In vitro evaluation of gentamicin release from a bioactive tricalcium silicate bone cement

Tricalcium silicate (Ca₃SiO₅) cement, a novel self-setting biomaterial, has been shown to exhibit good hydraulic properties and excellent bioactivity. In this study, gentamicin sulfate (GS) was integrated into cement pastes and in vitro release of GS from the Ca₃SiO₅ cement was performed in deionized water, phosphate buffer saline (PBS) and HCl solutions with different pH at 37 °C, respectively. The results showed that the initial fast release of GS was restricted to a low level and prolonged release of drugs was achieved in water and PBS. The prolonged GS release is attributed to the interaction of GS with the calcium silicate hydrate network and the formation of unique nano-to-micro porous structure after hydration. Furthermore, GS release from milled powders of the hydrated cement suggested that the constrained GS could be released at low pH environment or during the degradation of the cement. When the samples were soaked in PBS, a nano-structured apatite layer was formed on the surface of the cement, which resulted in a relatively lower GS release rate as compared to that in water. The results suggest that Ca₃SiO₅ cement might be used as bioactive bone implant materials with drug loading and prolonged release properties.