Anti-bacterial glass formulations for bone tissue engineering applications

[Excerpt] Introduction: One of the major problems in Bone Tissue Engineering (BTE) is the high probability of occurring bacterial contamination during preparation and surgical procedures. Bacterial strains such as Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa proved to be hard to eliminate from bone grafts [1]. Silica-based bioglasses, namely the silica-borate system, can take advantage of the well-known boron antibacterial properties [2, 3]. In fact, bioglasses have been used in BTE for several decades due to their biological activity and mechanical performance. The aim of this study is to evaluate the anti-bacterial properties of silica-borate glass formulations to use them within a BTE perspective. Materials and methods: Silica-borate glass compositions of general formula 0.20B2O3: 0.40SiO2: xMgO: yCaO: (0.35-x-y)SrO: 0.05Na2O (molar ratio, where x, y = 0.35 or 0.00, and x 6¼ y) were synthesized by melt quenching. The glass particles were ground and sieved to collect the particles with a size <63 lm. Glass particles’ cytotoxicity was assessed by direct contact with human osteosarcoma cell line during 3 days of incubation (37°C and 5% CO2). At different time points cell proliferation (DNA) and metabolic activity (MTS) was determined. Microbial susceptibility was measured using standardized inocula of P. aeruginosa ATCC27853, E. coli CECT 434, S. aureus ATCC 29213 in contact with glass samples. Preliminary studies were performed using adapted EUCAST Diffusion Method for 24 hours exposure. Broth dilution method was altered and performed by adding known amounts of glass particles directly in bacterial cultures for 24 hours period. After it colony forming units (CFUs) was assessed. All experiments were performed at least in triplicate. [...]