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Visualising phase change in a brushite-based calcium phosphate ceramic

View Article: PubMed Central - PubMed

ABSTRACT

The resorption of brushite-based bone cements has been shown to be highly unpredictable, with strong dependence on a number of conditions. One of the major factors is phase transformation, with change to more stable phases such as hydroxyapatite affecting the rate of resorption. Despite its importance, the analysis of phase transformation has been largely undertaken using methods that only detect crystalline composition and give no information on the spatial distribution of the phases. In this study confocal Raman microscopy was used to map cross-sections of brushite cylinders aged in Phosphate Buffered Saline, Foetal Bovine Serum, Dulbecco’s – Minimum Essential Medium (with and without serum). Image maps showed the importance of ageing medium on the phase composition throughout the ceramic structure. When aged without serum, there was dissolution of the brushite phase concomitant to the deposition of octacalcium phosphate (OCP) around the periphery of the sample. The deposition of OCP was detectable within five days and reduced the rate of brushite dissolution from the material. The use of serum, even at a concentration of 10vol% prevented phase transformation. This paper demonstrates the value of confocal Raman microscopy in monitoring phase change in biocements; it also demonstrates the problems with assessing material degradation in non-serum containing media.

No MeSH data available.


Bulk compositional analysis of powdered samples at each time point from the PBS ageing series acquired using (A) XRD and (B) Raman spectroscopy.
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f5: Bulk compositional analysis of powdered samples at each time point from the PBS ageing series acquired using (A) XRD and (B) Raman spectroscopy.

Mentions: Having found that CRM mapping of brushite cylinders was able to spatially determine phase change in media with different compositions, the study was extended to encompass a longer time series allowing a deeper investigation of the material evolution. Raman imaging mapping of cylinders dynamically aged in PBS for 50 days was performed and processed as before over the whole cylinder cross section (Fig. 4) and at a higher resolution over the edge region (Fig. 5). A 514 nm laser was used due to the minimal auto-fluorescence in PBS aged samples, enabling a higher signal intensity and access to a higher spectral resolution grating for improved differentiation of the PO4 peaks.


Visualising phase change in a brushite-based calcium phosphate ceramic
Bulk compositional analysis of powdered samples at each time point from the PBS ageing series acquired using (A) XRD and (B) Raman spectroscopy.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015027&req=5

f5: Bulk compositional analysis of powdered samples at each time point from the PBS ageing series acquired using (A) XRD and (B) Raman spectroscopy.
Mentions: Having found that CRM mapping of brushite cylinders was able to spatially determine phase change in media with different compositions, the study was extended to encompass a longer time series allowing a deeper investigation of the material evolution. Raman imaging mapping of cylinders dynamically aged in PBS for 50 days was performed and processed as before over the whole cylinder cross section (Fig. 4) and at a higher resolution over the edge region (Fig. 5). A 514 nm laser was used due to the minimal auto-fluorescence in PBS aged samples, enabling a higher signal intensity and access to a higher spectral resolution grating for improved differentiation of the PO4 peaks.

View Article: PubMed Central - PubMed

ABSTRACT

The resorption of brushite-based bone cements has been shown to be highly unpredictable, with strong dependence on a number of conditions. One of the major factors is phase transformation, with change to more stable phases such as hydroxyapatite affecting the rate of resorption. Despite its importance, the analysis of phase transformation has been largely undertaken using methods that only detect crystalline composition and give no information on the spatial distribution of the phases. In this study confocal Raman microscopy was used to map cross-sections of brushite cylinders aged in Phosphate Buffered Saline, Foetal Bovine Serum, Dulbecco’s – Minimum Essential Medium (with and without serum). Image maps showed the importance of ageing medium on the phase composition throughout the ceramic structure. When aged without serum, there was dissolution of the brushite phase concomitant to the deposition of octacalcium phosphate (OCP) around the periphery of the sample. The deposition of OCP was detectable within five days and reduced the rate of brushite dissolution from the material. The use of serum, even at a concentration of 10vol% prevented phase transformation. This paper demonstrates the value of confocal Raman microscopy in monitoring phase change in biocements; it also demonstrates the problems with assessing material degradation in non-serum containing media.

No MeSH data available.