Bioactive glasses (BGs), since their discovery in 1971 by L.L Hench, have been widely used for bone replacement and repair, and, more recently, they are becoming highly attractive for bone and soft tissue engineering applications. BGs have in fact the ability to form a strong bond with both hard and soft tissues once in contact with biological fluid. The enhanced interaction of BGs with the biological environment is based on their significant surface bioreactivity. This surface effect of BGs is, on the other hand, problematic for cell biology studies by standard (static) cell culture methods: an excessive bioreactivity leads in most cases to a rapid and dramatic increase of the pH of the surrounding medium, which results in cell death and makes cell culture tests on BG samples impossible. The BG research community has been aware of this for many years and numerous pre-treatments have been proposed by different groups worldwide to limit this problem. For the first time, we have reviewed in this paper the variety of surface preconditioning treatments that have been put forward over the years, we provide a summary of such pre-treatments used in laboratory practice, discussing and offering criteria that can be used for the determination of the optimal pre-treatment depending on BG composition and morphology of the sample tested (bulk, particulate, scaffolds). The information and discussion provided in this review should support best research practice when testing bioactive glasses in cell culture.

Standard treatment for bone defects is the biological reconstruction using autologous bone—a therapeutical approach that suffers from limitations such as the restricted amount of bone available for harvesting and the necessity for an additional intervention that is potentially followed by donor-site complications. Therefore, synthetic bone substitutes have been developed in order to reduce or even replace the usage of autologous bone as grafting material. This structured review focuses on the question whether calcium phosphates (CaPs) and bioactive glasses (BGs), both established bone substitute materials, show improved properties when combined in CaP/BG composites. It therefore summarizes the most recent experimental data in order to provide a better understanding of the biological properties in general and the osteogenic properties in particular of CaP/BG composite bone substitute materials. As a result, BGs seem to be beneficial for the osteogenic differentiation of precursor cell populations in-vitro when added to CaPs. Furthermore, the presence of BG supports integration of CaP/BG composites into bone in-vivo and enhances bone formation under certain circumstances.

Bone defect treatment belongs to the most challenging fields in orthopedic surgery and requires the well-coordinated application of mesenchymal stem cells (MSC) and differentiation factors. MSC isolated from reaming material (RMSC) and iliac crest (BMSC) in combination with bone morphogenetic protein-7 (BMP-7) and insulin-like growth factor-1 (IGF-1) have been used. The short half-life of both factors limit their applications: a burst release of the factor can probably not induce sustainable differentiation. We stimulated MSC in osteogenic differentiation medium with three different concentrations of BMP-7 or IGF-1: Group A was stimulated continuously, group B for 24 h and group C remained without any stimulation. Osteogenic differentiation was measured after seven and 14 days by alizarin red staining and alkaline phosphatase (ALP) activity. Continuous stimulation led to higher levels of osteogenic differentiation than short-term stimulation. This could lead to a reconsideration of established application forms for differentiation factors, aiming to provide a more sustained release.