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-e regions, 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-c domains, serving as signal reporters, enabled diacetylenes to assemble, polymerize, and fluoresce in response to the insertion of melittin into the L-e regions. Thus, biphasic nanodomains of the planar lipid bilayer finally endowed this sensor system with a detection range of 100 mu M to 50 nM and a limit of detection (LOD) of similar to 37 nM for melittin. This exceeded the operational performance of the colorimetric polydiacetylene vesicle solution 45 times, which reportedly ranged from 100 to 4 mu M with an LOD of similar to 1.7 mu M.