Browsing by Author "Rajshree Singh"

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Brominated Graphene as Mimetic Peroxidase for Sulfide Ion Recognition
(American Chemical Society, 2017) Shikha Singh; Kheyanath Mitra; Aparna Shukla; Rajshree Singh; Ravi Kumar Gundampati; Nira Misra; Pralay Maiti; Biswajit Ray
Brominated graphene (GBR) with ∼3% bromine content has shown novel peroxidase mimetic activity toward 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. Optimum activity has been observed at pH 4.48 and after a minimum ∼30 min of equilibration time. Among the different analytes studied using the sensor combining TMB, H2O2, and GBR in phosphate buffer of pH 4.48, the S2- ion has effectively shown a short duration of sensing (∼2 min) within the detection range of 0.04-1 mM. A calibration curve for S2- ion estimation has been constructed with the experimental linearity in 0.04-0.4 mM range and having the limit of detection (LOD) value of 25.3 μM. A standard addition experiment has validated the method. A paper strip sensor has been fabricated for successful detection of S2- ion. © 2016 American Chemical Society.
Cathodic contact glow discharge electrolysis: Its origin and non-faradaic chemical effects
(Institute of Physics, 2017) Susanta K. Sen Gupta; Rajshree Singh
Normal electrolysis (NE), at sufficiently high voltages, breaks down and undergoes a transition to a phenomenon called contact glow discharge electrolysis (CGDE) in which a sheath of glow discharge plasma encapsulates one of the electrodes, the anode or the cathode. The chemical effects of CGDE are highly non-faradaic e.g. a mixture of H2 and H2O2 plus O2 each in excess of the Faraday law value is liberated at the glow discharge plasma electrode from an aqueous electrolyte solution. Studies of cathodic CGDE, particularly its origin and chemical effects, in comparison to those of anodic CGDE have received significantly less attention and have not been studied in detail. The present paper is an attempt towards elucidation of the mechanisms of the growth of cathodic CGDE during NE and its non-faradaic chemical effects. The findings of the study have led to the inference that emission of secondary electrons from the metal cathode with sufficient kinetic energies, vaporization of the electrolyte solvent in the vicinity of the cathode surface induced by Joule heating and the onset of hydrodynamic instabilities in local vaporization contribute to the generation of the plasma at the cathode during NE. The findings have further shown that non-faradaic yields of CGDE at the cathode originate from energy transfer processes in two reaction zones: a plasma phase reaction zone around the cathode which accounts for ∼75% of the yields, and a liquid phase reaction zone near the plasma-catholyte solution interface accounting for the remaining ∼25% of the yields. © 2016 IOP Publishing Ltd.
Cell proliferation influenced by matrix compliance of gelatin grafted poly(D,L-Lactide) three dimensional scaffolds
(Elsevier B.V., 2018) Chelladurai Karthikeyan Balavigneswaran; Sanjeev Kumar Mahto; Arun Kumar Mahanta; Rajshree Singh; Mahalingam Rajamanickam Vijayakumar; Biswajit Ray; Nira Misra
Surface and mechanical properties of the biomaterials are determinants of cellular responses. In our previous study, star-shaped poly(D,L-Lactide)-b-gelatin (ss-pLG) was reported for possessing improved cellular adhesion and proliferation. Here, we extended our investigation to establish the cellular compatibility of gelatin-grafted PDLLA with respect to mechanical properties of biological tissues. In this view, linear PDLLA-b-gelatin (l-pLG) was synthesized and tissue-level compatibility of 1-pLG and ss-pLG against fibroblasts (L929), myoblasts (C2C12) and preosteoblasts (MG-63) was examined. The cell proliferation of C2C12 was significantly higher within l-pLG scaffolds, whereas L929 showed intensified growth within ss-pLG scaffolds. The difference in cell proliferation may be attributed to the varying mechanical properties of scaffolds; where the stiffness of l-pLG scaffolds was notably higher than ss-pLG scaffolds, most likely due to the variable levels of gelatin grafting on the backbone of PDLLA. Therefore, gelatin grafting can be used to modulate mechanical property of the scaffolds and this study reveals the significance of the matrix stiffness to produce the successful 3D scaffolds for tissue engineering applications. © 2018 Elsevier B.V.
Colorimetric detection of hydrogen peroxide and cholesterol using Fe3O4-brominated graphene nanocomposite
(Springer Science and Business Media Deutschland GmbH, 2022) Jaydeep Singh; Rajshree Singh; Shikha Singh; Kheyanath Mitra; Sourov Mondal; Sambhav Vishwakarma; Biswajit Ray
Fe3O4-brominated graphene (Fe3O4-GBR) nanocomposites were synthesized via an in situ method using the precursors FeSO4.7H2O and GBR in different (1:1, 1:2, 2:1, 1:5, 1:10, 1:20, and 5:1) weight ratios at pH 11.5. The Fe3O4-GBR (1:5) nanocomposite in combination with H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB) showed swift and superior intrinsic peroxidase mimetic enzyme activity compared with the other Fe3O4-GBR composites, GBR and Fe3O4, as observed by colorimetry. It was characterized using high-resolution scanning electron microscopy (HRSEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Its catalytic activity was optimized by varying different parameters, and the optimum conditions for peroxidase mimetic activity were observed using 100 μL Fe3O4-GBR (1 mg/mL), 50 μL TMB (1 mg/mL), and 200 μL H2O2(1 mM) in 400 μL of acetate buffer of pH 2.3 at 30 °C temperature. Kinetic analysis has revealed the Michaelis–Menten kinetic behavior of peroxidase activity with Michaelis–Menten constants (Km) and maximum initial velocities (Vmax) of 0.082 mM and 14.1 nMs−1 respectively, for H2O2 and 0.086 mM and 5.1 nMs−1, respectively for TMB. The limit of detection and linear range were found to be 49.6 μM and 100–880 μM, respectively, for H2O2 and 41.9 μM and 47.6–952.3 μM, respectively, for cholesterol. On this basis, a simple, swift, sensitive, selective, and reproducible colorimetric assay to detect cholesterol levels in blood serum samples using Fe3O4-GBR nanocomposite has been developed. Thus, Fe3O4-GBR composite as compared to Fe3O4 and GBR has shown better peroxidase mimicking activity for biosensing. Graphical abstract: [Figure not available: see fulltext.] © 2022, Springer-Verlag GmbH Germany, part of Springer Nature.
Colorimetric detection of hydrogen peroxide and glucose using brominated graphene
(Royal Society of Chemistry, 2017) Shikha Singh; Kheyanath Mitra; Rajshree Singh; Archana Kumari; Susanta Kumar Sen Gupta; Nira Misra; Pralay Maiti; Biswajit Ray
Very recently, we have reported a novel peroxidase mimetic material, brominated graphene (GBR) having ∼3% bromine content, which, in combination with H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB), has shown the property of S2- ion recognition (Anal. Chem., 2017, 89, 783-791). In the present work, we further have investigated the kinetic assay and colorimetric sensing ability of GBR towards hydrogen peroxide (H2O2) and glucose. The Michaelis-Menten constants (Km) and maximum initial velocities (Vmax) of GBR have been found to be 10.98 mM and 3.60 × 10-8 M s-1, respectively, for H2O2 and 0.83 mM and 0.68 × 10-8 M s-1, respectively, for TMB. A sensor combining TMB and GBR has been fabricated, which, upon addition to H2O2 or glucose with glucose oxidase solution at pH 4.48, showed colorimetrically a significant increase in the oxidation of TMB. The fabricated sensor system has displayed linearity for H2O2 and glucose estimation in the range 0.50-5.00 mM and 40-100 mM, respectively, and the corresponding limits of detection are found to be 0.417 and 28.41 mM, respectively. The present sensor system is also highly reproducible and selective. The results of real samples using this colorimetric method have been found to be comparable with the conventional auto-analyser method. © The Royal Society of Chemistry 2017.
Electrochemical sensing of hydrogen peroxide using brominated graphene as mimetic catalase
(Elsevier Ltd, 2017) Shikha Singh; Monali Singh; Kheyanath Mitra; Rajshree Singh; Susanta Kumar Sen Gupta; Ida Tiwari; Biswajit Ray
Recently we have reported the peroxidase mimicking ability of metal free brominated graphene (GBR) (Analytical Chemistry, 89, 783–791, 2017) at a pH less than 7.2. Here we report the novel catalase mimicking ability of GBR via electrochemical (electro-oxidation) detection of hydrogen peroxide (H2O2) at pH ≥ 7.2. We have fabricated successfully a low cost electrochemical sensor using GBR coated glassy carbon electrode (GCE) [(GBR-GCE)-working electrode] and showed its excellent cyclic voltametry (CV) response towards electro-oxidation of hydrogen peroxide (H2O2), which is so far shown by electrodes made of platinum-group metals like Pt, Ir, Ru etc. Thus, GBR has exhibited the dual mimicking ability as peroxidase and also as catalase under different conditions. A plausible mechanism of sensing of hydrogen peroxide has been proposed involving the formation of perhydroxyl radical (HO2˙) facilitated by GBR-GCE as the electrode. Calibration curves for H2O2 detection using both CV and differential pulse voltametry (DPV) techniques have been constructed over 0.1–10 mM linearity range with the limits of detection of 0.048 and 0.063 mM, respectively. This fabricated electrochemical sensor is highly selective, specific and its response current is least affected by the presence of interfering analytes. The results are found highly reproducible and the use of GBR has also minimized the problem and specificity associated with natural enzymes, as it can easily be stored at room temperature. Real samples have also been successfully analyzed using our fabricated sensor. © 2017 Elsevier Ltd
Highly selective fluorescence 'turn off' sensing of picric acid and efficient cell labelling by water-soluble luminescent anthracene-bridged poly(: N -vinyl pyrrolidone)
(Royal Society of Chemistry, 2019) Rajshree Singh; Kheyanath Mitra; Shikha Singh; Sudipta Senapati; Vijay Kumar Patel; Sambhav Vishwakarma; Archana Kumari; Jaydeep Singh; Susanta K. Sen Gupta; Nira Misra; Pralay Maiti; Biswajit Ray
A novel, water-soluble, luminescent anthracene-bridged AA-type bi-arm poly(N-vinylpyrrolidone) (ATC-PNVP) was synthesized using a click reaction between alkyne-terminated PNVP and 9,10-bis(azidomethyl)anthracene. The resultant anthracene-bridged PNVP (ATC-PNVP) was characterized using 1H NMR, FTIR, UV-Vis, and fluorescence spectroscopic methods and GPC analysis. ATC-PNVP showed effective fluorescence properties in an aqueous medium. It showed highly selective "turn off" sensing behaviour towards picric acid, a common nitro-aromatic explosive, with a wide linear range of detection of 0.01-0.3 mM and LOD value of 0.006 mM in water. ATC-PNVP-based paper sensors also showed very effective detection of picric acid in the concentration range 0.001-1.0 mM. Its binding with bovine serum albumin (BSA) was studied using steady-state, synchronous and 3D fluorescence spectroscopy and this study showed effective quenching of the intrinsic fluorescence of BSA and occurrence of a FRET-type interaction. Furthermore, this luminescent ATC-PNVP was efficiently used as a fluorescence microscopy labelling agent in NIH-3T3 and HeLa cells, and showed greater uptake and hence better fluorescent labelling in the cytosols of the tested cells than free 9,10-bis(azidomethyl) anthracene. The cell viability study also showed a very good biocompatible and non-toxic nature of ATC-PNVP at lower working concentrations towards each of the types of cells tested. © 2019 The Royal Society of Chemistry.
L-menthol-based initiators for atom transfer radical polymerization of styrene
(John Wiley and Sons Inc., 2019) Sambhav Vishwakarma; Archana Kumari; Kheyanath Mitra; Shikha Singh; Rajshree Singh; Jaydeep Singh; Susanta K. Sen Gupta; Biswajit Ray
Two new atom transfer radical polymerization (ATRP) initiators, 2-isopropyl-5-methylcyclohexyl 2-bromopropanoate (1) and 2-Isopropyl-5-methylcyclohexyl 2-bromo-2-methylpropanoate (2), have been synthesized by the reaction of 2-bromopropanoyl bromide and 2-bromo-2-methylpropanoyl bromide, respectively, with L-menthol and characterized by 1H and 13C NMR and FTIR spectroscopic studies. ATRP of styrene has successfully been carried out in a control manner using these initiators along with catalyst/ligand system consisting of Cu(I)Br/N,N,N/,N/,N//-pentamethyldiethylenetriamine. Polymerizations have yielded polystyrenes (PSts) of controlled molecular weight with low polydispersity index having a menthyl end group, as confirmed by 1H NMR and gel permeation chromatography [GPC]. The controlled nature of the polymerization has also been confirmed by kinetic study of the polymerization process monitored via 1H NMR and GPC. Initiator 2 has evolved as most efficient among the two. The obtained end-functional PSt has also been used as a macroinitiator for homochain extension with styrene and heterochain extension with methyl methacrylate to produce PSt-b-PMMA, showing the living nature of the polymerization process. In comparison with the PSt sample prepared using widely used initiator ethyl-2-bromo-isobutyrate with almost the same molecular weight and polydispersity, initiator 2-made L-menthyl-capped PSt has shown higher light transmission properties of its dichloromethane solution at ~259 nm, higher thermal stability, lower glass transition temperature, a broad melting temperature, and higher surface roughness over its film. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47964. © 2019 Wiley Periodicals, Inc.
L-menthol-based xanthate mediator for RAFT polymerization of vinyl acetate
(Taylor and Francis Inc., 2020) Sambhav Vishwakarma; Archana Kumari; Kheyanath Mitra; Shikha Singh; Rajshree Singh; Jaydeep Singh; Susanta K. Sen Gupta; Biswajit Ray
A xanthate RAFT agent 2-isopropyl-5-methylcyclohexyl 2-(ethoxycarbonothioyl)thio) propanoate has been synthesized via the reactions of L-menthol with 2-bromo-propionyl bromide in THF in the presence of triethylamine leading to the formation of 2-isopropyl-5-methylcyclohexyl 2-bromopropanoate followed by its reaction with potassium-O-ethyl xanthate in ethanol at room temperature and characterized by 1H, 13C NMR and FTIR. RAFT polymerization of vinyl acetate (VAc) using it has resulted in the formation of well-defined polyVAc in controlled manner. This is evidenced by (i) the observation of the pseudo first order kinetics upto ∼90% conversion, (ii) linear increment of molecular weight (unimodal GPC chromatogram) of the polymer keeping its PDI low with the progress of the reaction upto ∼90% conversion, (iii) the linear increment of the molecular weight of the polymers with low PDI on increasing monomer loading, (iv) chain-end analysis of the polymer using 1H NMR confirming the presence of the RAFT agent fragment at the polymer chain-ends, and (v) successful homo- and hetero-chain extension with VAc and NVP, respectively. L-Menthyl-capped polyvinyl acetate has shown higher (i) light transmission properties of its dichloromethane solution at ∼277 nm, (ii) thermal stability, and (iii) glass transition temperature in comparison to its non-L-Menthyl-capped homolog. © 2019, © 2019 Taylor & Francis Group, LLC.
Selective nitration of phenol to: O -nitrophenol in the presence of metal-free reduced graphene oxide at room temperature
(Royal Society of Chemistry, 2020) Sourov Mondal; Jaydeep Singh; Shikha Singh; Sambhav Vishwakarma; Kheyanath Mitra; Archana Kumari; Rajshree Singh; Susanta K. Sen Gupta; Biswajit Ray
We report here a reduced graphene oxide (RGO)-catalyzed ultra-efficient, highly selective and low temperature synthesis of o-nitrophenol using phenol and nitric acid in an equimolar ratio. The effects of various parameters such as concentration of reactants, type of catalyst, weight of the catalyst, solvent, temperature and time of reaction on the catalytic reaction have been explored. The optimum conditions for the catalytic nitration reaction have been observed using a 1 : 1 molar ratio of nitric acid to phenol in the presence of 50 mg RGO in dichloroethane at room temperature for 3 h with a turn over frequency (TOF) of 10.96 × 1017 molecules g-1 s-1 and a reaction rate of 12.17 × 1014 molecules mL-1 s-1. In order to explore the decrease in efficiency of the catalyst during reuse, both the parent catalyst and used catalyst have been characterized by XRD, Raman, SEM, EDX, BET and FT-IR. The large surface area of RGO promotes the catalytic activity of aromatic compounds via smooth and high conversion of products with fine regioselectivity. So this protocol opens up a new avenue for the selective synthesis of o-nitrophenol using reduced graphene oxide at room temperature. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Study of the Fluorescence Based Applications of Pyrene-Tagged Poly(N-vinyl-2-pyrrolidone)
(American Chemical Society, 2016) Kheyanath Mitra; Shikha Singh; Sumit Kumar Hira; Vijay Kumar Patel; Deovrat Singh; Sambhav Vishwakarma; Rajshree Singh; Archana Kumari; Partha Pratim Manna; Biswajit Ray
In this study we have explored the fluorescence based applications of luminescent pyrene-tagged PNVP (PyPNVP) reported in our previous work (Int. J. Polym. Mater. Polym. Biomater. 2016, 65, 269-276). PyPNVP has successfully acted as "turn off" chemosensor for metal ions Cu2+, Hg2+, and Pb2+. It has also successfully acted as a fluorescent probe for critical micellar concentration (CMC) determination of amphiphilic block copolymer of poly(d,l-lactide) and poly(N-vinylpyrrolidone) (PDLLA42-b-PNVP120) (Mn = 19 400 g/mol and PD = 1.52). It has also successfully shown an interaction with both plasmid and calf thymus (CT) deoxyribonucleic acids (DNAs) as evidenced by its fluorescence quenching. A different magnitude and type of quenching has been observed for both the cases which may be useful in distinguishing different kinds of DNAs. In order to further understand the potential of PyPNVP in various biotechnological processes, its binding property with bovine serum albumin (BSA) has also been studied. The efficient quenching of intrinsic fluorescence of BSA by PyPNVP through binding and the occurrence of the fluorescence resonance energy transfer (FRET) type of interaction have been studied using steady state, synchronous, and 3D fluorescence spectroscopies. Moreover, a fluorescence microscopic cell imaging study has revealed the significant uptake of PyPNVP in the nucleus of HEPG2 and U87 cells compared to free Py. In addition, the cytotoxicity study showed the tolerance of PyPNVP in all the cell lines tested with no significant cytotoxicity at lower concentrations. © 2016 American Chemical Society.
Study of the fluorescence based applications of water soluble (N, P) doped carbon dots synthesized via microwave assisted green pyrolysis
(Bentham Science Publishers, 2020) Rajshree Singh; Shikha Singh; Sudipta Senapati; Kheyanath Mitra; Jaydeep Singh; Susanta K.S. Gupta; Nira Misra; Pralay Maiti; Biswajit Ray
Background: Water soluble nitrogen and phosphorus doped carbon dots (CD) have been synthesized using citric acid, tris(2-aminoethyl)amine and orthophosphoric acid via one step microwave assisted pyrolytic method. Methods: The CD synthesized has been characterized using FTIR, UV-Vis, fluorescence spectroscopy and EDAX coupled with SEM techniques. Results: SEM study has shown the formation of nanosized CD with an average size of ~18 nm. Elemental analysis via EDAX has confirmed successful incorporation of nitrogen (30.8% wt) and phosphorus (5.7% wt) atoms in it. The steady state and 3D fluorescence spectroscopic studies have shown its efficient fluorescence emission with emission maxima in the region of ~450 nm. It has shown efficient “turn off” fluorescence behaviour towards transition metal ions like Fe2+ and Co2+ ions and toxic nitrophenolic compounds like p-nitrophenol and picric acid. Its efficient interaction with BSA has been revealed in terms of fluorescence quenching of BSA by steady state, synchronous and 3D fluorescence spectroscopy. It has shown very good in vitro biocompatibility and enhanced cell adhesion properties towards NIH 3T3 fibroblast cells. Moreover, fluorescence microscopy has shown significant uptake of CD by the tested cell line. Conclusion: Such bio-compatible nitrogen and phosphorous doped CD can be potentially useful to estimate metal ions, p-nitrophenol and picric acid using fluorescence spectroscopy and for fluorescence based bio-imaging. © 2020 Bentham Science Publishers.
Water Soluble Fluorescent Graphene Nanodots
(Wiley-VCH Verlag, 2018) Shikha Singh; Kheyanath Mitra; Sudipta Senapati; Rajshree Singh; Yajnaseni Biswas; Susanta K. Sen Gupta; Nira Misra; Tarun K. Mandal; Pralay Maiti; Biswajit Ray
Water soluble fluorescent graphene nanodots (GND) have been successfully prepared through a bottom up approach from brominated pyrene via alkaline hydrothermal condensation. FT-IR, UV-Vis, Raman, XRD, AFM, and TEM studies have shown the formation of −OH group rich nanodots having graphene features with an approximate size of 90 nm. Steady state and 3D fluorescence studies have shown efficient fluorescence emission with maximum at 540 nm upon excitation at 450 nm in pH≤7. Plasmid deoxyribonucleic acid (plasmid DNA) and bovine serum albumin (BSA) have shown their interaction with GND, which was studied via fluorescence quenching of GND and BSA, respectively. Selective quenching of the Förster resonance energy transfer (FRET) of BSA-GND conjugate via ascorbic acid (AA) has been used to construct a calibration curve for AA estimation with a linear range and limit of detection of 34.00–112.00 μmole/L and 31.343 μmole/L, respectively. GND has also shown concentration-dependent turn offchemosensing towards heavy metals like Pb2+, Cu2+, Hg2+ and Zn2+. In-vitromulticolor fluorescence imaging has been observed in GND-labelled HeLa (human cervical cancer) and NIH-3T3 (mouse embryonic fibroblast) cell lines with better uptake by HeLa cells. GND also has shown very high viability for both the cell lines up to the tested concentration of 300 μg/mL. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim