Supramolecular Aggregates from core-functionalized 1,8-naphthalimides: insights into self-assembling and sensing ability for drugs in water

Abstract

To monitor emerging pollutants in water, we herein describe three novel core-substituted, self-assembling 1,8-naphthalimide derivatives, applied as fluorescent sensors to detect drugs in water. These fluorophores differ for the substitution on the core and imide positions. We initially studied photophysical properties of the fluorophores by solvent-dependent UV–vis and fluorescence measurements and then investigated their self-assembly, finding that they mostly form J-aggregates in water and water/DMSO solutions, following an isodesmic pathway. We also obtained insights on the thermodynamic parameters of the aggregation process and characterized the aggregate morphology by Scanning Electron Microscopy. Subsequently, we studied how these supramolecular aggregates act as fluorescent sensors to detect in aqueous solutions drugs belonging to different classes, like non-steroidal, anti-inflammatory and antibiotic drugs. To this aim, we conducted fluorescence measurements in the presence of variable drug concentrations. The best-performing system could detect ketoprofen with limit of detection (LOD) and limit of quantification (LOQ) of 2.3 and 6.9 μM, respectively. Finally, we embedded the best-performing fluorophore onto solid supports including filter paper strips or polymer poly(3-hydroxybutirate) films. When these fluorophore-doped solids were soaked in ketoprofen solutions at different concentrations, significant quenching of emission was detected.