A new subtle and integrated detector to sense Hg2+ ions: A vision towards its applicability on water samples and live cells
Graphical abstract
Introduction
Detection of heavy metal ions in the surroundings has been emerging as an important research zone in the last few decades because of its impact on environment and human health. There has been a significant interest in the designing of excellent probes for the detection of mercury ions among the other heavy metal ions owing to its well-documented poisonous nature of various forms such as elemental (or metallic), inorganic (to which people may be exposed through their occupation) and organic (e.g., methylmercury, to which people may be exposed through their diet) [1], [2], [3], [4]. By comparing the effects of these three forms, the organic mercury (methyl mercury - CH3HgX, X = Cl, Br and I) has been renowned as a deadly one to both environment and biotic systems. The remaining two forms such as elemental and inorganic mercury are also changed to organic mercury by the bacteria present in the environment [5], [6], [7], [8], [9]. Eventhough, the mercury ions are hazardous, the usage is increased nowadays due to the vast industrial growth like mining industries (extraction of gold, coal, diamond etc.,), paint and pigment manufacturing industries as well as in electroplating works [10], [11], [12], [13], [14], [15]. As a result, the industry releases the wastes containing a tremendous amount of mercury ions to the environment which can be accumulated to the biotic system through consumption of food containing mercury ions [16], [17], [18]. Hence, the mercury ions get accumulated in the biological systems and lead to several diseases like damages in DNA and chromosomes, irregular brain function, disturbances in nervous systems, pink disease in babies (acrodynia), allergies like skin rashes and adverse reproductive effects as well as pulmonary toxicity (damages to sperms, ovum and miscarriages etc.,) [19], [20], [21], [22], [23], [24], [25]. To protect the human health, the USEPA (United States Environmental Protection Agency) had resolute the maximum level of Hg2+ ions contaminant in food and drinking water must be below 10 nM (2 ppb) [26], [27], [28]. Hence, an effectual method should be needed to detect the mercury ions in both environment and biotic system with high selectivity and rapid sensitivity.
Owing to the above reasons, fluorogenic chemosensor technique has been chosen as a desirable method rather than other traditional methods (atomic absorption spectroscopy, electrochemical analysis and inductively coupled plasma mass spectrometry) because the traditional methods require costly equipment with appropriate surrounding, need sample pre-treatment and consume more time to detect the metal ions [29], [30], [31], [32], [33], [34]. Moreover, fluorescence method possesses lot of merits like simple operation, naked eye detection, rapid responses towards analytes, easy data collection and cost-efficacy [35], [36], [37], [38], [39]. Generally, the chemosensors used for the detection of metal ions must possess a functionality (fluorescent/calorimetric) group and produce clear outputs in the spectral configurations. In this concern, the chemosensor with metal selective center have been serving as a valuable tool and are widely applied to recognize the significant analytes (metal ions) in the biological and ecological systems. Hence, for the photosensitive recognition of analytes, the changes will be occurring in the UV–Vis spectral patterns by following any one mechanism such as PET, ESIPT, FRET, TICT, ICT or MLCT [40], [41], [42], [43], [44]. For instance, Mani Vedamalai et al., constructed a “turn-on” chemosensor named as MSI (monostyryl boron dipyrromethane containing triazole group) on the basis of hindrance in ICT mechanism for the detection of Hg2+ ions in live cells with the detection limit of 1.864 × 105 M [45]. Kuppusamy Kanagaraj et al., designed a ESIPT based fluorescent “turn-off” probe to sense Hg2+ ions in CH3CN - H2O medium with the lowest detection limit of 1 × 10-12 M and made its utilization towards real water samples analysis [46]. PET and PCT mechanism related probe (sugar-quinoline) for tracking of mercury ions in water samples with the LOD value of 0.5 µM have been synthesized by Shengju Ou et al., [47]. Sait Malkondu et al., constructed a novel “turn on” perylene-bisimide dye to monitor Hg2+ ions (LOD = 2.20 ± 0.15 µM) with increased fluorescent enhancement (upto 20 folds) [48]. Huiliang Dai et al., prepared an environmental friendly water soluble probe for the recognition of Hg2+ ions in water system with the detection limit of 3 × 10-8 M [49]. Detection of mercury ions in waste water samples was done by Raju Nandhakumar et al., using a BINOL based “turn-on” receptor with the LOD value of 4.4 × 10-7 M [50]. Even though, many literatures were available to track mercury ions in the environment, it is still interested to develop a more flexible and versatile novel chemosensor moiety to detect mercury ions up to trace levels with better selectivity and sensitivity.
Therefore, in this work we uncovered a novel “TURN-ON” integrated probe BMC [(2,2’-((propane-2,2-diylbis(6-vinyloxy)-3,1-(phenylene))bis(methaneylylidene))dimalanonitrile] with suitable recognition moiety to detect the mercury ions with excellent biocompatibility and adaptability. Generally, these types of integrated “turn-on” probes are preferred in recent days because it possesses a unique recognition moiety to detect the analytes with outstanding selectivity and high sensitivity by minimizing interference of background species [51], [52], [53]. Moreover, the synthesized probe BMC selectively detects Hg2+ ions even in nanomolar concentration with rapid response over other competitive ions. Besides, the probe BMC could be effectually applied to track the mercury analyte in real samples and in live HeLa cancer cells (bioluminescence studies).
Section snippets
Materials and methods
All the chemicals used for the synthesis were acquired from Sigma-Aldrich. The solvents delivered by commercial suppliers were of analytical grade and hence they were used without any extra purification. The double distilled water was used all through the preparation process. The melting point was measured in an open capillary tube using Technico micro heating table and was uncorrected. To obtain the analytical data, Vario EL III Elemental analyzer was used. Absorption and emission spectra were
Design and synthesis
The precursor compounds 1, 2 and 3 were synthesized by following procedures provided in the electronic supplementary material. Detailed preparation methods for the probe BMC and control compound BM were given in experimental section. Overall scheme for the synthesis of probe BMC and control compound BM is charted in Scheme 1. The formation of the desired compounds was confirmed by the results of the micro analysis and spectral studies (1H NMR, 13C NMR and ESI–MS) (Figs. S1-S6).
Spectroscopic investigations of the probe BMC and control compound BM
The 1H NMR
Conclusions
A new integrated “turn-on” chemodosimeter for the detection of Hg2+ ions was successfully designed and characterized. The probe BMC shows an excellent selectivity along with rapid sensing and fluorescent enhancement activity towards Hg2+ ions over other competitive metal ions based on “oxy-mercuration reaction” with the LOD value of 18.4 nM. Further, the “oxy-mercuration reaction” followed by intramolecular cyclization reaction was confirmed by comparing the spectral properties of control
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors express their sincere thanks to Council of Scientific and Industrial Research (CSIR), New Delhi, India [grant no. 01 (2907)/17/EMR-II] and University Grants Commission (UGC), India [grant no. 540/20/DRS-I/2016(SAP-I)] for financial assistance.
References (58)
- et al.
Rhodamine-based fluorescent sensor for mercury in buffer solution and living cells
Dyes Pigm.
(2011) - et al.
A novel “turn-on” thiooxofluorescein-based colorimetric and fluorescent sensor for Hg2+ and its application in living cells
Talanta
(2017) - et al.
Rhodamine-assisted fluorescent strategy for the sensitive and selective in-field mapping of environmental pollutant Hg(II) with potential bioimaging
J. Lumin.
(2019) - et al.
Mercury levels along the food chain and risk for exposed populations
Environ. Res.
(1998) - et al.
A novel dithiourea-appended naphthalimide “on-off” fluorescent probe for detecting Hg2+ and Ag+ and its application in cell imaging
Talanta
(2019) - et al.
3-(Pyridine-4-thione)BODIPY as a chemodosimeter for detection of Hg(II) ions
Dyes Pigm.
(2012) - et al.
Benzothiazole based chemosensors having appended amino group(s): selective binding of Hg2+ ions by three related receptors
Inorg. Chim. Acta
(2017) - et al.
Detection of Hg2+ ion in aqueous media by new fluorometric and colorimetric sensor based on triazole–rhodamine
J. Photochem. Photobiol. A
(2015) - et al.
Naked-eye chromogenic and fluorogenic chemosensor for mercury(II) ion based on substituted distyryl BODIPY complex
Dyes Pigm.
(2019) - et al.
A new sensitive and selective chromogenic and fluorescent chemodosimeter for Hg(Ⅱ) in aqueous media and its application in live cell imaging
Dyes Pigm.
(2013)
Fluorescent chemosensor based on urea/thiourea moiety for sensing of Hg(II) ions in an aqueous medium with high sensitivity and selectivity: A comparative account on effect of molecular architecture on chemosensing
J. Mol. Struct.
A rhodamine B-based fluorescent sensor toward highly selective mercury (II) ions detection
Talanta
Photophysical investigations of a FRET-based bifluorophoric conjugate and its Hg(II) specific ratiometric ‘turn-on’ signaling
J. Photochem. Photobiol. A
A novel urea-linked dipodal naphthalene-based fluorescent sensor for Hg(II) and its application in live cell imaging
Talanta
Off-on fluorescent sensor based on the bis(2,4,7,8,9-pentamethyldipyrrolylmethene-3-yl)methane for detection of Cd2+ and Hg2+ cations
J. Lumin.
A selective turn-on fluorescent sensor for Hg(II) in living cells and tissues
Sens. Actuators B Chem.
A simple rhodanine-based fluorescent sensor for mercury and copper: the recognition of Hg2+ in aqueous solution, and Hg2+/Cu2+ in organic solvent
J. Photochem. Photobiol. A
Luminescent and chromogenic molecular probes based on polyamines and related compounds
Coord. Chem. Rev.
Propyl phthalimide-modified thiacalixphenyl[4]arene as a “turn on” chemosensor for Hg(II) ions
J. Lumin.
Luminescent sensors and switches in the early 21st century
Tetrahedron
A novel perylene-bisimide dye as “turn on” fluorescent sensor for Hg2+ ion found in DMF/H2O
Dyes Pigm.
Binol based “turn on” fluorescent chemosensor for mercury ion
J. Lumin.
Diverse benzothiazole based chemodosimeters for the detection of cyanide in aqueous media and in HeLa cells
Sens. Actuators B Chem.
Dual-channel responsive fluorescent sensor for the logic-controlled detection and bioimaging of Zn2+ and Hg2+
J. Mol. Liq.
An efficient “Ratiometric” fluorescent chemosensor for the selective detection of Hg2+ ions based on phosphonates: its live cell imaging and molecular keypad lock applications
Anal. Methods
A dual chemosensor for Cu2+ and Hg2+ based on a rhodamine-terminated water-soluble polymer in 100% aqueous solution
Analyst
A novel tryptamine-appended rhodamine-based chemosensor for selective detection of Hg2+ present in aqueous medium and its biological applications
Anal. Bioanal. Chem.
Fluorescence detection of Hg2+ based on Hg2+-induced formation of dsDNA
Chin. J. Anal. Chem.
Recent advances in sensitive and rapid mercury determination with graphene-based sensors
J. Mater. Chem. A
Cited by (5)
Bisphenol A derived chemosensors for various ionic species: Small progress, long way to go and ample opportunities
2023, Inorganica Chimica ActaRational design of diphenyl-λ<sup>5</sup>σ<sup>4</sup>-phosphinine based fluorescent probe for the selective detection of Hg<sup>2+</sup> ions: Real application in cell imaging and paper strips
2023, Journal of Photochemistry and Photobiology A: ChemistryCitation Excerpt :Numerous studies using this reactivity-based detection method concentrate on altering the fluorophore or adding other thiocarbonyl-based functionalities to fluorochromes, such as thiourea, thioamide, and thioester [21]. Chemodosimetry relies on Hg2+ ions for critical functions through many mechanisms, including the promotion of hydrolysis of the vinyl ether group and the mediation of desuflurization of the CS bond [12,18,22,23]. So far, many successful sensor probes for detecting Hg2+ ions have been made.
A “turn-on” fluorescent chemosensor for the meticulous detection of gallium (III) ion and its use in live cell imaging, logic gates and keypad locks
2023, Journal of Photochemistry and Photobiology A: ChemistryCitation Excerpt :There is a pressing need to develop effective and precise technologies to detect trace gallium for both health and economic reasons. Spectrophotometry, membrane, co-precipitation, extraction and chromatography, X-ray diffraction, calorimetry, fluorescence spectrometry, AAS, ICP-AES, ICP-MS, fluorimetry, polarography, and ion-selective electrodes have all been described as analytical methods for gallium determination [35–37]. However, in recent decades, fluorescence has developed a very selective, sensitive, low-cost, and quick deployment approach for detecting metal ions [38].