XRF Microscopy and its Applications in Biology

X-ray fluorescence microscopy is a quick and non-destructive method of determining the elemental composition of micro-scale samples. Nonetheless, one disadvantage, especially for biological samples, is that the measurements have to be performed in vacuum, which will dehydrate the samples and damage the typical water-containing samples (leaves, microorganisms, tissue, cells, etc.) used in biological/medical research.

To combat this difficulty, the unique X-ray guide tube technology of the XGT-5000 allows high spatial resolution analysis of all elements from sodium to uranium at atmospheric pressure, making it suitable for the safe composition analysis of hydrated samples, powders, and even liquids.

Gastric Ulcers and the Role of Zinc

The XGT is well equipped for the study of biological tissue, and within this analysis, it was used to understand the role of zinc in treating gastric ulcers. Upon analyzing the stomach of a rat with a large ulcer, increased zinc concentration was seen at the edges of the ulcer (Figure 1).

(Left) Transmitted x-ray image and (right) zinc XRF intensity image of ulcerated rat stomach without medication. The ulcer region is circled.

Figure 1. (Left) Transmitted x-ray image and (right) zinc XRF intensity image of ulcerated rat stomach without medication. The ulcer region is circled.

This analysis was undertaken prior to any use of medicine, suggesting that naturally occurring zinc in the body accumulates at the tumor site to aid healing. After treatment with a zinc-containing drug (Figure 2), large zinc concentrations are seen throughout the ulcer, suggesting the effectiveness of using zinc-containing drugs.

(Left) Transmitted x-ray image and (right) zinc XRF intensity image of ulcerated rat stomach following medication. The XRF image is taken from the highlighted region.

Figure 2. (Left) Transmitted x-ray image and (right) zinc XRF intensity image of ulcerated rat stomach following medication. The XRF image is taken from the highlighted region.

Otolith of Horse Mackerel

The otolith, or earstone, is formed by the stratification of any lime secreted from the inner wall of a fish head. Each otolith is unique in terms of its central “ditch” and its growth rings because it depends on the temperature of the sea water and other environmental factors. It is believed that there is some relation between the otolith structure and the fish’s age.

Horse mackerel head, and close up of otolith

Figure 3. Horse mackerel head, and close up of otolith

Analyzing the otolith patterns, or ‘day growth rings’, is thought to be a very promising technique for studying the life of a fish. Additionally, the ratio of trace elements in the make-up of the otolith is related to the environment the fish lives in. Studies combining these two types of data have been undertaken to help with conservation techniques.

Mapping the otolith using the XGT-5000 (Figure 4) provides results which clearly show the “ditch” and the patterning on the bone. The elemental composition of these complex features can be clearly imaged using the unique 10 ?m spatial resolution.

Micro-XRF mapped images of otolith.

Figure 4. Micro-XRF mapped images of otolith.

Summary

Biological samples can be easily and rapidly analyzed using the innovative XGT XRF technology with a spatial resolution which can be set as low as 10 µm. Some examples of processes that can be studied using this technology, without destroying the sample, include drug interactions and healing processes as well as characterization of biomaterials such as bone, which allows insight into organism growth and life cycles.

Acknowledgements

Data for gastric ulcer mapping was provided courtesy of Dr Takeshi Ohtsuka, Clinical Analytics, Kyoto Prefectural University of Medicine.

This information has been sourced, reviewed and adapted from materials provided by HORIBA Scientific.

For more information on this source, please visit HORIBA Scientific.

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