Abstract
Due to their high bioreactivity, the in-vitro analysis of bioactive glasses (BGs) can be challenging when it comes to maintaining a physiological pH. To improve BG biocompatibility, a heterogenic spectrum of preconditioning approaches, such as “passivation” of the BGs by incubation in cell culture medium, are used but have never been directly compared. In this study, the effect of passivation periods of up to 72 h on pH alkalization and viability of human bone marrow-derived mesenchymal stromal cells was evaluated to determine a time-efficient passivation protocol using granules based on the 45S5-BG composition (in wt%: 45.0 SiO2, 24.5 Na2O, 24.5 CaO, 6.0 P2O5) in different concentrations. pH alkalization was most reduced after passivation of 24 h. Cell viability continuously improved with increasing passivation time being significantly higher after passivation of at least 24 h compared to non-passivated 45S5-BG and the necessary passivation time increased with increasing BG concentrations. In this setting, a passivation period of 24 h presented as an effective approach to provide a biocompatible cell culture setting. In conclusion, before introduction of BGs in cell culture, different passivation periods should be evaluated in order to meet the respective experimental settings, e.g., by following the experimental protocols used in this study.
Highlights
Since the introduction of the 45S5-bioactive glass (BG) composition by Hench and coworkers in the late 1960s, the family of bioactive glasses (BGs) grew rapidly [1,2]
Before introduction of BGs in cell culture, different passivation periods should be evaluated in order to meet the respective experimental settings, e.g., by following the experimental protocols used in this study
The pH values measured in the media used for the passivation of 1 to 72 h were significantly higher than in the Dulbecco’s Modified Eagle’s Medium (DMEM) serving as control, that has not been in contact with BG (Figure 3a)
Summary
Since the introduction of the 45S5-bioactive glass (BG) composition (in wt%: 45.0 SiO2, 24.5 Na2O, 24.5 CaO, 6.0 P2O5) by Hench and coworkers in the late 1960s, the family of BGs grew rapidly [1,2]. For application in BTE, BGs are attractive due to the changes on their surface when in contact with physiological fluids that lead to strong bonding to surrounding tissues [5,6]. When new BG compositions are introduced to BTE applications, it is of particular interest to investigate their biological properties in-vitro, including cytotoxicity assays or their impact on osteogenic differentiation [8,9]. Calcium hydroxyl phosphate precipitates and crystallization leads to the formation of a hydroxycarbonate apatite layer. This layer is capable of incorporating organic components and allows living bone to bond as it is highly similar to bone mineral [10,11,12]
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