Newly developed bioactive borosilicate glasses: impact of boron on particles sintering and hASCs response.

Abstract

Event Abstract Back to Event Newly developed bioactive borosilicate glasses: impact of boron on particles sintering and hASCs response. Ayush Mishra1*, Minna Ojansivu2, 3*, Maeva Fabert1*, Nirajan Ohja1*, Erika Erasmus4*, Iakovos Sigalas4*, Susanna Miettinen2, 3 and Jonathan Massera1, 3* 1 Tampere University of Technology, Department of Electronics and Communications Engineering, Biomaterials and Tissue Engineering Group, Finland 2 University of Tampere, Adult Stem Cell Research Group, Finland 3 BioMediTech, Finland 4 University of the Witwatersrand, School of Chemical and Metallurgical Engineering, South Africa Introduction: Traditional bioactive glasses (BAG) face major drawbacks. They are prone to crystallization during hot working which inhibits the glass sintering and reduces the glass bioactivity[1]. Furthermore, studies have shown that, 14 years post-surgery, incomplete conversion of the glass into hydroxyapatite (HA) led to glass particles reminiscence[2]. Thus, there is a need for new BAG that can convert fully into HA while having thermal properties enabling sintering. Materials and Methods: Glasses based on the S53P4 (commercial glass) composition were processed with various B2O3/(SiO2+B2O3) ratio (0% (B0), 25% (B25), 50% (B50), 75% (B75) and 100% (B100)). The glasses’ characteristic temperatures were recorded using DTA. The structural properties of the materials were assessed by FTIR, Raman spectroscopy and 11B NMR. The dissolution test was performed by immersing glass particles in simulated body fluid (SBF) for up to 168h. The pH and Ca concentration (Atomic Absorption Spectrometry) were measured as a function of immersion time. The formation of HA was assessed using EDX/SEM and FTIR. Human adipose stem cells (hASC) were plated on top of glass discs and the biocompatibility of the materials confirmed by live/dead staining. Results and Discussion: In this presentation, we will show that upon immersion, the pH of all solutions increases due to glass dissolution. The Ca concentration in the SBF increases with increasing immersion time and B2O3 content. The largest increase in Ca content in the B100 glass containing solution is due to its faster dissolution rate. EDX/SEM analysis and FTIR showed precipitation of HA at all glass surfaces. B100 almost fully converted into HA after 168h in SBF. The addition of boron also decreases all characteristic temperatures due to the formation of Si-O-B bonds and planar [BO3] units. B50 possesses the largest hot working domain and also the crystallization peak with lower intensity. Therefore, this glass was selected for sintering experiments. Figure 1 shows a photograph of the sintered porous bodies obtained by sintering at 550, 575, 600 and 650oC for 1h. Samples sintered at 550 and 650oC were not further studied due to low mechanical properties and low porosity resepctively. The porosity varied from 1 (650oC) to 55% (575oC) with compression strength from 5 to 100Mpa. Scaffold from the glass B50 were also immersed in SBF and their mechanical properties slightly decrease with respect to immersion time. Figure 2 presents the live/dead staining images obtained at 14d. All glasses except B100 allow adhesion and proliferation of cells. However, with increasing boron content the proliferation of cells seems slightly reduced as compared to S53P4. Conclusion: Glass B50 was found to have good biocompatibility and thermal properties for hot working of BAG. The sintering temperature is rather low compared to sintering performed on commercial BAG. From the dissolution test, the addition of boron leads to a glass more prone to dissolution with higher conversion to HA, making this borosilicate glass system promising for use as scaffolds for tissue engineering. Academy of Finland