Analysis of human tissues using Energy Dispersive X Ray Fluorescence-Dark matrix determination for the application to cancer research

Background: X ray Fluorescence has been essayed as a suitable technique for the elemental quantification of trace element in human tissues, namely comparison of normal and cancerous tissue. However, accurate results depend on a robust quantification approach, namely correct evaluation of the samples' dark matrix. Methods: In order to determine the most suitable dark matrix composition for the quantification of such samples using the Fundamental Parameter approach, we have measured several Certified Reference Materials and essayed different dark matrix compositions to achieve the most accurate results. The resulting dark matrix was then applied to normal and tumor ovarian and prostate tissue samples, and the obtained results were compared with the ones obtained with a comparative method using external standard calibration curves. Results: Using a dark matrix composed of 10 % -H, 22 % -C, 3 % -N and 60 % -O yielded the best compromise in accuracy for the light and heavy elements. For the reduced sample size and conditions of this study, for both organs, the concentrations of transition metals decrease in tumor tissues, while the concentration of lighter elements, P and Cl, increases. On the other hand, there are elements that showed different behavior between the two types of tissue, namely Zn and S, that increase in prostate tumor tissue and decrease in ovarian tissue. Conclusion: An increase in precision was one of the improvements found with the newly developed method, as the FP-approach contemplates matrix effects and the influence of other elements in the analytes' quantification. Additionally, the determined dark matrix can be employed in any tissue analysis application by means of EDXRF.

Automated summary

X-ray Fluorescence is considered a suitable technique for elemental quantification in human tissues, with results showing differences in transition metals and lighter elements between normal and tumor tissues. The study developed an accurate quantification approach by determining the most suitable dark matrix composition and found improvements in precision and accuracy for tissue analysis applications.