Direct ink writing of highly bioactive glasses

Abstract

Graphical Abstract 5 6 7 Key words 8 Robocasting, direct ink writing, scaffold, Bioglass, amorphous, bone repair 9 10 Abstract 11 Direct ink writing (DIW) or Robocasting, is an additive manufacturing technique that offers the 12 opportunity to create patient specific bioactive glass scaffolds and high strength scaffolds for bone 13 repair. The original 45S5 Bioglass® composition crystallises during sintering and until now, robocast 14 glass scaffolds contained at least 51.9 mol% SiO2 or B2O3 to maintain their amorphous structure. 15Here, ICIE16 and PSrBG compositions, containing < 50 mol% SiO2, giving silicate network connectivity 16 close to that of 45S5, were robocast and compared to 13-93 composition. Results showed Pluronic F-17 127 can be used as a universal binder regardless of glass reactivity and that particle size distribution 18 affected the ink "printability". Scaffolds with interconnects of 150 µm (41-43% porosity) had 19 compressive strengths of 32-48 MPa, depending on the glass composition. Robocast scaffolds from 20 these highly reactive bioactive glasses promise greatly improved bone regeneration rates compared 21 with existing bioactive glass scaffolds. 22

Processing methods for making porous bioactive glass‐based scaffolds—A state‐of‐the‐art review

“…Robocast glass scaffolds can exhibit considerably high compressive strength, in most cases higher than that of cancellous bone (from 13 to 142 MPa, which is even higher than the strength of cortical bone 138 ). Using particle size ranging from 30 µm down to 1 µm and extrusion nozzles with diameters between 100 and 580 µm, it is possible to obtain glass structures having total porosity within 50-70 vol.% and pore dimensions varying from few hundreds of micrometers up to half a millimeter.…”

“…138 If glass particles are dispersed in the solution, Pluronic stabilizes them sterically by generating Van der Waals or hydrogen bonding with the surface of the particles using the hydroxyl groups in the polymeric chains. At a temperature around 0°C, Pluronic forms a liquid solution in water because it adsorbs on the polymer, extending the chains and making them to slide across each other.…”

“…When the temperature rises up to 40°C, the adsorption of water is energetically unfavorable and the polymeric chains form micelles and the solution changes from a fluid state to the gel one. 138 If glass particles are dispersed in the solution, Pluronic stabilizes them sterically by generating Van der Waals or hydrogen bonding with the surface of the particles using the hydroxyl groups in the polymeric chains. 136 It was observed that the presence of glass particles inside the Pluronic suspension lowers the temperature at which the state transition takes place.…”

“…135 A similar method was also used by Fu et al 136 to robocast high-strength 13-93 glass scaffolds. Substrates for printing in the air can be composed of only one layer: For example, Nommeots-Nomm et al 138 used commercial acetate sheets that are perfectly flat, cheap, and allow easy detachment of the printed structures after drying.…”

Robocasting: Prediction of ink printability in solgel bioactive glass

“…The intrinsic porosity of a solgel derived bioactive glass powder is a new critical feature, the effects of which need to be addressed. Direct ink writing of melt‐quenching glasses was already studied and is reasonably well documented . To the best of the authors’ knowledge, the processing of solgel glasses by robocasting was not yet investigated so far.…”