Storage of cell samples for ToF-SIMS experiments-How to maintain sample integrity

Area of Science:

• Biophysics
• Analytical Chemistry
• Cell Biology

Background:

• Reproducible time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of biological cells requires careful sample preparation and storage.
• Previous work highlighted the critical impact of preparation routines; this study addresses the effects of storage procedures.

Purpose of the Study:

• To investigate the influence of various wet and dry storage methods on human mesenchymal stem cell cultures.
• To evaluate the long-term stability of lipid and amino acid signals under different storage conditions using ToF-SIMS.

Main Methods:

• Human mesenchymal stem cell cultures were subjected to wet (buffer, water, alcohol) and dry (air-dried, freeze-dried, critical-point-dried) storage for 4 weeks.
• Samples were analyzed by ToF-SIMS immediately after preparation and after storage.
• Principal component analysis was used to compare spectra and assess signal degradation.

Main Results:

• All dry storage methods resulted in notable degradation of lipid and amino acid signals.
• Wet storage in alcohol also showed decreased signal intensities for lipids and amino acids.
• Wet storage in buffer or water showed no degradation after 4 weeks, but carries a risk of contamination.

Conclusions:

• Dry storage is not optimal due to faster degradation, possibly from oxidation and enzyme activity.
• Wet storage in buffer or water is recommended for short-term storage to minimize degradation, with regular solution changes advised to prevent contamination.