Speaker
Description
Introduction
Since the discovery of bioactive glasses (BG) in the late 60s [1], the research in this area has significantly increased to obtain compositions with multiple functionalities not only from the materials aspect but also to provide a favorable biological response for tissue regeneration. BGs have the ability to react with the surrounding environment and bond to hard tissue. This property is characterized by the formation of a hydroxycarbonate apatite (HCA) layer on the material with a similar composition to the inorganic component of bones. Simultaneously, the dissolution of BG takes place leading to the release of biologically active ions, which stimulate the formation of new tissue at a cellular level. The incorporation of metallic ions in the BGs composition has been considered to obtain glasses able to stimulate the formation of bones, support biological processes such as angiogenesis and provide an antibacterial effect on the implantation site [2].
Methodology
Silicate-based BG glasses were produced with the melt-quench method. The well-known 45S5 BG composition was considered as reference material and new compositions were obtained incorporating zinc, boron and strontium. The bioactive behavior was assessed in simulated body fluid and characterized via FTIR, SEM and XRD. In vitro cell studies were carried out using pre-osteoblast cells MC3T3-E1. Moreover, the antibacterial effect of BGs was determined via indirect and direct experiments with Gram-positive and Gram-negative bacteria, S. aureus and E. coli, respectively. Turbidity measurements, counting colony-forming units and metabolic assays were used.
Results
The formation of an HCA layer on the material’s surface was characterized by the detection of adsorption bands in FTIR spectra attributed to calcium phosphate and crystalline reflections of HCA. Which were also detected with XRD. The incorporation of the studied metallic ions delayed the formation of HCA compared to the non-doped 45S5 BG, which exhibited faster bioactivity after 1 day compared to 3 days for Sr-doped BGs and 7 days for B- and Zn-BGs. In terms of cell viability, the glasses containing boron and strontium outperformed the reference BG at all tested concentrations, whereas Zn-doped BG presented the lowest cell viability, particularly, at the highest BG concentration. The minimum inhibitory concentration of the dissolution products of BGs required to kill bacteria was lower for the Sr-doped BG and the reference 45S5 BG compared to the other glasses. However, all materials exhibited an antibacterial effect compared to the control sample (bacteria without BGs).
Conclusion
All studied BG compositions exhibited beneficial properties in terms of bioactivity and biological response. Although the bioactivity was slightly delayed, the in vitro biological assays showed a superior biological effect of Sr-doped BGs compared to control cells, control bacteria and to the other BGs. These results suggest a potential application of ion-doped BGs for bone regeneration.
References
[1] Hench L.L., J. Mater. Sci. Mater. Med. 17, 967–978 (2006)
[2] Hoppe, A., et al., Biomaterials. 32, 2757-2774 (2011)
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