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Wei Qin - One of the best experts on this subject based on the ideXlab platform.
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imprinted nanobead based disposable screen printed Potentiometric sensor for highly sensitive detection of 2 naphthoic acid
Materials Letters, 2018Co-Authors: Rongning Liang, Xiaofeng Yang, Wei QinAbstract:Abstract Currently, Potentiometric sensors based on various molecularly imprinted polymer (MIP) receptors have been successfully fabricated for detection of organic species. However, almost all of the previously developed Potentiometric sensors based on MIPs are in traditional liquid-contact mode in which lower detection limits have been restricted by zero-current transmembrane ion fluxes. Herein, a screen-printed Potentiometric sensor for determination of 2-naphthoic acid has been developed. It is based on the MIP nanobeads as the selective receptor and the electrochemically reduced graphene oxide film as the solid contact. Compared with the classical Potentiometric sensor, the proposed sensor based on nonequilibrium sensing mechanism exhibits remarkably improved detection sensitivity for 2-naphthoic acid with a low detection limit of 6.9 × 10−11 M.
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pulsed galvanostatic control of a polymeric membrane ion selective electrode for Potentiometric immunoassays
ACS Applied Materials & Interfaces, 2013Co-Authors: Jiawang Ding, Xuewei Wang, Wei QinAbstract:Pulsed galvanostatic control of ion fluxes across polymeric membrane ion-selective electrodes (ISEs) is an emerging field for Potentiometric sensing. Herein we report a novel Potentiometric enzyme immunoassay based on current-controlled release of an enzyme substrate, which eliminates the addition of marker ions in the sample solution. In this method, the carboxylated poly(vinyl chloride) matrix at the outer layer of the ISE membrane is employed to attach a primary antibody. A sandwich immunoassay with an alkaline phosphatase labeled antibody (ALP-Ab) as the reporter is used for the determination of human IgG (as a model protein). The large difference between the lipophilicity of the substrate ion and that of the product ion allows p-nitrophenyl phosphate to be used as the enzyme substrate for Potentiometric immunosensors. After the immunoreactions, the captured ALP-Ab catalyzes the hydrolysis of the substrate ions released at the sample-membrane interface by using the pulsed galvanostatic technique. This process can be Potentiometrically determined by measuring the open circuit potential of the ISE. Under optimal conditions, the potential response of the proposed immunosensor is proportional to the concentration of human IgG in the range of 50-1000 ng/mL with a detection limit of 30 ng/mL (3 sigma). Owing to simplicity and independence of sample volume and sample turbidity, the proposed Potentiometric immunoassay offers a viable alternative to those based on optical absorbance.
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Potentiometric sensing of nuclease activities and oxidative damage of single stranded dna using a polycation sensitive membrane electrode
Biosensors and Bioelectronics, 2013Co-Authors: Jiawang Ding, Wei QinAbstract:A simple, general and label-free Potentiometric method to measure nuclease activities and oxidative DNA damage in a homogeneous solution using a polycation-sensitive membrane electrode is reported. Protamine, a linear polyionic species, is used as an indicator to report the cleavage of DNA by nucleases such as restriction and nonspecific nucleases, and the damage of DNA induced by hydroxyl radicals. Measurements can be done with a titration mode or a direct detection mode. For the Potentiometric titration mode, the enzymatic cleavage dramatically affects the electrostatical interaction between DNA and protamine and thus shifts the response curve for the Potentiometric titration of the DNA with protamine. Under the optimized conditions, the enzyme activities can be sensed Potentiometrically with detection limits of 2.7 x 10(-4) U/mu L for S1 nuclease, and of 3.9 x 10(-4) U/mu L for DNase I. For the direct detection mode, a biocomplex between protamine and DNA is used as a substrate. The nuclease of interest cleaves the DNA from the protamine/DNA complex into smaller fragments, so that free protamine is generated and can be detected Potentiometrically via the polycation-sensitive membrane electrode. Using a direct measurement, the nuclease activities could be rapidly detected with detection limits of 3.2 x 10(-4) U/mu L for S1 nuclease, and of 4.5 x 10(-4) U/mu L for DNase I. Moreover, the proposed Potentiometric assays demonstrate the potential applications in the detection of hydroxyl radicals. It is anticipated that the present Potentiometric strategy will provide a promising platform for high-throughput screening of nucleases, reactive oxygen species and the drugs with potential inhibition abilities. (C) 2013 Elsevier B.V. All rights reserved.
Joseph Wang - One of the best experts on this subject based on the ideXlab platform.
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Tattoo-based Potentiometric ion-selective sensors for epidermal pH monitoring
The Analyst, 2013Co-Authors: Amay J Bandodkar, Gabriela Valdés-ramírez, Vinci W. S. Hung, Garrett Chan, Alexandra G. Martinez, Joshua Ray Windmiller, Julian Ramirez, Wenzhao Jia, Kagan Kerman, Joseph WangAbstract:This article presents the fabrication and characterization of novel tattoo-based solid-contact ion-selective electrodes (ISEs) for non-invasive Potentiometric monitoring of epidermal pH levels. The new fabrication approach combines commercially available temporary transfer tattoo paper with conventional screen printing and solid-contact polymer ISE methodologies. The resulting tattoo-based Potentiometric sensors exhibit rapid and sensitive response to a wide range of pH changes with no carry-over effects. Furthermore, the tattoo ISE sensors endure repetitive mechanical deformation, which is a key requirement of wearable and epidermal sensors. The flexible and conformal nature of the tattoo sensors enable them to be mounted on nearly any exposed skin surface for real-time pH monitoring of the human perspiration, as illustrated from the response during a strenuous physical activity. The resulting tattoo-based ISE sensors offer considerable promise as wearable Potentiometric sensors suitable for diverse applications.
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A Potentiometric tattoo sensor for monitoring ammonium in sweat
The Analyst, 2013Co-Authors: Tomas Guinovart, Joshua Ray Windmiller, Amay J Bandodkar, Francisco J Andrade, Joseph WangAbstract:The development and analytical characterization of a novel ion-selective Potentiometric cell in a temporary-transfer tattoo platform for monitoring ammonium levels in sweat is presented. The fabrication of this skin-worn sensor, which is based on a screen-printed design, incorporates all-solid-state Potentiometric sensor technology for both the working and reference electrodes, in connection to ammonium-selective polymeric membrane based on the nonactin ionophore. The resulting tattooed Potentiometric sensor exhibits a working range between 10(-4) M to 0.1 M, well within the physiological levels of ammonium in sweat. Testing under stringent mechanical stress expected on the epidermis shows that the analytical performance is not affected by factors such as stretching or bending. Since the levels of ammonium are related to the breakdown of proteins, the new wearable Potentiometric tattoo sensor offers considerable promise for monitoring sport performance or detecting metabolic disorders in healthcare. Such combination of the epidermal integration, screen-printed technology and Potentiometric sensing represents an attractive path towards non-invasive monitoring of a variety of electrolytes in human perspiration.
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Potentiometric detection of dna hybridization using enzyme induced metallization and a silver ion selective electrode
Analytical Chemistry, 2009Co-Authors: Jie Wu, Karin Y Chumbimunitorres, Michal Galik, David A Haake, Chongdee Thammakhet, Joseph WangAbstract:Here, we report on a highly sensitive Potentiometric detection of DNA hybridization. The new assay uses a low-volume solid-contact silver ion-selective electrode (Ag(+)-ISE) to monitor the depletion of silver ions induced by the biocatalytic reaction of the alkaline-phosphatase enzyme tag. The resultant potential change of the Ag(+)-ISE, thus, serves as the hybridization signal. Factors affecting the Potentiometric hybridization response have been optimized to offer a detection limit of 50 fM (0.2 amol) DNA target. The new Potentiometric assay was applied successfully to the monitoring of the 16S rRNA of E. coli pathogenic bacteria to achieve a low detection limit of 10 CFU in the 4 microL sample. Such Potentiometric transduction of biocatalytically induced metallization processes holds great promise for monitoring various bioaffinity assays involving common enzyme tags.
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Potentiometric stripping analysis at bismuth film electrode
Electroanalysis, 2002Co-Authors: Samo B Hocevar, Joseph Wang, Bozidar OgorevcAbstract:A bismuth-film electrode (BiFE) operated in the constant-current Potentiometric stripping mode exhibits an attractive performance for trace heavy metal detection. The BiFEs are prepared in situ on a glassy-carbon supporting electrode from the 0.1 M acetate buffer solution (pH 4.5) containing 500 μg/L of bismuth(III) together with target heavy metal ions. The constant-current Potentiometric stripping mode of such electrodes yields well-defined, undistorted, reproducible and sharp stripping signals (RSD 1.5% for cadmium, 2.5% for lead) with good resolution for multiple heavy metal measurements (Zn, Cd, Pb). Along with an extremely low baseline, low limit of detection (0.2 and 0.8 μg/L for cadmium and lead, respectively), and short deposition times, these electrodes compare favorably with “toxic” mercury film electrodes. Several key parameters of the constant-current Potentiometric stripping mode were examined and optimized, including the stripping current, deposition potential, and deposition time. The constant-current Potentiometric stripping mode of BiFE compares favorably to their voltammetric stripping analogues. Additional insights are given into application of BiFEs for constant-current Potentiometric stripping analysis.
Rongning Liang - One of the best experts on this subject based on the ideXlab platform.
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imprinted nanobead based disposable screen printed Potentiometric sensor for highly sensitive detection of 2 naphthoic acid
Materials Letters, 2018Co-Authors: Rongning Liang, Xiaofeng Yang, Wei QinAbstract:Abstract Currently, Potentiometric sensors based on various molecularly imprinted polymer (MIP) receptors have been successfully fabricated for detection of organic species. However, almost all of the previously developed Potentiometric sensors based on MIPs are in traditional liquid-contact mode in which lower detection limits have been restricted by zero-current transmembrane ion fluxes. Herein, a screen-printed Potentiometric sensor for determination of 2-naphthoic acid has been developed. It is based on the MIP nanobeads as the selective receptor and the electrochemically reduced graphene oxide film as the solid contact. Compared with the classical Potentiometric sensor, the proposed sensor based on nonequilibrium sensing mechanism exhibits remarkably improved detection sensitivity for 2-naphthoic acid with a low detection limit of 6.9 × 10−11 M.
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Soluble Molecularly Imprinted Polymer-Based Potentiometric Sensor for Determination of Bisphenol AF
Analytical chemistry, 2017Co-Authors: Huan Zhang, Ruiqing Yao, Ning Wang, Rongning LiangAbstract:Molecularly imprinted polymer (MIP)-based polymeric membrane Potentiometric sensors have been successfully developed for determination of organic compounds in their ionic and neutral forms. However, most of the MIP receptors in Potentiometric sensors developed so far are insoluble and cannot be well dissolved in the polymeric membranes. The heterogeneous molecular recognitions between the analytes and MIPs in the membranes are inefficient due to the less available binding sites of the MIPs. Herein we describe a novel polymeric membrane Potentiometric sensor using a soluble MIP (s-MIP) as a receptor. The s-MIP is synthesized by the swelling of the traditional MIP at a high temperature. The obtained MIP can be dissolved in the plasticized polymeric membrane for homogeneous binding of the imprinted polymer to the target molecules. By using neutral bisphenol AF as a model, the proposed method exhibits an improved sensitivity compared to the conventional MIP-based sensor with a lower detection limit of 60 nM. ...
Alexis Lycourghiotis - One of the best experts on this subject based on the ideXlab platform.
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differential Potentiometric titration development of a methodology for determining the point of zero charge of metal hydr oxides by one titration curve
Environmental Science & Technology, 2005Co-Authors: Kyriakos Bourikas, Christos Kordulis, Alexis LycourghiotisAbstract:A new methodology is presented, called differential Potentiometric titration (DPT), which allows the determination of the point of zero charge (pzc) of metal (hydr)oxides using only one Potentiometric curve. By performing extensive simulations of Potentiometric titrations for various model (hydr)oxides, we found that an inflection point in a H+cons,surf versus pH Potentiometric curve (H+cons,surf: hydrogen ions consumed on the surface of the (hydr)oxide) and a peak in the corresponding differential curve, dH+cons,surf/dpH versus pH, appear at a pH equal to the pzc assumed for a model (hydr)oxide. This distinguishable peak appears at the same position irrespective of the surface ionization and the interfacial model adopted as well as the assumed ionic strength. It was found that the aforementioned peak also appears in the high-resolution differential Potentiometric curves experimentally determined for four oxides (SiO2, TiO2, γ-Al2O3, and MgO) that are widely used in various environmental and other techno...
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Differential Potentiometric titration: Development of a methodology for determining the point of zero charge of metal (hydr)oxides by one titration curve
Environmental Science and Technology, 2005Co-Authors: Kyriakos Bourikas, Christos Kordulis, Alexis LycourghiotisAbstract:A new methodology is presented, called differential Potentiometric titration (DPT), which allows the determination of the point of zero charge (pzc) of metal (hydr)oxides using only one Potentiometric curve. By performing extensive simulations of Potentiometric titrations for various model (hydr)oxides, we found that an inflection point in a H+(cons,surf) versus pH Potentiometric curve (H+(cons,surf): hydrogen ions consumed on the surface of the (hydr)oxide) and a peak in the corresponding differential curve, dH+(cons,surf)/dpH versus pH, appear at a pH equal to the pzc assumed for a model (hydr)oxide. This distinguishable peak appears at the same position irrespective of the surface ionization and the interfacial model adopted as well as the assumed ionic strength. It was found that the aforementioned peak also appears in the high-resolution differential Potentiometric curves experimentally determined for four oxides (SiO2, TiO2, gamma-Al2O3, and MgO) that are widely used in various environmental and other technological applications. The application of DPT to the above-mentioned oxides provided practically the same pzc values as the corresponding ones achieved by using four different techniques as well as the corresponding isoelectric point (iep) values determined by microelectrophoresis. Differences between the pzc and iep values determined using various techniques in the case of MgO were attributed to the increasing dissolution of this oxide as pH decreases and the adsorption of cations (Mg2+, Na+) on the MgO/electrolytic solution interface.
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Potentiometric mass titrations experimental and theoretical establishment of a new technique for determining the point of zero charge pzc of metal hydr oxides
Journal of Physical Chemistry B, 2003Co-Authors: Kyriakos Bourikas, Christos Kordulis, John Vakros, Alexis LycourghiotisAbstract:In this paper, we present a novel methodology, called the Potentiometric mass titration (PMT) technique, for determining the point of zero charge (pzc) of mineral hydr(oxides) immersed in electrolytic solutions. Following PMT, the pzc is identified as the common intersection point (CIP) of the Potentiometric curve of the blank solution with the corresponding curves of the impregnating suspensions containing different amounts of the immersed mineral (hydr)oxides. Full experimental results related to the determination of pzc using the PMT technique and four traditional techniques (Potentiometric titrations, mass titrations, immersion, and microelectrophoresis (for determining the isoelectric point, equal to pzc in cases where no specific adsorption takes place)) are presented for four oxides, namely, MgO, γ-Al2O3, TiO2, and SiO2. The comparison of the pzc values determined by PMT, with the corresponding ones determined using the traditional methodologies, strongly suggested that the PMT technique can be use...
Jiawang Ding - One of the best experts on this subject based on the ideXlab platform.
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pulsed galvanostatic control of a polymeric membrane ion selective electrode for Potentiometric immunoassays
ACS Applied Materials & Interfaces, 2013Co-Authors: Jiawang Ding, Xuewei Wang, Wei QinAbstract:Pulsed galvanostatic control of ion fluxes across polymeric membrane ion-selective electrodes (ISEs) is an emerging field for Potentiometric sensing. Herein we report a novel Potentiometric enzyme immunoassay based on current-controlled release of an enzyme substrate, which eliminates the addition of marker ions in the sample solution. In this method, the carboxylated poly(vinyl chloride) matrix at the outer layer of the ISE membrane is employed to attach a primary antibody. A sandwich immunoassay with an alkaline phosphatase labeled antibody (ALP-Ab) as the reporter is used for the determination of human IgG (as a model protein). The large difference between the lipophilicity of the substrate ion and that of the product ion allows p-nitrophenyl phosphate to be used as the enzyme substrate for Potentiometric immunosensors. After the immunoreactions, the captured ALP-Ab catalyzes the hydrolysis of the substrate ions released at the sample-membrane interface by using the pulsed galvanostatic technique. This process can be Potentiometrically determined by measuring the open circuit potential of the ISE. Under optimal conditions, the potential response of the proposed immunosensor is proportional to the concentration of human IgG in the range of 50-1000 ng/mL with a detection limit of 30 ng/mL (3 sigma). Owing to simplicity and independence of sample volume and sample turbidity, the proposed Potentiometric immunoassay offers a viable alternative to those based on optical absorbance.
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Potentiometric sensing of nuclease activities and oxidative damage of single stranded dna using a polycation sensitive membrane electrode
Biosensors and Bioelectronics, 2013Co-Authors: Jiawang Ding, Wei QinAbstract:A simple, general and label-free Potentiometric method to measure nuclease activities and oxidative DNA damage in a homogeneous solution using a polycation-sensitive membrane electrode is reported. Protamine, a linear polyionic species, is used as an indicator to report the cleavage of DNA by nucleases such as restriction and nonspecific nucleases, and the damage of DNA induced by hydroxyl radicals. Measurements can be done with a titration mode or a direct detection mode. For the Potentiometric titration mode, the enzymatic cleavage dramatically affects the electrostatical interaction between DNA and protamine and thus shifts the response curve for the Potentiometric titration of the DNA with protamine. Under the optimized conditions, the enzyme activities can be sensed Potentiometrically with detection limits of 2.7 x 10(-4) U/mu L for S1 nuclease, and of 3.9 x 10(-4) U/mu L for DNase I. For the direct detection mode, a biocomplex between protamine and DNA is used as a substrate. The nuclease of interest cleaves the DNA from the protamine/DNA complex into smaller fragments, so that free protamine is generated and can be detected Potentiometrically via the polycation-sensitive membrane electrode. Using a direct measurement, the nuclease activities could be rapidly detected with detection limits of 3.2 x 10(-4) U/mu L for S1 nuclease, and of 4.5 x 10(-4) U/mu L for DNase I. Moreover, the proposed Potentiometric assays demonstrate the potential applications in the detection of hydroxyl radicals. It is anticipated that the present Potentiometric strategy will provide a promising platform for high-throughput screening of nucleases, reactive oxygen species and the drugs with potential inhibition abilities. (C) 2013 Elsevier B.V. All rights reserved.
