Abstract
To increase the biocompatibility of hydroxyapatite (HA), Ca10(PO4)6(OH)2, the Sr substitution of Ca into the HA structure was effected to yield Ca10-xSrx(PO4)6(OH)2(Sr-HA). For medical and dental applications, it is important that Sr-HA is prepared as a thin film so that the Sr fully substitutes the Ca sites in the HA structure and does not form segregated impurities consisting of Sr compounds. If the segregated Sr forms different amounts of different impurities, the dissolution of the Sr into the living body will not be reproducible across different samples. To confirm the Sr substitution into the Ca site in the HA structure, the systematic variation in the lattice constants of the Sr-HA with Sr content was evaluated as the first step. The a- and c-axis lengths were found to exhibit a linear relationship with the Sr content for six samples with different Sr contents, indicating that the prepared Sr-HA thin films likely possessed partial Sr substitution into the Ca sites of the HA structure. This result is an important first step in the accurate evaluation of the biological effects of Sr-HA thin films.
Highlights
Hydroxyapatite (HA), Ca10(PO4)6(OH)2, is widely applied as a component of medical and dental devices [1] [2] [3] [4] [5] owing to its excellent bone repairing ability via activating osteoblasts
We report the systematic variation of the lattice constants with the Sr content for Srsubstituted HA (Sr-HA) thin films prepared using pulsed laser deposition (PLD) for a region comprising a relatively low Sr amount of x ≤ 1.0
Considering a previous work where we found that the Sr/(Ca + Sr) and (Ca + Sr)/P of Sr-HA thin films can be highly controlled by the energy distribution of the ablation laser on the target [18] [19], these details are being studied and the control of the chemical composition of Sr-HA and HA thin films will be reported in a subsequent paper
Summary
Hydroxyapatite (HA), Ca10(PO4)6(OH), is widely applied as a component of medical and dental devices [1] [2] [3] [4] [5] owing to its excellent bone repairing ability via activating osteoblasts. As the first step to confirm the Sr2+ substitution into the Ca2+ site in the HA structure, the systematic relationship between the Sr content and the a- and c-axis lengths must be studied to determine a relatively low and appropriate Sr amount (Note that excess Sr may cause hypocalcaemia [17], etc., owing to the low absolute amount of Sr in the living body). Such studies have already been reported for bulk Sr-HA, as mentioned above [8] [13], there are no clear reports for the Sr-HA thin films. Verifying a certain amount of the substitution of Sr into Ca sites is an important step towards successfully applying Sr-HA into medical and dental devices before its biological properties can be examined
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