Biphasic Nano-Domains of Planar Lipid Bilayer Complexed with Fluorogenic Polymer Reporter Tailored for Antimicrobial Detection

We have fabricated an unexpected type of supported planar bilayer composed of receptor phospholipids and single-chained diacetylenes as fluorogenic reporters using protruded anchor moieties with a positive terminal charge. Nanoscale topographical and surface thermodynamic analyses, as well as molecular dynamics simulations, revealed the coexistence of well-dispersed liquid-condensed (L_c) domains forming nano-islands and liquid-expanded (L_e) region in the planar bilayer, enhancing sensitivity against a prototype of ubiquitous membrane-associated antimicrobial peptides, melittin. The L_eregions, acting as target receptors, enabled sensitive detection as the melittin adsorbed and inserted into these regions due to strong hydrophobic interactions between phospholipids and melittin. The L_cdomains, serving as signal reporters, enabled diacetylenes to assemble, polymerize, and fluoresce in response to the insertion of melittin into the L_eregions. Thus, biphasic nanodomains of the planar lipid bilayer finally endowed this sensor system with a detection range of 100 μMto 50 nM and a limit of detection (LOD) of ∼37 nM for melittin. This exceeded the operational performance of the colorimetric polydiacetylene vesicle solution 45 times, which reportedly ranged from 100 to 4 μM with an LOD of ∼1.7 μM.