A functional apatite with antibacterial efficacy for bone tissue infections

Silver, silicon co-substituted hydroxyapatite (Ag, Si-HA) was developed to provide bone repair coupled with antibacterial effect, with the aim to address the problems arise in the treatment of bone tissue infections. In this study, Ag, Si-HA demonstrated substantially reduced attachment of Staphylococcus aureus, Propionibacterium acnes, Escherichia coli, and Pseudomonas aeruginosa as compared to HA at 12 h. Being a prolific opportunistic pathogen in bone tissue infections, we investigated if P. aeruginosa could develop resistance against Ag, Si-HA. Our study showed that despite repeated exposure to fresh population of P. aeruginosa every 48 h, Ag, Si-HA exhibited effective antibacterial properties against the growth of P. aeruginosa over 168 h, indicating low risk of inducing bacterial resistance against Ag, Si-HA. As P. aeruginosa produces exotoxins and harbours endotoxins on its cell call, together these toxins could delay healing process. We therefore examined if the effect of these toxins released by P. aeruginosa during the antibacterial assessment on the attachment of mesenchymal stem cells on HA and Ag, Si-HA. Unlike HA, cell attachment on Ag, Si-HA was not affected by the addition of supernatant obtained from the antibacterial assessment of HA and Ag, Si-HA. This demonstrated that Ag, Si-HA could inhibit the growth of bacteria as well as minimise or prevent the detrimental effect from bacteria toxins.