Enriched fluoridation of octacalcium phosphate by ionic liquid treatment

Octacalcium phosphate (OCP) has attracted attention as a bone-repairing material with excellent bone regeneration ability, and F⁻ incorporation is expected to further promote bone formation. However, because OCP is easily converted to fluorapatite in an aqueous fluoride solution, it is difficult to incorporate a large amount of F⁻ while maintaining the crystalline structure of OCP. Therefore, in this study, we attempted to introduce F⁻ into OCP using an ionic liquid with high F⁻ concentration in a non-aqueous environment. OCP was incorporated with F⁻ in the form of ion pairs after treatment with an acetone solution of 1-ethyl-3-methylimidazolium tetrafluoroborate. The F⁻ content was approximately 9%, which was approximately 28 times greater than achieved in previous studies. The amount of OCP with F⁻ dissolved in acetate buffer was less than that of untreated OCP.