Self-assembly of a water soluble perylene and surfactant into fluorescent supramolecular ensembles sensitive to acetylcholinesterase activity

The modulation of assembly/disassembly of perylene diimide derivatives (PDIs) represents an intriguing challenge for fluorescence sensing purposes. Herein, an aminoacid-functionalized PDI (PDI-Thr) is selected as a conformationally-sensitive probe which transduces the modification of its aggregation state into an optical response. Photoluminescence measurements reveal that the emission of PDI-Thr in aqueous solution can be finely modulated by a cationic surfactant, myristoylcholine chloride (MyrCh). Fluorescence sensing studies illustrate that the PDI-Thr/MyrCh ensembles exhibit an emission intensity variation in response to the enzymatic activity of acetylcholinesterase, which is able to reverse the surfactochromic effect by catalyzing the hydrolysis of MyrCh. Detailed NMR investigations elucidate the supramolecular mechanism behind the sensing behavior. This study sheds light on the synergistic combination of electrostatic and hydrophobic interactions occurring between PDI-Thr and MyrCh, leading to the fluorescent ensemble which is responsible for the sensing performance. The discussed results outline that the development of fluorophore/surfactant ensembles based on water soluble PDIs have great potential for the label-free sensing of a wide range of analytes and enzymes.