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

Abstract

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 (Lc) domains forming nano-islands and liquid-expanded (Le) region in the planar bilayer, enhancing sensitivity against a prototype of ubiquitous membrane-associated antimicrobial peptides, melittin. The Leregions, 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 Lcdomains, serving as signal reporters, enabled diacetylenes to assemble, polymerize, and fluoresce in response to the insertion of melittin into the Leregions. 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.