Fluorescent Lower Rim 1,3-Dibenzooxadiazole Conjugate of Calix[4]arene in Selective Sensing of Fluoride in Solution and in Biological Cells Using Confocal Microscopy

Abstract

p- tert-Butyl-calix[4]arene was derivatized by integrating a benzooxadiazole fluorescent tag into its 1,3-arms at the lower rim to result in L and was characterized. L was titrated with 17 anions in THF and found selective for F ions with lowest detection limit of 109 ppb. L and F form a 1:1 complex. L self-assembles in THF to result in sheet like structures which converts into smaller spherical particles upon addition of F. The site of interaction of F was deduced based on H NMR spectroscopy and the coordination features by density functional theory (DFT) computations wherein six noncovalent interactions of the type X-H···F (where X = O, N, or C) were noticed. The sensing of F is reversible when titrated with Ca, and the reversibility was demonstrated for 10 cycles without losing sensitivity. The study has been extended to the biological cells using fluorescence and confocal microscopy. While L shows strong fluorescence in HeLa cells, increasing concentrations of F exhibited greater fluorescence quenching. Thus, L acts as a good sensor for F in solution as well as in biological cells, a rare and unique combination for a calixarene conjugate to exhibit such sensing behavior in dual media.

Dihomooxacalix[4]arene-Based Fluorescent Receptors for Anion and Organic Ion Pair Recognition

“…Fluorogenic moieties, such as naphthalene, anthracene and pyrene are among the most incorporated in the calixarene framework, leading to the development of fluorescent probes for anion and also ion-pair recognition. Examples of such fluorescent calix[4] arene [ 5 , 6 , 7 , 8 , 9 , 10 ], calix[5] arene [ 11 ] and calix[6]arene [ 12 , 13 , 14 ] receptors have been reported in the literature.…”

A Harmonized Applied and Theoretical Exploration for Nanomolar Level Recognition of Perilous F− and CN− by Multichannel Chemosensor: Proposition of Hg2+‐Mediated Logic Gate Imitator

“…Upon excitation at 410 nm, the chemosensor showed an enhanced emission spectrum at 505 nm, which started to diminish upon gradual addition of F À and CN À ( Figure 5). 8,16,38 The feasibility of the targeted anions triggered photoinduced electron transfer (PET) may be the basic reason of the fluorescence quenching of PMA. [22,45] Moreover, upon addition of same amount of F À and CN À the fluorescence quenching efficiency was found to be 55 % for F À and 50 % for CN À suggesting comparatively better binding affinity of PMA towards F À .…”

“…[4,42] F À is a conventional component of hypnotics, anesthetics, military nerve gases, psychiatric drugs, cockroach and rat poisons etc., while superfluity (> 1.5 ppm) of this anion causes dental fluorosis, depression, bone malady, collagen fracture, thyroid activity and even cancer. [5][6][7][8] Therefore, recognition of F À even at very low concentration is a noteworthy concern in recent times. [4,9] Conversely, detection of cyanide (CN À ) has also acquired substantial consciousness because of its various fatal consequences on the surroundings and the breathing beings.…”

“…Among various toxic anions, detection of fluoride (F − ) has gained substantial contemplation owing to its various effects in physiological systems . F − is a conventional component of hypnotics, anesthetics, military nerve gases, psychiatric drugs, cockroach and rat poisons etc ., while superfluity (>1.5 ppm) of this anion causes dental fluorosis, depression, bone malady, collagen fracture, thyroid activity and even cancer . Therefore, recognition of F − even at very low concentration is a noteworthy concern in recent times .…”

Synthesis of New Picolylamine Bearing Calix[8]arene Derivatives as Antiproliferative Agents for Colorectal Carcinoma

“…Inclusion of different functionalities in its structure enhance its biological properties such as enzyme inhibition, antiproliferative, antimicrobial, antiviral, and anti‐tumor activities . Moreover, calixarenes with different kind of biological functions have been designed for cancer diagnosis, treatment, and cell imaging . The application of calixarene as nanobasket in pharmaceutical industries has attracted much interest, owing to their desirable surface modification, biocompatibility, and superior stability.…”