X-ray microanalysis of biological specimens by high voltage electron microscopy

Area of Science:

• Cell Biology
• Microscopy
• Analytical Chemistry

Background:

• Electron microscopy offers physical methods like radioautography and X-ray microanalysis for cellular and tissue component analysis.
• X-ray microanalysis is crucial for qualitative and quantitative elemental analysis within biological structures.

Purpose of the Study:

• To detail the application of X-ray microanalysis with intermediate high voltage transmission electron microscopy for elemental quantification.
• To evaluate the effectiveness of this combined methodology on both endogenous and experimentally introduced elements in biological samples.

Main Methods:

• Utilized intermediate high voltage transmission electron microscopy (100-400 kV) with semi-thin sections for X-ray microanalysis.
• Employed various fixation and sectioning techniques, including cryo-methods, to preserve elemental integrity.
• Quantified histochemical reaction end-products (Ag, Ce, Au) and endogenous trace elements (Zn, Ca, S, Cl) and exogenous elements (Al).

Main Results:

• Signal-to-noise ratios (P/B ratios) for quantified elements increased with accelerating voltages up to 300-400 kV.
• Successfully detected and localized endogenous elements like Zn in mouse intestines, Ca in human ligaments, and S/Cl in mouse colonic cells.
• Quantified exogenous Al in mouse liver and kidney cells, with optimal detection at 300 kV.

Conclusions:

• X-ray microanalysis with intermediate high voltage electron microscopy (300-400 kV) provides high P/B ratios for accurate trace element quantification in biological specimens.
• This optimized methodology is highly valuable for microanalysis of diverse compounds and elements across various biological contexts.