Antimicrobial peptides at (lipid) interfaces: Insights from monolayer models

Antimicrobial peptides (AMPs) are key effectors of innate immunity that, beyond their canonical activity, exhibit promising therapeutic potential against cancer and cellular senescence. Their efficacy relies on selective membrane disruption driven by specific lipid signatures, yet quantifying these interactions in complex bilayer systems remains challenging. Lipid monolayers serve as powerful reductionist models to isolate the physicochemical determinants of this selectivity, effectively mimicking the outer leaflet of bacterial, cancerous, or senescent membranes. This review provides a critical analysis of how lipid composition, packing density, and phase behavior modulate AMP adsorption and insertion. We systematically integrate thermodynamic profiling (surface pressure, compressibility, mixing energy) with advanced structural and morphological characterization. Special emphasis is placed on how spectroscopic techniques (IRRAS, GIXD, SFG) and real-time microscopy (BAM, fluorescence, AFM) resolve peptide orientation, secondary structure induction, and lipid domain remodeling at the mesoscale. These experimental observables are bridged with Molecular Dynamics (MD) simulations, establishing a feedback loop between macroscopic measurements and atomistic resolution. By defining the advantages and limitations of monolayer models relative to vesicles and bilayers, we outline a rational framework for leveraging interfacial insights in the design of next-generation peptide therapeutics and nanobiotechnological applications.