Hi,
I immersed scaffold containing sodium alginate and CaCO3 in SBF solution for 28 days and observed the HA formation using SEM/EDX (Hitachi TM3030 Plus) with gold coating. This machine can go up to 15kV and the highest magnification with clear image only up to 5000. I followed Kokubo and Takadama 2006 for SBF solution preparation.
In my EDX results, the elements that can be detected only C, O, Na, Cl, Ca, Au. The P element always hard to be detected and only present in very minute percentage. So, I cannot get Ca/P ratio around 1.67.
Do you have any idea why this is happening? Thank you
All I can tell you is that EDX analysis mostly reveals the elements present in the surface of the material you are examining.
1. Get synthetic HA , check your system with it.
2. You cannot expect to get Ca/P ratio of 1.67 with any EDS system if you do not use proper standards. You have to perform quantitative analysis with standards.
I'm not familiair with HA formation on scaffolds but I understand that hydroxyapatite is "grown" onto your scaffold and that you're looking at a 3D structure.
Quantitative micro-analysis in an SEM requires more stringent conditions to be correctly applied : area of interest should at least be (bulk) conductive, smooth, anisotropic, homogeneous . Which is probably not the case with your sample.
The use of proper standards may allow you to get a ratio that might (or not) approach the 1.67 stoechiometry (I'd work at 10 kV for Ca and P) but I concur with former posts that EDX is not the method of choice for this and that you'll have more success using molecular spectroscopy of XRD.
Perhaps you do not have fully formed HA then the phosphorous concentration would be low. Also P Kalpha line is at 2.013 and Au Malpha line is at 2.120, if you coated heavy with the Au the Au might be absorbing the or the overlap maybe preventing the system to fully deconvoluting of the separate element peaks.
Mohammad Kooti: That is true. Thank you.
Md. Abdur Rahman
: Thank you for your suggestion, I will check the HPO4~2 and HCO3- content in my SBF.Vladimir Dusevich : Thank you for your suggestion. I will try to compare with synthetic HA.
Pierre Caulet : Yes, you are right. I am growing hydroxyapatite on my scaffold and observed it using SEM and EDX. But I cannot get the desired result. I will try using XRD as you have suggested. Thank you.
Clarissa A Wisner : Maybe you are right. The HA might not fully form. Do you have idea why HA not fully form even I had immersed it for 28 days? Thank you for sharing your opinion.
I can only speculate as to why the HA is not fully formed, could be your SBF is not the concentration you believe due to the original chemicals being contaminated or compromised. With out a comparison spectra of HA to compare it is difficult to say what exactly is the issue. Always run a spectra of the control to compare with so that you have a starting place to check if things are not as they should. Also you should coat with carbon when doing EDS.
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