An injectable borate bioactive glass cement for bone repair: Preparation, bioactivity and setting mechanism

There is a need for synthetic biomaterials to reconstruct bone defects using minimal invasive surgery. In this study, the preparation, bioactivity and setting mechanism of an injectable cement composed of borate bioactive glass particles and a chitosan solution was evaluated as a function of varying solid to liquid (SL) ratio. As the SL ratio increased from 1.0 g/ml to 2.5 g/ml, the injectability and initial setting time decreased from 97 ± 1% to 84 ± 10% and from 16.9 ± 0.9 min to 3.0 ± 0.5 min, respectively, while the compressive strength of the cement increased from 8 ± 2 MPa to 31 ± 2 MPa. The cement maintained its cohesiveness in a vigorously stirred aqueous medium. When immersed in phosphate-buffered saline, the glass phase reacted and converted to hydroxyapatite. The setting mechanism of the cement appeared to involve a combination of processes, such as the sol-gel transition of the chitosan solution, formation of an interlocked interface between the converted glass surface and the chitosan, and bonding between the converted glass surface and the functional groups of the chitosan. By controlling the reaction between the glass particles and the chitosan solution, injectable cements can be created with the requisite workability, degradation, strength and bioactivity for bone repair applications.