Kensaku Sonoda

Influence of emulsion on crystal growth of hydroxyapatite

The effect of an emulsion medium on the morphology and size of hydroxyapatite (HAp) nanoparticles was investigated. The HAp particles prepared in a pentaethyleneglycol dodecylether emulsion were smaller in size and in aspect ratio than those prepared from a non-emulsion. Morphological difference was also observed between the products prepared in the two systems. The edges of the HAp particles derived from the emulsion system were curved and rounded while those in the non-emulsion system were straight and truncated. These differences, deriving from the reaction media employed, indicated that a template effect of the emulsion can be utilized for controlling the size and habit of HAp nanoparticles.

A hydroxyapatite coating covalently linked onto a silicone implant material.

A novel composite consisting of hydroxyapatite (HAp) microparticles covalently coupled onto a silicone sheet was developed. Initially, an acrylic acid (AAc) -grafted silicone sheet with a 16.7 microg/cm(2) surface graft density was prepared by corona-discharge treatment. The surface of sintered, spherical, carbonated HAp particles with an average diameter of 2.0 microm was subsequently modified with amino groups. The amino group surface density of the HAp particles was calculated to be approximately one amino molecule per 1.0 nm(2) of particle surface area. These samples were characterized with Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. After the formation of ammonium ionic bonds between both samples under aqueous conditions, they were reacted at 180 degrees C for 6 h in vacuo to form covalent bonds through a solid-phase condensation. The HAp particles were coupled to the AAc-grafted silicone surface by a covalent linkage. Further improvements in the adhesive and bioactive properties of the HAp-coated silicone material are expected.