Novel Si-O-M-C (M= Sr, Zn, and B) bioactive glasses with outstanding high temperature crystallization resistance
Final Report Abstract
The present project has assessed the preparative access as well as the structure-bioactivity correlation in SiOC based materials. On one hand, the SiOC network architecture and phase composition have been modulated upon incorporation of additional elements. On the other hand, sol-gel method has been applied to synthesize SiOC materials with tunable specific surface area / porosity. The bioactivity of SiOC, assessed upon immersion in SBF solution, has been correlated to these structural features, i.e., network architecture, phase composition and porosity. The network architecture of SiOC can be modified in two ways: (i) network depolymerization by forming non-bridging-oxygens; (ii) tuning of the network carbon to network oxygen ratio. SiOC network can be depolymerized by incorporating alkaline earth metals (e.g., Ca), which act as network modifier. A slight depolymerization of SiOC network has a significant effect on improving the SiOC bioactivity upon SBF immersion. Furthermore, the network carbon to network oxygen ratio can be effectively decreased via incorporation of a small amount of boron, which acts as network former. However, a decrease of network connectivity related to the change of the network carbon to network oxygen ratio has only a slight effect on the SiOC bioactivity. The porosity of SiOC can be tuned by Ca modification via sol-gel process. The introduction of a Ca modifier (e.g., calcium nitrate) modifies the porosity of the xerogel precursors and subsequently the porosity of the resulting SiOC materials. In this way, mesoporous SiOC glassy materials possessing high specific surface area can be achieved. With increasing Ca content, gas evolution upon the decomposition of Ca modifier plays an important role on increasing the pore size in the resulting SiOC and macroporous SiOC can be obtained. At very high Ca content, calcium silicate crystallization dominates and its sintering at pyrolysis temperature closes pores and leads to nonporous SiOC based glass-ceramic. The porosity of SiOC materials is correlated to their varying specific surface area, which influences their bioactivity upon SBF immersion. Since the interaction between biomaterials and SBF solution occurs at the material surface, high specific surface area is beneficial for achieving high bioactivity. Correspondingly, the investigated mesoporous SiOC shows higher bioactivity than macroporous SiOC. The biological evaluation of the silicate-based and SiCaOC systems has demonstrated promising biocompatible behavior on bone precursor cells survivability and fibroblasts. Additionally, the boron and strontium containing materials promoted the secretion of VEFG significantly, a finding that was not observed in bare SiCaOC and 45S5. Moreover, a positive effect of the incorporated ions was detected compared to the reference glasses without a significant difference between the type of material (silicate or silicon oxycarbide). Further analysis needs to be completed on the osteogenic differentiation level to state differences between the type of glass as well as the individual effect of the doping ions. In conclusion, tailor-made network architecture, phase composition and porosity in SiOC glasses and glass-ceramics have been shown to provide improved bioactivity. Besides the influence on apatite forming ability, the depolymerization of SiOC network can tune Si release kinetics. It is expected that a phase composition design with therapeutic ions will induce therapeutic ion release; hence, the porosity of SiOC can be utilized for drug delivery or transport of growth factors. All these aspects should be assessed in a cellular environment in the future, in order to achieve a more comprehensive understanding of the structure-bioactivity correlation for SiOC materials. Future collaborative activities anticipated by the project partners may be focused on the investigation of cellular responses to released ions, particularly Si, Sr and B, from SiOC materials. A correlation of osteogenic and angiogenic effects to material structure would be crucial for designing clinically applicable bioactive SiOC materials. The FAU research group has started investigations in this regard. Furthermore, the high processability of SiOC precursors should be made use of to synthesize bioactive structures, such as 3D scaffolds or coatings. Particularly, wet-chemically based coating techniques, such as dipcoating or spin-coating, will be taken into consideration, since sol-gel method proves to be suitable for synthesizing Ca modified SiOC materials.
Publications
-
“Structure, energetics and bioactivity of silicon oxycarbide-based amorphous ceramics with highly connected networks”. J. Eur. Ceram. Soc. 2018, 38, 1311-1319
E. Ionescu, S. Sen, G. Mera, A. Navrotsky
-
"Apatite forming ability and dissolution behavior of boron- and calcium-modified silicon oxycarbides in comparison to silicate bioactive glass". ACS Biomaterials Sci. Eng. 2019, 5, 5337
F. Xie, I. Gonzalo, M. Ospina, R. Riedel, A. R. Boccaccini, E. Ionescu,
-
"Facile preparative access to bioactive SiCaOC-based glasses with tunable porosity". Materials 2019, 12(23), 3862
F. Xie, E. Ionescu, M. Arango Ospina, R. Riedel, A. R. Boccaccini
-
“Effect of Ca and B incorporation into amorphous silicon oxycarbide on its microstructure and phase composition”. J. Am. Ceram. Soc. 2019, 102, 7645
F. Xie, I. Gonzalo, G. Buntkowsky, H.-J. Kleebe, R. Riedel, A. Boccaccini, E. Ionescu
-
"Silicon oxycarbide based materials for biomedical applications”. Appl. Mater. Today 2020, 18, 100482
M. Ospina Arango, F. Xie, I. Gonzalo, R. Riedel, E. Ionescu, A. R. Boccaccini
