Polydopamine-Modified Substrates for High-Sensitivity Laser Desorption Ionization Mass Spectrometry Imaging

Area of Science:

• Analytical Chemistry
• Biotechnology
• Materials Science

Background:

• Mass spectrometry imaging (MSI) is crucial for biological research.
• Laser desorption ionization (LDI) is a key ionization technique in MSI.
• Developing advanced materials for LDI, such as matrix-free substrates, is an active research area.

Purpose of the Study:

• To develop a novel composite substrate for matrix-free LDI-MSI.
• To enhance light-to-heat conversion and sample-substrate contact for improved ionization.
• To apply the developed substrate for lipid profiling in biological samples and disease studies.

Main Methods:

• Fabrication of a composite substrate by coating polydopamine (PDA) film onto an antireflection (AR) surface.
• Utilizing the substrate's micro-/nanostructures to confine UV energy for localized heating and analyte desorption.
• Performing matrix-free LDI-MSI on human plasma and mouse brain tissue sections.
• Analyzing lipid profiles, including triacylglycerols and glycerophospholipids, in wild-type and obese mouse liver tissues.

Main Results:

• Successful desorption and ionization of lipids from human plasma and mouse brain tissue sections were achieved.
• Matrix-free LDI-MSI of approximately 30 lipid species in mouse brain sections was demonstrated at 50 μm spatial resolution.
• The method enabled the identification of significant differences in lipid profiles between wild-type and obese mouse liver tissues.
• The developed substrate simplified the MSI procedure.

Conclusions:

• The PDA-coated AR substrate is effective for matrix-free LDI-MSI.
• This approach offers a simplified and efficient method for lipidomic analysis in biological tissues.
• The technique shows promise for studying metabolic diseases like fatty liver disease through lipid profiling.