Browsing by Author "Roop Shikha Singh"

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A dual epitope-imprinted polymer@AuNP-MoS2 nanosheets-EQCM sensor for antibody free detection of SipD protein of Salmonella typhi bacteria with high selectivity
(Elsevier B.V., 2025) Akriti Srivastava; Ashish Kumar Kushwaha; Pinky Sagar; Anirban Parida; Roop Shikha Singh; Sanjay Kumar Srivastava; Richa Raghuwanshi; Gopal Nath; Meenakshi K. Singh
Dual-epitope imprinted EQCM sensor for selective and sensitive detection of Salmonella typhi bacterial protein is fabricated on gold nanoparticle decorated MoS2 nanosheets (AuNPs-MoS2NSs). Salmonella invasive protein D (SipD) binds to the needle protein and appears capable of interacting with the translocon complex to infect the host. Potential B cell antigenic epitope sequences from bacterial tip protein, SipD were intentionally tagged with cysteine and are used as dual templates to fabricate MIP sensor using methacryloyloxyethyl phosphorylcholine (MPC), benzyl methacrylate (BMA) and methacrylic acid (MAA) as monomers and N , N ′-methylene- bis -acrylamide as a crosslinker. The monomers chosen through docking produced a DEIP-EQCM sensor. The sensor was able to show specific binding towards the blood samples of infected patients, even in the presence of ‘matrix’ of ‘real’ samples and other plasma proteins. It has shown excellent specificity, sensitivity and selectivity in sensing range of 100–1000 nM with detection limit 1.65 nM (Epitope I) and 0.025 nM (Epitope II) and limit of quantification as 5.03 nM (Epitope I) and 0.075 nM (Epitope II) for the two epitope sequences imprinted. Sip D protein binding was substantiated by SDS-PAGE analysis. The repetitive experimental runs could not mutilate the specific geometries of respective imprinted cavities and the DEIP-EQCM sensor can be proposed for antibody free detection of Sip D protein. © 2025 The Authors.
Achieving flexibility/rigidity balance through asymmetric Donor−Acceptor scaffolds in pursuit of dual state emission with application in acidochromism
(Elsevier Ltd, 2021) Vishwa Deepak Singh; Ashish Kumar Kushwaha; Roop Shikha Singh
Three novel chalcone based asymmetrical D–A–D′–A'chromophores (C1–C3) have been designed and synthesized with intent to achieve dual state emission. It has been contemplated that introducing both flexible and rigid moieties to the D–A core will suffice for the emission in solution as well as solid state. In this regard flexible piperazine unit has been introduced along with rigid polyaromatic hydrocarbons anthracene, C1; pyrene, C2 and phenothiazine, C3 to afford an asymmetric D–A construct. The compounds have been thoroughly characterized by spectroscopic studies (1H, 13C, ESI–MS, UV/Vis and fluorescence). The compounds C1–C3 display varying degree of dual state emission as envisaged by photo-physical investigation in solution, aggregated and solid state along with quantum yield assessment. Notably the aggregation has been instigated in these compounds by taking advantage of relative hydrophilicity/hydrophobicity of different solvent systems. The revered intramolecular charge transfer (ICT) imparts substantial solvatochromism to these D−A constructs. The prudence of incorporation of heteroatomic phenothiazine unit to the designed chromophores is reflected in superior dual state emission and solvatochromism of C3. In addition, these compounds revealed remarkable acid–induced fluorescence quenching effect in solution and solid state as the emission of C1–C3 could be quenched by trifluoroacetic acid (TFA) significantly. © 2020 Elsevier Ltd
AIE active piperazine appended naphthalimide-BODIPYs: photophysical properties and applications in live cell lysosomal tracking
(Royal Society of Chemistry, 2019) Bhupendra Kumar Dwivedi; Roop Shikha Singh; Afsar Ali; Vinay Sharma; Shaikh M. Mobin; Daya Shankar Pandey
Piperazine appended naphthalimide-BODIPYs (NPB1-NPB4) exhibiting solvatochromism and aggregation-induced emission with a large Stokes shift (up to 146 nm) have been described. Separation of naphthalimide and BODIPY fluorophores by piperazine in these conjugates creates a donor-acceptor system and induces twisted intramolecular charge transfer, in addition to photoinduced electron transfer. The crucial role of naphthalimide, the alkyl chain length, the piperazine ring, and the solid-state packing on AIE has been extensively investigated by various studies. Superior cell permeability coupled with bio-compatibility of these conjugates offers a unique opportunity for their potential applications in live cell lysosomal tracking. © The Royal Society of Chemistry.
An unconventional mechanistic insight on aggregation induced emission in novel boron dipyrromethenes and their rational biological realizations
(American Chemical Society, 2016) Roop Shikha Singh; Ashish Kumar; Sujay Mukhopadhyay; Gunjan Sharma; Biplob Koch; Daya Shankar Pandey
Quinolone and quinoline based boron dipyrromethenes (BODIPYs) viz. BQN1 and BQN2 obtained by relative stabilization of keto and enol forms of N-methylated quinolones via minute substitutional variations (-H/-OCH3) have been reported. The relative disparity in degree of aromaticity arising from quinolone/quinoline strongly affects the free rotation of these molecules. The photophysical and structural characteristics of these compounds revealed an exceptional dissonance between restriction of intramolecular rotation (RIR) and aggregation induced emission (AIE) signifying competitive steric hindrance and conjugation. Despite being an AIE inactive dye, BQN1 experiences maximum RIR and excels as a viscosity sensitive hindered molecular rotor, while an effective J-aggregation irrevocably established AIE in BQN2. This is the first report dealing with utilization of AIE active BODIPY (BQN2) in fabrication of AIEgen loaded bovine serum albumin (BSA) nanoparticles with live cell imaging in human breast cancer cell line MDA-MB-231. Binding mode of human serum albumin (HSA) to BQN2 has also been determined by molecular docking studies. In addition, viscochromism of BQN1 has been visualized through apoptotic marking in the MDA-MB-231 cell line. © 2016 American Chemical Society.
Anticancer Activity of Iridium(III) Complexes Based on a Pyrazole-Appended Quinoline-Based BODIPY
(American Chemical Society, 2017) Rajendra Prasad Paitandi; Sujay Mukhopadhyay; Roop Shikha Singh; Vinay Sharma; Shaikh M. Mobin; Daya Shankar Pandey
A pyrazole-appended quinoline-based 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (L1, BODIPY) has been synthesized and used as a ligand for the preparation of iridium(III) complexes [Ir(phpy)2(L1)]PF6 (1; phpy = 2-phenylpyridine) and [(η5-C5Me5)Ir(L1)Cl]PF6 (2). The ligand L1 and complexes 1 and 2 have been meticulously characterized by elemental analyses and spectral studies (IR, electrospray ionization mass spectrometry, 1H and 13C NMR, UV/vis, fluorescence) and their structures explicitly authenticated by single-crystal X-ray analyses. UV/vis, fluorescence, and circular dichroism studies showed that complexes strongly bind with calf-thymus DNA and bovine serum albumin. Molecular docking studies clearly illustrated binding through DNA minor grooves via van der Waals forces and their electrostatic interaction and occurrence in the hydrophobic cavity of protein (subdomain IIA). Cytotoxicity, morphological changes, and apoptosis have been explored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Hoechst 33342 staining. IC50 values for complexes (1, 30 μM; 2, 50 μM) at 24 h toward the human cervical cancer cell line (HeLa) are as good as that of cisplatin (21.6 μM) under analogous conditions, and their ability to kill cancer cells lies in the order 1 > 2. Because of the inherent emissive nature of the BODIPY moiety, these are apt for intracellular visualization at low concentration and may find potential applications in cellular imaging and behave as a theranostic agent. © 2017 American Chemical Society.
Artificial light harvesting gel based on saponification-triggered gelation of aggregation-induced emissive BODIHYs
(Royal Society of Chemistry, 2024) Durgendra Yadav; Vishwa Deepak Singh; Ashish Kumar Kushwaha; Anjani Kumar; Roop Shikha Singh
The present work provides a detailed study on saponification-triggered gelation of ester-based BODIHYs (B1 and B2) derived from ethyl 4-(2-(benzo[d]thiazol-2-yl(cyano)methylene)-hydrazinyl)-benzoate (L1) and diethyl 5-(2-(benzo[d]thiazol-2-yl(cyano)methylene)hydrazinyl)-isophthalate (L2). The ligands and BODIHYs display good emission in the solution and solid states. This study describes the gelation of BODIHYs for the first time, wherein stable gels GL2 and GB2 were prepared via saponification-triggered gelation of L2 and B2, respectively. The gelation and optical properties of the ligands and BODIHYs were compared through single-crystal X-ray diffraction studies. This work further explores the prospect of artificial light harvesting (ALH) via fabrication of ALHSs in the solution {B1/rhodamine B (RhB) and B2/RhB} and gel states (GB2/RhB). It was observed that in the presence of RhB, the emission intensities of BODIHYs and the gel decreased but those of RhB increased. The significant overlapping between the absorption spectrum of RhB and emission spectra of aggregates/gel suggests the possibility of energy transfer via noncovalent interactions. In these systems, B1, B2 and GB2 served as donors, whereas RhB served as an acceptor. © 2024 The Royal Society of Chemistry.
Competitive ICT in asymmetric D−A Scaffolds showing visible solvatochromism, temperature-induced emission enhancement and AIE based acidochromism
(Elsevier B.V., 2022) Ashish Kumar Kushwaha; Yogesh Kumar; Surendra Kumar; Roop Shikha Singh
Meticulous attention to details of intramolecular charge transfer (ICT) has proved to be an effective strategy to design donor-acceptor fluorophores equipped with multichromic behaviour. Herein, we report three asymmetric donor-acceptor fluorophores bearing A′−D−A−D−A′ and D′−D−A−D−D′ scaffolds. The D−A−D core has been modified by appending pyridine/pyrimidine as additional acceptor and phenyl as additional donor and piperazine as flexible spacers. The asymmetric scaffold has equipped them with naked-eye solvatochromism even under daylight which further authenticated the effective charge separation in ground as well as excited state. The comparative account of photophysical behaviour displays the varying extent of twisted intramolecular charge transfer (TICT) owing to asymmetry. The interplay of restricted intramolecular rotation (RIR) and TICT leads to AIE induced H+ sensing and reversible acidochromism in PC1 which can be visualized by a comparatively uncommon acid induced emission enhancement. The activation of vibrational bands at higher temperature leads to a rare temperature induced emission enhancement in PC1−PC3. PC1 has been developed as the very first ‘turn-on’ thermochromic sensor based on β-diketone-boron difluoride (BF2bdk) complexes. © 2022 Elsevier B.V.
Corrigendum to ‘Recent developments in metal dipyrrin complexes: Design, synthesis, and applications’ [Coord. Chem. Rev. 414 (2020) 213269] (Coordination Chemistry Reviews (2020) 414, (S0010854519304175), (10.1016/j.ccr.2020.213269))
(Elsevier B.V., 2020) Roop Shikha Singh; Rajendra Prasad Paitandi; Rakesh Kumar Gupta; Daya Shankar Pandey
The authors regret that some of the copyright permissions were omitted from the published version of this review. The corrected figure captions are listed below. The authors apologize for this omission. Fig. 7. Examples of homoleptic complexes based on trivalent metal ions. Reprinted with permission from ref 56. Copyright @ 2006 American Chemical Society. Fig. 9. Structures of Fe(II) complexes of dipyrromethene. Reprinted with permission from ref 12. Copyright @ 2011 American Chemical Society. Fig. 10. Structure of complexes 2 (a), 3 (b) and 4 (c). Reprinted with permission from ref 11. Copyright @ 2009 American Chemical Society. Fig. 12. Chemical structure of dipyrrin 17 and Ga(III) complex 18. Reprinted with permission from ref 76. Copyright @ 2010 American Chemical Society. Fig. 18. Crystal structure of 80 and 81. Reprinted with permission from ref 77. Copyright 2009 The Royal Society of Chemistry. Fig. 22. Structure of metal complex 101. Reprinted with permission from ref 151. Copyright 2016 The Royal Society of Chemistry. Fig. 33. Zn2+ detection by dipyrromethanes 146–148. Reprinted with permission from ref 173. Copyright 2014 The Royal Society of Chemistry. Fig. 38. Complexation of 160 with Cd2+ and Hg2+ ions (a). Crystal structure of 161 (b). Reprinted with permission from ref 181. Copyright 2017 Centre National de la Recherche Scientifique (CNRS) and The Royal Society of Chemistry. Fig. 39. (a) Chemical structures of 162 and 163. Ar = t-Bu; (b) A photograph showing the color changes of 163 (25 mM) in the presence of various anions (40 equiv.) in DMSO; (c) UV–Vis spectral changes of 163 (10 μM) in the presence of F− (0–180 equiv.) in DMSO. Reprinted with permission from ref 186. Copyright 2010 The Royal Society of Chemistry. Fig. 40. (a) Chemical structures of 164–166; (b) and (c) image showing the color changes of probe 166 in the presence of different anions, (b) in CH2Cl2; (c) in DMSO–H2O. Reprinted with permission from ref 187. Copyright 2012 The Royal Society of Chemistry. Fig. 41. (a) Structures of compounds 167–169 bearing α-formyl groups; (b) photograph showing the color changes of solution of 167 in CHCl3 after addition of different anions (1.2 equiv). Reprinted with permission from ref 188. Copyright 2014 The Royal Society of Chemistry. Fig. 44. (a) ORTEP view of the metallotecton Δ-178b. (b) Showing 1-D zig-zag chains of metallotecton Δ-178b linked by hydrogen bonds involving two of the three carboxyl groups of each tecton. Reprinted with permission from ref 194. Copyright 2007 The Royal Society of Chemistry Fig. 45. Crystal structures of 179 and 180. Reprinted with permission from ref 57. Copyright 2009 The Royal Society of Chemistry. Fig. 46. Dimeric structure of dipyrrin 181 (a) and its nickel (II) complex 182 (b) as determined by X-ray crystallography. Representing a portion of the 1-D networks based on the [Formula presented] (12) connectivity pattern of 181 (c) and the distorted square planar/ tetrahedral coordination bonding motif in 182 (d). Reprinted with permission from ref 195. Copyright 2011 The Royal Society of Chemistry. Fig. 48. Showing space-filling representation of coordination polymers formed 199 (top right) and 200 (top left) and stick representation of 200 (bottom) viewed down the crystallographic c-axis, Reprinted with permission from ref 199. Copyright 2004 American Chemical Society. Fig. 49. Chemical structure of 201 (a), Molecular hexagons (b) and helical coordination polymers (c) comprising the supramolecular structure. Reprinted with permission from ref 200. Copyright © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Fig. 50. Chemical structure of 202 (a), ORTEP view of 203 (b) and Ag–π interaction 204. Reprinted with permission from ref 201. Copyright 2007 The Royal Society of Chemistry. Fig. 51. Chemical structures of 205–209 and crystal structure of 210. Reprinted with permission from ref 202. Copyright 2004 American Chemical Society. Fig. 52. (a) Layered structure in a crystal of 209 (b) Ribbon like structure and the packing diagram in a crystal of 210. The hydrogen bonds are denoted by dotted lines. Reprinted with permission from ref 202. Copyright 2004 American Chemical Society. Fig. 54. Chemical structure of 216 (a) and 2-D network (b) formed by its complex with Cu(OAc)2. Reprinted with permission from ref 205. Copyright 2009 The Royal Society of Chemistry. Fig. 56. (a) A portion of the 1-D CP observed in the crystalline phase for 221. (b) A portion of the 1-D hydrogen bonded network in the crystal structure of 222. Reprinted with permission from ref 25. Copyright 2012 The Royal Society of Chemistry. Fig. 59. Portions of the crystal structures of CPs 231–234. Reprinted with permission from ref 207. Copyright 2014 The Royal Society of Chemistry. Fig. 60. Chemical structure of 235, portions of crystal structures of 236 and 237. Reprinted with permission from ref 209. Copyright 2007 The Royal Society of Chemistry. Fig. 69. Chemical structures of 256 and 257. Absorption spectrum of 256 in MeCN. The green area covers excitations of the iridium complex due to LC and MLCT transitions, the red shaded region covers π–π* excitations of the NDI and the blue regions covers excitations of the TAA. The absorption spectrum of 257 (violet solid line) and corresponding phosphorescence spectrum (violet line), excitation spectrum (green solid line). Reprinted with permission from ref 217. Copyright 2013 PCCP Owner Societies. Fig. 72. (a) Image of a free-standing film of 268-SWCNT (thickness of 64 μm). (b) TEM image of 268-SWCNT subjected to electron energy-loss spectroscopy (EELS) mapping. EELS mapping for: (c) carbon K edge intensity and (d) Zn M2 and M3 edge intensities. (e) Overlapped image of (b) and (c). (f) Voltage-difference/temperature difference plots for pristine SWCNTs (black) and 33-SWCNT (orange). (Reprinted with permission from ref 221. Copyright 2015 The Royal Society of Chemistry. Fig. 73. Photoelectric conversion profile using 268 as an active material. (a) Image of a thin film of 268 on a SnO2 electrode. (b) Anodic photocurrent signal after irradiation of a working electrode (SnO2 substrate modified with 268 as shown in (a) with intermittent 500 nm light. (c) Action spectrum for the photocurrent generation (orange dots) and absorption spectrum of 268 on a SnO2 substrate (gray solid line). Reprinted with permission from ref 221. Copyright 2015 The Royal Society of Chemistry. Fig. 74. Structures of dipyrromethene ligand and bis(dipyrrinato)Zn(II) complex; nanosheet 269. Reprinted with permission from ref 222. Copyright © 2015, Springer Nature. Fig. 75. (a) Anodic current response after irradiation of the working electrode (SnO2 substrate modified with 36-layer 269) with intermittent 500 nm light (0.1 M tetrabutylammonium perchlorate with 0.05 M TEOA in acetonitrile) (b) action spectrum for the photocurrent generation (magenta dots) and absorption spectrum of 269 (black solid line). (c) Changes in UV–vis spectra upon stepwise depositions of single-layer 269 on a quartz substrate. (d) Showing linear relationship between the absorbance at 500 nm and number of deposition cycles. Reprinted with permission from ref 222. Copyright © 2015, Springer Nature. Fig. 76. Left: chemical structure of porphyrin–dipyrrin hybrid ligand 271. Right: a) Typical photoelectric conversion response upon irradiation of the 270-physisorbed photoanode with intermittent 440 nm monochromatic light. b) Action spectrum for the photocurrent generation (orange dots) and absorption spectrum of 270 (green solid line). Reprinted with permission from ref 223. 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Fig. 82. (a) Chemical structure of 286 (b) UV–vis spectra showing reductive conversion of Cr(VI) to Cr(III) AuNPs (c) AuNPs@prGO500 (d) The plot of conversion vs. time as monitored by UV–vis spectroscopy (e) Schematic presentation for Cr(VI) reduction on AuNPs@prGO500. Reaction conditions: HCOOH = 0.2 mL, [Cr2O72-] = 0.2 mM and catalytic amount = 1 mg/mL (25 µL) levels (0.1 μM to 0.1 M) in 50 mM phosphate buffer solutions at pH = 4.5. Reprinted with permission from ref 233. Copyright 2016 The Royal Society of Chemistry. Fig. 84. Crystal structure of Pd(II)bis-dipyrrinato complex 293 (Reprinted with permission from ref 237. 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) and Mn(III)-bis(phenolate)dipyrrin complex 294. Fig. 85. Crystal structures of U(VI) complex 295 (a) U(IV) complex 296 (b) and Fe(III) complexes 297 (c), 298 (d) and 299 (e), Reprinted with permission from ref 239 (Copyright 2017 American Chemical Society). Scheme 14. Synthesis and crystal structure of compound 100. Reprinted with permission from ref 150. Copyright 2011 The Royal Society of Chemistry. © 2020
Cyclometalated Ir(III) Complexes Involving Functionalized Terpyridine-Based Ligands Exhibiting Aggregation-Induced Emission and Their Potential Applications in CO2 Detection
(American Chemical Society, 2018) Vishwa Deepak Singh; Rajendra Prasad Paitandi; Bhupendra Kumar Dwivedi; Roop Shikha Singh; Daya Shankar Pandey
Synthesis of three novel terpyridine-based donor-acceptor (D-A) ligands (TP1, TP2, TP3) and cyclometalated iridium complexes [Ir(ppy)2TP1]+PF6 - (C1), [Ir(ppy)2TP2]+PF6 - (C2), and [Ir(ppy)2TP3]+PF6 - (C3) [ppy = 2-phenyl pyridine] involving these were described. The ligands and complexes were characterized by spectroscopic studies (1H, 13C, 19F, 31P, ESI-MS, UV-vis, and fluorescence). Crucial role of intermolecular interactions in aggregation-caused quenching (ACQ; C2) and aggregation-induced emission (AIE; C3) was rationalized by X-ray single-crystal analyses. Vital role of restricted intramolecular rotation (RIR) in inducing AIE upon aggregation via π-π interactions in these complexes was scrutinized by various studies. Because of strong intramolecular charge transfer these D-A based AIEgens exhibited solvatochromism. Further, AIE property of the complexes C1 and C3 was exploited toward detection of CO2. © 2018 American Chemical Society.
Design of EQCM-MIP sensing matrix for highly specific and sensitive detection of thyroglobulin
(Elsevier Ltd, 2022) Juhi Srivastava; Roop Shikha Singh; Meenakshi Singh
In this paper an electrochemical quartz crystal microbalance (EQCM)-MIP sensor for thyroglobulin had been developed by using 4-aminothiophenol (4-ATP) - methacrylic acid (MAA)- reduced graphene oxide (RGO) composite as a polymeric format for the first time. Thyroglobulin plays a central role in the biology of thyroid as active and exclusive support for thyroid hormone synthesis and storage. Measurement of serum thyroglobulin is primarily used to detect recurrence of follicular thyroid cancer following total thyroidectomy and radioactive iodine ablation. The MIP sensor was developed by electodeposition of 4-ATP-MAA-RGO composite on EQCM electrode in presence of template thyroglobulin. Due to the location of imprinted sites on the surface and high specific surface area, analyte molecules have good accessibility and high binding affinity to template molecules thus yielding a highly sensitive and efficient signal. The limit of detection of 0.02 ng/mL, without any crossreactivity and matrix effect indicates high sensitivity and selectivity for thyroglobulin. The sensor was appreciably selective to thyroglobulin in presence of probable interferents. The relative standard deviation for determination was 4.23%. Based on speediness and sensitivity, the sensor is reusable and shows a great improvement in selectivity and adsorption capacity over other sensors. © 2022 The Authors
Epitope imprinting of iron binding protein of Neisseria meningitidis bacteria through multiple monomers imprinting approach
(John Wiley and Sons Ltd, 2018) Neha Gupta; Roop Shikha Singh; Kavita Shah; Rajniti Prasad; Meenakshi Singh
Epitope imprinting is a promising technique for fabrication of novel diagnostic tools. In this study, an epitope imprinted methodology for recognition of target epitope sequence as well as targeted protein infused by bacterial infection in blood samples of patients suffering from brain fever is developed. Template sequence chosen is a ferric iron binding fbp A protein present in Neisseria meningitidis bacteria. To orient the imprinting template peptide sequence on gold surface of electrochemical quartz crystal microbalance (EQCM), thiol chemistry was utilized to form the self-assembled monolayer on EQCM electrode. Here, synergistic effects induced by various noncovalent interactions extended by multiple monomers (3-sulfopropyl methacrylate potassium-salt and benzyl methacrylate) were used in fabricating the imprinting polymeric matrix with additional firmness provided by N,N-methylene-bis-acrylamide as cross-linker and azo-isobutyronitrile as initiator. Extraction of template molecule was carried out with phosphate buffer solution. After extraction of epitope molecules from the polymeric film, epitope molecularly imprinted polymeric films were fabricated on EQCM electrode surface. Nonimprinted polymers were also synthesized in the similar manner without epitope molecule. Detection limit of epitope molecularly imprinted polymers and imprinting factor (epitope molecularly imprinted polymers/nonimprinted polymers) was calculated 1.39 ng mL−1 and 12.27 respectively showing high binding capacity and specific recognition behavior toward template molecule. Simplicity of present method would put forward a fast, facile, cost-effective diagnostic tool for mass health care. Copyright © 2018 John Wiley & Sons, Ltd.
Exquisite 1D Assemblies Arising from Rationally Designed Asymmetric Donor-Acceptor Architectures Exhibiting Aggregation-Induced Emission as a Function of Auxiliary Acceptor Strength
(Wiley-VCH Verlag, 2016) Roop Shikha Singh; Sujay Mukhopadhyay; Arnab Biswas; Daya Shankar Pandey
One-dimensional nanostructures with aggregation-induced emission (AIE) properties have been fabricated to keep the pace with growing demand from optoelectronics applications. The compounds 2-[4-(4-methylpiperazin-1-yl)benzylidene]malononitrile (PM1), 2-{4-[4-(pyridin-2-yl)piperazin-1-yl]-benzylidene}malononitrile (PM2), and 2-{4-[4-(pyrimidin-2-yl)piperazin-1-yl]benzylidene}malononitrile (PM3) have been designed and synthesized by melding piperazine and dicyanovinylene to investigate AIE in an asymmetric donor-acceptor (D-A) construct of A′-D-π-A- topology. The synthetic route has been simplified by using phenylpiperazine as a weak donor (D), dicyanovinylene as an acceptor (A), and pyridyl/pyrimidyl groups (PM2/PM3) as auxiliary acceptors (A′). It has been established that A′ plays a vital role in triggering AIE in these compounds because the same D-A construct led to aggregation-caused quenching upon replacing A′ with an electron-donating ethyl group (PM1). Moreover, the effect of restricted intramolecular rotation and twisted intramolecular charge transfer on the mechanism of AIE has also been investigated. Furthermore, it has been clearly shown that the optical disparities of these A′-D-π-A architectures are a direct consequence of comparative A′ strength. Single-crystal X-ray analyses provided justification for role of intermolecular interactions in aggregate morphology. Electrochemical and theoretical studies affirmed the effect of the A′ strength on the overall properties of the A′-D-π-A system. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Fine-Tuning of Saponification-Triggered Gelation by Strategic Modification of Peripheral Substituents: Gelation Regulators
(Wiley-VCH Verlag, 2016) Ashish Kumar; Roop Shikha Singh; Amit Kumar; Afsar Ali; Arnab Biswas; Daya Shankar Pandey
A pioneering approach towards controlling the efficiency of saponification assisted gelation in ethyl ester based ZnII-complexes have been described. Using four new ester containing bis-salen ZnIIcomplexes (C1–C4) involving different para-azo phenyl substituted ligands it has been clearly shown that gelation efficiency is greatly influenced by the electronic effects of the substituents (-H (C1), -CH3(C2), -NO2(C3), and -OCH3(C4)). Morphological, photophysical, and rheological investigations corroborated the experimental observations well and established that gelation efficiency was enhanced with electron-withdrawing characteristics of substituents (C4
Fluorogenic dual click derived bis-glycoconjugated triazolocoumarins for selective recognition of Cu(II) ion
(Elsevier Ltd, 2014) Divya Kushwaha; Roop Shikha Singh; Vinod K. Tiwari
Carbohydrate based fluorescent sensors S1 and S2 have been developed by fluorogenic dual click chemistry and are characterized by various spectroscopic techniques. Both the fluorescent probes displayed highly selective detection of Cu2+ ions by means of fluorescence quenching. The job plot experiment suggested 1:1 complexation of probes S1 and S2 with Cu2+ ions having detection limit of 6.99 μM and 7.30 μM, respectively. The binding constants for S1-Cu2+ and S2-Cu2+ complexation were evaluated to be 3.34 × 103 M-1 and 5.93 × 103 M-1, respectively. © 2014 Elsevier Ltd. All rights reserved.
Functional evaluation of novel chromon derivative compounds for recognition of G-quadruplex structure
(Elsevier B.V., 2024) Neha Neha; Prashant Ranjan; Surendra Kumar; Roop Shikha Singh; Daya Shankar Pandey; Parimal Das
Currently, G-quadruplex structure targeting strategies are considered as a promising anticancer approach. The purpose of this research is to expand the options for G-quadruplex targeting ligands, particularly emphasizing fluorescent ligands. Our study contributes to the field by providing additional choices for G-quadruplex binders with a notable focus on selectivity towards G-quadruplex topology over duplex DNA. In the search of selective and potent G-quadruplex binders, here we discuss an analysis of a few chroman derivatives ligands named A and C and their respective borondifluoride complexes B and D as a quadruplex targeting compounds which found to stabilize G-quadruplex structure. To investigate the binding characteristics of these molecules with G-quadruplex vs. duplex selectivity, In vitro biophysical studies were performed by steady-state fluorescence, UV–visible titration, fluorescent TO displacement assay, CD thermal melting, circular dichroism spectroscopy, and cellular imaging by employing both telomeric and PRCC G-quadruplex forming sequences. Our investigation shows that these chromam ligands and their complexes are able to selectively bind and stabilize parallel and mixed hybrid topology of G-quadruplex both In vitro and in cellular conditions. A molecular docking and MD simulation study also suggests the binding of these compounds with G-quadruplex conformation. Collectively our study suggests these chroman complexes for the first time as a potentially useful fluorescent chemical product for G-quadruplex specific ligands and expands an option for G-quadruplex targeting ligands. © 2024
Heteroleptic arene Ru(ii) dipyrrinato complexes: DNA, protein binding and anti-cancer activity against the ACHN cancer cell line
(Royal Society of Chemistry, 2016) Rakesh Kumar Gupta; Amit Kumar; Rajendra Prasad Paitandi; Roop Shikha Singh; Sujay Mukhopadhyay; Shiv Prakash Verma; Parimal Das; Daya Shankar Pandey
Four organometallic complexes [(η6-C6H6)RuCl(pmpzdpm)], 1; [(η6-C6H6)RuCl(pypzdpm)], 2; [(η6-C10H14)RuCl(pmpzdpm)], 3 and [(η6-C10H14)RuCl(pypzdpm)], 4 containing 5-(2-pyrimidyl-piperazine)phenyldipyrromethene (pmpzdpm) and 5-(2-pyridylpiperazine)phenyldipyrromethene (pypzdpm) have been designed and synthesized. The complexes 1-4 have been fully characterized by elemental analyses and spectroscopic studies (ESI-MS, IR, 1H, 13C NMR, UV-vis). Their electrostatic/intercalative interaction with CT DNA has been investigated by UV-vis and competitive ethidium bromide displacement studies while their protein binding affinity toward bovine serum albumin (BSA) was realized by UV-vis, fluorescence, synchronous and three dimensional (3D) fluorescence studies. The interaction with DNA and protein has further been validated by in silico studies. Cellular uptake, in vitro cytotoxicity and flow cytometric analyses have been performed to determine the mode of cell death against the kidney cancer cell line ACHN. Cell cycle analysis suggested that the complexes cause cell cycle arrest in the subG1 phase and overall results indicated that the in vitro antitumor activity of 1-4 lies in the order of 3 > 4 > 1 > 2 (IC50, 7.0 1; 8.0 2; 2.0 3; 4.0 μM, 4). © The Royal Society of Chemistry 2016.
Influence of substituents on DNA and protein binding of cyclometalated Ir(III) complexes and anticancer activity
(Royal Society of Chemistry, 2017) Sujay Mukhopadhyay; Roop Shikha Singh; Rajendra Prasad Paitandi; Gunjan Sharma; Biplob Koch; Daya Shankar Pandey
Synthesis of terpyridyl based ligands 3-([2,2′:6′,2′′-terpyridin]-4′-yl)-7-methoxy-2-(methylthio)-quinolone, (L1); 3-([2,2′:6′,2′′-terpyridin]-4′-yl)-6-methoxyquinolin-2(1H)-one, (L2); 3-([2,2′-:6′,2′′-terpyridin]-4′-yl)-6-methylquinolin-2(1H)-one (L3) and cyclometalated iridium(iii) complexes [[Ir(ppy)2L1]+PF6- (1), [Ir(ppy)2L2]+PF6- (2), [Ir(ppy)2L3]+PF6- (3) (2-phenylpyridine = Hppy)] involving these ligands has been described. The ligands L1-L3 and complexes 1-3 have been thoroughly characterized by elemental analyses, spectral studies (IR, 1H, 13C NMR, UV/vis and fluorescence) ESI-MS, and the structure of 3 has been unambiguously authenticated by single crystal X-ray analyses. UV/vis, fluorescence and circular dichroism spectroscopic studies showed rather efficient binding of 1 with CT-DNA (calf thymus DNA) and BSA (bovine serum albumin) relative to 2 and 3. Molecular docking studies unveiled binding of 1-3 with minor groove of CT-DNA via van der Waal's forces and electrostatically with the hydrophobic moiety of HSA (human serum albumin). The ligands and complexes exhibited moderate cytotoxicity towards MDA-MB-231 (breast cancer cell line) and significant influence on HeLa (cervical cancer cell line) cells. Cytotoxicity, morphological changes, and apoptosis have been followed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) assay, Hoechst 33342/PI (PI = propidium iodide) staining, cell cycle analysis by FACS (fluorescence activated cell sorting), and ROS (reactive oxygen species) generation by DCFH-DA (dichlorodihydrofluorescein diacetate) dye. Confocal microscopy images revealed that the drug efficiently initiates apoptosis in the cell cytosol. The IC50 values showed superior cytotoxicity of 1-3 against the HeLa cell line relative to cisplatin, and their ability to induce apoptosis is in the order 1 > 2 > 3. © The Royal Society of Chemistry 2017.
Interaction of ferrocene appended Ru(II), Rh(III) and Ir(III) dipyrrinato complexes with DNA/protein, molecular docking and antitumor activity
(Elsevier Masson SAS, 2014) Rajendra Prasad Paitandi; Rakesh Kumar Gupta; Roop Shikha Singh; Gunjan Sharma; Biplob Koch; Daya Shankar Pandey
Efficacy of the ferrocene appended piano-stool dipyrrinato complexes [(η6-C6H6)RuCl(fcdpm)] (1), [(η6-C10H14)RuCl(fcdpm)] (2), [(η6-C12H18)RuCl(fcdpm)] (3) [(η5-C5Me5)RhCl(fcdpm)] (4) and [(η5-C5Me5)IrCl(fcdpm)] (5) [fcdpm = 5-ferrocenyldipyrromethene] toward anticancer activity have been described. Binding of the complexes with calf thymus DNA (CT-DNA) and BSA (bovine serum albumin) have been thoroughly investigated by UV-Vis and fluorescence spectroscopy. Binding constants for 1-5 (range, 104-105 M-1) validated their efficient binding with CT-DNA. Molecular docking studies revealed interaction through minor groove of the DNA, on the other hand these also interact through hydrophobic residues of the protein, particularly cavity in the subdomain IIA. In vitro anticancer activity have been scrutinized by MTT assay, acridine orange/ethidium bromide (AO/EtBr) fluorescence staining, and DNA ladder (fragmentation) assay against Dalton's Lymphoma (DL) cells. Present study revealed that rhodium complex (4) is more effective relative to ruthenium (1-3) and iridium (5) complexes. © 2014 Elsevier Masson SAS. All rights reserved.
Luminescent N,O-chelated chroman-BF2 complexes: Structural variants of BODIPY
(2013) Roop Shikha Singh; Mahendra Yadav; Rakesh Kumar Gupta; Rampal Pandey; Daya Shankar Pandey
The synthesis and characterization of 5-(chromen-4-one)-dipyrromethane (1), 5-(6-methyl-chromen-4-one)-dipyrromethane (2), 5-(6-isopropyl-chromen-4-one)- dipyrromethane (3) and the respective chromans, 7-[2-pyrrolo]-pyrrole[1,2-a]12H pyrrolino[2,3-b]chroman-4-one (4), 4-methyl-7-[2-pyrrolo]-pyrrole[1,2-a]12H pyrrolino[2,3-b]-chroman-4-one (5) and 4-isopropyl-7-[2-pyrrolo]-pyrrole[1,2-a] 12H pyrrolino[2,3-b]-chroman-4-one (6) have been described. Chroman derivatives 4-6 have been used in the synthesis of highly stable, fluorescent, borondifluoride complexes (7-9). All the compounds have been fully characterised by various physicochemical techniques viz., elemental analyses, IR, HRMS, NMR (1H, 13C), electronic absorption, emission (solution and solid state), electrochemical and thermal studies. Crystal structures of dipyrromethanes 1 and 2, chroman derivative 6 and boron complexes 7-9 have been determined by X-ray single crystal analyses. Structural studies revealed that the formation of 4-6 takes place by DDQ mediated C-N coupling. The higher stability of 4-6 relative to their respective dipyrrins has been supported by theoretical studies. © The Royal Society of Chemistry 2013.
Lysosome-targeting solid state NIR emissive donor-acceptor molecules: a study on photophysical modulation through architectural distinction
(Royal Society of Chemistry, 2024) Ashish Kumar Kushwaha; Ankit Kumar Srivastava; Pradeep Kumar; Anjani Kumar; Saripella Srikrishna; Roop Shikha Singh
The prevalence of the D-A strategy in achieving red-shifted emission has been established through designing D-A molecules of D-A-D and A-D-A constructs. Architectural control over such D-A systems integrates solid state NIR emission with lysosome tracking and sets a multifarious goal of photophysical modulation in a comprehensive way. In particular, two compounds, CPM-1 (D-A-D) and CPM-2 (A-D-A), have been synthesized by introducing carbazole-based donors and difluoroboron acceptors. Lysosome targeting and imaging have been achieved through incorporation of a morpholine unit, which ultimately imparts viscosity sensitivity to the construct. The fluorophores exhibited significant emission in solution along with distinctive solvatochromism, viscochromism and TICT. A comparative account of these competitive photophysical properties revealed the superior charge transfer properties of the A-D-A construct (CPM-2), while the D-A-D molecule (CPM-1) was found to be a better molecular rotor with marked viscochromism. The solid state NIR emission has been found to be much more intense in CPM-1 relative to CPM-2, which further highlights the influence of structural aspects on photophysical behvaiour. Theoretical studies further established the distinctive characteristics of ground and excited states in these compounds. Owing to its excellent viscochromic behvaiour, CPM-1 has been successfully utilized in lysosome targeting in wild-type Drosophila fly gut tissues through co-localization studies. © 2024 The Royal Society of Chemistry.