Effects of curing and organic content on bioactivity and mechanical properties of hybrid sol–gel glass scaffolds made by indirect rapid prototyping
- 219 Downloads
We employed indirect rapid prototyping templating to fabricate bioactive and macroporous scaffolds for bone regeneration. This templating technique utilizes lost molds made of polycaprolactone by fused deposition modeling, in which the organic/ inorganic hybrid silica sol was filled and cured. Finally, the molds were dissolved and extracted, and the remaining macroporous hybrid glass constructs were recovered. The hybrid glass scaffolds offered a fully interconnected pore structure with 63–72% porosity measured by N2-pycnometry and Hg-intrusion. In bioactive sol–gel glasses one issue is the insufficient and inhomogeneous incorporation of calcium (II) ions. To address this problem we varied the curing conditions and tested the effect of the organic crosslinker on calcium retention. We strengthened the silica network by covalent crosslinking with trimethylolpropane ethoxylate which was functionalized with 3-(triethoxysilyl)propyl isocyanate. Those scaffolds showed compressive yield strengths of up to 12.7 MPa and compressive moduli between 18 and 288 MPa. Energy dispersive X-ray spectroscopy showed that a crosslinker content of 60% in the hybrids resulted in a homogeneous calcium distribution in the glass, in contrast to 40% where we found a layer of CaCl2 on the scaffold surface. The materials exhibited bioactivity in simulated body fluid which was monitored by scanning electron microscopy and X-ray powder diffraction.
KeywordsBinary Ternary Mechanical testing Bioactive Class-II hybrid Indirect rapid prototyping
The authors thank Prof. Dr.-Ing. Bernhard Rieger (Department of Mechanical and Energy Engineering, HTWK Leipzig, Germany) for access to the compression testing equipment, Jörg Lenzner (Department of Experimental and Semiconductor Physics, Leipzig University) for access to SEM and EDX. The authors would also like to thank the Saxon Ministry for Science and Arts (Grant no: 4-7531.60/64/18) and the German Research Council (DFG SFB/Transregio 67 A1) for financial support.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
- 1.Department of Health and Human Services, Food and Drug Administration. (2004) 510(k) Summary: NovaBone-AR-Resorbable Bone Graft Substitute. https://www.accessdata.fda.gov/cdrh_docs/pdf4/K041613.pdfGoogle Scholar
- 2.Bobyn JD, Mortimer ES, Glassman AH, Engh CA, Miller JE, Brooks CE (1992) Producing and avoiding stress shielding-laboratory and clinical observations of noncemented total hip arthroplasty. Clin Orthop Relat Res 274:79–96.Google Scholar
- 13.Hendrikx S, Kascholke C, Flath T, Schumann D, Gressenbuch M, Schulze P, Hacker MC et al. (2016) Indirect rapid prototyping of sol-gel hybrid glass scaffolds for bone regeneration - effects of organic crosslinker valence, content and molecular weight on mechanical properties. Acta Biomater 35:318–329CrossRefGoogle Scholar
- 18.Saravanapavan P, Jones JR, Verrier S, Beilby R, Shirtliff VJ, Hench LL, Polak JM (2004) Binary CaO-SiO2 gel-glasses for biomedical applications. Bio Med Mater Eng 14:467–486Google Scholar
- 32.Poologasundarampillai G, Yu B, Tsigkou O, Valliant EM, Yue S, Lee PD, Hamilton RW et al. (2012) Bioactive silica–poly(γ-glutamic acid) hybrids for bone regeneration: effect of covalent coupling on dissolution and mechanical properties and fabrication of porous scaffolds. Soft Matter 8:4822CrossRefGoogle Scholar
- 34.Brinker CJ, Scherer GW (1993) Sol-gel science: the physics and chemistry of sol-gel processing, 5th edn. Academic, Boston, MAGoogle Scholar
- 41.Hall BK (ed.) (1993) Mechanical properties of cortical and trabecular bone. CRC, London, TokyoGoogle Scholar