Control of Crystallinity of Hydroxyapatite Sheet

Abstract

A technique to control the crystallinity of hydroxyapatite (HA) was investigated for applications such as dentistry, regenerative medicine, cell culture scaffolding, and bio-sensors. An amorphous HA film was first produced by pulsed laser deposition. After deposition, it was separated from a substrate as a free-standing sheet. Annealing was then performed to control the crystallinity of the sheet. It was found that conventional annealing in an electric oven was not suitable for HA sheets, because it led to curling and cracking. Since such problems were assumed to be caused by thermal stress, annealing was next carried out with the HA sheet enclosed in HA powder in the center of a metal capsule. This method allowed annealing to be successfully carried out without causing any curling or cracking. Uniform pieces with dimensions of 10 mm × 10 mm cut from a large HA sheet were annealed at temperatures of 200 to 800 ºC and then examined using X-ray diffraction. It was found that the intensity of the diffraction peaks associated with crystalline HA changed with annealing temperature, and that the strongest peaks were observed for the sample annealed at 500 ºC. These results indicate that the crystallinity of the HA sheet can be controlled using the proposed method.

Pulsed laser deposition of pure fluoroapatite film without OH groups

“…A fabrication method for H‐Ap films based on pulsed laser deposition (PLD) has been previously developed by exploiting the nature of H‐Ap films, and so clearly the adaptation of this to F‐Ap films is of great interest to the development of new devices suitable for use in acidic environments. For example, it could be used to produce a stack of apatite sheets on the surface of a tooth to prevent dental caries caused by the lactic acid‐generating bacterium Streptococcus mutans . Alternatively, it could allow for the realization of apatite‐based chromatography microchips suitable for protein separation of very small specimen sizes at pH values of less than 5, which would represent a significant improvement over the pH 6.5 limit on existing H‐Ap chromatography in phosphate buffer solution.…”

C-Axis-Oriented Hydroxyapatite Film Grown Using ZnO Buffer Layer

“…H ydroxyapatite [HA: Ca 10 (PO 4 ) 6 (OH) 2 ] is used in various applications such as chromatography columns, 1,2) artificial bones, 3,4) bone cement, 5) dental implants, 6,7) dental treatment sheets, 8,9) drug delivery carriers, 10,11) scaffolds, 12,13) and adsorbents. 14,15) These applications utilize the unique characteristics or functions of HA such as its biocompatibility, osteoconductivity, protein adsorptivity, and ion exchangeability.…”