Browsing by Author "Ragini Singh"

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A new micro-contact imprinted l-cysteine sensor based on sol-gel decorated graphite/multiwalled carbon nanotubes/gold nanoparticles composite modified sandpaper electrode
(Elsevier, 2015) Bhim Bali Prasad; Ragini Singh
A new ultrasensing sandpaper electrode was fabricated using micro-contact imprinting technique for the detection of several diseases manifested at acute level depletion of l-cysteine. The concerted effect of molecularly imprinted polymer@graphite/multiwalled carbon nanotubes/gold nanoparticles/sol-gel composite led to the growth of a nanometer thin film coating on the surface of sandpaper electrode. Herein, the redox electron relay was channelized in between imprinted nanocomposite and aluminum stripe attached at the modified surface. Determination of the analyte (l-cysteine) could simply be performed by measuring differential pulse anodic stripping voltammetric signal of potassium ferricyanide used as an external probe. The limits of detection [0.26-0.30 ng mL-1 (3σRSD ≤ 2.5%)] obtained were free from any cross-reactivity and false-positive complications in aqueous, blood serum, and pharmaceutical samples. The proposed sensor can be used as a practical sensor for monitoring cysteine deficiency, particularly with HIV-infected patients. © 2015 Published by Elsevier B.V.
Development of imprinted polyneutral red/electrochemically reduced graphene oxide composite for ultra-trace sensing of 6-thioguanine
(Elsevier Ltd, 2016) Bhim Bali Prasad; Ragini Singh; Anil Kumar
The present work describes a novel method for the fabrication of a pencil graphite electrode modified with polyneutral red/electrochemically reduced graphene oxide (ERGO) composite, for sensing 6-thioguanine (anticancerus drug), in biological and pharmaceutical samples. Herein, the neutral red monomer was electro-polymerized in the presence of 6-thioguanine (template) at -0.9 V directly over ERGO nano sheets coated electrode. After the template extraction, an imprinted polymer coating on ERGO was obtained. The monomer-template (1:2) stoichiometry was optimized through density functional theory at the B3LYP/6-31 + G (d, p) level. In this work, graphene oxide (GO) sheets actually assumed exfoliated anionic texture which facilitated electro-statically deposition of cationic molecules of neutral red at neutral pH. These molecules were subsequently electro-polymerized accompanied with simultaneous electro-reduction of exfoliated GO. This resulted in highly electro-conductive polyneutral red coated ERGO nano sheets alongwith probable intercalation of the polymer into the space between the exfoliated two proximate ERGO layers. A perfect linearity in the current-concentration profile was observed for the analyte concentration in the range 0.124-78.0 ng mL-1, with the detection limit 0.02 ng mL-1 (S/N = 3), in aqueous medium. The proposed sensor assured a reliable analysis of ultra-trace 6-thioguanine in real samples. © 2016 Elsevier Ltd.
Development of water compatible imprinted polymer beads for piezoelectric sensing of ultra-trace 5,6-dihydrouracil in biological fluids
(Elsevier B.V., 2016) Bhim Bali Prasad; Anil Kumar; Ragini Singh
In this work, a novel water compatible molecularly imprinted polymer was synthesized in bead shape by the precipitation polymerization technique. Immobilization of such imprinted beads on the surface of quartz crystal microbalance (QCM) was made through Au-S links using the "surface-grafting to" approach. The imprinted beads revealed a superiority in terms of recapture ability of analyte in the large concentration range and sensitivity as compared to traditionally imprinted monolith films. The piezoelectric analysis of target analyte (5,6-dihydrouracil) with imprinted polymer beads was found to be highly selective and sensitive, without any cross-reactivity and false-positives, in real samples. A perfect linearity between the frequency shift and the analyte concentration was observed in the range 0.03-1.75 μM, with detection limits varying between 0.003-0.006 μM (S/N = 3) [cf., imprinted film modified QCM: 0.04-1.32 μM, limit of detection 0.01 μM (S/N = 3)]. The endogenous 5,6-dihydrouracil level was also obtained in the blood plasma sample which may help exploring concerned dihydropyrimidine dehydrogenase activity, on the basis of concentration ratio [dihydrouracil]/[uracil] in cancer patients undergoing chemotherapy with 5-fluorouracil supplementation. © 2016 Elsevier B.V. All rights reserved.
Gold nanorods: Vs. gold nanoparticles: Application in electrochemical sensing of cytosine β-d-arabinoside using metal ion mediated molecularly imprinted polymer
(Royal Society of Chemistry, 2016) Bhim Bali Prasad; Ragini Singh; Anil Kumar
The determination of an anticancer drug (cytosine arabinoside, Ara-C) in body fluids is very important due to its pharmaceutical and clinical significance. This drug is widely used for the treatment of cancer patients suffering from acute myeloid leukemia. In this study, a typical surface imprinting approach was adopted for the immobilization of imprinted nano film on a pencil graphite electrode decorated with gold nanorods/gold nano particles. For this, gold nanorods were attached first onto the electrode surface followed by their modification with a pre-polymer mixture. Herein, monomeric molecules (N-methacryloyl-l-cysteine) were coated via Au-S links on an electrode surface that had undergone metal ion mediated molecularly imprinted polymerization, in the presence of a template (Ara-C), crosslinker (ethylene glycol dimethacrylate) and initiator [2,2′-azobis(isobutyronitrile)]. Similar modification was carried out on a gold nanoparticles immobilized electrode for comparison, in terms of differential pulse anodic stripping voltammetric transduction and measurement sensitivity. An extended imprinting polymer (template-free) coating on the longitudinal surface of the gold nanorods was found to reveal higher electrode kinetics. This produced a better signal with enhanced detection sensitivity (k = 1.36 × 10-2, linearity range = 1.00-126.71 ng mL-1, limit of detection = 0.19 ng mL-1) of the drug than those (k = 1.75 × 10-3, linearity range = 3.00-107.21 ng mL-1, limit of detection = 0.75 ng mL-1) realized with a gold nanoparticles decorated imprinted polymer layer compressed in spherical curved space. Consequently, the proposed gold nanorods-based imprinted sensor is adjudged to be better in helping to monitor a dose-dependent antiproliferative effect of a drug and its supplementation in chemotherapy. © 2016 The Royal Society of Chemistry.
Molecularly imprinted polymer-based electrochemical sensor using functionalized fullerene as a nanomediator for ultratrace analysis of primaquine
(Elsevier Ltd, 2016) Bhim Bali Prasad; Anil Kumar; Ragini Singh
The present work describes a typical functionalized fullerene (C60)-based imprinted polymer composite for the modification of pencil graphite electrode. This employed 2,4,6-trisacrylamido-1,3,5-triazine as a functional monomer and an antimalarial drug, primaquine, as a template for the molecular imprinting with the “surface grafting-from” approach. Herein, functionalized fullerene actually served as a potential nanomediator to shuttle electron between the recognition sites and the electrode. Such modification induced electrocatalytic action and thereby greatly amplified the electrode kinetics with decreasing oxidation overpotential. This resulted in an increase of differential pulse anodic stripping current (∼5 fold) as compared to the corresponding traditionally imprinted polymer modified electrode. The template-monomer (1:2) stoichiometry was optimized applying density functional theory at B3LYP/6–31 + G (d, p) level. The proposed sensor was validated with the complex matrices of human blood plasma, urine, and pharmaceutics, without any matrix effect and cross-reactivity. A perfect linearity in the current-concentration profile was observed for primaquine in the wide concentration ranges: 2.7–848.5, 4.2–827.4, 3.4–795.2, and 4.8–803.2 nM for aqueous, blood plasma, urine, and pharmaceutical samples, respectively. The detection limit was observed to be as low as 0.80 nM (S/N = 3), in the aqueous environment. © 2016 Elsevier Ltd
Recent advances in various emerging vescicular systems: An overview
(Asian Pacific Tropical Biomedicine Press, 2012) Mayank Gangwar; Ragini Singh; R.K. Goel; Gopal Nath
Liposomes have been widely investigated since 1970 as drug carriers for improving the delivery of therapeutic agents to specific sites in the body. As a result, numerous improvements have been made to make this technology potential the treatment of certain diseases in the clinics. This review mainly focused on various aspects related to the vesicular system, including method of preparation, stabilization, drawbacks, and applications. Various types of vesicular systems such as liposomes, niosomes, transfersomes, pharmacosomes, and nanoparticle have been discussed briefly along with some other emerging vescicular systems (photosomes, archaesomes, genosomes, cryptosomes, discomes) focusing on cell specific gene transfer, photodynamic therapy and ligand mediated drug targeting. Present applications of the liposomes are in the immunology, dermatology, vaccine adjuvant, eye disorders, brain targeting, infective disease and in tumour therapy. The new developments in this field are of specific binding properties of a drug-carrying liposome to a target cell such as a tumor cell and specific molecules in the body (antibodies, proteins, peptides etc), stealth liposomes which are especially used as carriers for hydrophilic (water soluble) anticancer drugs like doxorubicin, mitoxantrone and bisphosphonate-liposome mediated depletion of macrophages. This review would help researchers working in the area of liposomal drug delivery. © 2012 Asian Pacific Tropical Biomedical Magazine.
Synthesis of fullerene (C60-monoadduct)-based water-compatible imprinted micelles for electrochemical determination of chlorambucil
(Elsevier Ltd, 2017) Bhim Bali Prasad; Ragini Singh; Anil Kumar
A novel water-compatible C60-monoadduct based imprinted micelles was synthesized by the self-assembly of vinylic-C60-monoadduct with sodium dodecylsulfate micellar system, in the presence of chlorambucil as a model template (anticancer drug). After template retrieval with acetonitrile, these imprinted micelles were immobilized at the surface of ionic liquid decorated carbon ceramic electrode. Herein, C60-monoadduct (the head group of micelle) actually served as a nanomediator for electronic transmission across multiple interfaces. Such modification induced electrocatalytic characteristics by decreasing analyte oxidation overpotential and thereby augmented the electrode kinetics. Consequently, the differential pulse anodic stripping transduction was realized to be approximately four-fold as compared to the corresponding electrode modified without C60-monoadduct. This revealed the potential role of fullerene as nanomediator in the signal transduction. Herein, ionic liquids facilitated electron transport by two-fold without any interfacial barrier through carbon layers than that realized with modified ceramic electrodes made in the absence of ionic liquids. A perfect linearity in the current-concentration profile under optimal conditions was observed for the analyte concentration in the range 1.47–247.20 ng mL-1, with the detection limits to the tune of 0.36 ng mL-1 (S/N=3) in aqueous and real samples. © 2017 Elsevier B.V.
Synthesis of novel monomeric graphene quantum dots and corresponding nanocomposite with molecularly imprinted polymer for electrochemical detection of an anticancerous ifosfamide drug
(Elsevier Ltd, 2017) Bhim Bali Prasad; Anil Kumar; Ragini Singh
This paper reports a typical synthesis of a nanocomposite of functionalized graphene quantum dots and imprinted polymer at the surface of screen-printed carbon electrode using N-acryloyl-4-aminobenzamide, as a functional monomer, and an anticancerous drug, ifosfamide, as a print molecule (test analyte). Herein, graphene quantum dots in nanocomposite practically induced the electrocatalytic activity by lowering the oxidation overpotential of test analyte and thereby amplifying electronic transmission, without any interfacial barrier in between the film and the electrode surface. The differential pulse anodic stripping signal at functionalized graphene quantum dots based imprinted sensor was realized to be about 3- and 7-fold higher as compared to the traditionally made imprinted polymers prepared in the presence and the absence of graphene quantum dots (un-functionalized), respectively. This may be attributed to a pertinent synergism in between the positively charged functionalized graphene quantum dots in the film and the target analyte toward the enhancement of electro-conductivity of the film and thereby the electrode kinetics. In fact, the covalent attachment of graphene quantum dots with N-acryloyl-4-aminobenzamide molecules might exert an extended conjugation at their interface facilitating electro conducting to render the channelized pathways for the electron transport. The proposed sensor is practically applicable to the ultratrace evaluation of ifosfamide in real (biological/pharmaceutical) samples with detection limit as low as 0.11 ng mL−1 (S/N=3), without any matrix effect, cross-reactivity, and false-positives. © 2017 Elsevier B.V.