Title:Intracellular and Extracellular Zinc Detection by Organic Fluorescent Receptor
Volume: 23
Issue: 24
Author(s): Muhammad Hanif, Muhammad Rafiq, Muhammad Mustaqeem, Muhammad A. Shaheen, Kaneez F. I. Qadri, Ishtiaq Qadri*Muhammad Saleem*
Affiliation:
- Department of Biologiy, Faculty of Sciences, King Abdulaziz University, PO Box 80216 Jeddah 21589,Saudi Arabia
- Department of Chemistry, University of Sargodha, Sub-campus Bhakkar-30000,Pakistan
Keywords:
Zinc sensor, organic skeletons, fluorescence, bioimaging, optical parameters, pH sensitivity, symmetrical heterocycles, hydrazine
derivatives.
Abstract: Keeping in view the ever growing demand and application of the organic small
molecules based sensitive and selective fluorescence detection strategies for the trace metallic
ions in the ecosystem, fluids and inside intracellular media, the present literature
survey was focused on the recent development on the organic skeleton based fluorescence
sensor for the zinc ion as Zn2+ is the second most abundant transition metal after iron in
human body. The prominent organic based skeletons introduced during the past three
years for zinc detection including azine, ((Z)-N´-(quinolin-2-ylmethylene)furan-2-
carbohydrazide), nicotinohydrazide, hydrazone, phenolic cage, 4-methyl-2,6-bis[(E)-(2-
(4-phenylthiazol-2-yl)hydrazono)methyl]phenol, bipyridine, N-(quinoline-8-yl)pyridine-2-
carboxamide, anthracene, Schiff base, salen, helicene, Carbon Quantum Dots (CDs) functionalized
with Calix[4]arene, coumarin, diaminomaleonitrile, peptide, hydroxypyrazole, salicylhydrazide were
discussed in detail with particular focus on ligand-zinc complexation mechanism, UV-visible and fluorescence
investigation, spectral variation, isosbestic emergence, limit of detection, ligand-zinc binding stoichiometry,
association/binding constant and applications for intracellular tracing of metallic contamination via confocal
fluorescence microscopic studies. Among the several discussed optical probes, rhodamine and fluorescein
based material offer appreciable sensitivity, exhibiting drawback of pH sensitivity. Probes based on these
ligands triggered “turn-on” signal even in the absence of metals upon fluctuation in pH e.g., acidic in former
case and basic in the latter case. Hydroxypyrazole-based ligands also showed detection signal variation by
switching the pH of the solution. Schiff base and bipyridyl scaffold were found to possess good ligation toward
the several transition metals. Azole, oxazole, thiazole, thiadiazole, hydrazine carboxamide and hydrazine carbothiomide
are the bioactive molecules exhibiting good cell viability and probes designed by using these central
nucleus might be better to invest for intracellular imaging. Symmetrical heterocyclic cage like probe
showed better chelation toward several transition metals and it is a good choice for the design and development
of sensor for simultaneous detection of several transition metals.