450+ experts on 30 subjects ready to help you just now
Starting from 3 hours delivery
Pssst… we can write an original essay just for you.
Any subject. Any type of essay. We’ll even meet a 3-hour deadline.Get your price
121 writers online
Hydrazine exposure leads to damage of all vital organs of the human and animal, which demands discovery of a rapid and quantitative detection method. A newly designed and synthesized probe showed good cell permeability, low cytotoxicity, fast fluorogenic recognition and “naked eye” detection of hydrazine below the TLV levels present in the living cells, drinking water and industrial effluent.
Keywords: Chemodosimeter, Colorimetric, Rapid fluorescent sensor, Hydrazine, Bioimaging.
Hydrazine (H2N-NH2) is a chemically strong base, nucleophile and reducing agent and its high reactivity leads to wide range of application especially in the industries for large scale production of high value aerospace propellants, pharmaceuticals, agrochemicals, polymers, dyes and chemicals . Flammable and detonable hydrazine is employed as an ingredient for rocket-fuels and air bag , syntheses of azobisformamide(AC) , diisopropyl carbonate and toluenesulfonhydrazide(TSH) , corrosion inhibitor for nuclear and electrical power plants , foaming polymers and alternative energy source to innovative new generation fuel cells. In spite of widespread application, hydrazine, its vapor and water solutions are explosive and poisonous in nature, which can be absorbed to humans and animals on exposure through dermal, oral and inhalation . The highly toxic hydrazine reduces the average life span of the industrial workers and damages their livers, kidneys, lungs, central nervous and respiratory systems . The threshold limit value (TLV) of hydrazine in drinking water must be maintained to be as low as 10 ppb . Therefore instantaneous detection of extremely hazardous hydrazine has significant interest and it is especially crucial in controlling its concentration levels in the industrial area, quantitative detection in human blood and drinking water.
The qualitative and quantitative detection of hydrazine by the conventional titrimetry , spectrochemistry , Electrochemistry , chemiluminescence , chromatography  and surface-enhanced Raman spectroscopy  are not viable for in vivo analyses. In this regards, modern fluorescent techniques are simple, inexpensive, rapid and real-time monitoring, which is ideal technique for in vivo detection of hydrazine . Thus, deprotection-based ﬂuorescence sensing for hydrazine has emerged as an important tool utilizing acetyl [16-21] 4-bromo butyrate [22-23] levulinate [24-25], phthalimides [26-29], aldehydes [30-31], malononitriles [32-34], benzoic acids [35-36], γ-oxo-1-pyrenebutyrates , trifluoroacetylacetonates  and acetylacetonates [29-40]. However, most of these fluorescent probes suffers from longer detect time. Recently, Chow et al.  reported ethylcyanoacetate protected probe for hydrazine having detection limit 12μM and detect within 8 min. This probe shows very poor water solubility as titration was done in buffer: DMSO (1:9). Due to lack of poor water solubility these probe may not be suitable for biological application. Li et al.  also reported similar protected probe for hydrazine having detection limit 1.6 μM and detect within 15 min. In case of this probe, absorption and fluorescence titration was carried out in water/DMSO (4:6). Our target is to design and synthesize almost completely water soluble probe as an efficient ‘‘naked-eye’’ indicator and chemodosimeter for rapid recognition of hydrazine present in human blood and drinking water with quite low detection limit.
The benzothiazole moiety was installed in our designed probe ethyl 3-(3-(benzo[d]thiazol-2-yl)-5-bromo-2-hydroxyphenyl)-2 cyanoacrylate (3, BBHC, Scheme 1) to achieve an excited state intramolecular photon transfer (ESIPT) process upon photoexcitation [44-45]. ESIPT leads to making “O” atom in the phenolic OH highly electronegative, which in turn will induce more positive character in carbon atom of -CN. In the presence of –Br and -CN, electrophilic nature of the C=C double bond is drastically enhanced towards nucleophilic hydrazine for rapid formation of coloured hydrazone, 2-(benzo[d]thiazol-2-yl)-4-bromo-6-(hydrazonomethyl) phenol (4, BBHP).
As a result, this recognition even observable through naked eye and fluorescence change, which will be help to detect hydrazine colorimetrically and fluorogenically in a quantitative measurement.
The designed probe (BBHC) was synthesized through oxidative cyclization of o-aminothiophenol with 5-bromosalicylaldehyde (Step 1, Scheme 2) to 2-arylbenzothiazole (1), formylation of 1 to 2 (Step 2), and piperidine catalyzed condensation (Step 3) of 2 with ethyl cyanoacetate to 3. The new probe was obtained in high yields and its structure was established through 1H NMR, 13C NMR and ESI MS spectroscopic analyses (ESI).
All materials were purchased from Sigma-Aldrich Chemicals Private Limited and were used without further purification. All solvents were purchased from domestic suppliers and were used after distillation. 1H-NMR and 13C-NMR spectra were recorded on Brucker 300 MHz instruments. CDCl3 was used as solvent with TMS as an internal standard. Chemical shifts are expressed in δ units and coupling constants in Hz. Melting points were determined on a hot-plate melting point apparatus in an open-mouth capillary and were uncorrected. UV-vis titration experiments were performed on a Perkin Elmer Lambda 750 spectrophotometer and fluorescence experiments using Perkin Elmer LS 55 with a fluorescence cell of 10 mm path. Column chromatography was carried out by using silica gel 60 (60−120 mesh).Time-correlated single photon counting (TCSPC) set-up is used to determine fluorescence life time.
A stock solution of the probe was prepared (c = 2 x 10-5 ML-1) in CH3CN: H2O (1:9, v/v). The solution of the guest anions, metal ions and amine containing compounds were prepared (2 x 10-4 ML-1) in CH3CN: H2O (1:9, v/v) at pH 7.1 by using 10 mM HEPES buffer. The solution of sensor was made ready by appropriate dilution technique. The spectra of these solutions were recorded by UV−Vis and ﬂuorescence methods.
To estimate the efficiency of BBHC to detect hydrazine endogenously 5 mL of venous blood was obtained from a healthy volunteer donor (Male, 32 year) with his informed consent. Peripheral blood mononuclear cells or PBMCs (lymphocytes and monocytes) were isolated within one hour of sampling by density gradient centrifugation using histopaque-1077 (Sigma) by centrifuging at 400 ×g for 30–40 min at room temperature. The middle layer or ‘buffy coats’ contains the PBMCs which were collected carefully and washed twice in phosphate buffered solution (PBS, pH 7.4). PBMCs were re-suspended in PBS and divided in six sets. Cells were incubated for 1 h 37 oC in dark with 10, 20, 30, 40 and 50 µM of N2H4 respectively along with 5 µM of BBHC. A separate PBMCs set was incubated simultaneously with 5 µM of BBHC but without N2H4. Intracellular fluorescence intensity was detected by fluorescence microscope (Carl Zeiss HBO 100) under 40X magnification in filter set 49 DAPI which gives emission peak for 464nm.
To determine cell viability against BBHC, PBMCs were treated with different concentrations of BBHC solution (2-20µM) for 1 h at 37 oC against control cell suspension with no added BBHC. Cell density remains 106 cells per well in a 96- well plate. 100µl of MTT solution (5mg/mL) was added to each well including control and incubated for 4 h. at 37 oC. The purple colored form zan crystals were dissolved with 100µl DMSO and the absorbance were measured at 570 nm. Cell viability was calculated using the following calculation.
It was easily prepared by immersing a TLC plate into the solution of BBHC (2 Χ 10-4 M) in CH3CN (1 mM) and exposing it to air to evaporate the solvent. The detection of hydrazine was carried out by inserting the TLC plate to the different concentration of hydrazine (1 mM) and evaporating solvent to dryness.
A solution of 2- aminothiophenol (2 mL, 2 mmol) and 5 bromosalicyldehyde (400 mg, 2 mmol) in EtOH (5 mL), aqueous H2O2 (30%, 12.0 mmol) and aquous HCl (37%, 8.5 mmol) was stirred at ambient temperature for 6 h. The solution was quenched by 10 mL H2O. The precipitate was filtered, washed with ethanol, dried under vacuum and recrystallized from EtOH to afford the desired product as a white solid (480mg, 79.47% yield).
The compound 1 (420 mg, 1.2 mmol), hexamethylenetetramine (420 mg, 3 mmol), and trifluoroacetic acid (5 mL) were added to a round bottomed flask,. The mixture was refluxed overnight. After the mixture was cooling down, the acid was neutralized with aqueous KOH solution. The precipitate was collected by filtration, and washed with water for several times. After drying under vacuum, compound 2 was obtained in >99% yield, and had the following spectral properties.
The compound 2 (100 mg, 0.3 mmol), ethylcyanoacetate (68 μL, 0.6 mmol), and 2-3 drops piperidine were dissolved in 10 mL ethanol. The mixture was refluxed for 3 h at 80 °C and cooled to room temperature. The final product (probe BBHC, 110 mg, 82%) was obtained by filtration and being washing with ethanol for three times.
BBHC was mixed with one equivalents of hydrazine in acetonitrile at room temperature to give a yellow solution. Upon removing the solvent, a solid product was obtained which was used for 1H-NMR and mass spectroscopy.
We provide you with original essay samples, perfect formatting and styling
To export a reference to this article please select a referencing style below:
Sorry, copying is not allowed on our website. If you’d like this or any other sample, we’ll happily email it to you.
Attention! This essay is not unique. You can get a 100% Plagiarism-FREE one in 30 sec
Sorry, we could not paraphrase this essay. Our professional writers can rewrite it and get you a unique paper.
Please check your inbox.
Want us to write one just for you? We can custom edit this essay into an original, 100% plagiarism free essay.Order now
Are you interested in getting a customized paper?Check it out!