Anti-Biofouling Electrochemical Sensor Based on the Binary Nanocomposite of Silica Nanochannel Array and Graphene for Doxorubicin Detection in Human Serum and Urine Samples

A disposable and portable electrochemical sensor was fabricated by integrating vertically-ordered silica mesoporous films (VMSF) and electrochemically reduced graphene (ErGO) on a screen-printed carbon electrode (SPCE). Such VMSF/ErGO/SPCEs could be prepared by a simple and controllable electrochemical method. Stable growth of VMSF on SPCE could be accomplished by the introduction of an adhesive ErGO nanolayer owing to its oxygen-containing groups and two-dimensional (2D) planar structure. An outer VMSF layer acting as a protective coating is able to prevent the leakage of the inner ErGO layer from the SPCE surface. Thanks to the electrostatic permselectivity and anti-fouling capacity of VMSF and to the good electroactive activity of ErGO, binary nanocomposites of VMSF and ErGO endow the SPCE with excellent analytical performance, which could be used to quantitatively detect doxorubicin (DOX) in biological samples (human serum and urine) with high sensitivity, good long-term stability, and low sample amounts.     

Effect of pre-treatment on the surface and electrochemical properties of screen-printed carbon paste electrodes

The effect of various electrochemical pre-treatment methods on the surface and electrochemical properties of screen-printed carbon paste electrodes (SPCE) prepared with three different commercial products was examined. It was observed that a positively charged redox couple, e.g., hexaammineruthenium(III), exhibited quasi-reversible behavior at the untreated SPCE. However, the cyclic voltammograms (CVs) of the SPCE prepared with general-purpose carbon inks did not exhibit clear redox peaks to other representative redox couples [e.g., hexacyanoferrate(III), hexachloroiridate(IV), dopamine, and hydroquinone] without activation. Electrochemical pre-treatment methods were sought in four different aqueous solutions, i.e., sulfuric acid, potassium chloride, sodium hydrogencarbonate, and sodium carbonate, applying various activation potentials. It was found that the pre-treatment procedure in saturated Na2CO3 solution at 1.2 V provides a mild and effective condition for activating the SPCE. By measuring the water contact angles at the SPCE surfaces and recording their SEM images, it was confirmed that the electrochemical pre-treatment effectively removes the organic binders from the surface carbon particles. A prolonged period of activation (> 5 min) or the use of high potentials (> 1.2 V) increased the capacitance of the electrode over 20 microF cm(-2). The pre-treated SPCE behaved like a random array microelectrode, exhibiting a sigmoidal-shaped CV at a slow scan rate. The short pre-anodization method in Na2CO3 solution was generally applicable to most SPCE prepared with general-purpose carbon inks.     

Fabrication of Silver Nanoparticles Decorated on Activated Screen Printed Carbon Electrode and Its Application for Ultrasensitive Detection of Dopamine

In the present study, we report the fabrication of silver nanoparticles (AgNPs) decorated on activated screen printed carbon electrode (ASPCE). The AgNPs were prepared by using Justicia glauca leaf extract as a reducing and stabilizing agent and the ASPCE was prepared by a simple electrochemical activation of screen printed carbon electrode (SPCE). The ASPCE/AgNPs shows a reversible electrochemical behaviour with enhanced response for DA than that of other modified SPCEs. Under optimum conditions, the electrochemical oxidation current response of DA is linear over the concentration range from 0.05 to 45.35 µM. The limit of detection is found as 0.017 µM with a high sensitivity of 7.85 µA µM^?1 cm^?2.     

Natural Melanin Nanoparticle‐decorated Screen‐printed Carbon Electrode: Performance Test for Amperometric Determination of Hexavalent Chromium as Model Trace

A biosensor was prepared with natural melanin nanoparticles (MNP) decorated on a screen‐printed carbon electrode (SPCE). Hexavalent chromium was selected as a well‐known heavy metal ion to be detected for testing the performance of novel biosensor. Natural MNP was extracted from cuttlefish (Sepia officinalis) ink. Surface decoration of SPCEs with MNP was performed by two different methods. The first one was layer‐by‐layer assembly (LBL‐A) for different cycle times(n). In the second one, plasma treatment of SPCE incorporated with evaporation‐induced self‐assembly (EI‐SA) techniques including different incubation times in MNP solutions. The performance of both modified SPCEs were tested for amperometric detection of Cr(VI) in various water samples, and peak reduction of Cr(VI) was determined at 0.33 V. Amperometric results showed wide linear ranges of 0.1–2 μM and 0.1–5 μM of Cr(VI) for SPCEs modified with 14n‐LBL‐A and 12h‐EI‐SA, respectively. The sensitivities of SPCEs modified with 14n‐LBL‐A and 12h‐EI‐SA techniques were 0.27 μA μM^?1 and 0.52 μA μM^?1, respectively. In addition, both modified SPCEs selectively detected Cr(VI) in a model aqueous system composed of certain other heavy metals and minerals, and tap and lake water samples. The LOD and LOQ values for 12h‐EI‐SA were 0.03 μM and 0.1 μM, respectively. This showed that MNP‐modified‐SPCEs generated via EI‐SA techniques have the potential to be an alternative to conventional detection methods such as ICP‐MS.     

A Simple Method to Tune Up Screen‐Printed Carbon Electrodes Applicable to the Design of Disposable Electrochemical Sensors

We report an easy method to tune up screen‐printed carbon electrodes (SPCEs) for application in fabricating disposable electrochemical sensors. Simply by ultrasonic polishing a bare SPCE in a γ‐Al₂O₃ slurry, the surface roughness was drastically smoothed coupled with a large increase in hydrophilicity. The as‐generated micromorphology on the surface of the SPCE was found to be ideal for the immobilization of catechol to minimize the overpotential in the sensitive detection of nicotinamide adenine dinucleotide (NADH) and hydrazine. Physical characterization by both XPS and AFM studies specify that the adsorption behavior is related to the carbon surface functionalities and the trapping of γ‐Al₂O₃ on the polished‐SPCE.     

Feasibility Study of Biosensors Based on Polymelamine‐modified Screen‐printed Carbon Electrodes

We herein report the use of melamine and a low‐cost screen‐printed carbon electrode (SPCE) as the base matrices for the preparation of an electrochemical biosensor. Following the electrochemical polymerization of melamine, the resulting polymelamine was deposited on the SPCE surface to give layers bearing –NH₂ functional groups, which allowed the attachment of anti‐IgE (immunoglobulin E) antibodies. The resulting anti‐IgE‐labeled SPCEs were then incubated with IgE solutions of various concentrations prior to analysis by chronoamperometry using Ru(NH₃)₆³⁺ as an electrochemical mediator. A logarithmic relationship was observed between the chronoamperometric current and the IgE concentration between 5.3 and 530 fM (i. e. over 2 orders of magnitude). In addition, a detection limit of 0.64 fM was achieved in addition to a recovery of 114 ± 14 % for a fetal bovine serum sample spiked with 16 fM IgE. Furthermore, only a small quantity of sample was required for analysis, and the IgE assay was suitable for use in a complex serum matrix without interference. We therefore expect that this novel system will be useful for monitoring the changes in blood IgE levels during the clinical treatment of allergic asthma and rhinitis.     

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Inorganic mercury ions (Hg²⁺) in laboratory prepared solutions were determined with a screen-printed carbon electrode (SPCE) coated with a polyaniline-methylene blue (PANI-MB) polymer layer. The structure and properties of the PANI-MB polymer layer were compared to that of normal polyaniline (PANI) in order to elucidate the structure of the PANI-MB layer. The electrically-conducting polymers were prepared by electrochemical polymerisation of monomer solutions of aniline, and mixed solutions of aniline with methylene blue onto respective screen-printed carbon electrodes (SPCEs). Scanning Electron Microscopy (SEM) analyses of the SPCE polymer coated electrodes have shown that nanostructured materials have formed with the diameters of the PANI nanoclusters and PANI-MB nanorods at approximately 200 nm. Anodic stripping voltammetry (ASV) was used to evaluate a solution composed of 1 × 10^?6 M Hg²⁺, in the presence of the SPCE/PANI-MB polymer sensor electrode. The Hg²⁺ ions were determined as follows: (i) pre-concentration and reduction on the modified electrode surface and (ii) subsequent stripping from the electrode surface during the positive potential sweep. The experimental conditions optimised for Hg²⁺ determination included the supporting electrolyte concentration and the accumulation time. The results obtained have shown that the SPCE/PANI-MB polymer sensor electrode operates optimally at a pH 2, with the supporting electrolyte concentration at 0.5 M HCl. A linear calibration curve was found to be in the range of 1 × 10^?8 M to 1 × 10^?5 M Hg²⁺ after 120 s of pre-concentration. The detection limit was calculated and found to be 54.27 ± 3.28 µg L^?1 of Hg²⁺. The results have also shown that a conducting polymer modified SPCE sensor electrode can be used as an alternative transducer for the voltammetric stripping and analysis of inorganic Hg²⁺ ions.     

The role of oxygen functionalities and edge plane sites on screen-printed carbon electrodes for simultaneous determination of dopamine,uric acid and ascorbic acid

The role of oxygen functionalities and edge plane sites on disposable screen-printed carbon electrodes (SPCE) was evaluated for simultaneous determination of dopamine, uric acid and ascorbic acid in this study. Both electrochemically preanodized and oxygen plasma treated SPCEs were adopted for the purpose of partially differentiating these two effects. Raman and XPS analyses verify that different treatment can indeed induce different surface characteristics. The electrocatalytic activity thereby increases by the substantial increase in surface bound carbon–oxygen functional groups and/or the generation of edge plane sites through surface reorientation. Possible mechanism is proposed to explain the voltammetric behavior. The peaks for dopamine, uric acid and ascorbic acid are especially well-resolved from each other at the electrochemically preanodized SPCE and simultaneous detection at neutral pH can thus be obtained by this simple approach.     

A Fast and Simple Ozone‐mediated Method towards Highly Activated Screen Printed Carbon Electrodes as Versatile Electroanalytical Tools

A facile and effective electrochemical activation method of screen printed carbon electrodes (SPCEs) has been performed using ozone gas. Activated SPCEs showed relevant improvements in the electrochemical properties such as an impedance reduction and better electroanalytical outcomes. Such improved properties were attributed to the increase of the electroactive surface area and the functionalization of the electrode surface with carbon‐oxygen groups onto the carbonaceous ink surface. The optimized activation method consisted in the performance of a voltammetric cycle between ?2 and 2 V at 10 mV s^?1 in 0.1 M NaOH solution with constant ozone gas bubbling. This activation procedure takes 12 min, which allows its use routinely prior to the electrode modifications and electroanalytical measurements. The resulting activated SPCEs exhibited superior sensitivities towards hydrogen peroxide, acetaminophen, hydroquinone and dopamine. This methodology might be considered as a strategy to attain SPCEs with improved electroanalytical properties for multiple applications.     

Electrochemical Sensing Platforms for HER2‐ECD Breast Cancer Biomarker Detection

Screening and early diagnosis are crucial to increase the success of cancer patients’ treatments and improve the survival rate. To contribute to this success, distinct electrochemical immunosensing platforms were developed for the analysis of the ExtraCellular Domain of the Human Epidermal growth factor Receptor 2 (HER2‐ECD) through sandwich assays on nanomaterial‐modified screen‐printed carbon electrodes (SPCEs). The most promising platforms showed to be SPCEs modified with (i) gold nanoparticles (AuNPs) and (ii) multiwalled carbon nanotubes combined with AuNPs. The antibody‐antigen interaction was detected using a secondary antibody labelled with alkaline phosphatase and 3‐indoxyl phosphate and silver ions as the enzymatic substrate. The electrochemical signal of the enzymatically generated metallic silver was recorded by linear sweep voltammetry. Under the optimized conditions, linear calibration plots were obtained between 7.5 and 50 ng/mL and the total assay time was 2 h 20 min, achieving LODs of 0.16 ng/mL (SPCE‐MWCNT/AuNP) and 8.5 ng/mL (SPCE‐AuNP), which are well below the established cut‐off value of 15 ng/mL for this cancer biomarker.     

Sensitive Quantification of Fe(III) in Food Samples at Screen Printed Carbon Electrode Modified with Graphene and Piroxicam by Catalytic Adsorptive Voltammetry

A new disposable sensitive voltammetric sensor for the determination of Fe(III) based on a graphene (G) and piroxicam (Pir) modified screen printed carbon electrode (Pir/G/SPCE) has been developed. The developed method is based on accumulation of Fe(III) on the surface of the prepared sensor strip, formation a complex with Pir and subsequent reduction the adsorbed chelated Fe(III) at ?0.03 V (vs. Ag/AgCl) coupled with the catalytic enhancement of bromate. Characterizations of the modified electrode surface were performed by field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray spectroscopy (EDX) and electrochemical impedance spectroscopy (EIS). Electrochemical behavior of the modified SPCEs was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimum conditions, the catalytic voltammetric method exhibited linear calibration plot in the concentration ranges of 1–100 ng mL^?1 and 100–3500 ng mL^?1 Fe(III) with a limit of detection of 0.3 ng mL^?1. The sensor strip displayed good reproducibility with 1.7 % relative standard deviation (RSD%). The developed method was successfully applied for the determination of iron in food samples such as vegetables, fruit, and cereal.     

Development of Electrochemical Paper‐based Glucose Sensor Using Cellulose‐4‐aminophenylboronic Acid‐modified Screen‐printed Carbon Electrode

The present work describes the fabrication of paper‐based analytical devices (μPADs) by immobilization of glucose oxidase onto the screen printed carbon electrodes (SPCEs) for the electrochemical glucose detection. The sensitivity towards glucose was improved by using a SPCE prepared from homemade carbon ink mixed with cellulose acetate. In addition, 4‐aminophenylboronic acid (4‐APBA) was used as a redox mediator giving a lower detection potential for improvement selectivity. Under optimized condition, the detection limit was 0.86 mM. The proposed device was applied in real samples. This μPAD has many advantages including low sample consumption, rapid analysis method, and low device cost.     

石墨烯基纳米复合物修饰印刷电极伏安法测定水中镉

构建了基于石墨烯(GS) -纳米金(Au)复合纳米微粒修饰印刷电极(SPCEs)的电化学传感器(SPCEs |GS/Au),建立了微分脉冲溶出伏安(DPSV)法测定水中痕量镉的电分析方法.采用扫描电镜(SEM)对电极表面进行了表征,DPSV法研究了镉的电化学性质.在优化实验条件下,溶出峰电流与Cd2+的质量浓度在2.5...     

Electrochemical Study of the Interaction of the Alkylating Agent Busulfan with Double Strand DNA

Damage of salmon sperm double strand ss dsDNA in solution or immobilized on screen‐printed carbon electrode (SPCE) induced by incubation of DNA with the antineoplastic alkylating agent busulfan (BUS) at various conditions was detected for the first time by simple electrochemical methods. Chemical changes in DNA bases can be detected through the altered electroactivity of the DNA. Electrochemical voltammetric sensing of damage caused by BUS to dsDNA in solution was monitored by the appearance of peaks diagnostic of the oxidation of guanine and adenine. Moreover, crystal violet, which interacts with the DNA immobilized on SPCEs, was used as an effective electroactive indicator, in combination with cyclic voltammetry and differential pulse voltammetry techniques to monitor the cross‐links or damage to DNA. The interaction between BUS and DNA were determined by the changes in the voltammetric peak of crystal violet. The effects of various conditions upon the crystal violet signal were investigated.     

Amperometric Magnetoimmunosensors for Direct Determination of D‐Dimer in Human Serum

Two different D‐dimer disposable amperometric immunosensing designs based on indirect competitive or sandwich formats and the use of carboxylic acid‐modified magnetic beads (COOH‐MBs) and screen‐printed carbon electrodes (SPCEs) have been developed and compared. In both approaches, the resulting modified MBs were magnetically captured on the surface of a SPCE which was used as the transducer for the electrochemical detection at ?0.20 V upon addition of H₂O₂, and hydroquinone (HQ). Both configurations exhibited linear ranges of clinical usefulness and detection limits quite below the clinical threshold (0.5 µg mL^?1 D‐dimer). The sandwich configuration has been successfully tested with serum samples.     

铁蛋白在修饰金电极上的直接电化学研究

利用巯基丙酸单分子层修饰金电极,获得了铁蛋白的直接电化学,用SPR表征了电极组装过程,循环伏安法研究了这一电子转移过程。比较了静电吸附与键合和固定2种修饰方法的不同,发现利用键合固定的方法并不能像细胞色素c那样得到稳定的电化学信号,这可能是由于经过多圈扫描以后,铁蛋白的构象发生了变化。一个电位调制的关于铁的释放与获取机理被进一步证实。     

Simultaneous Determination of Cr(III) and Cr(VI) by Differential Pulse Voltammetry Using Modified Screen‐Printed Carbon Electrodes in Array Mode

A new procedure for the speciation of chromium by means of differential pulse voltammetry using screen‐printed carbon electrodes (SPCEs) has been proposed. Two different modified carbon working, a Ag/AgCl reference and a carbon counter screen‐printed electrodes have been connected in array mode for the simultaneous determination of Cr(III) and Cr(VI). Mercury films or gold nanoparticles have been ground onto the SPCEs in order to improve their selectivity to each chromium species. The quantification of the peak currents observed at ?1.25 V in Hg‐SPCE and ?0.1 V in AuNPs‐SPCE were carried out. The method has been applied to the speciation of chromium in waste water from a tannery factory.     

Amperometric Biosensors for Tyramine Determination Based on Graphene Oxide and Polyvinylferrocene Modified Screen‐printed Electrodes

A comparison of the analytical characteristics of two tyramine biosensors, based on graphene oxide (GRO) and polyvinylferrocene (PVF) modified screen‐printed carbon electrodes (SPCE), is reported. Diamine oxidase (DAOx) or monoamine oxidase (MAOx) was immobilized onto the PVF/GRO modified SPCE to fabricate the biosensors. Surface characteristics and electrochemical behaviour of the modified SPCEs were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDX) and cyclic voltammetry (CV). Electrode surface composition and experimental variables such as pH and working potential were optimized in order to ensure a high performance. Under optimum experimental conditions, both DAOx/PVF/GRO/SPCE and MAOx/PVF/GRO/SPCE biosensors exhibited wide linear dynamic ranges for tyramine from 9.9×10^?7 to 1.2×10^?4 M and from 9.9×10^?7 to 1.1×10^?4 M, respectively. MAOx/PVF/GRO/SPCE biosensor showed higher sensitivity (11.98 μA mM^?1) for tyramine determination than the DAOx/PVF/GRO/SPCE biosensor (7.99 μA mM^?1). The substrate specifity of the biosensors to other biogenic amines namely histamine, putrescine, spermine, spermidine, tryptamine, β‐phenylethylamine and cadaverine was also investigated. The developed biosensors were successfully used for tyramine determination in cheese sample.     

Nanochannel Array on Electrochemically Polarized Screen Printed Carbon Electrode for Rapid and Sensitive Electrochemical Determination of Clozapine in Human Whole Blood

Rapid and highly sensitive determination of clozapine (CLZ), a psychotropic drug for the treatment of refractory schizophrenia, in patients is of great significance to reduce the risk of disease recurrence. However, direct electroanalysis of CLZ in human whole blood remains a great challenge owing to the remarkable fouling that occurs in a complex matrix. In this work, a miniaturized, integrated, disposable electrochemical sensing platform based on the integration of nanochannel arrays on the surface of screen-printed carbon electrodes (SPCE) is demonstrated. The device achieves high determination sensitivity while also offering the electrode anti-fouling and anti-interference capabilities. To enhance the electrochemical performance of SPCE, simple electrochemical polarization including anodic oxidation and cathodic reduction is applied to pretreat SPCE. The electrochemically polarized SPCE (p-SPCE) exhibits an enhanced electrochemical peak signal toward CLZ compared with bare SPCE. An electrochemically assisted self-assembly method (EASA) is utilized to conveniently electrodeposit a vertically ordered mesoporous silica nanomembrane film (VMSF) on the p-SPCE, which could further enrich CLZ through electrostatic interactions. Owing to the dual signal amplification based on the p-SPCE and VMSF nanochannels, the developed VMSF/SPCE sensor enables determination of CLZ in the range from 50 nM to 20 μM with a low limit of detection (LOD) of 28 nM (S/N = 3). Combined with the excellent anti-fouling and anti-interference abilities of VMSF, direct and sensitive determination of CLZ in human blood is also achieved.     

Electrochemical Sensing of Pb2+ and Cd2+ Ions with the Use of Electrode Modified with Carbon-Covered Halloysite and Carbon Nanotubes

A novel voltammetric method for the sensitive and selective determination of cadmium and lead ions using screen-printed carbon electrodes (SPCEs) modified with carbon-deposited natural halloysite (C_Hal) and multi-walled carbon nanotubes (MWCNTs) was developed. The electrochemical properties of the proposed sensor were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the morphology and structure were established by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). A two-factorial central composite design (CCD) was employed to select the composition of the nanocomposite modifying the electrode surface. The optimal measuring parameters of differential pulse anodic stripping voltammetry (DPASV) used for quantitative analysis were established with the Nelder–Mead simplex method. In the analytical investigation of Cd(II) and Pb(II) ions by DPASV, the MWCNTs/C_Hal/Nafion/SPCE exhibited a linear response in the concentration range of 0.1–10.0 µmol L⁻¹ (for both ions) with a detection limit of 0.0051 and 0.0106 µmol L⁻¹ for Pb(II) and Cd(II), respectively. The proposed sensor was successfully applied for the determination of metal ions in different natural water and honey samples with recovery values of 96.4–101.6%.