Piyush Sindhu Sharma

Università degli studi di Verona, Verona, Veneto, Italy

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Publications (19)54.15 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: Highly efficient enantioselective separation and quantitative recoveries of D- and L-tryptophan in aqueous and real samples can be achieved, with a monolithic molecularly imprinted polymeric fiber that serves both for micro-solid phase extraction and ultratrace sensing, without any false-positive (non-specific) contribution and cross-reactivity, in the range of 0.15-30.00 ng mL(-1) with detection limit as low as 0.0261 ng mL(-1) (relative standard deviation=0.64%, signal/noise=3). The proposed method combining molecularly imprinted micro-solid phase extraction fiber and a complementary molecularly imprinted polymer-carbon composite fiber sensor is proven to be useful for clinical diagnosis of stress-related diseases caused by acute tryptophan depletion.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 02/2011; 879(5-6):364-70. · 2.78 Impact Factor
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    ABSTRACT: The present review has sought to explore the technological advances that have been made in recent years towards the selective analysis of uric acid and critically evaluate how they could, in fact, be exploited as a basis for a multi analyte sensor incorporating uric acid detection. Numerous strategies have evolved in recent years but these have invariably focused on the manufacture and response characterization of discrete sensors. Various methods of obtaining selective detection such as use of uricase enzymes, nanoparticles, carbon nanotubes, polymers, conducting polymers and MIPs are also discussed along with the clinical relevance of UA determination.
    Electroanalysis 01/2011; 23(2):305 - 320. · 2.82 Impact Factor
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    ABSTRACT: The present work describes a new, simple, and easy method for the generation of stable molecularly imprinted sites in polymeric film, combining self-assembled monolayer and Layer-by-layer approaches through thermal cross-linking of the layered structures, onto the surface of silver electrode. Modified silver electrodes demonstrate enantiodifferentiation and sensitive (detection limits 0.0060 ng mL(-1) for L- and 0.0062 for D-thyroxine) determination of d- and l-thyroxine with the help of differential pulse anodic stripping voltammetric technique. The binding kinetics of thyroxine was explored using anodic stripping cyclic voltammetry and chronocoulometry. The sensor was also validated for D- and L-thyroxine determinations in biological and pharmaceutical samples.
    Analytica chimica acta 11/2010; 681(1-2):16-26. · 4.31 Impact Factor
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    ABSTRACT: Thyroxine is a known disease biomarker which demands a highly sensitive and selective technique to measure ultratrace level with enantiodifferentiation of its optical isomers (d- and l-), in real samples. In this work, an approach of hyphenation between molecularly imprinted micro-solid phase extraction and a complementary molecularly imprinted polymer-sensor was adopted for enantioseparation, preconcentration, and analysis of d- and l-thyroxine. In both techniques, the same imprinted polymer, coated on a vinyl functionalized self-assembled monolayer modified silver wire, was used as the respective extraction fiber as well as sensor material. This combination enabled enhanced preconcentration of test analyte substantially so as to achieve the stringent limit [limit of detection: 0.0084 ng mL(-1), RSD=0.81%, S/N=3 (d-thyroxine); 0.0087 ng mL(-1), RSD=0.63%, S/N=3 (l-thyroxine)] of clinical detection of thyroid-related diseases, without any problems of non-specific false-positive contribution and cross-reactivity.
    Journal of chromatography. A 06/2010; 1217(26):4255-66. · 4.19 Impact Factor
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    ABSTRACT: Electrochemical sensors demonstrating enantioselectivity to tryptophan enantiomers, with high selectivity and sensitivity, were fabricated by the use of a monolithic fiber of molecularly imprinted polymer-carbon composite. The recognition mechanism and performance of these sensors were evaluated by differential pulse anodic stripping voltammetry. The sensor imprinted for l-tryptophan not only discriminated the target from its analogues and other amino acids but also responded specifically in racemic mixture in aqueous, biological, and pharmaceutical samples. The binding kinetics of L-tryptophan was also established with the help of anodic stripping cyclic voltammetry and chronocoulometry. The detection limit for L-tryptophan was as low as 0.24 ng mL(-1) (signal/noise=3) which is appropriate for biomarking diseases, caused by an acute tryptophan-depletion, in clinical setting.
    Talanta 04/2010; 81(1-2):187-96. · 3.50 Impact Factor
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    ABSTRACT: A simple polymerization strategy is reported in this work which allows molecularly imprinted polymeric fiber (monolith) fabrication for direct use in sensing devices. This is advantageous for achieving higher degree of enrichment of target analyte (folic acid) from the complex matrices of real samples, without any surface fouling, cross-reactivity, and non-specific (false-positive) contributions. In order to measure serum folic acid at ultratrace level to detect spina bifida, a neural tube defect in mother, and other acute cases of proteomic diseases, the hyphenation between molecularly imprinted micro-solid phase extraction fiber and a complementary molecularly imprinted polymer-carbon composite fiber sensor has been found quite efficient. The primitive diagnosis of many chronic diseases is feasible by estimating folic acid as biomarker, with the detection limit as low as 0.0036 ng mL(-1) (relative standard deviation=0.13%, signal/noise=3) in human blood serum.
    Analytica chimica acta 03/2010; 662(1):14-22. · 4.31 Impact Factor
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    ABSTRACT: Molecularly imprinted polymers (MIPs) are often electrically insulating materials. Due to the presence of diffusion barrier(s) in between such MIP coating and electrode surface and the absence of a direct path for the conduction of electrons from the binding sites to the electrode, the development of electrochemical sensor is significantly restricted. The direct use of MIPs those possess intrinsic electron-transport properties, is highly limited. These problems are resolved by the design of an original, substrate-selective MIP-fiber sensor that combines conventional insulating MIP and conducting carbon powder in consolidated phase. A layer of conducting carbon particles, arranged orderly as 'carbon strip', is inducted in the polymer for direct electronic conduction. MIP-carbon composite (monolithic fiber) in this work is prepared via in situ free radical polymerization of a new monomer (2,4,6-trisacrylamido-1,3,5-triazine, TAT) and subsequent cross-linkage with ethylene glycol dimethacrylate, in the presence of carbon powder and template (folic acid), at 55 degrees C in a glass capillary. The detection of folic acid with the MIP-fiber sensor was found to be specific and quantitative (detection limit 0.20 ng mL(-1), RSD=1.3%, S/N=3), in aqueous, blood serum and pharmaceutical samples, without any problem of non-specific false-positive contribution and cross-reactivity.
    Biosensors & bioelectronics 02/2010; 25(9):2140-8. · 5.43 Impact Factor
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    ABSTRACT: An insulin-imprinted polymer was synthesized over the surface of vinyl group functionalized multiwalled carbon nanotubes, using phosphotidylcholine-containing functional monomer and cross-linker. Phosphotidylcholine is a major component of all biological membrane; its incorporation in polymer backbone assures water-compatibility, bio-compatibility and specificity to molecularly imprinted nanomaterials, without any cross-reactivity or interferences from biological sample matrices. An electrochemical sensor fabricated by modifying multiwalled carbon nanotubes-molecularly imprinted polymer onto the pencil graphite electrode, was used for trace level detection of insulin in aqueous, blood serum, and pharmaceutical samples (detection limit 0.0186 nmol L−1, S/N = 3), by differential pulse anodic stripping voltammetry. Additional cyclic voltammetry (stripping mode) and chronocoulometry experiments were performed to explore electrodics and kinetics of electro-oxidation of insulin.
    Electrochimica Acta. 01/2010;
  • Amit Kumar Patel, Piyush Sindhu Sharma, Bhim Bali Prasad
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    ABSTRACT: Zwitterionic molecularly imprinted polymeric chains were tethered to the sol–gel modified graphite electrode in brush pattern of high density, for the quantitative estimation of creatine at trace level, without any cross reactivity, in real samples. The modified electrode was activated by preanodization at +1.4V (vs. saturated calomel electrode) for the fast ion-exchange recapture of creatine, under mild basic condition (pH 7.1). The detection limit was as low as 1.3µgmL−1 (signal/noise=3) employing differential pulse, cathodic stripping technique.
    Thin Solid Films 01/2010; 518(10):2847-2853. · 1.60 Impact Factor
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    ABSTRACT: Contrary to the ‘substructure imprinting approach’ of larger molecule like folic acid, which often leads molecular recognition for both folic acid and structural analogues containing pteridine and glutamic acid substructures, a molecularly imprinted polymer capable of binding specifically folic acid has been prepared by stoichiometric imprinting process (template/monomer molar ratio, 1:3) creating multiple binding sites within the cross-linked hyperbranched polymer. Dendrimer-like chains were obtained by an ‘initiator-fragment incorporation radical polymerization’ technique involving a new trifunctional monomer, 2,4,6-trisacrylamido-1,3,5-triazine. An electrochemical sensor was developed for the selective and quantitative recognition of folic acid, using a preanodized sol–gel coated pencil graphite (grade 2B) electrode with imprinted polymer immobilized to its exterior surface. During preconcentration step at +0.8 V (with respect to Ag/AgCl), the analyte recapture at pH 2.5 in aqueous environment simultaneously involved mixed hydrophobically driven hydrogen bondings and ionic interactions with pteridine substructure and purely hydrogen bonding interactions with glutamic acid residue of folic acid. The encapsulated analyte was instantly oxidized and then cathodically stripped off responding differential pulse cathodic stripping voltammetric signal. The folic acid was selectively detected with a limit of detection of 0.002 μg mL−1(3σ, RSD ≤3.0%), without any cross-reactivities and real matrix complications.
    Sensors and Actuators B: Chemical. 01/2010;
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    ABSTRACT: Induced-fit responsive dopamine (DA) imprinted polymer, poly (melamine-co-chloranil), was used as a suitable coating material for the modification of a hanging mercury drop electrode. The zwitterionic conformation of the imprinted polymer responded differential pulse, cathodic stripping voltammetric current, without any false-positive or false-negative contributions of non-specific sorptions, in aqueous environment of complex matrices. The limit of detection (3σ) of dopamine was found to be as low as 0.148 ng mL−1, by the proposed sensor that could be considered a sensitive marker of dopamine depletion in Parkinson's disease (PD).
    Biochemical Engineering Journal. 01/2009;
  • Amit Kumar Patel, Piyush Sindhu Sharma, Bhim Bali Prasad
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    ABSTRACT: A voltammetric sensor based on a molecularly imprinted polymer (MIP) brush grafted to sol-gel film on graphite electrode is reported for the selective and sensitive analysis of barbituric acid (BA) in aqueous, blood plasma, and urine samples. The modified electrode was preanodised at +1.6 V (vs. saturated calomel electrode), where encapsulated BA involved hydrophobically induced hydrogen bondings, in MIP cavities exposed at the film/solution interface, at pH 7.0. Scanning electron microscopy (SEM) was employed to characterise the surface morphology of the resultant imprinted film of MIP brush. The differential pulse, cathodic stripping voltammetry (DPCSV) technique was employed to investigate the binding performance of the sol-gel-modified imprinted polymer brush, which yielded a linear response in the range of 4.95-100.00 microg mL(-1) of BA with a detection limit of 1.6 microg mL(-1) (S/N=3).
    International journal of pharmaceutics 01/2009; 371(1-2):47-55. · 2.96 Impact Factor
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    ABSTRACT: Main inborn errors of metabolism diagnosable through uracil (Ura) analysis and the therapeutic monitoring of toxic 5-fluorouracil (5FU) in dihydro pyrimidine dehydrogenase (DPD) deficient patients require a sensitive, reproducible, selective and accurate method. In this work, an artificial receptor in the format of molecularly imprinted polymer (MIP) brush 'grafted to' the surface of sol-gel immobilized on cost-effective homemade solid-phase microextraction (SPME) fibers, individually imprinted with either of Ura and 5FU, was used in combination with a voltammetric sensor duly modified with the same MIP. This combination provided up to 10- and 8.4-fold preconcentrations of Ura and 5FU, respectively, which was more than sufficient for achieving stringent detection limits in the primitive diagnosis of uracil disorders and fluoropyrimidine toxicity in DPD-deficient patients. The proposed method permits the assessment of Ura and 5FU plasma concentrations with detection limits pf 0.0245 and 0.0484 ng mL(-1) (RSD = 1.0-2.5%, S/N = 3), respectively, without any problems of non-specific false-positives and cross-reactivities in complicated matrices of biological samples.
    Biomedical Chromatography 12/2008; 23(5):499-509. · 1.95 Impact Factor
  • Amit Kumar Patel, Piyush Sindhu Sharma, Bhim Bali Prasad
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    ABSTRACT: An electrochemical creatinine sensor based on a molecularly imprinted polymer (MIP)-modified sol-gel film on graphite electrode was developed. The surface coating of MIP over sol-gel was advantageous to obtain a porous film with outwardly exposed MIP cavities for unhindered selective rebinding of creatinine from aqueous and biological samples. A fast differential pulse, cathodic stripping voltammetric response of creatinine can be obtained after being preanodized the sensor in neutral medium containing appropriate amount of creatinine at +1.8 V versus SCE for 120 s. A linear response over creatinine concentration in the range of 1.23 to 100 μg mL−1 was exhibited with a detection limit of 0.37 μg mL−1 (S/N=3).
    Electroanalysis 08/2008; 20(19):2102 - 2112. · 2.82 Impact Factor
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    ABSTRACT: Clinical manifestations owing to ascorbic acid deficiency demand an easy-to-use, rapid, robust and inexpensive technique, which can measure serum ascorbic acid at ultratrace level to attend the problem of hypovitaminosis C and acute cases of scurvy. In the present work, a novel molecularly imprinted polymer (MIP)-coated solid-phase microextraction (SPME) fiber that could be coupled to a complementary MIP-sensor was prepared with ascorbic acid as a template molecule. The characteristics and applications of this fiber were investigated. The same MIP receptor for both SPME and the corresponding sensor was able to enhance the preconcentration of analyte substantially so as to attain the stringent level of sensitivity in highly diluted aqueous, blood serum and pharmaceutical samples. The extraction yield of ascorbic acid (AA) with the MIP-coated fiber was found to be quantitative (detection limit 0.0396 ng mL(-1), RSD=2.3%, S/N=3) in aqueous samples without any problem of non-specific false positive results and cross-reactivity.
    Journal of Chromatography 08/2008; 1198-1199:59-66. · 4.61 Impact Factor
  • Bhim Bali Prasad, Piyush Sindhu Sharma, Dhana Lakshmi
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    ABSTRACT: The development of an easy-to-use, rapid, robust and inexpensive technique is required which can measure the basal concentration of uric acid (UA) lower than 1.0 x 10(-7)M ( approximately 0.017 mgL(-1)) in biological samples to attend the problem of hypouricemia. In the present work an artificial receptor for UA, silica gel-bonded molecularly imprinted polymer (MIP), was used as a sorbent for molecularly imprinted solid-phase extraction (MISPE) in column chromatography. The use of a sensor based on a MIP-modified hanging mercury drop electrode (HMDE), as reported from our laboratory, could estimate UA with detection limit as low as 0.024 mgL(-1) under the optimized conditions of differential pulse, cathodic stripping voltammetric (DPCSV) measurement. However, in the current investigation, with the use of the combination of MISPE followed by detection with a MIP-based HMDE sensor, the minimum detectable concentration could go down to 0.0008 mgL(-1) (RSD=0.63%, S/N=3). The same MIP receptor for both MISPE and the corresponding sensor was able to enhance the preconcentration of analyte substantially so as to attain the desired level of sensitivity; and that to without any interference (cross-reactivity) from other structurally related analogues including the major interferent like ascorbic acid prevalent in the aqueous environment of biological samples.
    Journal of Chromatography 12/2007; 1173(1-2):18-26. · 4.61 Impact Factor
  • Piyush Sindhu Sharma, Dhana Lakshmi, Bhim Bali Prasad
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    ABSTRACT: Primary creatine deficiency syndromes (CDS) are a new group of disorders caused by guanidinoacetate methyltransferase (GAMT) deficiency, which affects endogenous creatine biosynthesis with depletion of body creatine. A deficiency in creatine can be corrected by treatment with oral creatine supplementation and this necessitates a simple and sensitive screening method for early detection of creatine in dilute physiologic fluids. In this work an artificial receptor, molecularly imprinted polymer (MIP), for creatine was used both as a material for solid-phase extraction (SPE) and as a sensing element in a voltammetric sensor. Using the combination of molecularly imprinted solid-phase extraction (MISPE) with a complementary MIP sensor, the minimum detectable amount was found to be 0.0015 ng mL(-1) (RSD = 1.3%, S/N = 3). The MISPE-MIP sensor combination provided up to 60-fold preconcentration, which was more than sufficient for achieving the required quantification limit 50 ng mL(-1) (or 0.0025 ng mL(-1) after 2 x 10(4)-fold dilution) for creatine in human blood serum.
    Biomedical Chromatography 10/2007; 21(9):976-86. · 1.95 Impact Factor
  • Dhana Lakshmi, Bhim Bali Prasad, Piyush Sindhu Sharma
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    ABSTRACT: Molecularly imprinted polymers (MIP) have been elucidated to work as artificial receptors. In our present study, a MIP was applied as a molecular recognition element to a chemical sensor. We have constructed a creatinine sensor based on a MIP layer selective for creatinine and its differential pulse, cathodic stripping voltammetric detection (DPCSV) on a hanging mercury drop electrode (HMDE). The creatinine sensor was fabricated by the drop coating of dimethylformamide (DMF) solution of a creatinine-imprinted polymer onto the surface of HMDE. The modified-HMDE, preanodised in neutral medium at +0.4V versus Ag/AgCl for 120s, exhibited a marked enhancement in DPCSV current in comparison to the less anodised (</=+0.3V) HMDE. The creatinine was preconcentrated and instantaneously oxidised in MIP layer giving DPCSV response in the concentration range of 0.0025-84.0mugmL(-1) [detection limit (3sigma) 1.49ngmL(-1)]. The sensor was found to be highly selective for creatinine without any response of interferents viz., NaCl, urea, creatine, glucose, phenylalanine, tyrosine, histidine and cytosine. The non-imprinted polymer-modified electrode did not show linear response to creatinine. The imprinting factor as high as 9.4 implies that the imprinted polymer exclusively acts as a recognition element of creatinine sensor. The proposed procedure can be used to determine creatinine in human blood serum without any preliminary treatment of the sample in an accurate, rapid and simple way.
    Talanta 10/2006; 70(2):272-80. · 3.50 Impact Factor
  • Dhana Lakshmi, Piyush Sindhu Sharma, Bhim Bali Prasad
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    ABSTRACT: Uric acid (UA) sensor based on molecularly imprinted polymer-modified hanging mercury drop electrode was developed for sensitive and selective analysis in aqueous and blood serum samples. The uric acid-imprinted polymer was prepared from melamine and chloranil and coated directly onto the surface of a hanging mercury drop electrode, under charge-transfer interactions at +0.4 V (vs. Ag/AgCl), in model 303A electrode system connected with a polarographic analyzer/stripping voltammeter (PAR model 264A). The binding event of uric acid was detected in the imprinted polymer layer through differential pulse, cathodic stripping voltammetry (DPCSV) at optimized operational conditions [accumulation potential +0.4 V (vs. Ag/AgCl), accumulation time 120 s, pH 7.0, scan rate 10 mV s−1, pulse amplitude 25 mV]. The limit of detection for UA was found to be 0.024 μg mL−1 (RSD=0.64%, S/N=3). Under the optimized operational conditions, the sensor was able to differentiate between uric acid and other closely structural-related compounds and interfering substances. Ascorbic acid (AA), a major interferent in UA estimation, was not adsorbed on the surface of sensor electrode. The present sensor is, therefore, UA-selective at all concentrations of AA present in human blood serum samples. The précised and accurate quantification of UA have been made in the dilute as well as concentrated regions varying within limits 0.1–4.0 and 9.8–137.0 μg mL−1, respectively.
    Electroanalysis 04/2006; 18(9):918 - 927. · 2.82 Impact Factor

Publication Stats

99 Citations
947 Views
54.15 Total Impact Points

Institutions

  • 2011
    • Università degli studi di Verona
      • Department of Biotechnology
      Verona, Veneto, Italy
  • 2006–2011
    • Banaras Hindu University
      • Department of Chemistry
      Benares, Uttar Pradesh, India