Molecular Imprinting-Chemiluminescence Sensor for the Determination of Amoxicillin

The amoxicillin-imprinted polymer was synthesized with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The binding characteristic of the imprinted polymer to amoxicillin was evaluated by equilibrium binding experiments. Using the imprinted polymer as recognition material, 3-(3′-nitrophenyl)-5(2′-sulfonylphenylazo)-rhodanine (4NRASP) was synthesized by the authors and was used as chemiluminescence (CL) reagent. A novel chemiluminescence (CL) sensor for the determination of amoxicillin was developed based on the CL reaction of amoxicillin with potassium permanganate in an acidic medium. The sensor displayed excellent selectivity and high sensitivity. The linear response range of the sensor was from 5.0 × 10^?9 to 1.0 × 10^?6 g · mL^?1 (r = 0.9985) and the detection limit was 1.3 × 10^?9 g · mL^?1. The relative standard deviation for the determination of 1.0 × 10^?7 g · mL^?1 amoxicillin solution was 1.7% (n = 11). The sensor was applied to the determination of amoxicillin in urine samples with satisfactory results.     

牛血清白蛋白在超薄纳米二氧化钛膜表面的印迹与吸附

基于溶胶凝胶分子印迹方法,以溶胶二氧化钛TiO2为基质印迹了牛血清白蛋白分子。用1%的NaOH溶液可有效地除去纳米TiO2印迹膜中的模板分子。采用石英晶体微天平现场技术,研究了牛血清白蛋白在超薄纳米TiO2膜表面的吸附行为。研究表明,牛血清白蛋白在印迹膜和非印迹膜上的吸附量都随溶液浓度增加而增大,印迹膜具有吸附的特异性和可再生性,其吸附量是非印迹膜的3~5倍;在非印迹膜上的吸附符合Langmuir吸附模型,而在印迹膜上的吸附符合allosteric吸附模型;牛血清白蛋白在非印迹膜上的吸附量先随pH升高而增大,当pH为5左右时达到最大值,随后吸附量又随pH的增大而减小;而在印迹膜上其吸附量仅随pH增大而增大。     

Sensitive Chemiluminescence Determination of Three Thiol Compounds Based on Cu(II)-Catalyzing Luminol Reaction in the Absence of an Oxidant

Abstract

A simple and sensitive flow-injection chemiluminescence method was proposed for the determination of three thiol compounds, namely cysteine, acetylcysteine, and glutathione. Weak chemiluminescence was produced directly by the reaction of these mentioned compounds with luminol in an alkaline solution without adding any special oxidants. The chemiluminescence signal could be significantly enhanced by Cu(II). The proposed method allows the determination of 4.0 × 10^?9 to 1.0 × 10^?7 g/mL cysteine, 7.0 × 10^?10 to 1.0 × 10^?7 g/mL acetylcysteine, and 4.0 × 10^?9 to 1.0 × 10^?6 g/mL glutathione with the detection limits of 8 × 10^?10 g/mL, 2 × 10^?11 g/mL, and 7 × 10^?10 g/mL, respectively. The proposed method was applied to the analysis of some commercial formulations containing acetylcysteine.     

Electrodeposited sol-gel-imprinted sensing film for cytidine recognition on Au-electrode surface

A novel thin molecularly imprinted sol-gel film with specific recognition for cytidine was electrodeposited on the surface of piezoelectric quartz crystal (PQC) Au-electrode. In this method, a sufficiently negative potential was applied to the electrode surface to generate hydroxyl ions, which play the role of the catalyst for the hydrolysis and condensation of 3-(aminopropyl)trimethoxysilane (APTMS). The process of the preparation of the imprinted sol-gel film was investigated in detail by using the piezoelectric quartz crystal impedance (PQCI) technique and cyclic voltammetry. The thickness of the imprinted film was controlled easily by adjusting the applied potential and the deposited time. The binding capacity and the selectivity of the electrodeposited imprinted sol-gel film were also studied in detail by using PQCI, electrochemically impedance technique and capacitance technique. The electrodeposited imprinted sol-gel film exhibited high selectivity toward cytidine in comparison to interfering substances. The dissociation constant (K_d) in the nanomolar range indicated a strong imprinted interaction existing between the electrodeposited sol-gel-imprinted film and the template cytidine.     

Simplified determination of bacterial contamination by Escherichia coli using a flow injection system with piezoelectric detection

A rapid and automated method was developed for the determination of bacterial contamination and using Escherichia coli as a model microorganism. The method involves the use of a sensor connected to a flow injection (FI) system. The sample is introduced through a flow injection system into a piezoelectric quartz crystal (PQC) flow-cell. The resulting change of the resonance frequency is related to the bacterial contamination in the sample. The parameters associated with the flow system and the conditions for introducing the sample culture were optimized. Calibration curves are linear in the range from 3.2?×?10⁷ to 3.2?×?10⁹ cfu per mL^-1, with a correlation coefficient of 0.997. The reproducibility was between 3.1 and 7.6%, and the detection limit is 1.1?×?10⁷ cfu per mL^-1. The method allowed the determination of bacterial contamination in residual water and in samples of milk and chicken stock within 5 h, while the conventional plate count method requires 24 to 48 h. The results obtained by these two methods are in good agreement.

Enhanced adsorption of atrazine from aqueous solution by molecularly imprinted TiO2 film

TiO₂ film imprinted by atrazine molecule at the surface of quartz crystal was prepared using molecular imprinting and surface sol-gel process. The molecularly imprinted TiO₂ film was characterized by scanning electron microscopy and cyclic voltammetry, and the atrazine adsorption was investigated by quartz crystal microbalance (QCM) technique. In comparison with non-imprinted TiO₂ film, the molecularly imprinted TiO₂ film exhibits high selectivity for atrazine, better reversibility and a much higher adsorption capacity for the target molecule, the adsorption equilibrium constant estimated from the in situ frequency measurement is about 6.7 × 10⁴ M⁻¹, which is thirteen times higher than that obtained on non-imprinted TiO₂ film.     

A novel sensor based on multi-walled carbon nanotubes and boron-doped double-layer molecularly imprinted membrane for the analysis of SCZ in pharmaceutical and biological samples

ABSTRACT

A molecularly imprinted electrochemical sensor for the rapid detection of the anti-parasitic drug Secnidazole (SCZ) is reported. In this work, the build electrochemical sensor was based on a carbon paste electrode (CPE) modified with multi-wall carbon nanotubes (MWCNTs) and boron-embedded duplex molecularly imprinted composite membranes (B-DMICMs), that significantly increased the efficiency of the sensor for the detection of template molecule SCZ. Density functional theory (DFT) was employed to study the interactions between the template and monomers to select appropriate functional monomers for rational design of the B-DMICMs.The optimal experimental conditions were optimised for the factors affecting the performance of the sensor. Under the optimal conditions, the reduction peak currents of SCZ by differential pulse voltammetry increased linearly with SCZ concentration in the range from 3.0 × 10^?4 to 1.0 × 1.0^?6 mol L^?1 and 1.0 × 1.0^?6 to 1.91 × 10^?8 mol L^?1 with a detection limit of 1.72 × 10^?8 mol L^?1 for secnidazole, which is significantly lower than those in the currently used methods and in previous reports. This method offers low cost, sensitive and effective determination of SCZ and can potentially be used for detection of SCZ in pharmaceutical and biological samples with good precision and accuracy.     

Preparation of a novel molecularly imprinted polymer by a sol-gel process for on-line solid-phase extraction coupled with high performance liquid chromatography to detect trace enrofloxacin in fish and chicken samples

A molecularly imprinted functionalized sol-gel has been prepared by using enrofloxacin (ENRO) as a template, 3-aminopropyltriethoxysilane as the functional monomer, tetraethoxysilicane as a cross-linker. This ENRO-imprinted polymer was evaluated by static, kinetic adsorption and selective experiments. The polymer displays good selectivity, and fast kinetics in terms of adsorption and desorption. The material was applied as a sorbent for on-line determination of trace ENRO by high performance liquid chromatography, with a focus on biological matrices. At a loading flow rate of 1.0 mL min^-1 for sampling 50 mL, the enrichment factor and limit of detection (LOD; at S/N?=?3) are 566 and 8 ng L^-1, respectively. The peak area precision (the LOD for nine replicate detections of 0.1 µg L^-1 ENRO) is 4.4%. ENRO in fish and chicken muscle was determined at three spiked levels with recoveries ranging from 70% to 82%.     

QCM sensing of a chemical nerve agent analog via electropolymerized molecularly imprinted polythiophene films

The highly selective and sensitive detection of a chemical nerve agent analog pinacolyl methylphosphonate (PMP) was demonstrated using an electrochemically molecularly imprinted polymer (MIP) polythiophene film onto a quartz crystal microbalance (QCM) transducer surface. The fabrication and optimization of the sensor film was monitored by in situ electrochemistry‐QCM (EC‐QCM) measurements, which determined the change in mass and simultaneous change in redox properties of the polymer film. The film deposition, template loading, and template removal were evidenced by a combination of surface characterization techniques such as the attenuated total reflection infrared spectroscopy and high‐resolution X‐ray photoelectron spectroscopy. The fabricated MIP film demonstrated a limit of detection and a limit of quantification of ～60 and ～197 μM, respectively. The linear sensing range is between 125 and 250 μM concentration of PMP. Finally, theoretical modeling (AM1 semiempirical quantum calculations) studies revealed that a stable prepolymerization complex is formed in solution with the existence of H‐bonding interactions using the 2:1 monomer‐to‐template ratio. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Determination of Three Imidazole Derivatives by Flow-Injection Chemiluminescence

Abstract

A rapid, simple, and sensitive method was developed for the determination of three imidazole derivatives based on their quenching effect on bis(2,4,6-tricholorophenyl) oxalate (TCPO)–H₂O₂ chemiluminescence (CL) in the presence of rhodamine 6 G. Conditions affecting CL intensity were studied. With sodium dodecyl sulfate (SDS) as the additional agent, the relative standard deviation (RSD) was more twice the RSD without SDS. Under optimal conditions, good linear ranges were obtained from 1.0 × 10^?4 g/mL to 1.0 × 10^?6 g/mL, 1.0 × 10^?5 g/mL to 1.0 × 10^?7 g/mL, and 1.0 × 10^?5 g/mL to 7.0 × 10^?7 g/mL, with detection limits of 8.0 × 10^?7 g/mL, 7.0 × 10^?8 g/mL, and 8.0 × 10^?8 g/mL (S/N = 3) for hydrobenzole hydrochloride, thiamazole, and mizolastine, respectively. The RSDs for 13 consecutive injections of 1.0 × 10^?6 g/mL hydrobenzole hydrochloride, thiamazole, and mizolastine were 1.89%, 1.47%, and 1.69%, respectively, and satisfied results were obtained with the method applied to their pharmaceutical preparations. The possible CL mechanism was simply discussed.     

Electrochemical behaviors of ofloxacin and its voltammetric determination at carbon nanotubes film modified electrode

A multi-wall carbon nanotubes (MWNTs)-Nafion film-coated glassy carbon electrode (GCE) was fabricated and the electrochemical behavior of ofloxacin on the MWNTs-Nafion film-coated GCE were investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The oxidation peak current of ofloxacin increased significantly on the MWNTs-Nafion film modified GCE compared with that using a bare GCE. This nano-structured film electrode exhibited excellent enhancement effects on the electrochemical oxidation of ofloxacin. A well-defined oxidation peak attributed to ofloxacin was observed at 0.97 V and was applied to the determination of ofloxacin. The oxidation peak current was proportional to ofloxacin concentration in the ranges 1.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/L and 1.0 × 10⁻⁶ to 2.0 × 10⁻⁵ mol/L. A detection limit of 8.0 × 10⁻⁹ mol/L was obtained for 400 s accumulation at open circuit (S/N = 3). This method for the detection of ofloxacin in human urine was satisfactory. __________ Translated from Chinese Journal of Applied Chemistry, 2007, 24(5): 540–545 [译自: 应用化学]     

Preparation of Cu (II) imprinted polymer electrode and its application for potentiometric and voltammetric determination of Cu (II)

The Cu (II) imprinted polymer glassy carbon electrode (GCE/Cu-IP) was prepared by electropolymerization of pyrrole at GCE in the presence of methyl red as a dopant and then imprinting by Cu²⁺ ions. This electrode was applied for potentiometric and voltammetric detection of Cu²⁺ ion. The potentiometric response of the electrode was linear within the Cu²⁺ concentration range of 3.9 × 10^?6 to 5.0 × 10^?2 M with a near-Nernstian slope of 29.0 mV decade^?1 and a detection limit of 5.0 × 10^?7 M. The electrode was also used for preconcentration anodic stripping voltammetry and results exhibited that peak currents for the incorporated copper species were dependent on the metal ion concentration in the range of 1.0 × 10^?8 to 1.0 × 10^?3 M and detection limit was 6.5 × 10^?9 M. Also the selectivity of the prepared electrode was investigated. The imprinted polymer electrode was used for the successful assay of copper in two standard reference material samples.     

An Electrochemical Sensor for L-Tryptophan Using a Molecularly Imprinted Polymer Film Produced by Copolymerization of o-Phenylenediamine and Hydroquinone

An electrochemical sensor for L-tryptophan based on a molecularly imprinted polymer was developed. The sensing film was prepared by the co-electropolymerization of o-phenylenediamine and hydroquinone on a gold electrode in the presence of L-tryptophan as the template. The performance of the L-tryptophan sensor was characterized by cyclic voltammetry, differential pulse voltammetry, and alternating current impedance. Under the optimal experimental conditions, the relative current change was linear to the concentration of L-tryptophan in the range of 1.0 × 10^?8 to 1.0 × 10^?6 mol/L and a detection limit of 0.50 × 10^?8 mol/L was obtained. The sensor showed high sensitivity and selectivity for L-tryptophan. The imprinting factor was 3.58 and selectivity factors of L-tryptophan compared to analogs were larger than 2. The sensor also demonstrated good resistance to acidic, basic, and organic environments.     

Flow Injection Chemiluminescence Sensor with Novel Rhodanine Ramification for Determination of Fenfluramine Based on Molecularly Imprinted Polymer

Abstract

Flow injection chemiluminescence (FI-CL) with molecularly imprinted polymer (MIP) was applied to determine fenfluramine. The fenfluramine-imprinted polymer was prepared with acrylamide (AM) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. Methyl and sulfonic group were introduced to rhodanine matrix, and a novel rhodanine ramification 3MORASP was synthesized by the author, and it was used as chemiluminescence reagent. 3-(3′-Methoxyphenyl)-5(2′-sulfonylphenylazo)-rhodanine (3MORASP), first synthesized by the authors, was used as chemiluminescence (CL) reagent. The novel flow path of FI-CL was designed, which made three merged streams of reactants injected into MIP column move through different pathways simultaneously. Fenfluramine was detected based on the reaction of fenfluramine, 3MORASP, and potassium permanganate in an acidic medium. The CL intensity was correlated linearly with the concentration of fenfluramine over the range of 1.0 × 10^?7 to 5.0 × 10^?6 g · mL^?1, and the detection limit was 9.48 × 10^?9 g · mL^?1. The relative standard deviation (RSD) was 2.4% for determination of 1.0 × 10^?6 g · mL^?1 fenfluramine (n = 11). This method was successfully applied to the determination of fenfluramine in weight-reducing tonic.     

Sol-Gel Imprinted Polymers Based Electrochemical Sensor for Paracetamol Recognition and Detection

Molecular imprinting and sol-gel technique were combined to develop a molecular imprinted polymer (MIP) based electrochemical sensor in this work. With the successive modification of multi-walled carbon nanotubes (MWNTs) and gold nanoparticles (GNPs), a modified glassy carbon electrode (GCE) was immersed in a sol-gel solution in the presence of paracetamol (PR) for the electropolymerization to fabricate an imprinted sensor. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were employed to characterize the constructed sensor. The factors for the sensor preparation, the electropolymerization potential range, the monomer concentration, and the scan rate for the sensor preparation were optimized. The sensor displayed an excellent recognition capacity toward PR compared with other analogues. Additionally, the DPV peak current was linear to the PR concentration in the range from 8.0 × 10^?8 to 5.0 × 10^?5 mol/L, with a detection limit of 4.0 × 10^?8 mol/L. The prepared sensor also showed satisfactory reproducibility and regeneration capacity.     

Flow‐Injection Chemiluminescence Analysis of Cloperastione Hydrochloride

Abstract

A new chemiluminescence (CL) reaction was observed when cloperastine hydrochloride was injected into the reaction mixture after the CL reaction of Ce(IV) and sodium sulfite finished. A new flow injection CL method for the determination of cloperastine hydrochloride was established based on the CL reaction. The relative standard deviation (RSD) for the determination of cloperastine hydrochloride was 1.3% (n=11, c=1.0×10^?6 g/mL). The CL intensity responded linearly to the concentration of cloperastine hydrochloride in the range 2.0×10^?7～2.0×10^?5 g/mL (r=0.9962). The detection limit was 5×10^?8 g/mL cloperastine hydrochloride. The method had been applied to the determination of cloperastine hydrochloride in tablets with satisfactory results.     

Determination of Oxytetracycline with a Gold Electrode Modified by Chitosan-Multiwalled Carbon Nanotube Multilayer Films and Gold Nanoparticles

A molecularly imprinted electrochemical sensor was fabricated based on a gold electrode modified by chitosan-multiwalled carbon nanotube composite (CS-MWCNTs) multilayer films and gold nanoparticles (AuNPs) for convenient and sensitive determination of oxytetracycline (OTC). The multilayer of CS-MWCNTs composites and AuNPs were used to augment electronic transmission and sensitivity. The molecularly imprinted polymers (MIPs) were synthesized using OTC as the template molecule and o-phenylenediamine (OPD) as the functional monomer. They were modified on a gold electrode by electropolymerization. The electrochemical behavior of OTC at the imprinted sensor was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), and amperometry. The molecularly imprinted sensor showed high selectivity and excellent stability toward OTC. The linear range was from 3.0 × 10^?8 to 8.0 × 10^?5 mol/L, with a limit of detection (LOD) of 2.7 × 10^?8 mol/L (S/N = 3). The developed sensor showed good recovery in spiked samples analysis.     

Super-Paramagnetic Nanoparticles by Surface Imprinting on Graphene Oxide Modified Iron (II,III) with Application for the Determination of Ovalbumin by Absorption Spectroscopy

Protein surface imprinting produces materials capable of selective recognition and capture of proteins. Herein, a protein surface imprinted polymer on graphene oxide modified super-paramagnetic Fe₃O₄ nanoparticles is reported. The molecularly imprinted polymer was synthesized by ultrasound-assisted suspension polymerization, using ovalbumin as the template molecule, 3-aminophenylboronie acid as the functional monomer, and methylene-bis-acrylamide as the cross-linking agent. The nanoparticles were approximately 40 nanometers in size and super-paramagnetic. Moreover, these particles demonstrated considerably high adsorption capacity, fast adsorption kinetics, and selective binding affinities toward the template protein ovalbumin. The calibration curve of ovalbumin was linear from 5.0 × 10^?11 to 1.0 × 10^?10 molar. The limit of detection of ovalbumin was 2.0 × 10^?11 M. These results show that this super-paramagnetic material has potential for biological macromolecule separation and determination.     

Development of molecularly ımprınted polymer based quartz crystal mıcrobalance nanosensor for the determınatıon of tryptophan

ABSTRACT

In this study, a quartz crystal microbalance (QCM) nanosensor was prepared to detect tryptophan. QCM nanosensor was prepared through the formation of tryptophan memories on the gold surface of QCM electrode using Methacryloylamidohistidine-Cu(II)-tryptophan ([MAH-Cu(II)]-tryptophan) pre-organised monomer system. The designed pre-organised monomer system was characterised by use of Fourier Transform Infrared (FTIR) and Atomic Force Microscope (AFM) was used to characterise the QCM nanosensors. After the characterisation studies, imprinted and non-imprinted sensors were connected to QCM system to determine the binding of the target molecule, selectivity and the detection of the amount of target molecule in real samples. The results showed that the imprinted QCM nanosensor had high selectivity for tryptophan.     

Imprinting unique motifs formed from protein-protein associations

Lysozyme and cytochrome c were imprinted in aqueous media, both as individual proteins and in combination, together with the functional monomer 3-aminophenylboronic acid (APBA) using ammonium persulphate as the initiator. The polymers were formed as films on the gold surfaces of quartz crystal microbalance (QCM) electrodes. It was shown that the lysozyme imprinted polymer was capable of selective template recognition. Micro-calorimetry measurements were used to determine the ratio of lysozyme and cytochrome c giving rise to the maximum enthalpy change when combined in the presence of the functional monomer. Using this procedure a maximum enthalpic change was found when the two proteins were present in an equimolar ratio. A polymer, formed by jointly imprinting the proteins in this ratio, exhibited minimal recognition for the individual template proteins, but was however able to recognise them in combination, suggesting that the proteins when imprinted together interact to form a ‘new’ imprintable motif.The introduction of a series of protein solutions, comprising the imprint proteins in various ratios, to the lysozyme/cytochrome c imprinted films, showed that the films exhibit maximum affinity towards the proteins when they are presented in approximately the same mole ratio (57% cytochrome c and 43% lysozyme) as was used to form the original imprint (equimolar ratio).Frequency response profiles of the QCM electrodes carrying the films, as a function of time, showed the establishment of a new stable baseline (−4.3 Hz) after the electrode was challenged with template protein (1.39 × 10⁻⁹ mol) in less than 3 min.