Abstract
Bioactive glass scaffolds are used in bone and tissue biomedical implants, and there is great interest in their fabrication by additive manufacturing/3D printing techniques, such as robocasting. Scaffolds need to be macroporous with voids ≥100 m to allow cell growth and vascularization, biocompatible and bioactive, with mechanical properties matching the host tissue (cancellous bone for bone implants), and able to dissolve/resorb over time. Most bioactive glasses are based on silica to form the glass network, with calcium and phosphorous content for new bone growth, and a glass modifier such as sodium, the best known being 45S5 Bioglass®. 45S5 scaffolds were first robocast in 2013 from melt-quenched glass powder. Sol–gel-synthesized bioactive glasses have potential advantages over melt-produced glasses (e.g., greater porosity and bioactivity), but until recently were never robocast as scaffolds, due to inherent problems, until 2019 when high-silica-content sol–gel bioactive glasses (HSSGG) were robocast for the first time. In this review, we look at the sintering, porosity, bioactivity, biocompatibility, and mechanical properties of robocast sol–gel bioactive glass scaffolds and compare them to the reported results for robocast melt-quench-synthesized 45S5 Bioglass® scaffolds. The discussion includes formulation of the printing paste/ink and the effects of variations in scaffold morphology and inorganic additives/dopants.
Highlights
Robocasting is an additive manufacturing or 3D printing technique, in which designed 3D structures are built layer-by-layer by extruding a continuous filament of a paste/printing ink from a nozzle, guided by an automated computerized system (Figure 1) [1]
The extrusion speed and scaffold shape and size are all controlled by a computer-aided design–computer-aided manufacturing (CAD–CAM) [7] model, deposited layer-by-layer as a 3D structure [8] from an ink or paste formulated from a powder with liquid and polymeric additives
This because sol–gel-derived bioactive glasses results have proven problematic for robocasting, as surface areaisand porous structure of the glass powder in absorption of a significant portion the high specific surface area and porous structure of the glass powder results in absorption of a of the dispersing liquid from the suspension, impeding paste/ink formulation and greatly reducing significant portion of the dispersing liquid from the suspension, impeding paste/ink and printability
Summary
Robocasting is an additive manufacturing or 3D printing technique, in which designed 3D structures are built layer-by-layer by extruding a continuous filament of a paste/printing ink from a nozzle, guided by an automated computerized system (Figure 1) [1]. The extrusion speed and scaffold shape and size are all controlled by a computer-aided design–computer-aided manufacturing (CAD–CAM) [7] model, deposited layer-by-layer as a 3D structure [8] from an ink or paste formulated from a powder with liquid and polymeric additives. Figure in-situ images imagesof ofthe therobocasting robocastingprocess processwithin within bath, and Figure 1
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