Development of Borate-based Bioactive Glass Powders for the Additive Manufacturing of Resorbable Bone Implants

Abstract

This work reports the development of an optimised melt-quenching protocol for the synthesis of borate-based bioactive glass. The precursor mixture, prepared by an aqueous route and dried by spray drying, was thermally pretreated and subsequently melted using a “flash-melting” method, enabling high yields while limiting oxide evaporation. The properties of the as-obtained glass were subsequently investigated to validate its suitability for additive manufacturing in tissue engineering and regenerative medicine. XRD and FTIR analyses confirmed the amorphous nature of the glass and the formation of borate-phosphate network. Subsequent heat treatments confirmed the incorporation of the different oxides into the glass network, with the crystallisation of calcium and magnesium borate phases as well as a Na-Ca-Mg phosphate phase. Bioactivity was assessed by immersion of the glass in simulated body fluid, revealing the formation of an apatite-type phase after a few days. Indirect cytotoxicity tests revealed a severe cytotoxic response of glass extracts, highlighting the strong reactivity of borate-based bioactive glasses.

Partial dissolution of the quartz crucible during melting resulted in minor silicate contamination, highlighting the need for further investigation into more chemically inert crucible materials to achieve finer compositional control.

After optimisation of the grinding process, the glass powder was incorporated into a DLP (Digital Light Processing)-compatible slurry for the 3D printing of gyroid scaffolds. Printing showed to be feasible. However, printing, debinding and sintering parameters have to optimised to minimise diffusion effect during printing and efficiently remove carbon traces in final scaffolds respectively.