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This study describes the fabrication of a lab-made screen-printed electrode (LabSPE) and its sensing ability for the detection of butylated hydroxyanisole (BHA) which is a synthetic antioxidant utilized widely in food industries. The lab-made screen-printed electrodes were printed on a polycarbonate substrate stepwise via a screen-printing technique using various inks suitable for electrode templates and then modified for the detection of BHA. As for the design of the sensor, firstly, graphitic carbon nitride (g-C3N4) was synthesized electrochemically through the one-pot synthesis method. After the synthesis of Fe3O4 nanoparticles (Fe3O4 NPs), the surface of SPE was modified with the dual composite consisting of g-C3N4 and Fe3O4 NPs. Lastly, platinum nanoparticles (Pt NPs) were deposited electrochemically on the modified electrode in 0.5 M HCl solution containing 2 mM H2PtCl6 at a constant potential of 0.25 V for 45 s. After optimization of varied parameters such as pH of the electrolyte solution, deposition time, and deposition potential, the current responses of the sensor (Pt/g-C3N4–Fe3O4/LabSPE) toward BHA displayed linearity in the wide concentration range of 0.25 μM to 90 μM with a low detection limit of 0.053 μM. The selectivity of Pt/g- C3N4–Fe3O4/SPE was tested successfully in the presence of other antioxidants (BHT, TBHQ, GA, and PG). Moreover, the applicability of the proposed sensor for practical tests was verified by the detection of BHA in commercial samples.

Platinum dissolution in PEM fuel cells is an increasingly important indicator for the state-of-health and lifetime prediction of fuel cells in real applications. For this reason, portable online analysis tools are needed that can detect and quantify platinum with high sensitivity, selectivity, and accuracy in the product water of fuel cells. We validated the hanging mercury drop electrode (HMDE) and non-toxic bismuth film electrodes for the voltammetric determination of platinum for this purpose. Bismuth films were prepared by reductive deposition on both a glassy carbon solid state electrode and on a screen-printed electrode (film on-chip electrode). Both bismuth film electrodes could be successfully validated for the determination of platinum by adsorptive stripping voltammetry. An LOD of 7.9 μg/L and an LOQ of 29.1 μg/L were determined for the bismuth film solid state electrode, values of 22.5 μg/L for the LOD and of 79.0 μg/L for the LOQ were obtained for the bismuth film on-chip electrode. These numbers are still much higher than the results measured with the HMDE (LOD: 0.76 ng/L; LOQ: 2.8 ng/L) and are not sufficient to detect platinum in the product water of a fuel cell run in different load tests. The amount of dissolved platinum produced by a 100 W fuel cell stack upon dynamic and continuous high load cycling, respectively, was in the range of 2.9–4.1 ng/L, which could only be detected by the HMDE.

The Donnan membrane technique (DMT), in which a synthetic or natural solution (the “donor”) is separated from a ligand-free solution (the “acceptor”) by a cation-exchange membrane, is a recognized technique for measuring the concentration of a free metal ion in situ, with coupling to electrochemical detection allowing for the quantification of the free metal ion directly on site. However, the use of the DMT requires waiting for the free metal ion equilibrium between the donor and the acceptor solution. In this paper, we investigated the possibility of using the kinetic information and showed that non-equilibrium experimental calibrations of Cd and Pb with the ISIDORE probe could be used to measure free metal concentrations under conditions of membrane-controlled diffusion transport. The application of this dynamic approach made it possible to successfully determine the concentration of free Cd in synthetic and natural river samples. Furthermore, it was found that the determination of free Cd from the slope was not affected by the Ca concentration ratio between the acceptor and donor solution, as opposed to the traditional approach based on Donnan equilibrium. This ISIDORE probe appears to be a promising tool for determining free metal ions in natural samples.

The monitoring of antibiotic residues in foodstuffs by using rapid detection method is essential for food safety. In this work, the electrochemical sensor was developed by modification of screen-printed carbon electrode with graphene oxide, and then the ciprofloxacin (CIP) was detected based on the complexation of CIP with Mn2+. On modified electrode, the anodic stripping peak current response of Mn2+ was prohibited in the presence of CIP, and a peak current response of the complex was occurred. Thus, the peak current response of the complexation peak was employed as the indicating signal for CIP determination, which was more sensitive than the direct electrochemical oxidation response of CIP. Parameters that affect the signal response have been investigated in method. Under the optimum conditions, the peak current of the complexation peak was linearly correlated with the CIP content in the milk sample solution at 1.0 to 8.0 μM, and the linear correlation coefficients (R2) was 0.994. The limits of detection (LOD) was 0.30 μM. Recoveries of CIP in milk sample were ranged from 81.0 to 95.4% with relative standard deviations (RSDs) below 4.6%. The method showed high selectivity and sensitive, good reproducibility, indicated that this method has potential to be applied in CIP residue analysis.

In this study, we designed a new biosensing membrane for the development of an electrochemical glucose biosensor. To proceed, we used a chitosan-based hydrogel that entraps glucose oxidase enzyme (GOx), and we crosslinked the whole matrix using glutaraldehyde, which is known for its quick and reactive crosslinking behavior. Then, the stability of the designed biosensors was investigated over time, according to different storage conditions (in PBS solution at temperatures of 4 °C and 37 °C and in the presence or absence of glucose). In some specific conditions, we found that our biosensor is capable of maintaining its stability for more than six months of storage. We also included catalase to protect the biosensing membranes from the enzymatic reaction by-products (e.g., hydrogen peroxide). This design protects the biocatalytic activity of GOx and enhances the lifetime of the biosensor.

Stability-indicating methods are awesome tools to ensure the safety and efficacy of active pharmaceutical ingredients (APIs). An accurate comparative study involving the use of potentiometric sensors for the determination of bromazepam (BRZ) in the presence of its main product of degradation and impurity was performed by the fabrication of two membrane electrodes. A screen-printed electrode (SPE) and a solid-contact glassy carbon electrode (SCE) were fabricated and their performance optimized. The fabricated sensors showed a linear electrochemical response in the concentration range 1.0 × 10−6 M to 1.0 × 10−2 M. The electrodes exhibited Nernstian slopes of 59.70 mV/decade and 58.10 mV/decade for the BRZ-SPE and BRZ-SCE membrane electrodes, respectively. The electrochemical performance was greatly affected by the medium pH. They showed an almost ideal electrochemical performance between pH 3.0 and pH 6.0. The fabricated membranes were applied successfully for the quantification of BRZ in the presence of up to 90% of its degradation product. Moreover, a successful application of the fabricated electrodes was performed for the sensitive and selective quantification of BRZ in its tablet form without any pretreatment procedure.

To build a portable and sensitive method for monitoring the concentration of the flavonoid rutin, a new electrochemical sensing procedure was established. By using nitrogen-doped carbonized polymer dots (N-CPDs) anchoring few-layer black phosphorene (N-CPDs@FLBP) 0D-2D heterostructure and gold nanoparticles (AuNPs) as the modifiers, a carbon ionic liquid electrode and a screen-printed electrode (SPE) were used as the substrate electrodes to construct a conventional electrochemical sensor and a portable wireless intelligent electrochemical sensor, respectively. The electrochemical behavior of rutin on the fabricated electrochemical sensors was explored in detail, with the analytical performances investigated. Due to the electroactive groups of rutin, and the specific π-π stacking and cation–π interaction between the nanocomposite with rutin, the electrochemical responses of rutin were greatly enhanced on the AuNPs/N-CPDs@FLBP-modified electrodes. Under the optimal conditions, ultra-sensitive detection of rutin could be realized on AuNPs/N-CPDs@FLBP/SPE with the detection range of 1.0 nmol L−1 to 220.0 μmol L−1 and the detection limit of 0.33 nmol L−1 (S/N = 3). Finally, two kinds of sensors were applied to test the real samples with satisfactory results.

Background: Diazepam belongs to the group of 1,4-benzodiapines. It is used for the treatment of anxiety, convulsions and as muscle relaxants. The presence of a 4,5-azomethine group enables its electrochemical detection. Introduction: A screen-printed electrode modified with antimony film was used for the determination of diazepam in pharmaceutical preparations Methods: Electrode modification was done by ex-situ deposition of antimony on a commercially available screen-printed electrode. Parameters affecting the electroanalytical response of the sensor, such as deposition potential, deposition time, and antimony concentration, were examined and optimized. The modified electrode showed enhanced electroactivity for diazepam reduction compared to the unmodified electrode. Under optimal conditions, linear sweep voltammetry was used for the determination of the analyte. Results: The sensor showed linear dependence in the range from 0.5 to 10 μmol/L, the correlation coefficient was 0.9992. The limit of detection was 0.33 μmol/L, corresponding limit of quantification was 1.08 μmol/L. Modification enabled determination of diazepam in the presence of oxygen. Conclusion: The modified electrode was used for the determination of diazepam in tablets. Results confirmed the applicability of the electrochemical sensor.

We proposed a specially designed sequential injection (SI) amperometric system coupling with a bioreactor for in-line glucose monitoring in cell culture. The system is composed of three main parts which are the bioreactor, SI system, and electrochemical detection unit. The bioreactor accommodates six individual cell culture units which can be operated separately under different conditions. The SI system enables automatic in-line sampling and in-line sample dilution, with a specially designed mixing unit; therefore, it has the benefits of fast analysis time and less contamination risk. The use of 3D-printed microfluidic components, a mixing channel, and a flow cell helped to reduce operational time and sample volume. A disposable screen-printed electrode (SPE), modified with glucose oxidase (GOD), carbon nanotube, and gold nanoparticle, was used for detection. The developed system provided a linear range up to 3.8 mM glucose in cell culture media. In order to work with cell culture in higher glucose media, the in-line sample dilution can be applied. The developed SI system was demonstrated with mouse fibroblast (L929) cell culture. The results show that glucose concentration obtained from the SI system is comparable with that obtained from the conventional colorimetric method. This work can be further developed and applied for in vitro cell-based experiments in biomedical research.

Received: 14.07.22. Revised: 02.08.22. Accepted: 02.08.22. Available online: 16.08.22. Express determination of antibiotics is an extremely important task today. Portable electrochemical microdevices are a viable alternative to traditional methods of analysis. The development of such devices requires the study of redox processes in detail. This article is devoted to the comparative study of the electrochemical behavior of chloramphenicol in water solvents in standard laboratory and portable microelectrochemical cells. It was found that the electrochemical reduction of chloramphenicol proceeds via a 3-electron mechanism to the formation of a dimer. In the transition from the macrocell to the microcell, a decrease in the electrochemical reduction current and a shift of the peak potential to the cathode region are observed, which is apparently associated mainly with the type of the electrode material. The best characteristics of the direct electrochemical response were obtained in the differential pulse voltammetry mode. Under the selected operating parameters, the peak current of the electrochemical reduction of chloramphenicol is linearly dependent on the concentration of the antibiotic in the range of 2∙10–3–1∙10–5 M with a detection limit of 3∙10–5 M. Obtained characteristics are sufficient for the quality control of pharmaceuticals and can be improved through the use of organic and hybrid modifiers of the working electrode surface. This work was supported by the Presidential Grants Fund of the Russian Federation (grant no. MK-392.2022.1.3).

The rapid diagnosis of Pseudomonas aeruginosa infection is very important because this bacterium is one of the main sources of healthcare-associated infections. Pseudomonas quinolone signal (PQS) is a specific molecule for quorum sensing (QS) in P. aeruginosa, a form of cell-to-cell bacterial communication and its levels can allow the determination of the bacterial population. In this study, the development of the first electrochemical detection of PQS using screen-printed electrodes modified with carbon nanotubes (CNT-SPE) is reported. The electrochemical fingerprint of PQS was determined using different electrode materials and screen-printed electrodes modified with different nanomaterials. The optimization of the method in terms of electrolyte, pH, and electrochemical technique was achieved. The quantification of PQS was performed using one of the anodic peaks in the electrochemical fingerprint of the PQS on the CNT-SPE. The sensor exhibited a linear range from 0.1 to 15 µM, with a limit of detection of 50 nM. The sensor allowed the selective detection of PQS, with low interference from other QS molecules. The sensor was successfully applied to analysis of real samples (spiked urine and human serum samples, spiked microbiological growth media, and microbiological cultures).

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, Patrícia Rebelo (SFRH/BD/132384/2017) and João Pacheco (SFRH/BPD/101419/2014) are grateful to Fundação para a Ciência e a Tecnologia (FCT) and European Union (EU) for their grants, financed by POPH-QREN-Tipologia 4.1-Formação Avançada, funded by Fundo Social Europeu (FSE) and Ministério da Ciência, Tecnologia e Ensino Superior (MCTES). Isabel Seguro is grateful to the project Farmasense (39957) that was funded by Sistema de Incentivos à Investigação e Desenvolvimento Tecnológico de Portugal 2020, through the Programa Operacional do Norte (NORTE 2020) and the Fundo Europeu de Desenvolvimento Regional (FEDER). This work was further supported by UID/QUI/50006/2020 (LAQV-REQUIMTE) and the project PTDC/QUI-QAN/3899/2021 with funding from FCT/MCTES through national funds. The research was funded also by FCT and BiodivRestore Joint Call 2020–2021-European Union’s Horizon 2020 research and innovation programme under grant agreement No 101003777-BiodivRestore-406/DivRestore/0002/2020-BioReset-“Biodiversity restoration and conservation of inland water ecosystems for environmental and human well-being”

The need for agile and proper identification of drugs of abuse has encouraged the scientific community to improve and todevelop new methodologies. The drug lysergic acid diethylamide (LSD) is still widely used due to its hallucinogenic effects. The use ofvoltammetric methods to analyze narcotics has increased in recent years, and the possibility of miniaturizing the electrochemical equipmentallows these methods to be applied outside the laboratory; for example, in crime scenes. In addition to portability, the search for affordable andsustainable materials for use in electroanalytical research has grown in recent decades. In this context, employing paper substrate, graphite pen-cil, and silver paint to construct paper-based electrodes is a great alternative. Here, a paper-based device comprising three electrodes was drawnon 300 g/m2watercolor paper with 8B pencils, and its efficiency was compared to the efficiency of a commercially available screen-printedcarbon electrode. Square wave voltammetry was used for LSD analysis in aqueous medium containing 0.05 mol/L LiClO4. The limits of detec-tion and quantification were 0.38 and 1.27 mol/L, respectively. Both electrodes exhibited a similar voltammetric response, which was alsoconfirmed during analysis of a seized LSD sample, with recovery of less than 10%. The seized samples were previously analyzed by GCMStechnique, employing the full scan spectra against the software spectral library. The electrode selectivity was also tested against 3,4-methylene-dioxymethamphetamine (MDMA) and methamphetamine. It was possible to differentiate these compounds from LSD, indicating that the devel-oped paper-based device has potential application in forensic chemistry analyses., Financial support provided by the Polícia Científica do Estado de São Paulo for the partnership, and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP - Process 2016/23825-3), Fundação para a Ciência e Tecnologia, FCT, Portugal, (UID/QUI/00686/2016 and UID/QUI/00686/2019), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Process Capes Pro Forenses 25/2014).

Electrochemical biosensors have attracted significant attention as a novel tool for the sensitive detection of pathogens and contaminants, with the potential capability of rapid, on-site diagnosis. In this study, we intended to improve the sensitivity of electrochemical biosensor using Fe(CN)(6)(3)(-/)(4-) as redox marker, toward its application to norovirus aptasensors. Although many researchers have developed electrochemical aptasensors for various analytes using redox markers, the reported electrochemical conditions under which an aptasensor was examined varied across multiple studies. Here, we performed square-wave voltammetry (SWV) for electrodes modified with aptamer specific to murine norovirus and compared the reduction peak currents of Fe(CN)(6)(3-) under various conditions. Effects of working electrode materials and NaCI and [Ru(NH3)(6)]Cl-3 concentration in the electrolyte were examined. Among conditions we tested, the best sensitivity was obtained using a screen-printed gold electrode in an electrolyte containing 1M NaCl with 4 mM K-3[Fe(CN)(6)], in which the concentration of murine norovirus showed linearity with SWV peak current. This study provided useful information on the electrochemical measurement conditions regarding the development of electrochemical aptasensors.

Alzheimer's disease is one of the most common causes of dementia nowadays, and its prevalence increases over time. Because of this and the difficulty of its diagnosis, accurate methods for the analysis of specific biomarkers for an early diagnosis of this disease are much needed. Recently, the levels of unfolded isoform of the multifunctional protein p53 in plasma have been proved to increase selectively in Alzheimer's Disease patients in comparison with healthy subjects, thus entering the list of biomarkers that can be used for the diagnosis of this illness. We present here the development of an electrochemical immunosensor based on nanostructured screen-printed carbon electrodes for the quantification of unfolded p53 in plasma samples. The sensor shows a suitable linear range (from 2 to 50 nM) for its application in real blood samples and a very low limit of detection (0.05 nM). The concentration of unfolded p53 has been accurately detected in plasma of elderly people in healthy conditions, subjects with mild cognitive impairment (MCI) and Alzheimer's Disease (AD) subjects, obtaining results with no significant differences to those provided by an ELISA assay. These results support the possibility of measuring unfolded p53 levels with a cheap, simple and miniaturized device with a promising future for point-of-care applications in the early diagnosis of Alzheimer's dementia., This work has been supported by the FC-15-GRUPIN14-021 project from the Asturias Regional Government and the CTQ2014-58826-R and MINECO-18-CTQ2017-86994-R projects from the Spanish Ministry of Economy and Competitiveness (MINECO). O. Amor-Gutiérrez thanks Vicerrectorado de Investigación from University of Oviedo for the award of a grant “Ayudas para la realización de tesis doctorales” (PAPI-18-PF-13) through Plan de Apoyo y Promoción de la Investigación.

D-2-hydroxyglutaric acid (D2HG) is overproduced as a result of the D-2-hydroxyglutaric aciduria and relevant cancers, caused by gene mutation. Accurate analysis of D2HG could help rapid diagnosis of these diseases and allow for timely treatment. In this work, a D-2-hydroxyglutarate dehydrogenase from Ralstonia solanacearum (RsD2HGDH) is cloned and recombinantly expressed. This enzyme features the direct electron transfer to chemical electron mediators (such as methylene blue (MB)) in the absence of additional coenzymes. Therefore, NAD+, a natural electron acceptor for the commercial D2HGDH and usually known for being unstable and difficult for immobilization can be avoided in the preparation of biosensors. The RsD2HGDH and MB are co-immobilized on a two-dimensional material, Ti3C2 MXene, followed by drop-coating on the gold screen-printed electrode (AuSPE) to construct a compact and portable biosensor. The D2HG in samples can be catalyzed by RsD2HGDH, where the current change is measured by chronoamperometry at −0.23 V. The biosensor shows a D2HG detection range of 0.5 to 120 µM (R2 = 0.9974) with a sensitivity of 22.26 μA mM−1 cm−2 and a detection limit of 0.1 µM (S/N = 3). The biosensor retains 72.52% performance of its incipient state after 30 days of storage. The samples of D2HG-containing fetal bovine serum and artificial urine were analyzed with the recovery of 99.56% to 106.83% and 97.30% to 102.47% further indicating the great application potential of our portable D2HG biosensor.

The aim of the presented Master Thesis was to study an electrochemical behaviour of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) resulting in the founding of optimum conditions for their voltammetric determination at a screen-printed carbon electrode (SPCE) using DC voltammetry (DCV) and differential pulse voltammetry (DPV). Voltammetric behaviour of both compounds was investigated in dependence on the pH of the medium (realized using Britton-Robinson buffer). The optimum pH for the voltammetric determination of 2,4-D on the SPCE was chosen to be pH 5,0 for both voltammetric techniques, and, for 2,4-DCP, it was chosen to be pH 6,0 for both voltammetric techniques. The determination of 2,4-D at a concentration of 1·10-4 μmol·L-1 showed good repeatability for both voltammetric techniques used (1.3% for DCV and 0.7% for DPV), and, for 2,4-DCP, it showed acceptable repeatability for both voltammetric techniques used (1.3% for DCV and 4.8% DPV). Under optimum conditions, the calibration dependence of 2,4-D was measured for DCV in the concentration range of 10-100 μmol·L-1 , with limit of quantification (LOQ) of 1.0 μmol·L-1 and limit of detection (LOD) 0.3 μmol·L-1 . Under optimum conditions, the calibration dependence of 2,4-D was measured for DPV in the concentration range...

Developing simple, cost-effective, easy-to-use, and reliable analytical devices if of utmost importance for the food industry for rapid in-line checks of their products that must comply with the provisions set by the current legislation. The purpose of this study was to develop a new electrochemical sensor for the food packaging sector. More specifically, we propose a screen-printed electrode (SPE) modified with cellulose nanocrystals (CNCs) and gold nanoparticles (AuNPs) for the quantification of 4,4′-methylene diphenyl diamine (MDA), which is one of the most important PAAs that can transfer from food packaging materials into food stuffs. The electrochemical performance of the proposed sensor (AuNPs/CNCs/SPE) in the presence of 4,4′-MDA was evaluated using cyclic voltammetry (CV). The modified AuNPs/CNCs/SPE showed the highest sensitivity for 4,4′-MDA detection, with a peak current of 9.81 μA compared with 7.08 μA for the bare SPE. The highest sensitivity for 4,4′-MDA oxidation was observed at pH = 7, whereas the detection limit was found at 57 nM and the current response of 4,4′-MDA rose linearly as its concentration increased from 0.12 μM to 100 μM. Experiments using real packaging materials revealed that employing nanoparticles dramatically improved both the sensitivity and the selectivity of the sensor, which can be thus considered as a new analytical tool for quick, simple, and accurate measurement of 4,4′-MDA during converting operations.

We fabricated a new electrochemical 4-aminophenol sensor based on a nanocomposite of Co3O4 nanoparticles and graphite carbon nitride (Co3O4@g-C3N4), used for the modification of a screen-printed electrode (Co3O4@g-C3N4/SPE). The synthesized nanocomposite was characterized using field-emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction and Fourier transform-infrared (FT-IR) techniques. The electro-oxidation of 4-aminophenol in phosphate buffer solution (pH = 7.0) was investigated via cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The peak current of oxidation in the optimized conditions had a linear relationship with various 4-aminophenol contents (0.05–780.0 μM) with a correlation coefficient of 0.9996 and the limit of detection (S/N = 3) of 1.5 × 10−8 M. The developed method was successful to determine 4-aminophenol in real specimens, with acceptable outcomes.

On-site quantitative detection provides the opportunity for accurate and timely health care, clinical diagnosis, environmental monitoring, and food analysis. A variety of portable electrochemical detection instruments have been developed at present for on-site quantitative detection use, including commercially available portable potentiostats, but the reality is that these electrochemical detection devices still have the problem of narrow output voltage range and detection current range, and their performance of output voltage resolution and detection current resolution is still unsatisfactory. The narrow voltage or current range makes it difficult for some chemical reactions with peaks outside the range to proceed, and the insufficiency of voltage resolution and detection current resolution are key parameters restricting the detection accuracy of existing devices. In this regard, it is urgent to carry out partial transformation of the existing device to increase the use range and detection accuracy of the device. In the current work, a smartphone-based electrochemical on-site quantitative detection device was developed. The device comprises a portable small potentiostat, a smartphone equipped with a specially designed Android electrochemical detection application, and a disposable sensor (NiONP modified screen-printed electrode [SPE]). The potentiostat can realize electrochemical detection methods, including cyclic voltammetry, chronoamperometry, and differential pulse voltammetry. In addition, the potentiostat can output a potential range − 2.047 ~ + 2.047 V with a current detection sensitivity scale 1×10−8 ~ 1×10−3 A, and the current detection range could reach ±10 nA ~ ±10 mA. Most importantly, the current detection resolution of the potentiostat can reach 0.003% (3.125 pA on ± 10 nA range). The smartphone was used for communicating with the potentiostat, setting detection parameters, and mapping voltammograms in real time. The SPE was modified with nickel oxide nanoparticles and perfluorinated resin solution, which were employed as sensors to convert and amplify the electrochemical current response during the on-site quantitative detection. Results indicated that the device features excellent performance for the lactate detection. The device covered a linear range 0.1 ~ 30 mM on lactate detection with the correlation coefficient (R2) reaching 0.997.

Nickel is one of the most common allergens found in cosmetics: a high exposure to nickel can cause serious effects on human health, as contact dermatitis or eczema. Considering the spread of this type of allergy among the population and the predominant use of cosmetic products, use portable and easy-to-use devices, which allow a quick and accurate assessment of nickel above the permitted limits, could represent a valid and alternative tool for the protection of human health. In this study, we developed a hybrid paper-polyester printed strip for fast, simple, and low-cost determination of nickel at concentrations consistent with the allowable limits in cosmetics, exploiting the differential pulse adsorptive stripping voltammetry in the presence of dimethylglyoxime as Nicomplexing agent. We report a novel configuration to produce an integrated fully-printed electrochemical device, in which the screen-printed electrode, printed on polyester, is successfully combined with a wax-printed filter paper disk in order to allow the investigation in treatment of complex matrices such as cosmetics ones. In addition, the use of filter paper allows to store all the reagents necessary for carrying out the determination. The method developed has allowed to work with small amount of sample (microliters level), obtaining a detection limit equal to 2 µM in standard solution and 5 µM in the two chosen matrices, namely cream and a synthetic gel. In order to evaluate the applicability, the device was also tested for the analysis of two commercial products, obtaining satisfactory results in terms of sensitivity and repeatability. The accuracy has been also evaluated by inductively coupled plasma-mass spectrometry (ICP-MS) measurements, with high correlation between the two approaches

Made available in DSpace on 2022-05-01T11:07:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 This paper reports the versatile preparation of three-dimensional nanostructured porous platinum (3DnpPt) directly on the surface of a screen-printed electrode via a simple electrochemical method and its application for the simultaneous voltammetric determination of hesperidin (HES) and narirutin (NAR) in residual water from the citrus industry. The surface morphology of the electrode was characterized by field-emission scanning electron microscopy (FEG-SEM), electron diffraction X-ray (EDX), X-ray photoelectron spectroscopy (XPS), and by the electrochemical impedance spectroscopic (EIS) technique. The results obtained from the voltammetric studies conducted showed that the sensor has good electrocatalytic activity and selectivity for HES and NAR oxidation. The linear scanning voltammetry (LSV) technique employed yielded linear ranges of 10 µmol L−1 to 0.4 mmol L−1 and 10 µmol L−1 to 0.5 mmol L−1, with detection limits of 6.61 µmol L−1 and 0.21 µmol L−1, and amperometric sensitivity of 0.52 A L mol−1 and 0.79 A L mol−1 for HES and NAR, respectively. The proposed 3DnpPt-SPE sensor also exhibited good repeatability and high selectivity, as well as long-term stability. The sensor was successfully applied in residual water sample for the simultaneous quantification of HES and NAR where good recovery rates were obtained. Institute of Chemistry São Paulo State University (UNESP) Institute of Chemistry São Paulo State University (UNESP), 55 Prof. Francisco Degni St. Bioenergy Research Institute (IPBEN) São Paulo State University (UNESP), 55 Prof. Francisco Degni St. Institute of Chemistry São Paulo State University (UNESP) Institute of Chemistry São Paulo State University (UNESP), 55 Prof. Francisco Degni St. Bioenergy Research Institute (IPBEN) São Paulo State University (UNESP), 55 Prof. Francisco Degni St.

In this work, a novel portable and wireless intelligent electrochemical nanosensor was developed for the detection of 6,7-dihydroxycoumarin (6,7-DHC) using a modified screen-printed electrode (SPE). Black phosphorene (BP) nanosheets were prepared via exfoliation of black phosphorus nanoplates. The BP nanosheets were then mixed with nano-diamond (ND) to prepare ND@BP nanocomposites using the self-assembly method, achieving high environmental stability. The nanocomposite was characterized by SEM, TEM, Raman, XPS and XRD. The nanocomposite was used for the modification of SPE to improve its electrochemical performances. The nanosensor displayed a wide linear range of 0.01–450.0 μmol/L with a low detection limit of 0.003 μmol/L for 6,7-DHC analysis. The portable and wireless intelligent electrochemical nanosensor was applied to detect 6,7-DHC in real drug samples by the standard addition method with satisfactory recoveries, which extends the application of BP-based nanocomposite for electroanalysis.

Pesticides are largely used at worldwide level to improve food production, fulfilling the needs of the global population which is increasing year by year. Although pesticides are beneficial for crop production, their extensive use has serious consequences for the pollution of the produced food as well as for soil and groundwaters. Indeed, it is reported that 50% of sprayed pesticides reach different destinations other than their target species, including soil, surface waters, and groundwaters. For this reason, we developed a flower-like origami paper-based device for pesticides detection in aerosol phase for precision agriculture. In detail, the paper-based electrochemical platform detects paraoxon, 2,4-dichlorophenoxyacetic acid, and glyphosate at ppb levels by measuring their inhibitory activity towards three different enzymes namely butyrylcholinesterase, alkaline phosphatase, and peroxidase enzyme, respectively. This integrated electrochemical device is composed of three office paper-based screen-printed electrodes and filter paper-based pads loaded with enzymes and enzymatic substrates. The pesticide detection is carried out by measuring through chronoamperometric technique the initial and residual enzymatic activity by using a smartphone-assisted potentiostat and evaluating the percentage of inhibition, proportional to the amount of aerosolized pesticides. This paper-based device was able to detect the three classes of pesticides in aerosol phase with limits of detection equal to 30 ppb, 10 ppb, and 2 ppb, respectively for 2,4-D, glyphosate, and paraoxon.

In this work, novel platforms for paracetamol sensing were developed by the deposition of Bi2O3, Bi5O7NO3 and their heterostructures onto screen-printed carbon-paste electrodes. An easy and scalable solid state synthesis route was employed, and by setting the calcination temperatures at 500 °C and 525 °C we induced the formation of heterostructures of Bi2O3 and Bi5O7NO3. Cyclic voltammetry measurements highlighted that the heterostructure produced at 500 °C provided a significant enhancement in performance compared to the monophases of Bi2O and Bi5O7NO3, respectively. That heterostructure showed a mean peak-to-peak separation Ep of 411 mV and a sensitivity increment of up to 70% compared to bare electrodes. A computational study was also performed in order to evaluate the geometrical and kinetic parameters of representative clusters of bismuth oxide and subnitrate when they interact with paracetamol.

In addition to their antioxidant and antimicrobial action in functional foods, beverages, and in some dermato-cosmetic products, olive phenolic compounds are also recognized for their role in the prevention of diabetes and inflammation, treatment of heart disease and, consequently, of the numerous chronic diseases mediated by the free radicals. In recent years, attention has increased, in particular, regarding one of the most important compound in extra virgin olive oil (EVOO) having glycosidic structure, namely verbocoside, due to the existence in the literature of numerous studies demonstrating its remarkable contribution to the prophylaxis and treatment of various disorders of the human body. The purpose of this study was the qualitative and quantitative determination of verbascoside in commercial EVOOs from different regions by means of a newly developed sensor based on a screen-printed carbon electrode (SPCE) modified with graphene oxide (GPHOX), on the surface of which a pentapeptide was immobilized by means of glutaraldehyde as cross-linking agent. The modified electrode surface was investigated using both Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. This newly developed sensor has shown a high sensibility compared to the unmodified electrode, a low detection limit (LOD) of up to 9.38 × 10−8 M, and a wide linearity range between 0.1 µM and 10.55 µM. The applicability of the modified sensor was confirmed by detecting verbascoside in ten different EVOOs samples using the cyclic voltammetry (CV) method, with very good results. The validation of the electroanalytical method was performed by using the standard addition method with very good recoveries in the range of 97.48–103.77%.

Electrochemical (EC) biosensors are potentially useful tools for detection of DNA and RNA cancer biomarkers. Gold screen-printed electrodes (AuSPEs) are especially popular due to their easy manufacturing and surface modifications, making them useful candidates in biosensor fabrication. On the other hand, biosensors based on AuSPEs are still not often applied to clinical samples from cancer patients or compared with routine laboratory methods. Therefore, we tried to address these challenges by developing AuSPE-based biosensor for detection of DNA from two highly oncogenic types of human papillomavirus (HPV), HPV16 and HPV18, that cause cervical cancer in women. We coupled loop-mediated isothermal amplification (LAMP) of HPV DNA from fifteen clinical samples, with the capture of amplified products at the surface of the AuSPE and with final EC detection in a multielectrode format. We show excellent selectivity of designed primers and probes by comparing HPV-positive and HPV-negative cancer cell lines, and most importantly, very good sensitivity and specificity of the proposed biosensor for detection of clinical samples when compared to the PCR used as a gold standard. Electrochemical (EC) biosensors are potentially useful tools for detection of DNA and RNA cancer biomarkers. Gold screen-printed electrodes (AuSPEs) are especially popular due to their easy manufacturing and surface modifications, making them useful candidates in biosensor fabrication. On the other hand, biosensors based on AuSPEs are still not often applied to clinical samples from cancer patients or compared with routine laboratory methods. Therefore, we tried to address these challenges by developing AuSPE-based biosensor for detection of DNA from two highly oncogenic types of human papillomavirus (HPV), HPV16 and HPV18, that cause cervical cancer in women. We coupled loop-mediated isothermal amplification (LAMP) of HPV DNA from fifteen clinical samples, with the capture of amplified products at the surface of the AuSPE and with final EC detection in a multielectrode format. We show excellent selectivity of designed primers and probes by comparing HPV-positive and HPV-negative cancer cell lines, and most importantly, very good sensitivity and specificity of the proposed biosensor for detection of clinical samples when compared to the PCR used as a gold standard.

We developed a novel hydroxylamine sensor through the surface modification of screen-printed electrode (SPE) with NiCo2O4 nanoparticles/reduced graphene oxide (RGO) nanocomposite (NiCo2O4/RGO/SPE). We assessed the electrochemical response of hydroxylamine on the as-fabricated sensor, confirming the high electrocatalytic impact of hydroxylamine oxidation. The electrode produced sensitively responded to hydroxylamine under optimized conditions, with a low limit of detection (2.0 nM) and broad linear dynamic range (0.007–385.0 µM). The presence of NiCo2O4 combined with the modification of RGO resulted in sensitive detection and signal amplification of hydroxylamine oxidation. The proposed sensor was used to determine the existence of hydroxylamine in water samples.

A selective and facile voltammetric method based on titanium dioxide nanoparticles and Nafion (Nafion/TiO2 NPs) on the screen-printed electrode (SPE) was proposed for olopatadine determination. Followed by the synthesis of TiO2 nanoparticles, various methods, including high-resolution transmission electron microscopy (HR-TEM), ultraviolet-visible spectroscopy (UV-Vis), energy-dispersive X-ray (EDX) Raman spectrum, and electrochemical impedance spectroscopy (EIS) were utilized to characterize the nanomaterials. Nafion/TiO2 on the screen-printed electrode (NFN/TiO2/SPE) was used to determine olopatadine in concentration ranges of 0.01 to 0.07 and 0.07 to 14.6 µM with a limit of quantification as low as 7.0 nM, via differential pulse voltammetry technique. The NFN/TiO2/SPE offered a high-performance ability to determine olopatadine in the eye drop sample with satisfactory recovery data of 98.2–99.0 %. Also, the developed electrode showed good reproducibility, repeatability, and high selectivity features. The obtained results indicate that NFN/TiO2/SPE could be utilized as an appropriate candidate for electrochemical olopatadine sensing.

A SPEC/AuNPs/PMB modified electrode was prepared by electrodeposition and electro-polymerization. The electrochemical behavior of reduced nicotinamide adenine dinucleotide (NADH) on the surface of the modified electrode was studied by cyclic voltammetry. A certain amount of substrate and glutamate dehydrogenase (GLDH) were coated on the modified electrode to form a functional enzyme membrane. The ammonia nitrogen in the water sample could be calculated indirectly by measuring the consumption of NADH in the reaction. The results showed that the strength of electro-catalytic current signal was increased by two times, the catalytic oxidation potential was shifted to the left by 0.5 V, and the anti-interference ability of the sensor was enhanced. The optimum substrate concentration and enzyme loading were determined as 1.3 mM NADH, 28 mM α-Ketoglutarate and 2.0 U GLDH, respectively. The homemade ceramic heating plate controlled the working electrode to work at 37 °C. A pH compensation algorithm based on piecewise linear interpolation could reduce the measurement error to less than 3.29 μM. The biosensor exhibited good linearity in the range of 0~300 μM with a detection limit of 0.65 μM NH4+. Compared with standard Nessler’s method, the recoveries were 93.71~105.92%. The biosensor was found to be stable for at least 14 days when refrigerated and sealed at 4 °C.

Herein, we report on a new type of ethanol biosensor based on a screen-printed electrode modified with poly(allylamine hydrochloride). The alcohol dehydrogenase was immobilized on the surface of the sensor using the sol–gel matrix. Working parameters such as applied potential, pH, NAD+ concentration, storage conditions were optimized. A response range between 0.05 and 2 mM was found with a sensitivity of 13.45 ± 0.67 µA/mM·cm2 and a detection limit of 20 µM. The developed biosensor was used to detect ethanol in commercial beverages with good accuracy.

A copper film modified glassy carbon electrode (CuF/GCE) and a novel copper film with carbon nanotubes modified screen-printed electrode (CuF/CN/SPE) for anodic stripping voltammetric measurement of ultratrace levels of Cd(II) are presented. During the development of the research procedure, several main parameters were investigated and optimized. The optimal electroanalytical performance of the working electrodes was achieved in electrolyte 0.1 M HCl and 2 × 10−4 M Cu(II). The copper film modified glassy carbon electrode exhibited operation in the presence of dissolved oxygen with a calculated limit of detection of 1.7 × 10−10 M and 210 s accumulation time, repeatability with RSD of 4.2% (n = 5). In the case of copper film with carbon nanotubes modified screen-printed electrode limit of detection amounted 1.3 × 10−10 M for accumulation time of 210 s and with RSD of 4.5% (n = 5). The calibration curve has a linear range in the tested concentration of 5 × 10−10–5 × 10−7 M (r = 0.999) for CuF/GCE and 3 × 10−10–3 × 10−7 M (r = 0.999) for CuF/CN/SPE with 210 s accumulation time in both cases. The used electrodes enable trace determination of cadmium in different environmental water samples containing organic matrix. The validation of the proposed procedures was carried out through analysis certified reference materials: TM-25.5, SPS-SW1, and SPS-WW1.

Wearable sweat sensors offer the possibility of continuous real-time health monitoring of an individual at a low cost without invasion. A variety of sweat glucose sensors have been developed thus far to help diabetes patients frequently monitor blood glucose levels through sweat glucose as a surrogate marker. The present study demonstrates the development and characterization of a three-dimensional paper-based microfluidic electrochemical integrated device (3D PMED) for measuring glucose concentration in sweat in real-time via simple, non-invasive, capillary-action-based sample collection. The device was selective for glucose, and it detected glucose accurately in the clinically relevant range (0~2 mM) in an off-body setup. To the best of our knowledge, this is the first time NEXAR™ has been used for biosensing applications. Further, the developed glucose sensor has acceptable sensitivity of 16.8 µA/mM/cm2. Importantly, in an on-body setup, the device achieved a significant amperometric response to sweat glucose in a very short amount of time (a few seconds). With detailed investigations, this proof-of-concept study could help further the development of sensitive and selective sweat-based glucose sensing devices for real-time glucose monitoring in diabetes patients.

Oleuropein (OLEU) is an important indicator of the quality and authenticity of extra virgin olive oils (EVOO). Electrochemical sensors and biosensors for the detection of oleuropein can be used to test the adulteration of extra virgin olive oils. The present study aimed at the qualitative and quantitative determination of oleuropein in commercial EVOO samples by applying electrochemical techniques, cyclic voltammetry (CV) and square wave voltammetry (SWV). The sensing devices used were two newly constructed enzyme biosensors, supported on single-layer carbon-nanotube-modified carbon screen-printed electrode (SPE/SWCNT) on whose surface tyrosinase (SPE/SWCNT/Tyr) and laccase (SPE/SWCNT/Lac) were immobilized, respectively. The active surfaces of the two biosensors were analyzed and characterized by different methods, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR) and the results confirmed the efficient immobilization of the enzymes. SPE/SWCNT/Tyr was characterized by a low detection limit (LOD = 9.53 × 10−8 M) and a very good sensitivity (0.0718 μA·μM−1·cm−2) over a wide linearity range from 0.49 to 11.22 μM. The process occurring at the biosensor surface corresponds to kinetics (h = 0.90), and tyrosinase showed a high affinity towards OLEU. The tyrosinase-based biosensor was shown to have superior sensitive properties to the laccase-based one. Quantitative determination of OLEU in EVOOs was performed using SPE/SWCNT/Tyr and the results confirmed the presence of the compound in close amounts in the EVOOs analysed, proving that they have very good sensory properties.

In this work, Ni-Co layered double hydroxide (Ni–Co LDH) hollow nanostructures were synthesized and characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and Fourier-transform infrared spectroscopy (FT-IR) techniques. A screen-printed electrode (SPE) surface was modified with as-fabricated Ni–Co LDHs to achieve a new sensing platform for determination of sumatriptan. The electrochemical behavior of the Ni–Co LDH-modified SPE (Ni-CO LDH/SPE) for sumatriptan determination was investigated using voltammetric methods. Compared with bare SPE, the presence of Ni-Co LDH was effective in the enhancement of electron transport rate between the electrode and analyte, as well as in the significant reduction of the overpotential of sumatriptan oxidation. Differential pulse voltammetry (DPV) was applied to perform a quantitative analysis of sumatriptan. The linearity range was found to be between 0.01 and 435.0 μM. The limits of detection (LOD) and sensitivity were 0.002 ± 0.0001 μM and 0.1017 ± 0.0001 μA/μM, respectively. In addition, the performance of the Ni-CO LDH/SPE for the determination of sumatriptan in the presence of naproxen was studied. Simultaneous analysis of sumatriptan with naproxen showed well-separated peaks leading to a quick and selective analysis of sumatriptan. Furthermore, the practical applicability of the prepared Ni-CO LDH/SPE sensor was examined in pharmaceutical and biological samples with satisfactory recovery results.

This paper investigates the electrochemical behavior of p-aminophenol (PAP) on commercially available carbon screen-printed electrodes (CSPEs) and gold screen-printed electrodes (GSPEs) at neutral and basic pHs for the development of inexpensive immunoassays. The electrochemical oxidative signal from PAP results from its adsorption to the electrode. The formation of self-assembled monolayers on gold electrodes prevented PAP adsorption but also reduced its oxidative current, confirming that adsorption increases signal production. On bare electrodes, PAP adsorption results in oxidative current variability depending on the electroactive surface area of the screen-printed electrode. This variability could not be remedied by cleaning and reusing the same GSPE. Decreasing the PAP concentration to 3.8 μM greatly improved the consistency of the measurements, suggesting that the adsorption of PAP is concentration-dependent. Multiple PAP oxidations on the same electrode caused polymerization, limiting PAP in continuous monitoring applications. Infrared and Raman spectroscopy allow the distinction between adsorbed PAP and electropolymerized PAP on the surface of a gold wafer. The results from this study suggest that the use of PAP production in immunoassays with SPEs must be fine-tuned, and electrodes must be cleaned or disposed of between measurements.

In the recent years, point-of-care (POC) devices are continuously being demanded in the healthcare field due to the advantages of low-cost, easy-to-use, rapid and on-site detection. Among all kinds of POC devices, electrochemical biosensors are superior candidates because of the miniaturization simplicity, fast analysis and high selectivity nature to the sensing analytes. Traditional fabrication method of electrochemical biosensors by drop-casting process suffers from uneven thickness of functionalization layer and low reproducibility. Nowadays, inkjet printing has been a promising technique for biosensor fabrication. The merits, such as precise position, micro-dispensing, minimum contamination, less waste and potentiality for mass production as valuable features of inkjet printing, have attracted significant attention by researchers. However, there are still some issues that need to be addressed to promote inkjet printing technique for the POC applications. The most important problems include: 1. deficient investigation towards the effect of inkjet printing on the sensing element of biosensor, which is critical for the improvement of the sensor performance; 2. inadequate printing strategy for multi-functional layers printing, which is essential for the development of a stable and sensitive biosensor ; 3. lack of demonstration for the construction of inkjet-printed biosensor system towards point-of-care testing, which will be significant for the development of POC devices. To bridge these gaps, I firstly studied the influence of mechanical stress on the biological materials of enzymes based on the pressure wave propagation mechanism. Then, based on the first enzyme printing study, a reagentless enzyme-based biosensor was fabricated through a novel multi-layer printing strategy. In the end, to demonstrate the inkjet-printed biosensor for point-of-care analyte detection, a smartphone-supported biosensor system was constructed, consisting of a smartphone, an Android APP, a portable potentiostat and a functionalized scree-printed electrode (SPE) via inkjet printing. In general, the investigation of inkjet printing technique towards fabrication of POC devices opens a door for further research and development of an increasing variety of inkjet-printed POC devices. Through the work presented in this dissertation, I thoroughly investigated the effect of printing on enzymes, and substantially build upon the multi-layer printing strategy and biosensor system for inkjet-printed POC devices. The work in this research paves a way toward creating high performance, low-cost, easy-to-use and rapid POC diagnostic devices.

This work demonstrates the analysis of epinephrine (EP) and uric acid (UA) in a single drop (the volume of the test solution was only 50 µL) using a screen-printed carbon electrode (SPCE) sensor and square-wave voltammetry (SWV). The limit of detection, limit of quantification, linearity, accuracy, precision, and robustness were validated. The normality of the experimental data was tested and confirmed for both methods. Heteroscedasticity was checked by residual analysis followed by a statistical F-test. The latter was confirmed for both analytes. The low relative standard deviations (RSD) at all calibration points and repetitive slopes justified the use of a calibration curve, therefore, the standard addition methodology was avoided (the latter is common in electroanalysis, but time-consuming). Since the conditions for using an ordinary least squares (OLS) regression were not met, weighted linear regression (WLR) was used to improve the accuracy of the analytical results at low concentrations of the analytes. In this manner, the best weighted model was determined and used for the quantification. A comparison was made between the OLS and WLR methods to show the necessity of using the WLR method for EP and UA analysis. The newly developed and validated methods were also shown to be effective in the analysis of real samples. The content of EP in an EP auto-injector and UA in human urine was tested by employing the best weighted model. For EP and UA, the accuracy in terms of the average recovery value was 101.01% and 94.35%, and precision in terms of RSD was 5.65% and 2.75%, respectively. A new analytical methodology is presented that uses a low volume (a single drop), and it offers the advantage of electroanalysis for on-site analysis, where conventional chromatographic techniques cannot be easily employed. Furthermore, the developed technique has additional advantages in terms of speed, cost, and miniaturization.

Current work proposes an inimitable composite, with great electrical conductivity and quite enhanced surface area, (including conducting polymers (poly (cathechol)), Cu2O–carbon dots and green synthesized gold nanoparticles) for detecting acute carcinoembryonic antigen. At current work, the electropolymerization was offered instead of enzyme-catalyzed polymerization of poly (catechol). Four cost-effective electrochemical techniques (Differential Pulse Voltammetry, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Crono amperometry) were engaged to investigate aptasensors construction, immobilization, hybridization, sensitivity, selectivity, repeatability, long-term stability and real PCR sample detections. According to the data, the values of Ipeak is linearly related to the logarithm of the concentrations of carcinoembryonic antigen in the range from 1.0 pg mL-1 to 0.001 g mL-1, with a detection limit of 0.19 pg mL-1 for the target antigen (carcinoembryonic antigen). Keywords: conducting polymer, carbon quantum dots, green synthesize, elctrosynthesize, screen-printed electrode, carcinoembryonic antigen. Keywords: conducting polymer, carbon quantum dots, green synthesize, elctrosynthesize, screen-printed electrode, carcinoembryonic antigen

In this work, an electrochemical enzyme-linked oligonucleotide array to achieve simple and rapid multidetection of aflatoxin B1 (AFB1) is presented. The assay is based on a competitive format and disposable screen-printed cells (SPCs). Firstly, the electrodeposition of poly(aniline-anthranilic acid) copolymer (PANI-PAA) on graphite screen-printed working electrodes was performed by means of cyclic voltammetry (CV). Aflatoxin B1 conjugated with bovine serum albumin (AFB1-BSA) was then immobilized by covalent binding on PANI-PAA copolymer. After performing the affinity reaction between AFB1 and the biotinylated DNA-aptamer (apt-BIO), the solution was dropped on the modified SPCs and the competition was carried out. The biotinylated complexes formed onto the sensor surface were coupled with a streptavidin-alkaline phosphatase conjugate. 1-naphthyl phosphate was used as enzymatic substrate; the electroactive product was detected by differential pulse voltammetry (DPV). The response of the enzyme-linked oligonucleotide assay was signal-off, according to the competitive format. A dose-response curve was obtained between 0.1 ng mL−1 and 10 ng mL−1 and a limit of detection of 0.086 ng mL−1 was achieved. Finally, preliminary experiments in maize flour samples spiked with AFB1 were also performed.

Paper-based devices are always more gaining a relevant position in the field of sensors. The continuous demand for affordable, simple, sustainable, and portable devices, is making paper as the ideal basis towards the realization of analytical tools for the easy self-testing. In this work, we demonstrate, for the first time, the development of a disposable paper-based printed electroanalytical strip for reliable, rapid, and high-throughput detection of glutathione in blood. The detection is based on the thiol-disulfide exchange reaction, which produces a detectable compound easily oxidizable at a Prussian Blue/carbon black nanocomposite involving a favorable low-interference overpotential. This nanocomposite is mixed within a carbon-based conductive ink and successively screen-printed onto a wax-patterned filter paper. The employment of paper provides a reagent-free device, as a consequence of the reagents pre-loading within the testing area. After the experimental conditions have been optimized, glutathione has been detected up to 10 mM, with a detection limit of 60 μM, and a sensitivity of (0.102 ± 0.005) μA/mM. This sensor showed satisfactory repeatability (relative standard deviation equal to 10%, for detection of glutathione 1 mM), especially by considering the hand-made manufacturing process. The “real-world” applicability of this strip has been evaluated by quantifying blood glutathione at physiological levels and by recovery studies achieving satisfactory values.

Made available in DSpace on 2019-10-06T16:21:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-06-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A screen-printed disposable electrode made of carbon ink modified with CuPc, P6LC and Nafion film is proposed as a low-cost and simple analytical method for sensitive determination of 17β-estradiol in different matrices. The electrochemical behaviour of 17β-estradiol was evaluated by cyclic voltammetry in the potential range from 0 to 0.55 V at a scan rate of 0.05 V s −1 using 0.1 mol L −1 phosphate buffer (pH 5.0) as supporting electrolyte. One oxidation peak was observed during anodic potential scanning, at a potential of 0.39 V. Under optimized experimental conditions, using the differential pulse voltammetry (DPV) technique, the proposed sensor showed a linear concentration range for 17β-estradiol between 8.0 × 10 −8 to 7.3 × 10 −6 mol L −1 , and detection limit of 5.0 × 10 −9 mol L −1 . The CuPc-P6LC-Nafion/SPE F sensor showed good selectivity, sensitivity, stability, reproducibility, and repeatability; it is a low-cost disposable device and shows no interference in DPV experiments. The proposed sensor was successful when applied to environmental and synthetic urine samples, with recoveries close to 100%. Department of Analytical Chemistry Institute of Chemistry State University of São Paulo (UNESP) Department of Chemistry Federal University of São Carlos Department of Analytical Chemistry Institute of Chemistry State University of São Paulo (UNESP) CAPES: 0674/2018 CNPq: 160150/2015-9 FAPESP: 2014/50945-4 CNPq: 306650/2016-9 CNPq: 405546/2018-1 CNPq: 465571/2014-0

How to fabricate scale low-cost microfluidic device for detection of biomarkers owns a great requirement. Herein, it is for the first time reported that a new microfluidic device based on bonding polydimethylsiloxane microfluidic channels onto the substrate of a screen-printed electrode with coating glass solution was fabricated for electrochemical sensing of prostate-specific antigen (PSA). Compared to traditional microfabrication processes, this method is simple, fast, low cost, and also suitable for mass production. The prepared screen-printed electrode-based microfluidic device (CASPE-MFD) was used for the detection of the PSA in human serum. The prepared CASPE-MFD had a detection limit of 0.84 pg/mL (25.8 fM) and a good linearity with PSA concentration ranging from 0.001 to 10 ng/mL, which showed a great promise platform toward the development of miniaturized, low-cost electrochemical microfluidic device for use in human health, environmental monitoring, and other applications. Electronic supplementary material The online version of this article (10.1186/s11671-019-2857-6) contains supplementary material, which is available to authorized users.

The bacterial photosynthetic reaction centre (RC) is a membrane spanning protein that, upon illumination, promotes the reduction of a ubiquinone molecule withdrawing electrons from cytochrome c2. This photo-activated reaction has been often exploited, in suitably designed photoelectrochemical cells, to generate photocurrents sustained by the reduction at the working electrode of the photo-oxidized electron donor or by the oxidation of the electron acceptor. In this work we have explored in more detail the factors affecting the photocurrent generation in commercially available screen-printed electrochemical cells containing an electrolyte solution where RC proteins and suitable mediators are solubilized. In particular, the role of the applied potential and the influence of concentration and structure of acceptor and donor molecules have been assessed. We show that efficient generation of cathodic photocurrents in a three electrode configuration occurs at an applied potential of 0.0 V versus quasi-ref Ag (the open circuit potential of the system measured in the dark) in presence of ferrocenemethanol and decylubiquinone, which proved to guarantee high performances as electron donor and acceptor respectively. Moreover, we employed a set of differential equations, describing reaction and diffusion processes, for modelling with high accuracy the chronoamperometry profiles recorded at variable RC concentrations. This model allowed us to estimate the kinetic parameters relevant to the chemical and electrochemical reactions triggered by light and to get a snapshot of the electrolyte composition in the bulk and electrode surroundings at different times from the light exposure. The characteristic time course of the photocurrent, showing a fast rise to a peak value followed by a slower decay, has been therefore explained as the result of the strict interconnection between the dynamical processes involved.

An electrochemical method for the determination of the catalytic activity of L-asparaginase (ASNase) from Erwinia carotovora was proposed. Our approach is based on the electrooxidation of amino acids from L-asparaginase polypeptide backbones. The electrochemical behavior of ASNase on electrodes obtained by screen-printing modified with single-wall carbon nanotubes (SPE/SWCNTs) as sensing elements demonstrated a broad oxidation peak at 0.5–0.6 V centered at 0.531 ± 0.010 V. We have shown that in the presence of the substrate L-asparagine, the oxidation current of the enzyme was reduced in a concentration-dependent manner. The specificity of electrochemical analysis was confirmed in experiments with glycine, an amino acid with no substrate activity on ASNase and does not reduce the oxidation peak of L-asparaginase. The addition of glycine did not significantly influence the amplitude of the oxidation current. The innovative aspects of the proposed electrochemical sensor are the direct monitoring of ASNase catalytic activity and a reagentless approach, which does not require additional reagents or labels.

Pseudomonas aeruginosa is a ubiquitously distributed soil and water bacterium and is considered an opportunistic pathogen in hospitals. In cystic fibrosis patients, for example, infections with P. aeruginosa can be severe and often lead to chronic or even fatal pneumonia. Therefore, rapid detection and further identification are of major importance in hospital hygiene and infection control. This work shows the electrochemical properties of five P. aeruginosa key metabolites considering their potential use as specific signaling agents in an electrochemical sensor system. The pure solutes of pyocyanin (PYO), Pseudomonas quinolone signal (PQS), pyochelin (PCH), 2-heptyl-4-hydroxyquinoline (HHQ), and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) were analyzed by different electrochemical techniques (cyclic and square wave voltammetry) and measured using a Gamry Reference 600+ potentiostat. Screen-printed electrodes (DropSens DRP110; carbon working and counter, silver reference electrode) were used to determine signal specificities, detection limits, as well as pH dependencies of the substances. All of the compounds were electrochemically inducible with well-separated oxidation and/or reduction peaks at specific peak potentials relative to the reference electrode. Additionally, all analytes exhibited linear concentration dependency in ranges classically reported in the literature. The demonstration of these properties is a promising step toward direct multiplexed detection of P. aeruginosa in environmental and clinical samples and thus, can make a significant contribution to public health and safety.

Smart monitoring has been studied and developed in recent years to create faster, cheaper, and more user-friendly on-site methods. The present study describes an innovative technology for investigative monitoring of heavy metal pollution (Cu and Pb) in surface water. It is composed of an autonomous surface vehicle capable of semiautonomous driving and equipped with a microfluidic device for detection of heavy metals. Detection is based on the method of square wave anodic stripping voltammetry using carbon-based screen-printed electrodes (SPEs). The focus of this work was to validate the ability of the integrated system to perform on-site detection of heavy metal pollution plumes in river catchments. This scenario was simulated in laboratory experiments. The main performance characteristics of the system, which was evaluated based on ISO 15839 were measurement bias (Pb 75%, Cu 65%), reproducibility (in terms of relative standard deviation: Pb 11–18%, Cu 6–10%) and the limit of detection (4 µg/L for Pb and 7 µg/L for Cu). The lowest detectable change (LDC), which is an important performance characteristic for this application, was estimated to be 4–5 µg/L for Pb and 6–7 µg/L for Cu. The life span of an SPE averaged 39 measurements per day, which is considered sufficient for intended monitoring campaigns. This work demonstrated the suitability of the integrated system for on-site detection of Pb and Cu emissions from large and medium urban areas discharging into small water bodies., Open access funding provided by University of Natural Resources and Life Sciences Vienna (BOKU). The research leading to the presented results received funding from the research project INTCATCH 2020, “Development and application of Novel, Integrated Tools for monitoring and managing Catchments” supported by the European Union’s Horizon 2020 research and innovation programme, under the grant agreement No. 689341. The ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa program of the Spanish Ministry of Economy, Industry, and Competitiveness (MINECO, Grant No. SEV-2017–0706).

Phosphate is considered to be an important biogenic element and responsible for eutrophication in aquatic ecosystems, existing in both dissolved and absorbed forms. Due to the complex matrix of coastal seawater, a high sensitivity and anti-interference method for phosphate detection is required for environmental protection. In this study, a novel electrochemical method was proposed based on reduced graphene oxide-ordered mesoporous carbon screen-printed electrode (rGO-OMC/SPE) analysis, allowing sensitivity and reliable determination of phosphate in turbid coastal waters. Combining the good absorption capacity of OMC with the excellent electroconductivity of rGO, the fabricated electrode exhibits improved signal responses, enhanced by up to 43-fold. The platform was evaluated using turbidity interference test with good recovery percentages comprised between 96% and 105% in different phosphate concentration, and salinity interference test between 92% and 105%, respectively. A linear range from 0.2 to 150 μM phosphate was achieved, with a detection limit of 0.05 μM (s/n = 3). The fabricated platform was successfully used for on-site analysis of phosphate in turbid coastal waters. This reliable and effective method for the analysis of phosphate in turbid coastal waters allows for sensitivity and anti-interference determination, while also representing a significant step towards comprehensive and convenient analysis of phosphorus species.

Made available in DSpace on 2021-06-25T12:29:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) PROJ. AUX/PE/PROEX The present work reports the development of a sensitive and selective method for ethinylestradiol detection using screen-printed electrode (SPE) modified with functionalized graphene (FG), graphene quantum dots (GQDs) and magnetic nanoparticles coated with molecularly imprinted polymers (mag@MIP). The performance of the mag@MIP sensor was compared with that of a non-molecularly imprinted sensor (mag@NIP). Chemical and physical characterizations of the mag@NIP and mag@MIP sensors were performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) techniques. The electrochemical behavior of the electrodes investigated, which included (mag@MIP)-GQDs-FG-NF/SPE, (mag@NIP)-GQDs-FG-NF/SPE, GQDs-FG-NF/SPE and FG-NF/SPE, was evaluated by cyclic voltammetry. The results obtained show a significant increase in peak current magnitude for (mag@MIP)-GQDs-FG-NF/SPE. Using square wave voltammetry experiments, the efficiency of the (mag@MIP)-GQDs-FG-NF/SPE sensor was also tested under optimized conditions. The linear response range obtained for ethinylestradiol concentration was 10 nmol L-1 to 2.5 mu mol L-1, with limit of detection of 2.6 nmol L-1. The analytical signal of the (mag@MIP)-GQDs-FG-NF/SPE sensor suffered no interference from different compounds and the sensor exhibited good repeatability. The proposed sensor was successfully applied for ethynilestradiol detection in river water, serum and urine samples, where recovery rates between 96 to 105% and 97-104% were obtained for environmental and biological samples, respectively. Univ Fed Sao Carlos, Dept Chem, Rod Washington Luis Km 235,POB 676, BR-13560970 Sao Carlos, SP, Brazil State Univ Sao Paulo, Inst Chem, Dept Analyt Chem, BR-14801970 Araraquara, SP, Brazil INCT DATREM, BR-14801970 Araraquara, SP, Brazil State Univ Sao Paulo, Inst Chem, Dept Analyt Chem, BR-14801970 Araraquara, SP, Brazil CAPES: 001 CNPq: 150184/2019-0 CNPq: 405546/2018-1 CNPq: 408050/2018-7 FAPESP: 2017/10118-0 FAPESP: 2016/10012-4 FAPESP: 2019/00677-7 FAPESP: 2020/01050-5 PROJ. AUX/PE/PROEX: 0674/2018 CAPES

Submitted by Sheila MONTEIRO (sheila.monteiro@ufma.br) on 2021-04-15T12:44:36Z No. of bitstreams: 1 WILLIAN-VELOSO.pdf: 2136971 bytes, checksum: 722d9cf19366bb1ea4fdb85a660c82e4 (MD5) Made available in DSpace on 2021-04-15T12:44:36Z (GMT). No. of bitstreams: 1 WILLIAN-VELOSO.pdf: 2136971 bytes, checksum: 722d9cf19366bb1ea4fdb85a660c82e4 (MD5) Previous issue date: 2021-02-15 Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão - FAPEMA Macrolides are a group of drugs used in the treatment of infectious diseases, both in human and veterinary medicine. Currently these molecules are among the four most used antimicrobials in the world. The presence of these compounds in inadequate concentrations can be a trigger to a series of problems both directly and indirectly, such as allergic reactions in sensitive individuals and the emergence of resistant strains of bacteria. This work investigated the potential application of carbon black Super P as a modifier for screen-printed carbon electrodes (SPCE’s) in a Batch Injection Analysis system with Amperometric detection (BIA-AMP) to determine four macrolide antibiotics (erythromycin, azithromycin, clarithromycin and roxithromycin). Previous modifier’s parameters optimization have shown that the ideal carbon black concentration and suspension volume are, respectively, 7.0 mg mL-1 and 10 µL. Initial voltammetric studies carried out with erythromycin, a prototype compound, demonstrated the redox process characteristics of this class of antibiotics. In addition, it was also possible to define the support electrolyte (Sörensen buffer) and pH of the medium (7.8) ideal for the development of the method. Hydrodynamic voltamograms respective to each antibiotics were constructed to define the work potential used in all amperometric measurements. BIA system parameters optimization showed ideal values respectively equal to: injection volume (100 µL) and dispensing speed (100 µL s-1). Under these conditions, a precision study was carried out to obtain the DPR value of 0.983% (n = 25) and an analytical frequency estimated at 125 injections per hour. The proposed method presented a linear range of 1 - 190 µmol L-1 for erythromycin (R = 0.999), azithromycin (R = 0.998) and roxithromycin (R = 0.999) and 10 - 190 µmol L-1 for clarithromycin (R = 0.998). Thus, the method was applied to determine these four compounds in a water sample, collected in a pond located on the Federal University of Maranhão campus, and in pharmaceutical samples. Addition-recovery studies were performed on both samples, in which recovery values between 96.0 and 104.7% were obtained for the tests carried out on an environmental sample and between 95.6 and 105.1% for the tests carried out on medicine samples, proving the good accuracy of the method, which proved to be a verry attractive alternative from an economic and portability point of view. Os macrolídeos são um grupo de medicamentos empregados no tratamento de doenças infeciosas, tanto na medicina humana quanto veterinária, estando atualmente entre os quatro antimicrobianos mais utilizados no mundo. A presença desses compostos em concentrações inadequadas pode desencadear uma série de problemas diretos, como reações alérgicas em indivíduos sensíveis, e de forma indireta, com o surgimento de cepas de bactérias resistentes. No presente trabalho foi investigado a potencialidade de aplicação do carbon black Super P como modificante para eletrodos impressos de carbono (SPCE’s) em sistema de Análise por Injeção em Batelada com detecção Amperométrica (BIA-AMP) para determinação de quatro antibióticos macrolídeos (eritromicina, azitromicina, claritromicina e roxitromicina). Otimizações prévias do modificante mostraram que a concentração de carbon black e o volume do modificante ideais são, respectivamente, 7,0 mg mL-1 e 10 µL. O estudo voltamétrico inicial realizado com a eritromicina, composto protótipo para os demais, demonstrou as características do processo redox desta classe de antibióticos, além disso, por meio deste pôde-se definir o eletrólito de suporte (tampão Sörensen) e o pH do meio (7,8) ideais para o desenvolvimento do método. Voltamogramas hidrodinâmicos foram construídos com cada um dos antibióticos para definição do potencial de trabalho a ser utilizado nas medidas amperométricas. Foram otimizados os parâmetros relacionados ao sistema BIA, e os valores ideais obtidos para cada um deles foi: volume de injeção (100 µL) e velocidade de dispensa (100 µL s-1). Nessas condições, um estudo de repetibilidade foi realizado obtendo-se valor de DPR de 0,983 % (n = 25) e uma frequência analítica estimada em 125 injeções h-1. O método apresentou faixa linear de 1 – 190 µmol L-1 para eritromicina (R = 0,999), azitromicina (R = 0,998) e roxitromicina (R = 0,999) e de 10 – 190 µmol L-1 para a claritromicina (R = 0,998). Dessa forma, o método foi aplicado na determinação desses quatro compostos em amostra ambiental de água, coletada em uma lagoa localizada no campus da Universidade Federal do Maranhão, e em amostras farmacêuticas. Testes de adição e recuperação foram realizados em ambas as amostras, nos quais se obteve valores de recuperação entre 96,0 e 104,7% para os testes realizados em amostra ambiental e entre 95,6 e 105,1% para os testes realizados em amostras de medicamentos, comprovando a boa exatidão do método, o qual, além disso, mostrou-se uma alternativa bastante atraente do ponto de vista econômico e de portabilidade.