Three-Dimensional Mass Spectrometric Imaging of Biological Structures Using a Vacuum-Compatible Microfluidic Device

Area of Science:

• Analytical Chemistry
• Biophysics
• Materials Science

Background:

• Secondary-ion mass spectrometry (SIMS) is a powerful tool for 2D and 3D molecular imaging of biological structures.
• Traditional sample fixation methods for SIMS are often complex, difficult to control, and limit 3D molecular analysis.
• In situ liquid SIMS has shown promise for studying liquids and interfaces.

Purpose of the Study:

• To develop a more convenient and controllable method for 3D molecular imaging of biological samples using SIMS.
• To adapt in situ liquid SIMS for freeze-fixation of biological specimens.
• To enable accurate depth calibration for 3D imaging of frozen biological samples.

Main Methods:

• Development of a novel vacuum-compatible microfluidic device for in situ liquid SIMS.
• Implementation of freeze-fixation of biological samples within the microfluidic device.
• Determination of ice sputter rates using a 20 keV Ar1800+ ion beam and molecular dynamics simulations.
• 3D molecular imaging of frozen homogenized milk.

Main Results:

• The new microfluidic device facilitates convenient and controllable freeze-fixation of biological samples.
• Sputter yield of Ar1800+ on ice was determined to be 1500 (±8%) water molecules per ion, consistent with simulations.
• Successful 3D molecular imaging of frozen homogenized milk revealed network structures of organic and inorganic species.

Conclusions:

• The developed vacuum-compatible microfluidic device significantly enhances 3D molecular imaging of biological samples using in situ liquid SIMS.
• This method offers improved control and convenience for sample preparation and imaging.
• The findings are expected to benefit diverse research fields requiring detailed 3D molecular analysis of biological structures.