Biomimetic synthesis of enamel-like hydroxyapatite on self-assembled monolayers

Hydroxyapatite (HAp) crystals mimicking tooth enamel in chemical composition and morphology were formed on sulfonic-terminated self-assembled monolayer (SAM) in 1.5SBF with F- at 50 degrees C for 7 days. F- ions showed a marked effect on the composition and morphology of deposited HAp crystals. In the absence of F- ions, HAp containing CO32- were formed on SAM, and worm-like crystals of 200-300 nm in length aggregated to form a spherical morphology. When F- was added, HAp crystals containing both CO32- and F- were formed on SAM. Needleshaped crystals of high aspect ratio and 1-2 mu m in length grew elongated along the c-axial direction. In addition, these needle-shaped crystals grew in bundles, mimicking HAp crystals in tooth enamel. After the process of ripening, the needles in bundle grew to large size of up to 10 mu m in length, and still kept no crystal-crystal fusion like enamel HAp crystals. The formation of enamel-like HAp can be attributed to the substitute of F- for OH- by disturbing the normal progress of HAp formation on SAM. The results suggest potential applications in preparing a novel dental material by a simple method. (C) 2006 Elsevier B.V. All rights reserved.