glass and glass-ceramic released silica and lithium ions in culture media, but release rate was lower for the glass-ceramic. Both samples did not affect chondrocyte viability and proliferation.Graphical

Highlights

Lithium has been used clinically for more than half a century as a mood stabilising oral drug [1]
Upon the addition of the lithium precursors, the pH of the solution containing lithium citrate increased from 1 to 5.3, whereas no change was observed with lithium nitrate or 100S
Differences in gelation were noticed between the two solutions: (1) The sol containing lithium nitrate gelled in 3 days, which was expected as the condensation reaction is the limiting reaction in the sol–gel process when performed at a pH \ 2 [30]; (2) the sol containing lithium citrate gelled in 1 h

Summary

Introduction

Lithium has been used clinically for more than half a century as a mood stabilising oral drug [1]. J Sol-Gel Sci Technol (2017) 81:84–94 formation of proteoglycan-rich extracellular matrix in chondrogenic culture of mesenchymal stem cells. These findings are of particular interest since cartilage is one of the most challenging tissues to regenerate, since it is avascular. Lithium has been incorporated into ordered mesoporous sol–gel glass scaffolds (Li-MBG, 80 mol% SiO2; 10 mol% CaO, 5 mol% P2O5 and 5 mol% Li2O) [12,13,14]. The release of lithium from Li-MBG had a beneficial effect on the proliferation and cementogenic differentiation of human periodontal ligament-derived cells via the activation of Wnt and SHH signalling pathways. Li-MBG enhanced the regeneration of osteochondral defects in rabbits compared to Li-free MBG

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Conclusion