Towards bone regeneration: Hybrid sol-gel and spray-drying production of bioactive glass for additive manufacturing

Scaling up the production of bioactive glasses for bone tissue engineering while preventing crystallisation remains a critical challenge. Achieving a strictly amorphous state is essential for optimal bioactivity, yet conventional large-scale thermal treatments often trigger phase separation or crystallisation. To address this issue, this work develops a novel, scalable, and fully aqueous sol-gel synthesis combined with a spray-drying process, capable of producing a quasi-amorphous 68S-like silicate bioactive glass powder (69.33 SiO2, 24.39 CaO, 4.87 P2O5, 1.41 Na2O, in wt.%) at a 0.5 kg per day scale. By using low-cost water glass as both the silica and sodium precursor, rapid and eco-friendly gelation is achieved. Beyond the mere scale-up of the process, a key technological advance of this route lies in the optimization of a washing protocol. This step systematically removes nitrate by-products and stabilizes the low-sodium amorphous network, effectively suppressing crystallisation pathways during subsequent calcination at 500°C. This stable amorphous product exhibits exceptional bioactivity, triggering accelerated biomimetic hydroxyapatite growth within one day of incubation in Simulated Body Fluid (SBF). Furthermore, the spray-dried powder possesses optimised particle morphology and physicochemical properties specifically tailored for vat photopolymerisation. Complex, high-resolution 3D bone scaffolds were successfully printed by stereolithography (SLA) to demonstrate the usefulness of the synthesized powder. This sustainable manufacturing route effectively bridges the gap between fundamental glass science and advanced additive manufacturing, offering an economically viable pathway towards highly bioactive, patient-specific clinical grafts.