Tip-enhanced laser ablation sample transfer for biomolecule mass spectrometry

Area of Science:

• Analytical Chemistry
• Surface Science
• Nanotechnology

Background:

• Traditional mass spectrometry sample preparation can be laborious and may introduce contamination.
• Precise manipulation and transfer of minute quantities of analytes are crucial for high-sensitivity analysis.
• Atomic force microscopy (AFM) offers high spatial resolution for surface imaging and manipulation.

Purpose of the Study:

• To develop and demonstrate a novel method for transferring molecules from thin films to a substrate for off-line mass spectrometry.
• To utilize AFM tip-enhanced laser ablation for precise material removal and collection.
• To enable analysis of both small and large molecules using laser desorption ionization (LDI) and matrix-assisted laser desorption ionization (MALDI).

Main Methods:

• Employing an AFM with a gold-coated silicon tip to ablate material from thin films using a 355 nm Nd:YAG laser.
• Transferring ablated material onto a suspended silver wire positioned near the sample surface.
• Analyzing transferred small molecules (anthracene, rhodamine 6G) via LDI and larger molecules (angiotensin II, bovine insulin) via MALDI.

Main Results:

• Successful transfer of approximately 100 femtograms (fg) of material from 1 μm ablation spots with an estimated 3% efficiency.
• Demonstrated feasibility of analyzing both small organic molecules and larger biomolecules using the developed technique.
• Integration of AFM for precise targeting and laser ablation for material removal and collection.

Conclusions:

• AFM tip-enhanced laser ablation provides a highly localized method for sample transfer in mass spectrometry.
• This technique is versatile, accommodating different molecule types and mass spectrometry ionization methods.
• The method shows promise for sensitive analysis of trace amounts of analytes.