Structural, mechanical and biological characteristics of 3D printed implants – ups and downs

abstract

English

The objective of the profiBONE project is to establish close multidisciplinary cooperation between Czech and Icelandic partners with a focus on research and development of biofunctionalized polymer-ceramic ink for low- temperature 3D printing of patient-specific bone implants. The premise is to improve the mechanical, degradation, osteoinductive, and antibacterial properties of bone implants by modifying the ceramic cement with a binder based on biodegradable synthetic polymers, bioactive polysaccharides, and proteins. The advantage of this approach is avoiding the denaturation conditions such as radiation (laser or UV) or high temperatures. The whole process takes place at laboratory temperature (printing) or at 37 °C (curing of the final product). Therefore, it is possible to add bioactive additives directly to the paste during printing without losing their biological activity. This procedure also guarantees an even distribution of bioactive substances in the implant, which positively affects their release and the complex function of the implant. Within the profiBone project, we modified the input composite bone paste for printing (already developed at CEITEC) with bioactive polymers (e.g., chitosan provided by Genís h.f.) and proteins (mainly osteoinductive and antibacterial provided by Czech institutions) to achieve desired properties. The implant must be fully resorbable at a rate corresponding to the healing of the defect and will be fully replaced by newly formed functional bone tissue. Consequently, we have created and developed a new CAD program and custom G-codes for designing and printing samples with defined porosity and structure. The parameters of both the printer and the composite paste were optimized for direct 3D printing of samples with different extrusion coefficients, compositions, degradation times, and mechanical properties. For example, we have provided mechanical tests under compressive loading to determine their compressive strength, elastic gradient, absorbed energy, and energy absorption efficiency (IceTec and CTU Prague). The results showed that the use of different internal structures greatly affects not only the resulting mechanical properties but also the suitability for cell seeding, where the original regular structure was inappropriate. The modified structure prevented cells from falling through the scaffolds and ensured the uniform inoculation of the materials with SAOS-2 cells for all types of samples with different internal porosity. The in vitro biocompatibility tests on differentiated bone cells and mesenchymal stem cells are being performed gradually. The osseointegration properties of the printed implants are monitored using an established rat femur bone defect model and are tested on a new rat parietal cranial bone defect model.

resorbable bone cement, low-temperature 3D printing, bioactive polymers, thermosensitive polymers, cells

VOJTOVÁ, L.; VIŠTEJNOVÁ, L.; ÖRLYGSSON, G.; CHUEN HOW, N.; HLINÁKOVÁ, K.; LYSÁKOVÁ, K.; KLEIN, P.; ŽÍDEK, J.; MENČÍK, P.; PŘIKRYL, R.; SEDLÁČEK, R.; VLTAVSKÝ, M.; SUCHÝ, T.

21. 8. 2022

Iceland

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