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The analysis of opiates is of vital interest in drug abuse monitoring and research. This review presents a general overview of the electrochemical methods used for detection and quantification of opiates in a variety of matrices. Emphasis has been placed on the voltammetric methods used for study and determination of morphine, codeine, and heroin. Specific issues that need to be solved and better explained as well as future trends in the use of electrochemical methods in the examination of opiates are also discussed. [ABSTRACT FROM AUTHOR]

A square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC) using a glassy carbon electrode were evaluated for the determination of codeine in pharmaceutical preparations. The interference of several compounds, such as acetaminophen, guaiacol, parabens, ephedrine, acetylsalicylic acid and caffeine, that usually appear associated with codeine pharmaceutical preparations was studied. It was verified that these electroanalytical methods could not be used with acetaminophen present in the formulations and that with guaiacol, parabens or ephedrine present the use of the FIA-EC system was impracticable. A detection limit of 5 µmol L-1 and a linear calibration range from 40 to 140 µmol L-1 was obtained with the SWV method. For the flow injection analysis procedure a linear calibration range was obtained from 7 to 50 µmol L-1 with a detection limit of 3 µmol L-1 and the FIA-EC system allowed a sampling rate of 115 samples per hour. The results obtained by the two methods, SWV and FIA-EC, were compared with those obtained using reference methods and demonstrated good agreement, with relative deviations lower than 4%. [ABSTRACT FROM AUTHOR]

Abstract: In cancer, screening and early detection are critical for the success of the patient's treatment and to increase the survival rate. The development of analytical tools for non‐invasive detection, through the analysis of cancer biomarkers, is imperative for disease diagnosis, treatment and follow‐up. Tumour biomarkers refer to substances or processes that, in clinical settings, are indicative of the presence of cancer in the body. These biomarkers can be detected using biosensors, that, because of their fast, accurate and point of care applicability, are prominent alternatives to the traditional methods. Moreover, the constant innovations in the biosensing field improve the determination of normal and/or elevated levels of tumour biomarkers in patients’ biological fluids (such as serum, plasma, whole blood, urine, etc.). Although several biomarkers (DNA, RNA, proteins, cells) are known, the detection of proteins and circulating tumour cells (CTCs) are the most commonly reported due to their approval as tumour biomarkers by the specialized entities and commonly accepted for diagnosis by medical and clinical teams. Therefore, electrochemical immunosensors and cytosensors are vastly described in this review, because of their fast, simple and accurate detection, the low sample volumes required, and the excellent limits of detection obtained. The biosensing strategies reported for the six most commonly diagnosed cancers (lung, breast, colorectal, prostate, liver and stomach) are summarized and the distinct phases of the sensors’ constructions (surface modification, antibody immobilization, immunochemical interactions, detection approach) and applications are discussed. [ABSTRACT FROM AUTHOR]

Major depressive disorder is a widespread condition with antidepressants as the main pharmacological treatment. However, some patients experience concerning adverse reactions or have an inadequate response to treatment. Analytical chromatographic techniques, among other techniques, are valuable tools for investigating medication complications, including those associated with antidepressants. Nevertheless, there is a growing need to address the limitations associated with these techniques. In recent years, electrochemical (bio)sensors have garnered significant attention due to their lower cost, portability, and precision. Electrochemical (bio)sensors can be used for various applications related to depression, such as monitoring the levels of antidepressants in biological and in environmental samples. They can provide accurate and rapid results, which could facilitate personalized treatment and improve patient outcomes. This state-of-the-art literature review aims to explore the latest advancements in the electrochemical detection of antidepressants. The review focuses on two types of electrochemical sensors: Chemically modified sensors and enzyme-based biosensors. The referred papers are carefully categorized according to their respective sensor type. The review examines the differences between the two sensing methods, highlights their unique features and limitations, and provides an in-depth analysis of each sensor. [ABSTRACT FROM AUTHOR]

The increase in anthropogenic pollution raises serious concerns regarding contamination of water bodies and aquatic species with potential implications on human health. Pharmaceutical compounds are a type of contaminants of emerging concern that are increasingly consumed and, thus, being frequently found in the aquatic environment. In this sense, an electrochemical sensor based on an unmodified and untreated carbon fiber paper (CPS—carbon paper sensor) was simply employed for the analysis of trimethoprim antibiotic in fish samples. First, the analytical conditions were thoroughly optimized in order for the CPS to achieve maximum performance in trimethoprim determination. Therefore, an electrolyte (0.1 M Britton–Robinson buffer) pH of 7 was selected and for square wave voltammetry parameters, optimum values of amplitude, frequency and step potential corresponded to 0.02 V, 50 Hz, and 0.015 V, respectively, whereas the deposition of analyte occurred at +0.7 V for 60 s. In these optimum conditions, the obtained liner range (0.05 to 2 µM), sensitivity (48.8 µA µM−1 cm−2), and LOD (0.065 µM) competes favorably with the commonly used GCE-based sensors or BDD electrodes that employ nanostructuration or are more expensive. The CPS was then applied for trimethoprim determination in fish samples after employing a solid phase extraction procedure based on QuEChERS salts, resulting in recoveries of 105.9 ± 1.8% by the standard addition method. [ABSTRACT FROM AUTHOR]

In this work, a highly sensitive label-free immunosensor for detection of the main biomarker of Alzheimer’s disease (AD), amyloid beta 1–42 (Aβ (1–42)), is presented. A gold electrode was modified with a mercaptopropionic acid (MPA) self-assembled monolayer, electrodeposited gold nanoparticles (AuNPs) and a monoclonal antibody mAb DE2B4 to recognize Aβ; all the relevant experimental variables were optimized. Antibodies were functionalized through chemical modification (thiolation) to promote the antibody immobilization on the AuNPs surface with proper orientation which enabled the direct detection of Aβ(1–42). Scanning electron microscopy, square-wave voltammetry and electrochemical impedance spectroscopy were used to characterize the construction of the biosensor. Using the proposed immunosensor, Aβ(1–42) was specifically detected within the linear range of 10–1000 pg mL −1 with a 5.2 pg mL −1 and 17.4 pg mL −1 detection and quantification limit, respectively; recovery values for the tested spiking levels ranged from 90.3 to 93.6%. The immunosensor enables rapid, accurate, precise, reproducible and highly sensitive detection (14.6% reduction mL pg −1 ) of Aβ with low-cost and opens the possibilities for diagnostic ex vivo applications and research-based in vivo studies. [ABSTRACT FROM AUTHOR]

A novel molecularly imprinted polymer (MIP) has been developed based on a simple and sustainable strategy for the selective determination of citalopram (CTL) using screen-printed carbon electrodes (SPCEs). The MIP layer was prepared by electrochemical in situ polymerization of the 3-amino-4 hydroxybenzoic acid (AHBA) functional monomer and CTL as a template molecule. To simulate the polymerization mixture and predict the most suitable ratio between the template and functional monomer, computational studies, namely molecular dynamics (MD) simulations, were carried out. During the experimental preparation process, essential parameters controlling the performance of the MIP sensor, including CTL:AHBA concentration, number of polymerization cycles, and square wave voltammetry (SWV) frequency were investigated and optimized. The electrochemical characteristics of the prepared MIP sensor were evaluated by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Based on the optimal conditions, a linear electrochemical response of the sensor was obtained by SWV measurements from 0.1 to 1.25 µmol L−1 with a limit of detection (LOD) of 0.162 µmol L−1 (S/N = 3). Moreover, the MIP sensor revealed excellent CTL selectivity against very close analogues, as well as high imprinting factor of 22. Its applicability in spiked river water samples demonstrated its potential for adequate monitoring of CTL. This sensor offers a facile strategy to achieve portability while expressing a willingness to care for the environment. [ABSTRACT FROM AUTHOR]

Abstract: Celiac disease (CD) is a gluten-induced autoimmune enteropathy characterized by the presence of antibodies against gliadin (AGA) and anti-tissue transglutaminase (anti-tTG) antibodies. A disposable electrochemical dual immunosensor for the simultaneous detection of IgA and IgG type AGA and anti-tTG antibodies in real patient's samples is presented. The proposed immunosensor is based on a dual screen-printed carbon electrode, with two working electrodes, nanostructured with a carbon–metal hybrid system that worked as the transducer surface. The immunosensing strategy consisted of the immobilization of gliadin and tTG (i.e. CD specific antigens) on the nanostructured electrode surface. The electrochemical detection of the human antibodies present in the assayed serum samples was carried out through the antigen–antibody interaction and recorded using alkaline phosphatase labelled anti-human antibodies and a mixture of 3-indoxyl phosphate with silver ions was used as the substrate. The analytical signal was based on the anodic redissolution of enzymatically generated silver by cyclic voltammetry. The results obtained were corroborated with commercial ELISA kits indicating that the developed sensor can be a good alternative to the traditional methods allowing a decentralization of the analyses towards a point-of-care strategy. [Copyright &y& Elsevier]

The availability of more efficient analytical methods that answer the world's demands is a challenge and their development continues to be a difficult task. In this work the construction of an electrochemical cell, based on low-cost and accessible materials, that can be easily constructed and used for electroanalytical purposes, is described. Pencil leads were used as electrodes and a transparency sheet as the base. This cell was used as transducer for developing an amperometric biosensor for the quantification of histamine, which is the only biogenic amine regulated by law. The analysis was based on the use of diamine oxidase as biorecognition element, hexacyanoferrate(III) as electron-transfer mediator, and chronoamperometry, at +0.5 V during 100 s, to record the analytical signal. A linear relationship between histamine concentration and the analytical signal was established between 5.0 and 35 mg L−1 and a low limit of detection (1.0 mg L−1) was achieved. The analysis of different fish species (sardine and tuna) was performed, obtaining recovery values between 102% and 110%. The stability of the sensor is noteworthy: it maintained 95% of the initial analytical signal after 15 days. [Display omitted] • A simple electrochemical cell consisting of three graphite pencil leads was created. • A cheap histamine biosensor using 0.5-mm pencil leads as electrodes was developed. • The sensor showed satisfactory linear range (5–35 mg L−1) and reproducibility (<4%). • The sensor showed suitable stability (95% signal after 15 days) and selectivity. • The sensor provided good recoveries when applied to spiked fish samples. [ABSTRACT FROM AUTHOR]

Abstract: Mucin-16 (MUC16) is the established ovarian cancer marker used to follow the disease during or after treatment for epithelial ovarian cancer. The emerging science of cancer markers also demands for the new sensitive detection methods. In this work, we have developed an electrochemical immunosensor for antigen MUC16 using gold nanoelectrode ensemble (GNEE) and ferrocene carboxylic acid encapsulated liposomes tethered with monoclonal anti-Mucin-16 antibodies (αMUC16). GNEEs were fabricated by electroless deposition of the gold within the pores of polycarbonate track-etched membranes. Afterwards, αMUC16 were immobilized on preformed self-assembled monolayer of cysteamine on the GNEE via cross-linking with EDC-Sulfo-NHS. A sandwich immunoassay was performed on αMUC16 functionalized GNEE with MUC16 and immunoliposomes. The differential pulse voltammetry was employed to quantify the faradic redox response of ferrocene carboxylic acid released from immunoliposomes. The dose–response curve for MUC16 concentration was found between the range of 0.001–300UmL−1. The lowest detection limit was found to be 5×10−4 UmL−1 (S/N=3). We evaluated the performance of this developed immunosensor with commercial ELISA assay by comparing results obtained from spiked serum samples and real blood serum samples from volunteers. [Copyright &y& Elsevier]

Abstract: The immobilization and electro-oxidation of guanine and adenine as DNA bases on glassy carbon electrode are evaluated by square wave voltammetric analysis. The influence of electrochemical pretreatments, nature of supporting electrolyte, pH, accumulation time and composition of DNA nucleotides on the immobilization effect and the electrochemical mechanism are discussed. Trace levels of either guanine or adenine can be readily detected following short accumulation time with detection limits of 35 and 40ngmL−1 for guanine and adenine, respectively. The biosensors of guanine and adenine were employed for the voltammetric detection of antioxidant capacity in flavored water samples. The method relies on monitoring the changes of the intrinsic anodic response of the surface-confined guanine and adenine species, resulting from its interaction with free radicals from Fenton-type reaction in absence and presence of antioxidant. Ascorbic acid was used as standard to evaluate antioxidant capacities of samples. Analytical data was compared with that of FRAP method. [Copyright &y& Elsevier]

An electrochemical magnetic immunosensing strategy was developed for the determination of HER2-ECD, a breast cancer biomarker, and breast cancer cells in human serum. A sandwich assay was performed on carboxylic acid-functionalized magnetic beads (MBs) using a screen-printed carbon electrode (SPCE) as transducer surface. The affinity process was detected using electroactive labels; core/shell streptavidin-modified CdSe@ZnS Quantum Dots (QDs). Cd2+ ions, released from the QDs, were determined by differential pulse anodic stripping voltammetry (DPASV). An assay time of 90 min, with an actual hands-on time of about 20 min, a linear range between 0.50–50 ng·mL−1 of HER2-ECD and a limit of detection of 0.29 ng·mL−1 were achieved. Analysis of live breast cancer cells was also performed using the optimized assay. Breast cancer cell lines SK-BR-3 (a HER2-positive cell line), MDA-MB-231 (a HER2-negative cell line) and MCF-7 (a cell line with low HER2 expression) were tested. The selectivity of the assay towards SK-BR-3 cells was confirmed. A concentration-dependent signal that was 12.5× higher than the signal obtained for the HER2-negative cells (MDA-MB-231) and a limit of detection of 2 cells·mL−1 was obtained. [ABSTRACT FROM AUTHOR]

Abstract Recent studies have shown that besides the well-known T 3 (triiodothyronine) and T 4 (thyroxine) there might be other important thyroid hormones, in particular T 0 AM (thyronamine) and T 1 AM (3-iodothyronamine). The absence of a large number of studies showing their precise importance might be explained by the limited number of analytical methodologies available. This work aims to show an electroanalytical alternative making use of electropolymerized molecularly imprinted polymer (MIPs). The MIPs' polymerization is performed on the surface of screen-printed carbon electrodes (SPCEs), using 4–aminobenzoic acid (4-ABA) as the building and functional monomer and the analyte T 0 AM as the template. The step-by-step construction of the SPCE-MIP sensor was studied by cyclic voltammetry (CV) and by electrochemical impedance spectroscopy (EIS). After optimization, by means of square-wave voltammetry, the SPCE-MIP showed suitable selectivity (in comparison with other thyroid hormones and catechol amines), repeatability (intra-day of 3.9%), a linear range up to 10 μmol L−1 (0.23 × 103 μg dL−1) with an r2 of 0.998 and a limit of detection (LOD) and quantification (LOQ) of 0.081 and 0.27 μmol L−1 (1.9 and 6.2 μg dL−1), respectively. Graphical abstract fx1 Highlights • First time a sensor was developed for T 0 AM (thyronamine); • Electroanalytical methodology for T 0 AM; • Molecularly imprinted polymers (MIPs) were developed for T 0 AM; • MIPs' polymerization (4–aminobenzoic acid to a poly(4-aminobenzoic acid) film) occurred in the surface of screen-printed carbon electrodes (SPCEs); • The SPCE-MIP selectively analyzed T 0 AM by square-wave voltammetry (SWV). [ABSTRACT FROM AUTHOR]

Nitric oxide radical (NO) is a signalling molecule involved in virtually all forms of life. Its relevance has been leading to the development of different analytical methodologies to assess the temporal and spatial fluxes of NO under the complex biological milieu. Third‐generation electrochemical biosensors are promising tools for in loco and in vivo NO quantification and, over the past years, heme proteins and porphyrins have been used in their design. Since there are some limitations with the biorecognition element directly adsorbed onto the electrode surface, nanomaterials (carbon nanotubes, gold nanoparticles, etc.) and polymers (cellulose, chitosan, nafion®, polyacrylamide, among others) have been explored to achieve high kinetics and better biosensor performance. In this review, a broad overview of the field of electrochemical third‐generation biosensors for NO electroanalysis is presented, discussing their main characteristics and aiming new outlooks and advances in this field. [ABSTRACT FROM AUTHOR]

The incidence of breast cancer has been increasing over the years. To control and monitor this disease several tumor biomarkers have been proposed for early diagnosis, patient follow-up and/or treatment guidance. The only serum breast cancer biomarker in current use is the cancer antigen 15-3 (CA 15-3). In this work a molecularly imprinted polymer (MIP)-based electrochemical (voltammetric) sensor to monitor breast cancer was developed, based on direct surface imprinting of CA 15-3 on a screen-printed gold electrode (Au-SPE). The imprinting was performed in two steps: (1) adsorption of CA 15-3 on the surface of the Au-SPE and (2) electropolymerization of 2-aminophenol around the adsorbed protein. After extraction of the imprinted protein voltammetric analysis was conducted using hexacyanoferrate(II/III) as redox probe, measuring the signals before and after protein binding. The sensor was characterized by voltammetric techniques and electrochemical impedance spectroscopy, and the analytical responses of imprinted and non-imprinted polymer sensors were studied. A linear relationship between the peak current intensity of the redox probe and the logarithm of CA 15-3 concentration was established between 5 and 50 U mL −1 , achieving a limit of detection of 1.5 U mL −1 . The prepared MIP-sensor provides fast (15 min) analysis and is cheap, easy to prepare, disposable and could easily be integrated in small portable point-of care devices. [ABSTRACT FROM AUTHOR]

Naloxone (NLX) is a pharmaceutical used as opioid antagonist. A molecular imprinted polymer electrochemical sensor for simple and rapid detection of NLX was prepared through the modification of commercial available screen printed carbon electrode (SPCE). The SPCE was modified with multi-walled carbon nanotubes (MWCNT) by drop coating to increase the signal response and improve the sensitivity. The MIP preparation was carried out via in situ electropolymerization using 4-aminobenzoic acid (4-ABA) as functional monomer. The morphology of the obtained sensor was characterized by scanning electron microscopy (SEM). Several parameters controlling the preparation and performance of the MIP sensor were studied and optimized. The electrochemical behavior of NLX at MIP and control non-imprinted (NIP) sensor was evaluated by differential pulse voltammetry (DPV), demonstrating a better MIP response and the success of the imprinting. The proposed MIP/MWCNT/SPCE sensor showed a linear relationship between peak current intensity and NLX concentration in the range between 0.25 and 10.0 μM, with limits of detection (LOD) and quantification (LOQ) of 0.20 μM and 0.67 μM respectively. The repeatability and reproducibility were also tested with relative standard deviations (RSD) of 4.6 and 9.6% respectively. Moreover, the applicability of the method was successfully confirmed with detection of NLX in biological samples (urine and human serum). The sensor is promising to be used for screening NLX in point-of-care people with opioid overdose. [ABSTRACT FROM AUTHOR]

The extraction of Ara h 6 (a peanut allergen) from a complex chocolate-based food matrix was optimized by testing different temperatures, extraction times, and the influence of additives (NaCl and skimmed milk powder) in a total of 36 different conditions. Analyses were carried out using an electrochemical immunosensor. Three conditions were selected since they allowed the extraction of the highest levels of Ara h 6. These extractions were performed using 2 g of sample and 20 ml of Tris-HNO 3 (pH = 8) containing: a) 0.1 M NaCl and 2 g of skimmed milk powder at 21 °C for 60 min; b) 1 M NaCl and 1 g of skimmed milk powder at 21 °C for 60 min; and c) 2 g of skimmed milk powder at 60 °C for 60 min. Recoveries were similar or higher than 94.7%. This work highlights the importance to adjust extraction procedures regarding the target analyte and food matrix components. [ABSTRACT FROM AUTHOR]

Regardless the controversies surrounding genetically modified organisms (GMO), their cultivation is constantly increasing and in according to the EU legislation, labeling is mandatory for products containing EU-authorized-GMO higher than 0.9%. Thereby, new analytical strategies for rapid and effective detection of GMO on foodstuffs are required. In this work, an electrochemical immunosensor for effective determination of Cry1Ab protein from MON810 transgenic maize (EU-authorized-GMO) is described. The immunosensor was developed onto indium tin oxide (ITO) electrodes modified by 3-aminopropyltrimethoxysilane (APTES) monolayer to covalently immobilize Anti-Cry1Ab polyclonal antibodies. The protein interaction with the polyclonal antibody (PAb) recognition platform was directly monitored and measured by cyclic voltammetry and electrochemical impedance spectroscopy using commercially Cry1Ab protein. After the analytical features optimization a linear response from 1 to 10 ng mL −1 , a limit of detection (LOD) of 0.37 ng mL −1 and a limit of quantification (LOQ) of 1.23 ng mL −1 – which provided accurate results (RSD < 7.5%) – were achieved. The immunosensor allowed a simple and fast detection of Cry1Ab protein extracted from maize seeds with different GM maize mass percentages (0%, 0.5%, 1%, 2.5% and 5%). To crosscheck the detection of Cry1Ab protein, an enzyme-linked immunosorbent assay (ELISA) was used. The results indicate that the immunosensor is suitable for the transgenic protein Cry1Ab detection in GM maize representing a successfully tool to verify the compliance of the EU regulations. [ABSTRACT FROM AUTHOR]

The remarkable features of a carbon fiber paper sensor (CP) were employed for detection of the estrogenic hormone 17α-ethinylestradiol (EE2), considered a contaminant of emerging concern due to its potential ecotoxicity and widespread in the aquatic ecosystems. In this work, an unpreceded CP pre-treatment study was conducted with the (Il)-hexacyanoferrate(III) ion pair, however a bare sensor without pre-treatment revealed higher efficiency on the oxidation of EE2 compared to a chemical and electrochemical pre-treated CP and a gold nanoparticles modified CP, being thus selected for EE2 determinations. The analytical conditions were thoroughly optimized in terms of electrolyte pH (pH 7), differential pulse voltammetry parameters (modulation time 0.003 s, amplitude 0.09 V, interval time 0.1 s and step potential 0.01 V), and analyte preconcentration potential (0.4 V) and time (180 s). The hormone can be determined by the CP in a wide linear range from 0.1 to 1000 nM, achieving a detection limit of 0.14 ± 0.005 nM and an outstanding sensitivity of 1636 ± 232 μA μM−1 cm−2 in the lowest linear zone (0.1–1 nM). The sensor was validated in river water and fish reaching good recoveries (91.2 ± 4.6 to 109.0 ± 7.1%), reproducibility and repeatability. Moreover, the sensor showed high selectivity to EE2 in the presence of several potential interfering compounds and frequently prescribed drugs, though it could not discriminate the similar hormone, 17β-estradiol, being the total concentration obtained in this case. CP-based sensors emerge as efficient electroanalytical tools, suggesting that modification of the surface may not always be beneficial in terms of sensitivity. [Display omitted] • A simple and effective carbon paper sensor was used for 17α-ethinylestradiol sensing. • The best analytical signal was obtained with an untreated and unmodified carbon paper. • The optimized sensor achieved high sensitivity (1636 μA μM−1 cm−2) and LOD of 0.14 nM. • Application in complex samples of fish resulted in recoveries from 102 to 109%. • Carbon paper sensors can be become valuable tools in the electroanalytical field. [ABSTRACT FROM AUTHOR]

Simple, cost-effective and reliable tools for the quantification of genetically modified organisms (GMO) in food and feed are highly demanded to enforce labelling legislation in the EU. Herein, we report a novel method for quantitative analysis of genetically modified soybean with the event GTS-40-3-2, also known as Roundup Ready (RR) soybean, using magnetoassays with electrochemical detection, coupled to DNA amplification by end-point polymerase chain reaction (PCR). For the proposed work, two DNA sequences were targeted via hybridisation onto magnetic beads, one specific for the transgenic event and the other for the taxon or species-specific lectin gene. Enzymatic labelling was performed to obtain an electrochemically active product measured by chronoamperometry. By optimising the number of PCR cycles, among other parameters, two magnetoassays coupled to PCR were successfully accomplished and linearity was obtained in the ranges of 53–4425 and 1093–88,496 DNA copies for the event-specific and lectin sequences, respectively. The proposed method provides accurate and precise RR soybean quantitative results, being effectively compared to those obtained by real-time PCR, as the reference method. These findings confirm the suitability of the method as an alternative tool for GMO quantification. [ABSTRACT FROM AUTHOR]

In this work, a norfloxacin selective modified glassy carbon electrode (GCE) based on a molecularly imprinted polymer (MIP) as electrochemical sensor was developed. A suspension of multi-walled carbon nanotubes (MWCNTs) was deposited on the electrode surface. Subsequently, a molecularly imprinted film was prepared by electropolymerization, via cyclic voltammetry of pyrrole (PPy) in the presence of norfloxacin (NFX) as the template molecule. A control electrode (NIP) was also prepared. Scanning electron microscopy (SEM) and cyclic voltammetry in a ferrocyanide solution were performed for morphological and electrochemical characterisation, respectively. Several experimental parameters were studied and optimised. For quantification purposes the MIP/MWCNT/GCE was immersed in NFX solutions for 10 min, and the detection was performed in voltammetric cell by square wave voltammetry. The proposed sensor presented a linear behaviour, between peak current intensity and logarithmic concentration of NFX between 1 × 10 −7 and 8 × 10 −6 M. The obtained results presented good precision, with a repeatability of 4.3% and reproducibility of 9% and the detection limit was 4.6 × 10 −8 M ( S/N = 3). The developed sensor displayed good selectivity and operational lifetime, is simple to fabricate and easy to operate and was successfully applied to the analysis of NFX in urine samples. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor for ochratoxin A (OTA) detection was fabricated through the modification of a glassy carbon electrode (GCE) with multiwalled carbon nanotubes (MWCNTs) and a molecularly imprinted polymer (MIP). The MWCNTs dramatically promoted the sensitivity of the developed sensor, while polypyrrole (PPy) imprinted with OTA served as the selective recognition element. The imprinted PPy film was prepared by electropolymerization of pyrrole in the presence of OTA as a template molecule via cyclic voltammetry (CV). The electrochemical oxidation of OTA at the developed sensor was investigated by CV and differential pulse voltammetry (DPV). The developed MIP/MWCNT/GCE sensor showed a linear relationship, when using DPV, between peak current intensity and OTA concentration in the range between 0.050 and 1.0 μM, with limits of detection (LOD) and quantification of 0.0041 μM (1.7 μg/L) and 0.014 μM (5.7 μg/L) respectively. With the developed sensor precise results were obtained; relative standard deviations of 4.2% and 7.5% in the evaluation of the repeatability and reproducibility, respectively. The MIP/MWCNT/GCE sensor is simple to fabricate and easy to use and was successfully applied to the determination of OTA in spiked beer and wine samples, with recoveries between 84 and 104%, without the need of a sample pre-treatment step. [ABSTRACT FROM AUTHOR]

Atorvastatin (ATV) is a statin member consumed in high quantities worldwide. In response to that, the occurrence of ATV in environmental waters has become a reality, highlighting the need of rapid and sensitive analytical devices for its monitoring. In this work, the first electrochemical molecularly imprinted polymer (MIP) sensor for the detection of ATV in water samples is presented. Computational studies were conducted based on quantum mechanical (QM) calculations and molecular dynamics (MD) simulations for rational selection of a suitable functional monomer and to study in detail the template-monomer interaction, respectively. The sensor was prepared by electropolymerisation of the selected 4-aminobenzoic acid (ABA) monomer with ATV, acting as template, on screen printed carbon electrode (SPCE). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were applied to characterise the modified electrode surfaces. The quantitative measurements were carried out with differential pulse voltammetry (DPV) in 0.1 M phosphate buffer (pH = 7). After investigation and optimisation of important experimental parameters, a linear working range down to 0.05 μmol L−1 was determined with a correlation coefficient of 0.9996 and a limit of detection (LOD) as low as 0.049 μmol L−1 (S/N = 3). High sensitivity and selectivity of the prepared sensor were demonstrated with the ability to recognise ATV molecules over its closer structural analogues. Moreover, the sensor was quickly and successfully applied in spiked water samples, proving its potential for future on-site monitoring of ATV in environmental waters. [Display omitted] • A disposable electrochemical MIP sensor for atorvastatin (ATV) detection was designed. • Efficient prediction of a functional monomer was achieved based on QM calculations. • MD simulations allowed to understand the ATV-monomer interaction. • High selectivity and sensitivity were obtained by a direct detection method. • The sensor was successfully applied in water samples. [ABSTRACT FROM AUTHOR]

A novel sensitive electrochemical sensor was developed by electropolymerization of pyrrole (PY) and molecularly imprinted polymer (MIP) which was synthesized onto a glassy carbon electrode (GCE) in aqueous solution using cyclic voltammetry in the presence of Trimethoprim (TMP) as template molecules. Furthermore, a previous electrode modification was performed by deposition of a suspension of graphene on the electrode's surface. The performance of the imprinted and non-imprinted (NIP) films was evaluated by impedance spectroscopy (EIS) and cyclic voltammetry (CV) of a ferric solution. The molecularly imprinted film exhibited a high selectivity and sensitivity toward TMP. The sensor presented a linear range, between peak current intensity and logarithm of TMP concentration between 1.0×10−6 and 1.0×10−4 M. The results were accurate (with recoveries higher than 94%), precise (with standard deviations less than 5%) and the detection limit was 1.3×10−7 M. The new sensor is selective, simple to construct and easy to operate. The MIP sensor was successfully applied to quantify TMP in urine samples. [ABSTRACT FROM AUTHOR]

• Molecularly imprinted polymer sensor for bisphenol-A was developed. • Molecular interactions of Bisphenol-A on polymer was computationally analysed. • Bisphenol-A imprinted polypyrrole electrochemically synthesised on the reduced graphene oxide film. • Bisphenol-A detected in bovine milk and water samples stored from polycarbonate bottles. Bisphenol A (BPA) contamination from food packaging material has been a major concern in recent years, due to its potential endocrine-disrupting effects on humans, especially infants and children. This paper reports the detection of BPA using an electrochemical sensor based on molecularly imprinted polymer (MIP). Electrochemically reduced graphene oxide coated glassy carbon electrode used for this study. Density functional theory (DFT) at B3LYP/6–31 + G (d,p) level was used to calculate the molecular-level interaction between BPA and MIP. The pyrrole electrochemically polymerized in the presence of template molecule BPA on the electrode surface. BPA imprinted cavities were formed by removing entrapped BPA molecules from the polypyrrole film. MIP electrode was used for the determination of BPA in standard and real samples by differential pulse voltammetry. The peak current shows the linear relationship to the logarithmic concentration of BPA between 750 and 0.5 nmolL−1 with a correlation coefficient, R2 = 0.992. The limit of detection was found to be 0.2 nmolL−1 (S/N = 3). The reproducibility and repeatability of the sensor were also studied. [ABSTRACT FROM AUTHOR]

• First time a selective MIP electrochemical sensor was developed for Furazolidone (FZD). • QM calculations and MD simulations were used to select the best functional monomer and the optimum polymerisation conditions. • The sensor constructed based on MIP-CPE-MWCNTs showed high selectivity and sensitivity. • The proposed sensor was successfully applied for FZD detection in water samples without any pre-treatment step. Determination of antibiotics in environmental waters is an important global issue. Although furazolidone (FZD) was banned from use in food-producing animals, owing to its mutagenic and carcinogenic effects, this antibiotic has been illegally used across the world and its presence in environment have being noted. In this work, the first selective molecularly imprinted polymer (MIP) was developed for electrochemical detection of FZD. It was constructed based on the modification of the traditional carbon paste electrode (CPE) with MIP microparticles, followed by introduction of multi-walled carbon nanotubes (MWCNTs). Quantum mechanical (QM) calculations and molecular dynamics (MD) simulations were performed to allow rational selection of an appropriate functional monomer and to simulate the best pre-polymerisation conditions, respectively. The MIP were synthetized by polymerization using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as monomer and FZD as template molecule. The MIP microparticles were then incorporated on CPE-MWCNTs and the electrochemical analysis of FZD were evaluated by differential pulse voltammetry (DPV). After optimisation of experimental conditions, the MIP-CPE-MWCNTs sensor exhibited a good linear response over the concentration range of 0.01 μM to 1 μM with a correlation coefficient of 0.9995. The limit of detection (LOD) was found to be 0.03 μM (S/N = 3). Due to high imprinting efficiency the sensor displayed selectivity to recognise FZD molecules and it was successfully applied in water samples where excellent recovery values (over 90 %) were obtained. The proposed sensor provides an efficient and promising sustainable strategy for monitorisation of FZD in environmental waters. [ABSTRACT FROM AUTHOR]

The ever-increasing presence of contaminants in environmental waters is an alarming issue, not only because of their harmful effects in the environment but also because of their risk to human health. Pharmaceuticals and pesticides, among other compounds of daily use, such as personal care products or plasticisers, are being released into water bodies. This release mainly occurs through wastewater since the treatments applied in many wastewater treatment plants are not able to completely remove these substances. Therefore, the analysis of these contaminants is essential but this is difficult due to the great variety of contaminating substances. Facing this analytical challenge, electrochemical sensing based on molecularly imprinted polymers (MIPs) has become an interesting field for environmental monitoring. Benefiting from their superior chemical and physical stability, low-cost production, high selectivity and rapid response, MIPs combined with miniaturized electrochemical transducers offer the possibility to detect target analytes in-situ. In most reports, the construction of these sensors include nanomaterials to improve their analytical characteristics, especially their sensitivity. Moreover, these sensors have been successfully applied in real water samples without the need of laborious pre-treatment steps. This review provides a general overview of electrochemical MIP-based sensors that have been reported for the detection of pharmaceuticals, pesticides, heavy metals and other contaminants in water samples in the past decade. Special attention is given to the construction of the sensors, including different functional monomers, sensing platforms and materials employed to achieve the best sensitivity. Additionally, several parameters, such as the limit of detection, the linear concentration range and the type of water samples that were analysed are compiled. Image 1 • Contaminant analysis faces great challenges because of their variety and levels. • Advantages of MIPs as recognition elements: low-cost, robustness, reusability. • Main inconvenient of MIP-based sensors for environmental analysis: sensitivity. • Discussion of MIP-based electrochemical sensors for environmental analysis. • Discussion of advances and trends in MIP-based electrochemical sensors. [ABSTRACT FROM AUTHOR]

• Detection of cancer biomarkers in biological fluids is useful for early diagnosis. • An electrochemical immunomagnetic bioassay was developed for HER2-ECD detection. • Magnetic beads constitute a versatile tool for the construction of the assay. • The assay was selective towards the target protein and live breast cancer cells. • The assay was successfully tested in the analysis of human serum. Despite the evolution of targeted therapies in oncology, some challenges such as screening and early diagnosis of cancer-related biomarkers still remain. The analysis of the Human Epidermal growth factor Receptor 2 (HER2) in biological fluids provides essential information for effective treatments. In this work we report the development of an electrochemical immunomagnetic bioassay for the analysis of the extracellular domain of HER2 (HER2-ECD) in human serum and cancer cells. Biomodified carboxylic acid functionalized magnetic beads (COOH-MBs) were used as the capture probe and an antibody labelled with alkaline phosphatase (AP) as the signalling probe. In the presence of HER2-ECD a sandwich complex was formed on the MBs, which were magnetically attracted to the surface of a screen-printed carbon electrode (SPCE). After the addition of 3-indoxyl phosphate and silver ions, used as the enzymatic substrate, the immunological interaction was detected by linear sweep voltammetry. Two linear concentration ranges were established: one between 5.0 and 50 ng/mL and another between 50 and 100 ng/mL. The developed assay provided a clinically useful detection limit (2.8 ng/mL) and has an adequate precision (V x0 < 5%). The assay provided accurate results and was selective towards the target biomarker. Additionally, CTCs were analysed in human serum and a detection limit of 3 cells/mL was achieved for the HER+ breast cancer cell line SK-BR-3. [ABSTRACT FROM AUTHOR]