Scanning ion microprobe assessment of biological sample preparation techniques

Area of Science:

• Materials Science
• Biophysics
• Analytical Chemistry

Background:

• High lateral resolution imaging is crucial for understanding biological sample composition.
• Conventional preparation methods like chemical fixation or lyophilization can alter ion distribution and ultrastructure.
• Accurate correlation of ultrastructure and bioaccumulation requires preserving in vivo ion concentrations.

Purpose of the Study:

• To investigate different preparation techniques for high lateral resolution scanning ion microprobe imaging of biological samples.
• To determine the optimal method for preserving in vivo ion distribution and ultrastructure.
• To evaluate ion translocations induced during sample preparation.

Main Methods:

• Comparison of chemical fixation and plastic embedding versus frozen-cut and lyophilized sections.
• Development and application of resin-embedding for frozen biological samples.
• Utilizing the University of Chicago Ion Microprobe for imaging and ion analysis.
• Analysis of ion translocations during sample preparation using ion microprobe imaging.

Main Results:

• Chemically fixed and plastic-embedded specimens yield the sharpest histological maps.
• Frozen-cut and lyophilized sections present challenges in correlating ultrastructure and bioaccumulation.
• Resin-embedding of frozen samples offers a compromise, maintaining in vivo ion distribution in flat sections.
• Observed rapid decrease in intracellular potassium/sodium ratio (K+/Na+) in a fast-frozen blood droplet example.

Conclusions:

• Resin-embedding of frozen biological samples is the preferred method for high lateral resolution scanning ion microprobe imaging.
• This technique best preserves the in vivo ion distribution, enabling accurate bioaccumulation studies.
• Understanding ion translocations during preparation is vital for reliable biological sample analysis.