Browsing by Author "Sambhav Vishwakarma"

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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.
Converting CO2into heterocyclic compounds under accelerated performance through Fe3O4-grafted ionic liquid catalysts
(Royal Society of Chemistry, 2022) Niraj K. Vishwakarma; Shikha Singh; Sambhav Vishwakarma; Ajay Kumar Sahi; Vijay Kumar Patel; Shiva Kant; Sanjeev Kumar Mahto
Solid supported catalysts such as amines are in high demand for the chemical fixation of CO2 into commodity chemicals. Here, we demonstrate an accelerated platform for 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-ionic liquid (IL) catalyzed CO2 fixation via the grafting of DBU-ILs over magnetically separable Fe3O4 nanoparticles (MNPs). The DBU-ILs were covalently immobilized over Fe3O4 MNPs utilizing the thio-ene reaction of allyl-DBU with -SH modified Fe3O4 MNPs. The DBU-IL-grafted Fe3O4 (Fe3O4@DBU-ILs) materials were characterized by Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and vibrating-sample magnetometry (VSM). TEM revealed that the MNPs have a spherical structure with a particle size of 12-20 nm. VSM showed the gradual decrease in magnetization after stepwise grafting from Fe3O4 to Fe3O4@DBU-ILs. The efficacy of the two different Fe3O4@DBU-ILs, Fe3O4@[HDBU+][TFE-] and Fe3O4@[HDBU+][AcO-] prepared by neutralization of Fe3O4@DBU with 2,2,2-trifluoroethanol (TFE) and acetic acid (AcOH), was investigated by simultaneous fixation of CO2 into the important heterocyclic compounds quinazoline-2,4(1H,3H)-dione and benzimidazolone. This approach shows excellent recyclability with a nominal decrease (2-3%) in product yields after each cycle. In particular, the energy-dispersive X-ray spectroscopy (EDX) mapping of Fe3O4@[HDBU+][TFE-] used for five cycles demonstrated significant leaching of TFE. Interestingly, after retreatment with TFE, Fe3O4@[HDBU+][TFE-] showed a similar yield to that of a fresh catalyst. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Doxorubicin loaded pH responsive biodegradable ABA-type Amphiphilic PEG-b-aliphatic Polyketal-b-PEG block copolymer for therapy against aggressive murine lymphoma
(Elsevier Inc., 2020) Sumit Kumar Hira; Kheyanath Mitra; Prateek Srivastava; Shikha Singh; Sambhav Vishwakarma; Ranjeet Singh; Biswajit Ray; Partha Pratim Manna
A novel ABA-type polyethylene glycol (PEG)-b-polyketal (PK)-b-PEG block copolymer was synthesized via click reactions between the monoazido-monomethoxy-PEG and dialkyne terminated aliphatic polyketal with no carboxylic/amide linkages. Formation of the novel block copolymer was confirmed by 1H NMR, GPC, TGA, and DSC studies. The formed copolymer has shown faster degradation at acidic pH. Self-assembly of this block copolymer (average size 6.2 nm) was assessed by fluorescence study using pyrene as a probe. Doxorubicin loaded block copolymeric micelles (69.9 nm) have shown pH dependent elevated drug release at pH 6.4, indicating its potential as a pH responsive nano-carrier for anticancer therapy. The nano-sized copolymer demonstrated tumoricidal activities against the lymphoma of murine and human origin with significant levels of growth inhibition and apoptosis. Therapy with doxorubicin loaded copolymer reduced the tumor size and augmented the life span of the tumor bearing animals with improved histopathological parameters, compared with the untreated control. © 2019 Elsevier Inc.
Effect of L-menthol chain-end on the optical rotation, chirality, tacticity and thermal properties of polystyrene prepared by ATRP and polyvinylacetates prepared by RAFT polymerization: A molecular weight dependence study
(Elsevier Ltd, 2021) Sambhav Vishwakarma; Archana Kumari; Kheyanath Mitra; Shikha Singh; Zhiyi Song; Masayoshi Bando; Tamaki Nakano; Susanta Kumar Sen Gupta; Biswajit Ray
Two series of L-menthol-tagged homopolymers: one polystyrenes (PSt) and the other polyvinylacetates (PVAc) having different molecular weights have been synthesized via ATRP of styrene, and RAFT polymerization of vinyl acetate, respectively. Optical rotation study has established the magnitude of the optical rotation value for the both polymer series has been found decreasing exponentially with the increase of their molecular weights. CD study has revealed an exponential decrease in the molar ellipiticity values at 235 nm with the increase in the DPs of polymers in both the polymer systems. Formed PSts and PVAcs are atactic and slightly syndiotactic, respectively. With increase in the chain length of the polymers, glass-transition temperature (Tg) values have been found increasing exponentially in both systems. Therefore, living radical polymerization using suitable ATRP initiator or, RAFT agent containing suitable chiral moiety can be useful in inducing chirality in polymers up to high chain length. © 2020 Elsevier Ltd
Effect of n-Alkyl Side Chain Length on the Thermal and Rheological Properties of PolyN-(3-(alkylamino)-N-(3-(isopropylamino)-3-oxopropyl)acrylamide) Homopolymers
(John Wiley and Sons Inc, 2021) Archana Kumari; Sambhav Vishwakarma; Kheyanath Mitra; Chuangbi Chen; Shuming Cui; Biswajit Maiti; Sourov Mondal; Chandra Sekhar Biswas; Pralay Maiti; Florian J. Stadler; Biswajit Ray
Four new N-isopropylacrylamide- and N-n-alkyl amine-based acrylamide monomers, N-(3-(alkylamino)-N-(3-(isopropylamino)-3-oxopropyl) acrylamide (Mn) (n = 4, 8, 10, 12) are successfully synthesized and polymerized via reversible addition-fragmentation chain-transfer polymerization (polyMn, n = 4, 8, 10, and 12), which are characterized by gel permeation chromatography, 1H NMR, Fourier transform infra red spectroscopy, thermo-gravimetry-differential thermal analysis, differential scanning calorimetry (DSC), and rheology. All polymers are thermally stable and undergo a two-step degradation process at ≈280 and ≈375 °C. Glass transition temperature (Tg)s of these polymers decrease gradually from 99.6 to 52.5 °C with increasing n-alkyl side chain length. The rheology of these polymers in melt state agrees to a typical Rouse-melt behavior and allows for confirming the Tg determined from DSC. Benzyl alcohol solution rheology proves a weak structural build-up, in particular for polyM12. Comparison of the quantum chemical calculations of polyMns with n = 4–8 reveals increase in backbone helicity with increasing n-alkyl side chain length. © 2021 Wiley-VCH GmbH.
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.
In Vitro Anticancer Drug Delivery Using Amphiphilic Poly(N-vinylpyrrolidone)-b-Polyketal-b-Poly(N-vinylpyrrolidone) Block Copolymer as Micellar Nanocarrier
(Wiley-Blackwell, 2018) Kheyanath Mitra; Sumit Kumar Hira; Shikha Singh; Niraj Kumar Vishwakarma; Sambhav Vishwakarma; Uttam Gupta; Partha Pratim Manna; Biswajit Ray
We have first synthesized acid-degradable alkyne-terminated aliphatic polyketal and thereof synthesized novel pH-responsive double hydrophilic amphiphilic block copolymer of poly(N-vinyl pyrrolidone) (PNVP) and aliphatic polyketal (PK) (PNVP-b-PK-b-PNVP via click chemistry upon reaction with azide-terminated PNVP. Formation of block copolymer is confirmed by proton nuclear magnetic resonance, gel permeation chromatography, thermogravimetry, differential scanning calorimetry, and fluorescence spectroscopy techniques. pH-dependent degradation study of the block copolymer shows faster degradation at lower pH. Transmission electron microscopy (TEM) has revealed the formation of tiny (∼3.8 nm) micellar nanoparticles. Loading of the anticancer drugs doxorubicin (Dox) and imatinib in the micelle is confirmed from UV-Visible, and TEM studies. Drug release study from drug-loaded micelles has shown that imatinib is being released faster than Dox and both systems have shown higher load release at acidic pH of 6.4. Doxorubicin- and imatinib- loaded micelles demonstrate significant tumoricidal properties against parental and drug resistant human erythroleukemia K-562 and Dalton's lymphoma cells with respect to enhanced cellular uptake, cytotoxicity and growth inhibition. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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.
Synthesis of ABA-type double hydrophilic amphiphilic PU-based block copolymers of poly(N-Vinylpyrrolidone) and poly(N-isopropylacrylamide) via click chemistry
(Bellwether Publishing, Ltd., 2021) Niraj Kumar Vishwakarma; Vijay Kumar Patel; Payel Mitra; K. Ramesh; Kheyanath Mitra; Sambhav Vishwakarma; Krishnendu Acharya; Nira Misra; Pralay Maiti; Biswajit Ray
Double hydrophilic ABA-type amphiphilic polyurethane (PU)-based poly(N-vinylpyrrolidone) (PNVP)-b-PU-b-PNVP and poly(N-isopropylacrylamide) (PNIPAM)-b-PU-b-PNIPAM triblock copolymers have successfully been synthesized via the combination of the step-growth polymerization, reversible addition-fragmentation chain transfer (RAFT) polymerization and azide-alkyne click reaction. All polymers are characterized by 1H NMR, FTIR, and gel permeation chromatography. The cmcs of PNVP-b-PU-b-PNVP block copolymers increase with increase in PNVP block length: 0.0019 mg/mL for PNVP39-b-PU-b-PNVP39 and 0.005 mg/mL for PNVP68-b-PU-b-PNVP68. The iron-chelating ability and the reducing power of PNVP68-b-PU-b-PNVP68 are superior to that of PNVP owing to the presence of urethane moiety of PU block in copolymer. The LCST of PNIPAM-b-PU-b-PNIPAM are lower than that of PNIPAM (33 °C): 23.5 and 25.5 °C for PNIPAM42-b-PU-b-PNIPAM42 and PNIPAM66-b-PU-b-PNIPAM66, respectively. © 2020 Taylor & Francis Group, LLC.