Maria Łączka

Gel-derived bioglass as a compound of hydroxyapatite composites.

Despite the excellent biocompatibility of hydroxyapatite and bioglass, their clinical applications are limited to non-load-bearing implants and implant coatings due to their low mechanical properties. We have developed two different composites made of hydroxyapatite (HA) and gel-derived bioglasses designated S2 (80 mol% SiO(2)-16 mol% CaO-4 mol% P(2)O(5)) or A2 (40 mol% SiO(2)-54 mol% CaO-6 mol% P(2)O(5)). We show that the combination of hydroxyapatite with either bioglass results in better composite bioactivity and biocompatibility compared to HA alone. We used a commercially available hydroxyapatite that was sintered with varying additions (10%, 50%) of A2 or S2 bioglass. Scanning electron microscopy and x-ray diffraction were used to characterize the microstructure and phases of the composites. The elastic properties of bioglass/HA composites were analyzed with the use of the pulse ultrasonic technique. The bioactivity (surface activity) of the composites was assessed by determining the changes of surface morphology and composition after soaking in simulated body fluid (SBF) for 7 and 14 days. The biocompatibility of the obtained composites was then assessed in vitro using adult human bone marrow stromal cells. Cells were seeded on the material surfaces at a density of 10(4) cells cm(-2) and cultured for 7 days in non-differentiating and osteogenic conditions. The number of live cells was estimated in both standard and osteogenic cultures, followed by alkaline phosphatase (ALP) activity assay in osteogenic cultures. We determined that 10 wt% addition of A2 (E = 12.24 GPa) and 50 wt% addition of S2 (E = 16.96 GPa) to the HA base results in higher Youngs modulus of the composites compared to pure hydroxyapatite (E = 9.03 GPa). The rate of Ca-P rich layer formation is higher for bioglass/HA composites containing A2 bioglass compared to the composites containing S2 bioglass. Evaluation of cell growth on the bioglass/HA composites showed that the incorporation of either 50 wt% S2 or 50 wt% A2 into the hydroxyapatite base significantly improves cell viability when compared to cells grown on pure HA. Also the cellular activity of ALP, an early marker of osteoblasts, increases with the amount of bioglass addition to the composites.

Ectopic bone formation by gel-derived bioactive glass-poly-L-lactide-co-glycolide composites in a rabbit muscle model

In this study we aimed to assess the in vivo osteoinductive properties of two composite scaffolds made of PLGA (poly-L-lactide-co-glycolide) and two types of gel-derived bioactive glasses, namely a high silica S2 bioactive glass (S2-PLGA composites) or high lime A2 bioactive glass (A2-PLGA composites). To achieve that, the potential of the composites to induce ectopic bone formation in a rabbit muscle has been examined along with the control PLGA scaffold. Cylinder-like scaffolds of 7  ×  3 mm (width  ×  height) were implanted into pouches created in the latissimus dorsi muscle of 18 New Zealand rabbits. The tissue sections were obtained at 6, 12 or 24 weeks post-surgery (six rabbits per each time point) and stained with hematoxylin-eosin. The process of wound healing, the formation of collagen-rich connective tissue and its transition to cartilage were examined by Sirius red and Alcian blue histological stainings. We also performed immunohistochemical verification of the presence of osteoblast- and osteoclast- like cells in the vicinity of the scaffolds. A typical foreign body reaction and wound healing process was observed for all implanted scaffolds. Osteoblast- and osteoclast-like cells were observed in the vicinity of the scaffolds as determined by the immunohistochemical staining for Osteocalcin, BMP-2 and Cathepsin K. Compared to plain PLGA scaffolds, numerous osteoblast-like cells were observed 12 weeks post implantation near the composites and the scaffolds gradually degraded as bone formation proceeded. S2-PLGA and A2-PLGA composites display osteoinductive properties in vivo. Furthermore, they are more effective at inducing ectopic bone formation in a rabbit muscle compared to plain PLGA. Thus these SBG-PLGA composite scaffolds have potential for clinical applications in dental and/or orthopedic-bone tissue engineering.

Bioactive Glass-Ceramic Porous Sinters

Bioglasses and bioactive glass-ceramics have found increasingly wide application in medicine and dentistry. Using sol-gel method, is possible to obtain glass and glass-ceramic bioactive materials of new generation, characterized the higher bioactivity than melted bioglasses. These materials can be produced in various final forms, as powders, thin layers on different base and porous sinters. Production of porous bioactive sinters from gel-derived powders is a new problem and the parameters controlling this process are not recognized yet. The aim of the study was to obtain porous bioactive sinters from gel-derived powders of the SiO2-CaO-P2O5 system of four various chemical compositions (S2, II, I, A2) and the characterization of properties of these new materials. The starting powders differ from each other in the content of the basic components, at the molar ratio of CaO to SiO2 equals 0.2-1.35. To obtain the porous sinters a method of burning additions and deposition of the casting slip on the polymeric sponge was used. Sintering was realized in several stages, at the maximal temperature 1200oC. By selecting appropriate conditions of sintering, a durable material of high open porosity up to 77 % was obtained. Its porous structure was characterized by a prevailing number of small micropores of similar dimensions, uniformly distributed in the material. The phase composition of obtained sinters was determined by the X-ray diffraction method. All sinters represented glass-ceramic materials with apatite, cristoballite and calcium silicates as a main crystalline phases. In order to preliminary determination bioactivity of obtained sinters, test in vitro in simulated body fluid SBF was conducted. It was found that hydroxyapatite formation on the sinter surface occurs only in the case of biomaterials of highest calcium concentration.