Naphthalimide-phenanthroimidazole incorporated new fluorescent sensor for “turn-on” Cu2+ detection in living cancer cells

Sellamuthu Anbu, Anup Paul, Kalpana Surendranath, Ahmed Sidali, Armando J. L. Pombeiro

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12 Citations (Scopus)


In recent years, fluorescent sensors have emerged as attractive imaging probes due to their distinct responses toward bio-relevant metal ions. However, the bioimaging application main barrier is the ‘turn-off’ response toward paramagnetic metal ions such as Cu 2+ under physiological conditions. Herein, we report a new sensor (2-methyl(4-bromo-N-ethylpiperazinyl-1,8-naphthalimido)-4-(1H-phenanthro[9,10-d]imidazole-2-yl) phenol) NPP with multifunctional (Naphthalimide, Piperazine, Phenanthroimidazole) units for fluorescent and colourimetric detection of Cu 2+ in an aqueous medium. Both absorption and fluorescence spectral titration strategies were used to monitor the Cu 2+-sensing property of NPP. The NPP displays a weak emission at ca. 455 nm, which remarkably enhances (⁓3.2-fold) upon selective binding of Cu 2+ over a range of metal ions, including other paramagnetic metal ions (Mn 2+, Fe 3+, Co 2+). The stoichiometry, binding constant (K a) and the LOD (limit of detection) of NPP toward Cu 2+ ions were found to be 1:1, 5.0 (± 0.2) × 10 4 M −1 and 6.5 (± 0.4) × 10 −7 M, respectively. We have also used NPP as a fluorescent probe to detect Cu 2+ in live (human cervical HeLa) cancer cells. The emission intensity of NPP was almost recovered in HeLa cells by incubating ‘in situ’ the derived Cu 2+ complex (NPP-Cu 2+) in the presence of a benchmark chelating agent such as EDTA (ethylenediaminetetraacetate). The fluorescent emission of NPP was reverted significantly in each cycle upon sequencial addition of Cu 2+ and EDTA to the NPP solution. Overall, NPP is a novel, simple, economic and portable sensor that can detect Cu 2+ in biological and environmental scenarios.

Original languageEnglish
Article number111466
JournalJournal of Inorganic Biochemistry
Early online date24 Apr 2021
Publication statusPublished - Jul 2021


  • Cu -sensors
  • Mannich base
  • Napthalimide
  • Optical sensors
  • Phenanthroimidazole
  • Turn on sensors

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