Bioactive Glass (BG) ICIE16 Shows Promising Osteogenic Properties Compared to Crystallized 45S5-BG

Abstract

The ICIE16-bioactive glass (BG) (48.0 SiO2, 6.6 Na2O, 32.9 CaO, 2.5 P2O5, 10.0 K2O (wt %)) has been developed as an alternative to 45S5-BG, the original BG composition (45.0 SiO2, 24.5 Na2O, 24.5 CaO, 6.0 P2O5 (wt %)), with the intention of broadening the BG sintering window while maintaining bioactivity. Because there is a lack of reports on ICIE16-BG biological properties, the influence of ICIE16-BG on viability, proliferation, and osteogenic differentiation of human mesenchymal stromal cells (MSCs) was evaluated in direct comparison to 45S5-BG in this study. The BGs underwent heat treatment similar to that which is required in order to fabricate scaffolds by sintering, which resulted in crystallization of 45S5-BG (45S5-CBG) while ICIE16 remained amorphous. Granules based on both BGs were biocompatible, but ICIE16-BG was less harmful to cell viability, most likely due to a more pronounced pH alkalization in the 45S5-CBG group. ICIE16-BG outperformed 45S5-CBG in terms of osteogenic differentiation at the cellular level, as determined by the increased activity of alkaline phosphatase. However, granules from both BGs were comparable regarding the stimulation of expression levels of genes encoding for osseous extracellular matrix (ECM) proteins. The addition of therapeutically active ions to ICIE16-BG might further improve its ability to stimulate ECM production and should be investigated in upcoming studies.

Impact of Zinc- or Copper-Doped Mesoporous Bioactive Glass Nanoparticles on the Osteogenic Differentiation and Matrix Formation of Mesenchymal Stromal Cells

“…Cell viability and alkaline phosphatase (ALP) activity as a marker of cellular osteogenic differentiation were assessed using a combined fluorescence-based assay following a previously published protocol [ 26 ]. Since it correlates with cell number and viability [ 27 , 28 , 29 ], metabolization of fluorescein diacetate (FDA) was quantified to determine cell viability. The conversion of 4-methylumbelliferyl phosphate (4-MUP), an ALP substrate, was measured as it correlates directly with ALP activity [ 26 ].…”

“…A fluorescence microscopy-based live/dead-assay was performed to visualize cell morphology and viability. While FDA was applied for detection of viable cells, potentially remaining dead cells were visualized with propidium iodide (PI), as PI cannot pass viable cell membranes and, therefore, intercalates into DNA of compromised cells [ 27 , 28 , 29 ]. After discarding CCM, staining solution composed of 8 µg/mL FDA and 20 µg/mL PI (Life Technologies) in DPBS was added and incubated at 37 °C for 5 min.…”

Preconditioning of Bioactive Glasses before Introduction to Static Cell Culture: What Is Really Necessary?

“…Thus, the individuality of every setting makes a reassessment of adequate passivation periods inevitable. Further aspects impacting the primary biocompatibility of a setting are the BG-morphology (e.g., particle size and surface area) and -composition that are leading to altered ion release kinetics [ 16 , 18 , 19 , 37 , 43 , 44 ]. In this study, the concentration of ions released to the CCM has not been determined, as the dissolution characteristics of the 45S5-BG are well known [ 16 , 19 , 45 , 46 , 47 ].…”

“…Apart from a compromise of cell viability, rapid pH changes in cell culture medium can confound the interpretation of cellular function [ 17 ]. Therefore, when introduced to cell culture studies, BGs have to be prepared using so-called preconditioning procedures such as “passivation” by introducing the BGs to cell culture medium for a certain period of time before allowing contact to cells [ 8 , 18 ] to prevent the cells from the initial burst release of ions and its consequences.…”

Combined Fluorescence-Based in Vitro Assay for the Simultaneous Detection of Cell Viability and Alkaline Phosphatase Activity during Osteogenic Differentiation of Osteoblast Precursor Cells

“…ALP is known to be an early marker of osteogenic differentiation on a cellular level, thus correlating with the activity and presence of osteoblasts that develop from bone precursor cells during differentiation [ 2 , 8 ]. However, ALP is also expressed in other cell types, e.g., pluripotent stem cells [ 9 ].…”