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In this work, we report a low-cost and highly sensitive electrochemical sensor for detecting As(III) in water. The sensor uses a 3D microporous graphene electrode with nanoflowers, which enriches the reactive surface area and thus enhances its sensitivity. The detection range achieved was 1–50 ppb, meeting the US-EPA cutoff criteria of 10 ppb. The sensor works by trapping As(III) ions using the interlayer dipole between Ni and graphene, reducing As(III), and transferring electrons to the nanoflowers. The nanoflowers then exchange charges with the graphene layer, producing a measurable current. Interference by other ions, such as Pb(II) and Cd(II), was found to be negligible. The proposed method has potential for use as a portable field sensor for monitoring water quality to control hazardous As(III) in human life. [ABSTRACT FROM AUTHOR]

A label-free electrochemical aptamer-based sensor has been fabricated for alpha-fetoprotein (AFP) detection. Platinum nanoparticles on carboxylated-graphene oxide (PtNPs/GO-COOH) modified screen-printed graphene-carbon paste electrode (SPGE) was utilized as an immobilization platform, and the AFP aptamer was employed as a bio-recognition element. The synthesized GO-COOH helps to increase the surface area and amounts of the immobilized aptamer. Subsequently, PtNPs are decorated on GO-COOH to enhance electrical conductivity and an oxidation current of the hydroquinone electrochemical probe. The aptamer selectively interacts with AFP, causing a decrease in the peak current of the hydroquinone because the binding biomolecules on the electrode surface hinder the electron transfer of the redox probe. Effects of aptamer concentration and AFP incubation time were studied, and the current changes of the redox probe before and after AFP binding were investigated by square wave voltammetry. The developed aptasensor provides a linear range from 3.0–30 ng mL−1 with a detection limit of 1.22 ng mL−1. Moreover, the aptamer immobilized electrode offers high selectivity to AFP molecules, good stability, and sensitive determination of AFP in human serum samples with high recoveries. [ABSTRACT FROM AUTHOR]

A molecularly imprinted polymer (MIP) and a nanocomposite prepared from gold nanoparticles (AuNP) and poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) were deposited on a screen-printed carbon electrode (SPCE). The nanocomposite was prepared by one-pot simultaneous in-situ formation of AuNPs and PEDOT:PSS and was then inkjet-coated onto the SPCE. The MIP film was subsequently placed on the modified SPCE by co-electrodeposition of o-phenylenediamine and resorcinol in the presence of the antibiotic nitrofurantoin (NFT). Using differential pulse voltammetry (DPV), response at the potential of ~ 0.1 V (vs. Ag/AgCl) is linear in 1 nM to 1000 nM NFT concentration range, with a remarkably low detection limit (at S/N = 3) of 0.1 nM. This is two orders of magnitude lower than that of the control MIP sensor without the nanocomposite interlayer, thus showing the beneficial effect of AuNP-PEDOT:PSS. The electrode is highly reproducible (relative standard deviation 3.1% for n = 6) and selective over structurally related molecules. It can be re-used for at least ten times and was found to be stable for at least 45 days. It was successfully applied to the determination of NFT in (spiked) feed matrices and gave good recoveries.Schematic representation of a voltammetric sensor for the determination of nitrofurantoin. The sensor is based on a screen-printed carbon electrode (SPCE) modified with an inkjet-printed gold nanoparticles-poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) nanocomposite and a molecularly imprinted polymer. [ABSTRACT FROM AUTHOR]

A novel paper-based electrochemical biosensor was developed using an anthraquinone-labeled pyrrolidinyl peptide nucleic acid (acpcPNA) probe (AQ-PNA) and graphene-polyaniline (G-PANI) modified electrode to detect human papillomavirus (HPV). An inkjet printing technique was employed to prepare the paper-based G-PANI-modified working electrode. The AQ-PNA probe baring a negatively charged amino acid at the N-terminus was immobilized onto the electrode surface through electrostatic attraction. Electrochemical impedance spectroscopy (EIS) was used to verify the AQ-PNA immobilization. The paper-based electrochemical DNA biosensor was used to detect a synthetic 14-base oligonucleotide target with a sequence corresponding to human papillomavirus (HPV) type 16 DNA by measuring the electrochemical signal response of the AQ label using square-wave voltammetry before and after hybridization. It was determined that the current signal significantly decreased after the addition of target DNA. This phenomenon is explained by the rigidity of PNA-DNA duplexes, which obstructs the accessibility of electron transfer from the AQ label to the electrode surface. Under optimal conditions, the detection limit of HPV type 16 DNA was found to be 2.3 nM with a linear range of 10–200 nM. The performance of this biosensor on real DNA samples was tested with the detection of PCR-amplified DNA samples from the SiHa cell line. The new method employs an inexpensive and disposable device, which easily incinerated after use and is promising for the screening and monitoring of the amount of HPV-DNA type 16 to identify the primary stages of cervical cancer. [ABSTRACT FROM AUTHOR]

[Display omitted] • A disposable SPGE coupled with monolithic µ-SPE for MDMA detection was proposed. • The monolithic sorbent showed high performance for MDMA extraction before analysis. • The fabricated SPGE offered simple and rapid manufacture, low cost, and portability. • No interference effect from other substances was observed for MDMA analysis. • The developed method was applied for MDMA determination in forensic applications. The development of a productive assay to quantify 3,4-methylenedioxymethamphetamine (MDMA) levels in human urine samples is crucial in forensic applications. In this work, we examine the use of a disposable screen-printed graphene electrode coupled with in-tip monolithic micro-solid-phase extraction (µ-SPE) for the highly selective and sensitive determination of MDMA. To satisfy this requirement, we employ a sensor based on graphene nanomaterials integrated into a compact electrochemical device to enhance the sensitivity. In-tip monolithic µ-SPE is a facile and highly effective route for extraction and preconcentration (enrichment factor ∼ 10) to improve the sensitivity. The combination of our µ-SPE and an electrochemical sensor exhibits a remarkable performance in terms of sensitivity and selectivity for MDMA analysis. A wide linear range is observed within 0.10–10.00 µg mL−1, and the lowest limit of detection is calculated to be 0.03 µg mL−1. Moreover, no interference effect from other substances is observed for MDMA detection. The feasibility of the proposed assay is evaluated, and it is successfully used in MDMA determination in human urine samples with high accuracy, precision, reproducibility, stability, and reliability. Therefore, this novel proposed method is well suited as a compact disposable device for MDMA determination in forensic applications and can be employed by relevant government organizations to correctly identify MDMA levels in narcotic addicts. [ABSTRACT FROM AUTHOR]

Abstract Vibrio parahaemolyticus is one of the most important foodborne pathogens that cause various life-threatening diseases in human and animals. Here, we present a rapid detection platform for V. parahaemolyticus by combining loop-mediated isothermal amplification (LAMP) and disposable electrochemical sensors based on screen-printed graphene electrodes (SPGEs). The LAMP reactions using primers targeting V. parahaemolyticus toxR gene were optimized at an isothermal temperature of 65 °C, providing specific detection of V. parahaemolyticus within 45 min at the detection limit of 0.3 CFU per 25 g of raw seafood. The LAMP amplicons can be effectively detected using unmodified SPGEs, redox active molecules namely Hoechst-33258 and a portable potentiostat. Therefore, the proposed system is particularly suitable as a point-of-care device for on-site detection of foodborne pathogens. Graphical abstract An innovative integrated Point-of-Care system consisting of LAMP and electrochemical sensors using screen-printed electrodes, Hoechst-33258 redox probe and mini-potentiostat is demonstrated for rapid, sensitive and specific detections of V. parahaemolyticus , achieving a low detection limit of 0.3 CFU/25 g of seafood and a short run time of 45 min fx1 [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A screen-printed electrochemical sensor was integrated on EWOD-based lab-on-a-chips. • The chips could control an analyte concentration with T-junction EWOD electrodes. • The system could effectively analyze the concentrations of K 4 Fe(CN) 6 and H 2 O 2. • The results showed medium sensitivity, moderate detection limits and high stability. • The total analysis time including droplet mixing and CV measurement was shorter than 14 s. Abstract In this work, a screen-printed electrochemical detector was fabricated on a digital electrowetting-on- dielectric (EWOD) microfluidic chip for the first time and employed for rapid chemical analysis. The digital microfluidic system consisted of a T-junction EWOD platform for merging buffer and analyte droplets and an electrochemical detector at the end of T-junction. The detector comprised three electrodes including carbon working, carbon counter and silver/silver chloride reference electrodes. The system was successfully fabricated by microfabrication and screen-printing processes and tested for electrochemical analyses of potassium hexacyanoferrate and hydrogen peroxide. The analyte and buffer droplets were controlled to mix with different concentrations and detected at the electrochemical detector using cyclic voltammetry. The results showed good detection performances with medium sensitivity, moderate detection limits, high stability and good reproducibility. In addition, the total analysis time including droplet mixing and CV measurement was shorter than 14 s. Therefore, the EWOD chip with integrated screen-printed carbon electrodes was a promising candidate for rapid automated chemical analysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel preparation method for nanocomposites, with CuPc immobilized on graphene in PANI matrix. [•] The Gr/CuPc/PANI enhanced selectivity and sensitivity of detecting AA due to graphene. [•] The constructed AA sensor shows excellent performances. [Copyright &y& Elsevier]

Abstract: In this work, a new paper-based electrochemical sensor is developed as a low-cost and disposable point-of-care device for pre-screening purpose. Electrodes of this new sensor are fabricated using two printing techniques, i.e. screen-printing for base material and inkjet-printing for modifying functional material, and the performance of fabricated sensors for Ascorbic acid detection is demonstrated. The paper-based device consists of three electrodes including Polyaniline (PANI) modified Screen-Printed Carbon Electrode (SPCE) as working electrode and two bare SPCEs as reference and counter electrodes. Three SPCEs are initially screen-printed on a filter paper, and PANI is consecutively inkjet-printed on the designated working SPCE. Its electrochemical performances are systematically investigated towards Ascorbic acid using Cyclic Voltammetry (CV) with different Acetate buffer pHs and numbers of printed-PANI layers. The CV results show that the optimal buffer pH and number of PANI layers are 4.0–5.0 and 5, respectively. Consequently, real-time detection of Ascorbic acid concentration is performed using Chronoamperometry technique under the optimal conditions from previous CV studies. From the results, the sensor exhibits a good sensitivity of 17.7μA/mM and a moderately low limit-of-detection of 30±3μM in a concentration range of 30–270μM. According to cost versus performance, the utilization of paper-based sensor with inkjet-printed PANI modified SCPE is an alternative choice for low-cost and disposable point-of-care applications. [Copyright &y& Elsevier]

Abstract: In this work, a simple and sensitive inkjet-printed graphene-poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (GP-PEDOT:PSS) on screen printed carbon electrode (SPCE) is developed for detection of salbutamol (SAL), a prohibited drug in sport. GP-PEDOT:PSS dispersed solution is prepared for use as an ink by one-step electrolytic exfoliation from a graphite electrode. GP-PEDOT:PSS layers are then printed on SPCEs by dimatrix inkjet material printer and their electrochemical behaviors are characterized. It is found that SAL oxidation peak responses of PEDOT:PSS modified and GP-PEDOT:PSS modified SPCE electrodes are approximately 30 and 150 times higher than that of unmodified SPCE, respectively. In addition, excellent analytical features with a wide dynamic range of 500μM, a low detection limit (3S/N) of 1.25μM and low matrices’ interference in pharmaceutical samples have been achieved. Therefore, inkjet-printed GP-PEDOT:PSS SPCE is a promising candidate for advanced electrochemical sensing applications. [Copyright &y& Elsevier]

Abstract: A microfabicated flow injection device has been developed for in-channel electrochemical detection (ECD) of a β-agonist, namely salbutamol. The microfluidic system consists of PDMS (polydimethylsiloxane) microchannel and electrochemical electrodes formed on glass substrate. The carbon nanotube (CNT) on gold layer as working electrode, silver as reference electrode and platinum as auxiliary electrode were deposited on a glass substrate. Silver, platinum, gold and stainless steel catalyst layers were coated by DC-sputtering. CNTs were then grown on the glass substance by thermal chemical vapor deposition (CVD) with gravity effect and water-assisted etching. 100-μm-deep and 500-μm-wide PDMS microchannels fabricated by SU-8 molding and casting were then bonded on glass substrate by oxygen plasma treatment. Flow injection and ECD of salbutamol was performed with the amperometric detection mode for in-channel detection of salbutamol. The influences of flow rate, injection volume, and detection potential on the response of current signal were optimized. Analytical characteristics, such as sensitivity, repeatability and dynamic range have been evaluated. Fast and highly sensitive detection of salbutamol have been achieved. Thus, the proposed combination of the efficient CNT electrode and miniaturized lab-on-a-chip is a powerful platform for β-agonists detection. [Copyright &y& Elsevier]

[Display omitted] • Carbon paste with IL and graphene was used to screen-print electrochemical electrodes. • Optimal design had 15.70 mm2 WE and 12.57 mm2 CE active area, and 25 mm overall length. • PMPlm ionic liquid gave the highest CV response at an optimal PMPlm content of 1.0 w%. • SPIL-GE provided enhanced CV responses to (Fe(CN) 6)3-/4-, dopamine and hydroquinone. In this work, a highly sensitive and disposable screen-printed ionic liquid-graphene electrode (SPIL-GE) was developed for electrochemical sensing. The paste for screen printing was facilely prepared by mixing IL with electrolytically exfoliated graphene in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (GP/PEDOT/PSS) and carbon paste (CP) via ball milling. The IL-GP paste was then screen printed to form working and counter electrodes (WE & CE) followed by screen printing of Ag/AgCl reference electrode and insulator layer on a polyethylene substrate. Electrode geometries were optimized for electrochemical sensing, arriving at an optimal design with an overall electrode length of 25 mm, and CE and WE active areas of 15.70 and 12.57 mm2, respectively. SPIL-GEs employing six ILs with imidazolium and pyridinium cations were assessed for electrochemical sensing of K 3 Fe(CN) 6. The pyridinium-type IL, namely 3-methyl-1-propylpyridinium bis(trifluoromethyl sulfonyl)imide (PMPlm), was found to exhibit the highest CV peak currents compared with other ILs at an optimal PMPlm content of 1.0% (w/w). Characterization with scanning electron microscopy and Fourier-transform infrared spectroscopy confirmed the presence of PMPlm, GP/PEDOT/PSS and CP in SPIL-GEs. The electrochemical performance of the optimal SPIL-GE towards the three common analytes including ferri/ferro cyanide (Fe(CN) 6)3-/4- redox couple, dopamine and hydroquinone were compared with the screen-printed carbon and graphene electrodes (SPCE & SPGE). From the results, the SPIL-GE demonstrated larger anodic currents with lower oxidation potentials for the three analytes than SPGE and SPCE, respectively. Therefore, the SPIL-GE could be a potential candidate for advanced electrochemical sensing applications. [ABSTRACT FROM AUTHOR]