Abstract
3D printing emerged as a potential game-changer in the field of biomedical engineering. Robocasting in particular has shown excellent capability to produce custom-sized porous scaffolds from pastes with suitable viscoelastic properties. The materials and respective processing methods developed so far still need further improvements in order to obtain completely satisfactory scaffolds capable of providing both the biological and mechanical properties required for successful and comprehensive bone tissue regeneration. This work reports on the sol-gel synthesis of an alkali-free bioactive glass and on its characterization and processing ability towards the fabrication of porous scaffolds by robocasting. A two-fold increase in milling efficiency was achieved by suitably adjusting the milling procedures. The heat treatment temperature exerted a profound effect on the surface area of mesoporous powders. Robocasting inks containing 35 vol.% solids were prepared, and their flow properties were characterized by rheological tests. A script capable of preparing customizable CAD scaffold geometries was developed. The printing process was adjusted to increase the technique’s resolution. The mechanical properties of the scaffolds were assessed through compressive strength tests. The biomineralization ability and the biological performance were assessed by immersing the samples in simulated body fluid (SBF) and through MTT assays, respectively. The overall results demonstrated that scaffolds with macro porous features suitable for bone ingrowth (pore sizes of ~340 μm after sintering, and a porosity fraction of ~70%) in non-load-bearing applications could be successfully fabricated by 3D printing from the bioactive glass inks. Moreover, the scaffolds exhibited good biomineralization activity and good biocompatibility with human keratinocytes, suggesting they are safe and thus suited for the intended biomedical applications.
Highlights
Subtractive manufacturing, consisting of removing, treating, and shaping a feed material into a product with desired properties and shapes, has been the paradigm in manufacturing and industrial processes
In the recent past, technological developments in the manufacturing and digital fields have led to the candidacy of additive manufacturing (AM) as a potential gateway into a new industrial revolution [1]
Perhaps the biggest impact of AM is its ability to create intricate and customizable geometries not feasible through traditional methods, which is useful when coupled with finite element method (FEM) analysis to produce more efficient parts, to model unique designs for expositions, or to produce extremely precise implants that can be custom-fitted into patients, opening up a whole new paradigm in biomedical engineering, the regulation and success rate of these custom devices presents a possible legal nightmare [1]
Summary
Subtractive manufacturing, consisting of removing, treating, and shaping a feed material into a product with desired properties and shapes, has been the paradigm in manufacturing and industrial processes. Robocasting is a 3D printing technique that uses a triaxial (XYZ) dispenser to extrude a polymeric, metallic, or ceramic slurry in a layer-by-layer fashion, and the extruded filament fuses with the existing layers. This simple technique relies mostly on the viscoelastic properties of the pastes, which impose design limitations since arching or overhanging features as well as hollow segments are impossible to reproduce without the use of supporting or sacrificial materials. This simplicity allows, great flexibility in the choice of printing materials [12]. Cesarano et al [14] established three criteria that a ceramic ink should follow:
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