Metastable amorphous calcium carbonate (ACC), formed as a precursor of crystalline carbonated apatite/hydroxyapatite in human bone, can be stabilized by inorganic polyphosphate. The resulting CaCO₃/polyP, containing small amounts of vaterite, has osteogenic potential and potential application as a scaffold material for bone implants.

Treating large bone defects represents a major challenge in traumatic and orthopedic surgery. Bone tissue engineering provides a promising therapeutic option to improve the local bone healing response. In the present study tissue biocompatibility, systemic toxicity and tumorigenicity of a newly developed composite material consisting of polylactic acid (PLA) and 20% or 40% bioglass (BG20 and BG40), respectively, were analyzed. These materials were seeded with mesenchymal stem cells (MSC) and endothelial progenitor cells (EPC) and tested in a rat calvarial critical size defect model for 3 months and compared to a scaffold consisting only of PLA. Serum was analyzed for organ damage markers such as GOT and creatinine. Leukocyte count, temperature and free radical indicators were measured to determine the degree of systemic inflammation. Possible tumor occurrence was assessed macroscopically and histologically in slides of liver, kidney and spleen. Furthermore, the concentrations of serum malondialdehyde (MDA) and sodium oxide dismutase (SOD) were assessed as indicators of tumor progression. Qualitative tissue response towards the implants and new bone mass formation was histologically investigated. BG20 and BG40, with or without progenitor cells, did not cause organ damage, long-term systemic inflammatory reactions or tumor formation. BG20 and BG40 supported bone formation, which was further enhanced in the presence of EPCs and MSCs. This investigation reflects good biocompatibility of the biomaterials BG20 and BG40 and provides evidence that additionally seeding EPCs and MSCs onto the scaffold does not induce tumor formation.

The main aim of the work was the fabrication of novel silver releasing nanocomposite scaffolds, for bone treatment, by the gas foaming/particulate-leaching technique. Silver doped bioactive glass nanoparticles were used as a filler, to provide the scaffolds with bioactivity, as well as anti-bacterial properties. Nanocomposite scaffolds containing 0, 20 and 40wt% glass contents were prepared and coded as PAg0, PAg20 and PAg40, respectively. The scaffolds were characterized by SEM/EDXA, FTIR and TGA. Examination of SEM microphotographs showed that, the produced scaffolds had well interconnected structures. For PAg0, PAg20 and PAg40, the maximum pore sizes were about 250, 150 and 100μm, respectively, while their porosities % were 92%, 89% and 83%, respectively. Degradation studies were carried out, by incubating the scaffolds in simulated body fluid, for a month. Results revealed the possibility to modulate and improve the degradation of the scaffolds by increasing their glass contents. The final weight losses measured for PAg0, PAg20 and PAg40 were 12.76%, 14.61% and 17.42%, respectively. On the other hand, the highest water absorption values recorded for those scaffolds were 61.89%, 240.36% and 270.87%, respectively, indicating that, the addition of glass nanoparticles to the scaffolds improved their water absorption abilities. Both PAg20 and PAg40 induced an apatite layer on their surfaces, had anti-bacterial effect in agar plates, and their silver releasing profiles followed a diffusion-controlled mechanism. Therefore they could be used for bone treatment