Pyridoanthrone-based chromo-fluorogenic amphiphiles for selective CN− detection and their bioimaging application

Abstract

Cyanide anion (CN−) is one of the most hazardous chemicals for humans but is inevitably used in various purposes. In this study, we prepared fluorescent pyridoanthrone-based probes 1 and 3 with an N-octyl viologen pendant to detect this toxic anion. Among various anions, the presence of CN− only turned over a large fluorescence enhancement of these viologen probes, giving an LOD of 1 and 10 nM for probes 1 and 3, respectively. These probes also enabled for ‘naked-eye detection’ thanks to the generation of vivid pink color in the presence of this anion. Other probes (2, 4 and 5) with no N-octyl viologen pendant were also capable of selectively sensing CN−, but clearly inferior to probes 1 and 3 in terms of detection sensitivity. The sensitive and fast CN− detection was ascribed to the efficient addition reaction of each N-octyl viologen probe with CN−, leading to the generation of a highly fluorescent hydrolyzed product, isolated as a pyridoanthrone amine derivative. Due to the presence of hydrophobic and aromatic-aromatic interactions as well as H-bonding between probe molecules, the probes organized into self-assemblies with the positive surfaces in aqueous solution, allowing fast addition reactions between the probe and CN− to produce color and fluorescence emission. Probe 1 proved effective at detecting CN− content in HeLa cells and could be used as a solid state for inexpensive and convenient detection of CN−. The current system was fully studied by various analytical methods such as UV–vis, fluorescence, and 1H NMR spectroscopy, DLS, FE-SEM images, TEM, DFT calculations, HRMS and X-ray crystallography.