Selective Coordination of Cu2+ and Subsequent Anion Detection Based on a Naphthalimide-Triazine-(DPA)2 Chemosensor

Abstract

A new fluorescent chemosensor for copper (II) and subsequent anion sensing was designed and fully characterized. The sensor consisted of a 1,8-naphthalimide core, bearing two terminal dipicolylamine (DPA) receptor units for binding metal cations, and an ethoxyethanol moiety for enhanced water solubility. The DPA units are connected to position 4 of the fluorophore via a triazine-ethylenediamine spacer. Fluorescence titration studies of the chemosensor revealed a high selectivity for Cu2+ over other divalent ions, the emissions were strongly quenched upon binding, and a stability constant of 5.52 log units was obtained. Given the distance from DPA chelating units and the fluorophore, quenching from the Cu2+ complexation suggests an electron transfer or an electronic energy transfer mechanism. Furthermore, the Cu2+-sensor complex proved to be capable of sensing anionic phosphate derivatives through the displacement of the Cu2+ cation, which translated into a full recovery of the luminescence from the naphthalimide. Super-resolution fluorescence microscopy studies performed in HeLa cells showed there was a high intracellular uptake of the chemosensor. Incubation in Cu2+ spiked media revealed a strong fluorescent signal from mitochondria and cell membranes, which is consistent with a high concentration of ATP at these intracellular sites.

1,8‐Naphthalimide‐Based Chemosensors: A Promising Strategy for Detection of Metal Ions in Environmental and Biological Systems

“…The limit of detection of 70 for Cu 2+ ions was found to be 2.06 μM with a 1 : 1 binding ratio as analyzed by Job's plot. In addition, the low cellular toxicity of the probe supported its practical applicability in biological studies on intracellular ATP accumulation [123] …”

“…In addition, the low cellular toxicity of the probe supported its practical applicability in biological studies on intracellular ATP accumulation. [123] Cangiotti et al (2021) synthesized a 1,8-napthalimide-based zero-generation polyamidoamine (PAMAM) dendrimer ( 72) for the recognition of Cu 2 + ions. Its synthesis involved peripheral modification of the primary amino group of naphthalimide core moiety 71 followed by subsequent nucleophilic substitution of the nitro group with N-methyl piperazine at ambient temperature to yield compound 72 in good yield (Scheme 13).…”

Acyl hydrazone‐based supramolecular polymer for ultrasensitive detection of Fe3+, Pd2+, H2PO4− and its application for Suzuki coupling reactions

“…[11][12][13][14][15] It is well known that many anions and cations are essential micronutrients in living organisms, and that ion levels are stable, excessive, or lack could seriously affect the health of organisms. [16][17][18][19] For example, Fe 3+ deficiency leads to anemia and overloading causes organ damage and tissue inflammation. 20,21 Similarly, excessive phosphate (H 2 PO 4 À ) can seriously affect kidney function, and a sudden drop in levels may lead to abnormal heart rhythms and even death.…”

Progress in the Development of Biosensors Based on Peptide–Copper Coordination Interaction

“…In addition, divalent copper ions are paramagnetic and easy to combine with electron chelating groups with appropriate cavity volume. This will cause the change of electron or energy transfer mode when the organic molecules are excited, resulting in the reduction or quenching of the fluorescence signal [ 10 , 11 , 12 , 13 , 14 ]. The design of biosensors based on the intrinsic fluorescence quenching ability and the redox activity of copper ions has been widely covered by researchers.…”