Water dispersible hydroxyapatite nanoparticles functionalized by a family of aminoalkyl phosphates

Abstract A series of aminoalkyl phosphates (AAP-n, with carbon number n ranging from 2 to 6) are used as surface modifiers to prepare hydroxyapatite hydrocolloids. The resulting nanoparticles (Cn-HA) possess a core-shell structure where an ionized layer of calcium-(AAP-n) complex [ + H 3 N-(CH 2 ) n -OPO 3 Ca] encapsulates each hydroxyapatite core. Long-term colloidal stability is achieved due to the electrostatic repulsion among the suspending particles. The incorporation of AAP-n results in a preferential crystal growth along c -axis, showing an increasing aspect ratio of particles from C2-HA to C6-HA. Preliminary cell culture using osteoblast-like MG63 cells shows no cytotoxicity associated with the as-prepared Cn-HA particles. The functional amino groups around the nanoparticles could be used to graft various organic chains to prepare homogeneous HA/polymer composites as bone grafting materials.