Disposable Sensor Research Articles

Impedimetry-Based Disposable Sensor for the Detection of Urea in Aqueous Media

The article presents a novel, disposable paper–dielectric urea sensor that uses adhesive copper tapes as electrodes. The electrodes are coated with layers of wax, urease, and poly(methyl methacrylate) (PMMA). The wax layer keeps the paper–dielectric sensor dry even in aqueous media, whereas the urease–PMMA layer improves the sensitivity. An ac impedimetry-based sensing technique is presented, which is developed from the electrical impedance spectroscopy (EIS) of the sensing system. Several case studies are performed to determine a suitable operating frequency, measurement time, and primary sensing variable. A precalibration before the measurement is proposed for each sensor for quality check and grading of the sensor to improve its accuracy. Separate sensing equations are proposed for different groups of sensors using linear regression in a semilog plane (with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{{2}} \ge {0.89}$ </tex-math></inline-formula> ). An electronic interface is also presented to design a prototype of a portable, inexpensive urea detection meter. As per the experimental data, the fabricated sensor has a detection range of 0.16–175 mM (1–1050 mg/dL), an accuracy of ±2.8%, a yield rate of 91%, and a shelf life of more than three months. It has a minimum sensitivity of 0.83 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> for one decade change in concentration.

Integration of smart nanomaterials for highly selective disposable sensors and their forensic applications in amphetamine determination

Screening drugs on the street and biological samples pose a challenge to law enforcement agencies due to existing detection methods and instrument limitations. Herein we present a graphene-assisted molecularly imprinted polymer nanoparticle-based sensor for amphetamine. These nanoparticles are electroactive by incorporating ferrocene in their structure. These particles act as specific actuators in electrochemical sensors, and the presence of a ferrocene redox probe embedded in the structure allows the detection of non-electroactive amphetamine. In a control approach, nanoparticles were covalently immobilised onto electrochemical sensors by drop-casting using silanes. Alternatively, nanoparticles were immobilised employing 3D printing and a graphene ink composite. The electrochemical performance of both approaches was evaluated. As a result, 3D printed nanoMIPs/graphene sensors displayed the highest selectivity in spiked human plasma, with sensitivity at 73 nA nM−1, LOD of 68 nM (RSD 2.4%) when compared to the silane drop cast electrodes. The main advantage of the optimised 3D printing technology is that it allows quantitative determination of amphetamine, a non-electroactive drug, challenging to detect with conventional electrochemical sensors. In addition, the cost-efficient 3D printing method makes these sensors easy to manufacture, leading to robust, highly selective and sensitive sensors. As proof of concept, sensors were evaluated on the street specimens and clinically relevant samples and successfully validated using UPLC-MS.

Sensitivity and reusability of a simple microbial fuel cell-based sensor for detecting bisphenol A in wastewater

Polycarbonate plastic processing wastewater contains high concentrations of bisphenol A (BPA), requiring a real-time technology to monitor wastewater containing BPA. Since the activity of electrogenic microorganisms on the anode surface of the microbial fuel cell (MFC) sensor is inhibited by exposure to contaminants, the toxicity of contaminants in wastewater can be determined by observing the variation in voltage output from the MFC sensor. The simple MFC sensor that is developed in this work exhibited a significant decrease in voltage output in BPA-containing wastewater concentration of 5–100 mg/L. Sensitivity analysis revealed that the voltage change (ΔV) was strongly correlated with the BPA concentration, with R2 as high as 0.97. This study was the first to investigate the number of repeated uses of the MFC sensor, using sodium acetate as the regeneration solution for the MFC sensor, leading to a successful recovery of detection performance. However, as the number of uses increased (up to the third or fourth use), the ΔV of the MFC sensor for BPA gradually decreased and the sensitivity decreased significantly from 0.238 mV/mg/L to 0.027 mV/mg/L. In the low BPA concentration range (≦20 mg/L), the MFC sensor can be reused up to 5 times, demonstrating that the proposed MFC sensor can be reused. Microorganisms contribute to the power generation of the MFC sensor, which can be exploited in the detection of pollutants, enabling the determination of wastewater toxicity and providing early warnings of thereof. Conventional MFC sensors are complex and lack the ability to explore repeated use, so they are not easily applied to actual wastewater detection. The proposed MFC sensor has many advantages such as simplicity, rapid detection, and reusability, solving the problem of the high cost of using disposable MFC sensors and making them feasible for practical use.

Home-Based Electrochemical Rapid Sensor (HERS): A Diagnostic Tool for Bacterial Vaginosis.

Bacterial vaginosis (BV) is the most frequently occurring vaginal infection worldwide, yet it remains significantly underdiagnosed as a majority of patients are asymptomatic. Untreated BV poses a serious threat as it increases one's risk of STI acquisition, pregnancy complications, and infertility. We aim to minimize these risks by creating a low-cost disposable sensor for at-home BV diagnosis. A clinical diagnosis of BV is most commonly made according to the Amsel criteria. In this method, a fish-like odor, caused by increased levels of trimethylamine (TMA) in vaginal fluid, is used as a key diagnostic. This paper outlines the development of a Home-Based Electrochemical Rapid Sensor (HERS), capable of detecting TMA in simulated vaginal fluid (sVF). Instead of odor-based detection of volatilized TMA, we identify TMA in trimethylammonium form by utilizing HERS and a potentiometric readout. We fabricated the ion selective electrode using a carbon-black-coated cotton string and a TMA-selective membrane consisting of calix[4]arene and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. When paired with a standard reference electrode, our device was able to quantify TMA concentration in deionized (DI) water, as well as sVF samples at multiple pH levels with a clinically relevant limit of detection (8.66 µM, and theoretically expected Nernstian slope of 55.14 mV/decade).

Non-enzymatic disposable electrochemical sensors based on CuO/Co3O4@MWCNTs nanocomposite modified screen-printed electrode for the direct determination of urea

A new electrochemical impedimetric sensor for direct detection of urea was designed and fabricated using nanostructured screen-printed electrodes (SPEs) modified with CuO/Co3O4 @MWCNTs. A facile and simple hydrothermal method was achieved for the chemical synthesis of the CuO/Co3O4 nanocomposite followed by the integration of MWCNTs to be the final platform of the urea sensor. A full physical and chemical characterization for the prepared nanomaterials were performed including Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle, scanning electron microscope (SEM) and transmission electron microscopy (TEM). Additionally, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical properties the modified electrodes with the nanomaterials at different composition ratios of the CuO/Co3O4 or MWCNTs. The impedimetric measurements were optimized to reach a picomolar sensitivity and high selectivity for urea detection. From the calibration curve, the linear concentration range of 10−12–10−2 M was obtained with the regression coefficient (R2) of 0.9961 and lower detection limit of 0.223 pM (S/N = 5). The proposed sensor has been used for urea analysis in real samples. Thus, the newly developed non-enzymatic sensor represents a considerable advancement in the field for urea detection, owing to the simplicity, portability, and low cost-sensor fabrication.

Heterostructure of amorphous nickel boride anchored 2D-layered cobalt selenide nanosheets as a disposable strip sensor for detection of toxic pollutant 5-nitroquinoline in aquatic samples

The development of disposable electrode-based sensors is of great importance for the electrochemical monitoring of toxic pollutants in wastewater systems, which are often present and mutually inhibiting during sample detection. In this work, a distinctive approach was taken to use an electrochemical heterostructure sensor with chemically reduced nickel boride (Ni3B) nanoparticles anchored in two-dimensional (2D) layered cobalt selenide (CoSe) nanosheets. The prepared hybrid structure (2D CoSe/Ni3B) enables large active sites and a strong synergistic effect between nanostructures to improve the electrocatalytic activity in the detection of water pollutant 5-nitroquinoline (5-NQ) with a disposable screen-printed carbon electrode (SPCE). The 2D CoSe/Ni3B/SPCE exhibits a reduction peak potential of −0.63 V for 5-NQ, with an increased reduction peak current compared to that of other electrodes. The fabricated disposable strip electrode is suitable for the electrochemical testing of pollutants. The proposed hybrid 2D CoSe/Ni3B/SPCE disposable sensor showed a wide linear range of 0.2–378 μM and a low detection limit of 0.042 μM for 5-NQ. The developed 2D CoSe/Ni3B hybrid nanostructure-based disposable sensor efficiently detects 5-NQ in hazardous water contaminants by voltammetric analysis and showed acceptable recoveries. Based on the results, it is believed that the proposed work provides a clear idea for the fabrication of transition metal-based metal boride and selenide heterostructures with excellent catalytic activity for the electrochemical detection of various pollutants in real-time monitoring.

Fraud monitoring using a new disposable photoluminescence sensor in milk

A new, sensitive, and room-temperature On/Off photoluminescence sensor was developed for rapid, low-cost and convenient on-site determination of melamine (MEL) in dairy products using dithizone (Dz)-capped Eu3+ doped lithopone (LIT) particles (Dz/Eu3+-LIT) with the help of Pb2+ ions as the fluorescent probe. The interaction of Pb2+ ions with Dz led to form a rigid structure on the surface of Dz/Eu3+-LIT and turned on the luminescence intensity of the particles. The sensing mechanism is based on a simple complex formation strategy that quenches the luminescence signal of Pb2+-Dz/Eu3+-LIT complex by interaction with MEL. Polyvinyl alcohol (PVA) was used as the supporting material for the sensing particles and glutaraldehyde (GA) modifier was used to give the support insolubility property and make it suitable for water-based applications. The potential interferences including amino acids, ions, and other components had no significant effect on the luminescence quenching of the sensor. Under optimum conditions, there was a good linear relationship between the signal intensity of the probe and MEL concentration in the range of 10 to 1000 μg L-1 with a limit of detection (LOD) of 2.95 μg L-1. The relative standard deviation (RSD%) for 5 replicate measurements of MEL solution (50 μg L-1) was obtained 2.23 %. The developed method was applied to the determination of MEL concentrations in raw milk and milk infant powder and recovery values ranging from 98.9 to 102.1 % were obtained.

Sensitive detection of African swine fever virus p54 based on in-situ amplification of disposable electrochemical sensor chip

Sensitive detection of African swine fever virus (ASFV) is important to reduce the loss of pig industry. A highly sensitive disposable electrochemical sensor chip for the detection of ASFV p54 was developed by combining in-situ loop-mediated isothermal amplification (LAMP) with electrochemical sensing technology. The disposable electrochemical sensor chip was prepared by screen printed carbon electrode (SPCE) covered with polydimethylsiloxane membrane as micro-electrolytic cell, and the primers designed according to the virus were fixed on the gold nanoparticles (Au NPs) modified SPCE. The target gene was amplified by in-situ LAMP within 42 min, and the deposition of Au NPs can promote the electron transfer, enhance the electrochemical signal of [Fe(CN)6]3-/4- probe and improve the sensitivity. The detection range of the biosensor was 1.0 × 10-12-1.0 × 10-6 g/L, the detection limit was 3.0 × 10-13 g/L (0.48 copies/µL). In addition, the sensor has good results for the detection of real samples and has broad application prospects.

A Disposable Electrochemical Sensor for Lead Ion Detection Based on In Situ Polymerization of Conductive Polypyrrole Coating

Lead, a toxic heavy metal, is considered one of the most serious pollutants in the water environment, posing a grave threat to human health and the global ecosystem. In this work, a simple, fast and sensitive sensor strategy for detecting trace lead ions (Pb2+) in water was proposed. The disposable electrochemical sensor was fabricated with a screen-printed carbon electrode (SPCE), and the working electrode was modified in a single step with in situ polymerized phytic acid functionalized polypyrrole (PA-PPy). Differential pulse anodic stripping voltammetry (DPASV) was employed to realize the efficient detection of Pb2+ in the range of 10–600 nM with a low detection limit of 0.43 nM (S/N = 3). The PA-PPy@SPCE sensor exhibits good stability, repeatability and anti-interference performance, indicating a promising application for real sample detection, and satisfactory recoveries were obtained when detecting Pb2+ in real tap water samples. Furthermore, the rapid sensor strategy with in situ polymerization of phytic acid functionalized polypyrrole composite material enables large-scale Pb2+ sensor preparation.Graphical Abstract

The Integration of Reference Electrode for ISFET Ion Sensors Using Fluorothiophenol-Treated rGO

Ion-sensitive field-effect transistors (ISFETs) detect specific ions in solutions that enable straightforward, fast, and inexpensive sensors compared to other benchtop equipment. However, a conventional reference electrode (RE) such as Ag/AgCl is limited on the miniaturization of the sensor. We introduce reduced graphene oxide (rGO), which serves as a new RE, when fluorinated (F-rGO) using fluorothiophenol through the π-π interaction. The circular RE is integrated between a fabricated microscale two-channel ISFET, which is capable of detecting two kinds of ions on an indium tin oxide (ITO) thin-film substrate, using the photolithography process. F-rGO bound to this circular region to function as an RE in the ISFETs sensor, which operated stably in solution and showed a relatively high transconductance (gm) value (1.27 mS), low drift characteristic (3.2 mV), and low hysteresis voltage (±0.05 mV). It detected proton (H+) ions in a buffer solution with high sensitivity (67.1 mV/pH). We successfully detected Na+ (62.1 mV/dec) and K+ (57.6 mV/dec) ions in human patient urine using a two-channel ISFET with the F-rGO RE. The F-rGO RE will be a suitable component in the fabrication of low-cost, mass-produced, and disposable ISFETs sensors.

A Disposable Screen Printed Electrodes with Hexagonal Ni(OH)2 Nanoplates Embedded Chitosan Layer for the Detection of Depression Biomarker.

Serotonin (5-hydroxytryptamine (5-HT)) is one of the important neurotransmitters which is released from the endocrine system. An abnormal level of this biomarker leads to several neurological diseases. The accurate assessment of serotonin is the utmost option to start treatment in the early stages of the disease. The current work is focused on the development of a disposable, screen-printed electrochemical sensor for the depression biomarker, serotonin in the physiological pH medium (pH 7.4) with the aid of a hexagonal, Ni(OH)2-nanoplate (NH-HNP)-embedded chitosan (Chit) and modified, screen-printed carbon electrode (SPCE). Initially, hexagonal nanoplates of Ni(OH)2 were synthesized by an eco-friendly and simple hydrothermal method. The prepared materials were well characterized by advanced analytical techniques to examine the physicochemical properties of the synthesized Ni(OH)2 hexagonal nanoplates. From the cyclic voltametric (CV) analysis, it was found that the oxidative current response of 5-HT at a NH-HNP-modified SPCE has about fivefold higher current values than over bare SPCE. The scan rate studies of NH-HNP-Chit/SPCE electrodes revealed that the oxidation mechanism of 5-HT is controlled by the diffusion behavior of the analyte. Differential pulse voltammetric tests of the NH-HNP-Chit/SPCE electrode exhibited a linear response in the dynamic concentration range of 0.1 to 30 µM, with a detection limit of about 60 nM. The sensor response is very reproducible from electrode to electrode, and the deactivation or surface-fouling of the sensor was not observed within the several experimental measurements. The sensor exhibited excellent storage stability over a period of twenty days. Finally, the fabricated, disposable SPCE sensor has shown respectable activity for the detection of depression biomarker 5-HT from synthetic urine and saliva samples.

Titelbild: Electrochemical Cell‐Free Biosensors for Antibody Detection (Angew. Chem. 8/2023)

Programmable antigen-conjugated gene circuits which, upon recognition of a target antibody, trigger the cell-free transcription of an RNA sequence that can be consequently detected with a disposable electrochemical sensor, were designed by Sara Bracaglia, Simona Ranallo, and Francesco Ricci in their Research Article (e202216512). The cell-free electrochemical biosensor allows the sensitive, specific, selective, and multiplexed detection of different antibodies in blood serum. Programmable antigen-conjugated gene circuits which, upon recognition of a target antibody, trigger the cell-free transcription of an RNA sequence that can be consequently detected with a disposable electrochemical sensor, were designed by Sara Bracaglia, Simona Ranallo, and Francesco Ricci in their Research Article (e202216512). The cell-free electrochemical biosensor allows the sensitive, specific, selective, and multiplexed detection of different antibodies in blood serum. NMR Spectroscopy Cluster Compounds Supramolecular Chemistry Carbon Dioxide Fixation

Carbon Nanotube Fiber-Based Flexible Microelectrode for Electrochemical Glucose Sensors.

Electrochemical sensors are gaining significant demand for real-time monitoring of health-related parameters such as temperature, heart rate, and blood glucose level. A fiber-like microelectrode composed of copper oxide-modified carbon nanotubes (CuO@CNTFs) has been developed as a flexible and wearable glucose sensor with remarkable catalytic activity. The unidimensional structure of CNT fibers displayed efficient conductivity with enhanced mechanical strength, which makes these fibers far superior as compared to other fibrous-like materials. Copper oxide (CuO) nanoparticles were deposited over the surface of CNT fibers by a binder-free facile electrodeposition approach followed by thermal treatment that enhanced the performance of non-enzymatic glucose sensors. Scanning electron microscopy and energy-dispersive X-ray analysis confirmed the successful deposition of CuO nanoparticles over the fiber surface. Amperometric and voltammetric studies of fiber-based microelectrodes (CuO@CNTFs) toward glucose sensing showed an excellent sensitivity of ∼3000 μA/mM cm2, a low detection limit of 1.4 μM, and a wide linear range of up to 13 mM. The superior performance of the microelectrode is attributed to the synergistic effect of the electrocatalytic activity of CuO nanoparticles and the excellent conductivity of CNT fibers. A lower charge transfer resistance value obtained via electrochemical impedance spectroscopy (EIS) also demonstrated the superior electrode performance. This work demonstrates a facile approach for developing CNT fiber-based microelectrodes as a promising solution for flexible and disposable non-enzymatic glucose sensors.

A disposable and low-cost laser-scribed graphene electrochemical sensor for simultaneous detection of hydroquinone, paracetamol and methylparaben

• A new disposable LSG sensor was fabricated using Polyetherimide substrate. • Sensor presented high reproducibility, sensitivity, and selectivity. • A LSG sensor was applied to simultaneous detection of emerging pollutants. • A porous graphene-like material with high electrochemical performance was developed. A novel and inexpensive laser-scribed graphene (LSG) sensor using polyetherimide (PEI) substrate was fabricated using CO 2 laser. The material was characterized by scanning electron microscopy (SEM), Raman spectroscopy, and electrochemical techniques, demonstrating a high porous carbonaceous material, which resulted in an electroactive area with 3.4-fold enhancement compared to geometric area and a high heterogeneous electron transfer rate constant (k°) of 3.20x10 -2 cm/s for ferricyanide redox probe. As a proof of applicability, the LSG-PEI sensor was applied for simultaneous detection of hydroquinone (HQ), paracetamol (PA), and methylparaben (MP) emerging pollutants (EP) in tap water and natural (lake) water samples, providing recoveries between 93.1% and 118% with limits of detection of 9.42x10 -8 , 3.23x10 -7 , and 2.95x10 -7 mol/L for HQ, PA, and MP, respectively.

Fabrication and characterization of a flexible and disposable impedance-type humidity sensor based on polyaniline (PAni).

This work presents a highly sensitive, economical, flexible, and disposable humidity sensor developed with a facile fabrication process. The sensor was fabricated on cellulose paper using polyemaraldine salt, a form of polyaniline (PAni), via the drop coating method. A three-electrode configuration was employed to ensure high accuracy and precision. The PAni film was characterized using various techniques including ultraviolet-visible (UV-vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The humidity sensing properties were evaluated through electrochemical impedance spectroscopy (EIS) in a controlled environment. The sensor exhibits a linear response with R 2 = 0.990 for impedance over a wide range of (0%-97%) relative humidity (RH). Further, it displayed consistent responsiveness, a sensitivity of 1.1701 Ω/%RH, acceptable response (≤220 s)/recovery (≤150 s), excellent repeatability, low hysteresis (≤2.1%) and long-term stability at room temperature. The temperature dependence of the sensing material was also studied. Due to its unique features, cellulose paper was found to be an effective alternative to conventional sensor substrates according to several factors including compatibility with the PAni layer, flexibility and low cost. These unique characteristics make this sensor a promising option for use in specific healthcare monitoring, research activities, and industrial settings as a flexible and disposable humidity measurement tool.

Simultaneous quantitative detection of hematocrit and hemoglobin from whole blood using a multiplexed paper sensor with a smartphone interface.

We report a highly accurate single-step label-free testing technology for simultaneous and independent hematocrit (Hct) and hemoglobin (Hb) level detection from a drop of whole blood by employing a disposable paper strip sensor interfaced with a portable impedimetric device. The paper strip is fabricated by in situ automated printing of a customized electrode template on the non-glossy side of a commercially available photo paper substrate followed by graphite deposition. The integrated platform device technology additionally includes a compact detection cum readout unit comprising a high precision impedance converter system that combines an on-board frequency generator with an analog-to-digital converter evaluation board, collectively interfaced with a central processor, calibration circuit, and smartphone. Employing a dispensed blood sample volume of 25 μL, the device is shown to have a sensitivity of 92 Ω/Hct and 287 Ω/Hb at an optimal frequency of 57 kHz. The respective linear response regimes appear to be wide enough to cover physiologically relevant limits, with excellent stability and reproducibility. Validation with clinical samples reveals limits of detection of Hct and Hb levels as low as 4.66% and 1.89 g dL-1, respectively, which are beyond the quantitative capability of commonly used affordable point of care test kits. The envisaged paradigm of rapid, robust, highly accurate, energy-efficient, simple, user-friendly, multiplex portable detection, obviating any possible ambiguities in interpretation due to common artefacts of colorimetric detection technologies such as optical interference with the image analytical procedure due to the inherent redness of blood samples and background illumination, renders this ideal for deployment in resource-limited settings.

A disposable and sensitive non-enzymatic glucose sensor based on a 3D-Mn-doped NiO nanoflower-modified flexible electrode.

Herein, nanoflower-shaped Mn-doped NiO nano-enzyme composites with high catalytic performance and excellent conductivity were grown on 3D flexible carbon fiber cloth (CFC) via hydrothermal and calcination methods to construct an efficient flexible glucose-sensitive detection electrode. For electrochemical-based sensors, high conductivity is a prerequisite for reliable data acquisition. To avoid the problems associated with using insulating Nafion or paraffin binders, we adopted a strategy of directly growing Mn-doped NiO onto the electrode surface, thereby avoiding interference due to the oxidization of species present in real samples at higher redox potentials, since Ni2+/Ni3+ has low redox potential. Therefore, the electrode has a linear range of 3-5166 μM for glucose detection, with a detection limit as low as 0.28 μM, showing excellent selectivity and reproducibility. The composite-modified electrode provides accurate detection results with real human serum samples, which are in full agreement with those of commercial blood glucose meters. In addition, we tested the glucose content in tea and sorghum fermentation broth at different stages, further expanding the application range of the Mn-NiO sensors. The nano-enzyme sensor fabricated herein offers a new idea for further integration into wearable flexible electronic devices for accurate glucose detection.

A disposable and sensitive sensor based on a ZIF-8@graphene modified carbon paper electrode for the quantitative determination of luteolin.

Rapid and accurate determination of luteolin is of great significance for pharmaceutical quality control. Herein, a disposable and sensitive luteolin sensor was fabricated by a hydrothermal method with carbon paper as substrate where ZIF-8 grew on GR in situ. Notably, the large specific surface area of ZIF-8 provided active sites on the electrode surface and the ability of GR to promote electron transfer greatly improved the sensitivity towards the oxidation of luteolin. Under the optimum conditions, the ZIF-8@GR/CP showed excellent detection performance for luteolin with a linear detection range of 0.04-3.2 μM and 3.2-120 μM, with LOD of 12 nM (S/N = 3). Furthermore, this disposable and sensitive sensor was successfully applied for the quantitative detection of luteolin in a capsule of Lamiophlomis rotata.

Single-step electropolymerization on a printed sensor towards a conductive thin film polymer for the simultaneous determination of drug metabolites: 5-aminosalicylic acid and sulfapyridine.

Amino acid conductive polymers can easily form a thin film on a sensor surface by an electrochemical process. Therefore, we are pioneers in reporting the electropolymerization of L-methionine on the surface of a screen-printed graphene electrode to obtain a disposable electrochemical sensor for determining drug metabolites (5-aminosalicylic acid (5-ASA) and sulfapyridine (SPD)) of sulfasalazine (SSZ) simultaneously. In this work, the developed sensor was facilely created through a single step of electropolymerization under mild conditions (0.1 M phosphate buffer pH 7.0) using cyclic voltammetry. Important parameters in the synthesis process were systematically investigated followed by surface composition and morphology studies. Then, analytical performances, comprising sensitivity, selectivity, stability, reproducibility, and sample preparation, were carefully evaluated. Under optimal conditions, the proposed methodology demonstrated a highly sensitive and selective simultaneous detection of 5-ASA and SPD with wide linear dynamic ranges of 1-50 μM and 80-250 μM and low detection limits of 0.60 and 0.57 μM for 5-ASA and SPD, respectively. To evaluate the potential of the designed sensor, it was successfully applied by simultaneously determining 5-ASA and SPD in real human urine samples on the same day (intra-day study) and on three different days (inter-day study).

A portable molecularly imprinted polymer-modified microchip sensor for the rapid detection of perfluorooctanoic acid.

High-performance electrochemical sensors have attracted intensive interest in real-time environmental safety monitoring, the Internet of Things, and telemedicine applications. A key limitation to field measurement of pollutant distribution is the lack of a highly sensitive and selective monitoring platform, thus severely hindering the decentralized monitoring of pollutant exposure risk. Hence, a sensor was developed in this study by using a molecularly imprinted polymer (MIP). Specifically, Cu2O@C@NiCo2O4, with a large surface area and high conductivity, was coated onto the Au electrode surface and further modified by the anodic electro-polymerization of o-phenylenediamine (o-PD) using perfluorooctanoic acid (PFOA) as the template, followed by template removal for activation, thus obtaining the Au/Cu2O@C@NiCo2O4/MIP electrode. Particularly, an effective monitoring platform derived from this sensor was designed to achieve cost-effective pollution detection. Au/Cu2O@C@NiCo2O4/MIP was employed in a disposable microchip sensor for the sensitive detection of PFOA, exhibiting an ultra-low limit of detection (LOD) of 19.46 ng L-1 in a linear range of 207-4140 ng L-1 along with satisfactory sensitivity, selectivity, and reproducibility, which reveal its great potential in the low-cost and efficient field detection of PFOA in coastal seawater. These promising results indicate a bright future for such microchip-sensor-supported PFOA tele-sensing platforms in aiding environmental safety and blue earth protection. We will persist in refining this method to enhance the sensitivity of the sensor for PFOA detection in polluted coastal areas.