Bijan Eftekhari Yekta

Phosphate based-glass ceramics in the system of P₂O₅-CaO-Na₂O-SiO₂-TiO₂ were obtained by the sintering method. For evaluating the effect of strontium and zinc, different amounts of these elements were doped in the parent glass instead of calcium oxide. Sintering behavior of the glasses was evaluated through the measurement of bulk density, liquid absorption, and open porosity percentages. Based on the results, 600 °C was determined as the optimum sintering temperature. Based on the X-Ray diffractometry, calcium pyrophosphate was precipitated during the sintering process as the main crystallized phase. It is worth noting that changing the parent glass composition led to its phase transformation. Variation in the pH and ion concentration in the simulated body fluid as well as weight loss percentages of the samples were considered to evaluate the dissolution behavior of the samples. The in vitro tests showed that increasing the amount of strontium and zinc intensified the dissolution rate. According to scanning electron micrographs, hydroxyapatite nuclei precipitated on the surfaces of the samples after three days of simulated body fluid (SBF) soaking; but, they were dissolved in the solution after 28 days due to the dissolution of the substrate. Some residues of the grown apatite-like layer were observed on the surface of the composition when 25 and 2.5 molar percent of calcium were substituted for strontium and zinc, respectively.

The effect of cross‐linker 3‐glycidyloxypropyl trimethoxysilane (GPTMS) on the injectability, bioactivity, rheology, washout resistance, and cellular behavior of bio‐nano composite pastes containing a sol–gel derived bioactive glass (BG), chitosan (Cn), and gelatin (Gel), were studied. The results indicated that the structural integrity of the samples in the stimulated body fluid (SBF) was improved from 80% to 90% with the increase in the GPTMS content. In addition, the viscosity and injectability of the paste were affected, so that the later changed from 96% to 73% and the former changed from 132 × 10³to 210 × 10³ Pa.s, with addition of 20 wt% GPTMS. Furthermore, the bioactivity of the pastes was improved with the use of GPTMS. No toxicity was observed in the cellular studies of the GPTMS containing paste after 7 days, and the cells kept their shape and were attached firmly to the paste surface. The results of the present work showed that the use of GPTMS was beneficial in enhancing the properties of injectable paste.

Bioactive glass (BG) represents a promising biomaterial for bone healing; here injectable BG pastes biological properties were improved by the addition of gelatin or chitosan, as well as mechanical resistance was enhanced by adding 10 or 20 wt% 3-Glycidyloxypropyl trimethoxysilane (GPTMS) cross-linker. Composite pastes exhibited bioactivity as apatite formation was observed by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) after 14 days immersion in simulated body fluid (SBF); moreover, polymers did not enhance degradability as weight loss was >10% after 30 days in physiological conditions. BG-gelatin-20 wt% GPTMS composites demonstrated the highest compressive strength (4.8 ± 0.5 MPa) in comparison with the bulk control paste made of 100% BG in water (1.9 ± 0.1 MPa). Cytocompatibility was demonstrated towards human mesenchymal stem cells (hMSC), osteoblasts progenitors, and endothelial cells. The presence of 20 wt% GPTMS conferred antibacterial properties thus inhibiting the joint pathogens Staphylococcus aureus and Staphylococcus epidermidis infection. Finally, hMSC osteogenesis was successfully supported in a 3D model as demonstrated by alkaline phosphatase release and osteogenic genes expression.

Bioactive glass (BG) represents a promising biomaterial for bone healing; here injectable BG pastes biological properties were improved by 25 wt% gelatin or chitosan, as well as mechanical resistance was enhanced by adding 10 or 20 wt% 3-Glycidyloxypropyl trimethoxysilane (GPTMS) cross-linker. Composites exhibited bioactivity as apatite formation was observed by SEM and XRD after 14 days immersion in SBF; moreover, polymers did not enhance degradability as weight loss was >10% after 30 days in physiological conditions. BG-gelatin-20 wt% GPTMS composites demonstrated the highest compressive strength (4.8±0.5 MPa) in comparison with 100% BG control (1.9±0.1 MPa). Cytocompatibility was demonstrated towards human mesenchymal stem cells (hMSC), osteoblasts progenitors and endothelial cells. The presence of 20 wt% GPTMS conferred antibacterial properties thus inhibiting the joint pathogens Staphylococcus aureus and Staphylococcus epidermidis infection. Finally, hMSC osteogenesis was successfully supported in a 3D model as demonstrated by alkaline phosphatase release and osteogenic genes expression.