Introduction:​ Currently there are approximately two million bone defect cases treated annually worldwide with a projection to increase yearly. While bone has the ability to heal spontaneously, some defects require surgical intervention using natural or synthetic grafts to facilitate bone regeneration. Bioglass 45S5 is an inorganic, material commonly utilized as a grafting material due to its favorable osteoconductive, osteoinductive, resorption capabilities. Combined with 3D printing to fabricate three-dimensional structures can enhance the bone regenerative properties of the material. This study aimed to characterize Bioglass 45S5 scaffolds and compare its chemical and physical properties to traditional material, β-TCP.

Materials & Methods:​ Raw Bioglass 45S5 powder was synthesized using the sol-gel method. Bioglass 45S5 and β-TCP powders were fabricated into colloidal gel suspensions to be used for 3D printing. The scaffolds were designed using CAD software and fabricated using a custom-built 3D printer. After synthesizing and before extruding, the colloidal gels were subjected to an amplitude oscillation test to evaluate their rheological properties. Thermogravimetric analysis (TGA) was performed on green-state and sintered materials to measure weight loss as a function of heating. X-Ray diffraction (XRD) spectra were collected to identify the crystalline phases and Fourier Transform Infrared Spectrometer (FTIR) was performed to identify functional groups and covalent bonding. Microcomputed Topography (micro-CT) scans were collected from both Bioglass 45S5 and β-TCP scaffolds (n=6/group) to perform 3D reconstruction and measure free volume. Scanning Electron Microscopy (SEM) was used to observe surface and cross-sectional morphology as well as perform EDS Elemental Analysis.

Results:​ The oscillation amplitude test yielded both gels to be within the appropriate range for extrusion, e.g., shear thinning, through a thin orifice. The Bioglass 45S5 colloidal gel had a higher storage modulus relative to that of β-TCP. TGA profiles of both green-state Bioglass 45S5 and βTCP showed a higher decrease in weight % relative to their sintered counterparts. The TGA profile of green-state Bioglass 45S5 yielded a higher decrease of weight % relative to the green-state βTCP. XRD spectra for Bioglass 45S5 indicated characteristic peaks for Ca3Na6O18Si6, while the spectra for β-TCP yielded peaks that are representative of the ceramic. Both spectra indicate that Bioglass 45S5 and β-TCP crystallized after sintering. FTIR spectra for Bioglass 45S5 show peaks that correspond to Si-O stretching, Si-O bonding, P-O bending bonds, and carbonate group. The FTIR spectra of β-TCP show the peaks that correspond to PO4 and P2O7 groups. The free volume % of Bioglass 45S5 was relatively higher than that of β-TCP.

Conclusion:​ Raw β-TCP and Bioglass were both fabricated into colloidal gel suspensions, successfully printed and subsequently completed physiochemical analysis. After printing and postprocessing, scaffolds maintained the desired geometrical structure. XRD and FTIR spectra confirmed the chemical and crystalline representative characteristics of Bioactive 45S5, confirming successful synthesis. EDS elemental analysis confirmed the presence of respective elements in Bioglass 45S5 and β-TCP. Volumetric analysis and SEM images indicated that Bioglass 45S5 was associated with a higher porosity relative to β-TCP. Further studies, specifically in vitro cellular studies, need to be conducted to assess if a higher porosity and surface area are favorable for improving bone regeneration.