Atomic Force Microscopy to Characterize Antimicrobial Peptide-Induced Defects in Model Supported Lipid Bilayers

Area of Science:

• Biophysics
• Materials Science
• Biochemistry

Background:

• Antimicrobial peptides (AMPs) are crucial for innate immunity but can damage host cell membranes, limiting their therapeutic use.
• Understanding AMP-membrane interactions is complex due to variations in peptide structure, membrane composition, and analytical limitations.

Purpose of the Study:

• To investigate the membrane interaction mechanisms of two distinct AMPs, alamethicin and indolicidin.
• To utilize Atomic Force Microscopy (AFM) to visualize and quantify peptide-induced membrane damage.
• To compare peptide interactions with zwitterionic lipid bilayers, mimicking mammalian cell membranes.

Main Methods:

• Examined the interaction of alamethicin (neutral, α-helical) and indolicidin (cationic, non-α-helical) with supported lipid bilayers (SLBs) composed of egg phosphatidylcholine.
• Employed AFM imaging and roughness analysis to observe peptide-induced membrane alterations.
• Utilized SLBs on quartz supports as a model for mammalian cell membranes.

Main Results:

• Alamethicin at 5 µM caused significant membrane defects, and at 10 µM, it completely removed the lipid bilayer.
• Indolicidin induced smaller, transient holes in the membrane at both 5 and 10 µM concentrations.
• AFM roughness analysis indicated a peak in surface roughness post-peptide injection, followed by a gradual decrease.

Conclusions:

• AFM is a valuable tool for elucidating the dynamic interactions between AMPs and cell membranes.
• The distinct membrane disruption patterns of alamethicin and indolicidin highlight structure-dependent mechanisms.
• Findings can guide the selection and design of more effective AMPs for therapeutic and antimicrobial applications.