Scanning force microscopy based rapid force curve acquisition on supported lipid bilayers: experiments and...

Area of Science:

• Materials Science
• Biophysics
• Surface Science

Background:

• Solid-supported lipid bilayers are crucial models for cell membranes.
• In situ imaging of membrane properties in liquid is challenging due to hydrodynamic effects.
• Pulsed force mode scanning force microscopy (PFM-SFM) offers potential for simultaneous topography and material property mapping.

Purpose of the Study:

• To investigate the challenges of PFM-SFM imaging of lipid bilayers in aqueous environments.
• To explain the observed contrast inversions in stiffness and adhesion images.
• To provide insights for optimizing PFM-SFM experimental parameters for reliable material contrast.

Main Methods:

• In situ PFM-SFM imaging of phase-separated lipid bilayers (cholesterol, sphingomyelin, 1,2-dioleyl-phosphatidylcholine) in aqueous solution.
• Computer simulations using a simple harmonic oscillator model.
• Analysis of experimental parameters including driving frequency, amplitude, and trigger setting.

Main Results:

• Hydrodynamic damping significantly impacts cantilever motion in liquid, hindering simultaneous material property and topography imaging.
• Observed contrast inversion in stiffness and adhesion images is dependent on experimental parameters.
• Simulations successfully explain experimental findings and the influence of hydrodynamic damping.

Conclusions:

• Optimizing PFM-SFM parameters based on simulation insights is essential for obtaining interpretable results.
• This work paves the way for high-speed, reliable material contrast imaging of lipid membranes.
• Understanding and mitigating hydrodynamic damping is critical for accurate in situ AFM studies.