Disposable Electrodes Research Articles

Synthetic Biology Toolbox, Including a Single-Plasmid CRISPR-Cas9 System to Biologically Engineer the Electrogenic, Metal-Resistant Bacterium Cupriavidus metallidurans CH34.

Cupriavidus metallidurans CH34 exhibits extraordinary metabolic versatility, including chemolithoautotrophic growth; degradation of BTEX (benzene, toluene, ethylbenzene, xylene); high resistance to numerous metals; biomineralization of gold, platinum, silver, and uranium; and accumulation of polyhydroxybutyrate (PHB). These qualities make it a valuable host for biotechnological applications such as bioremediation, bioprocessing, and the generation of bioelectricity in microbial fuel cells (MFCs). However, the lack of genetic tools for strain development and studying its fundamental physiology represents a bottleneck to boosting its commercial applications. In this study, inducible and constitutive promoter libraries were built and characterized, providing the first comprehensive list of biological parts that can be used to regulate protein expression and optimize the CRISPR-Cas9 genome editing tools for this host. A single-plasmid CRISPR-Cas9 system that can be delivered by both conjugation and electroporation was developed, and its efficiency was demonstrated by successfully targeting the pyrE locus. The CRISPR-Cas9 system was next used to target candidate genes encoding type IV pili, hypothesized by us to be involved in extracellular electron transfer (EET) in this organism. Single and double deletion strains (ΔpilA, ΔpilE, and ΔpilAE) were successfully generated. Additionally, the CRISPR-Cas9 tool was validated for constructing genomic insertions (ΔpilAE::gfp and ΔpilAE::λPrgfp). Finally, as type IV pili are believed to play an important role in extracellular electron transfer to solid surfaces, C. metallidurans CH34 ΔpilAE was further studied by means of cyclic voltammetry using disposable screen-printed carbon electrodes. Under these conditions, we demonstrated that C. metallidurans CH34 could generate extracellular currents; however, no difference in the intensity of the current peaks was found in the ΔpilAE double deletion strain when compared to the wild type. This finding suggests that the deleted type IV pili candidate genes are not involved in extracellular electron transfer under these conditions. Nevertheless, these experiments revealed the presence of different redox centers likely to be involved in both mediated electron transfer (MET) and direct electron transfer (DET), the first interpretation of extracellular electron transfer mechanisms in C. metallidurans CH34.

A Deep Learning Approach to Organic Pollutants Classification Using Voltammetry.

This paper proposes a deep leaning technique for accurate detection and reliable classification of organic pollutants in water. The pollutants are detected by means of cyclic voltammetry characterizations made by using low-cost disposable screen-printed electrodes. The paper demonstrates the possibility of strongly improving the detection of such platforms by modifying them with nanomaterials. The classification is addressed by using a deep learning approach with convolutional neural networks. To this end, the results of the voltammetry analysis are transformed into equivalent RGB images by means of Gramian angular field transformations. The proposed technique is applied to the detection and classification of hydroquinone and benzoquinone, which are particularly challenging since these two pollutants have a similar electroactivity and thus the voltammetry curves exhibit overlapping peaks. The modification of electrodes by carbon nanotubes improves the sensitivity of a factor of about ×25, whereas the convolution neural network after Gramian transformation correctly classifies 100% of the experiments.

Sequential Injection Amperometric System Coupling with Bioreactor for In-Line Glucose Monitoring in Cell Culture Application

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.

Flicker electroretinogram in newborn infants

PurposeTo develop and validate a flicker electroretinogram (ERG) protocol in term-born neonates as a potential tool for assessing preterm infants at risk of developing retinopathy of prematurity.MethodsA custom flicker ERG protocol was developed for use with the hand-held RETeval® electrophysiology device. Feasibility of measuring flicker ERG through closed eyelids and without mydriasis was established in a pilot study enabling optimisation of the test protocol. Following this, healthy term-born neonates (gestational age 37–42 weeks) were recruited at the Neonatology clinic of the University Hospital Zurich. Flicker ERG recordings were performed using proprietary disposable skin electrodes during the first four days of life when the infants were sleeping. Flicker stimuli were presented at 28.3 Hz for a stimulus series at 3, 6, 12, 30, and 50 cd·s/m2, with two measurements at each stimulus level. Results were analysed offline. Flicker ERG peak times and amplitudes were derived from the averaged measurements per stimulus level for each subject.Results28 term-born neonates were included in the analysis. All infants tolerated the testing procedure well. Flicker ERG recording was achieved in all subjects with reproducible flicker ERG waveforms for 30 and 50 cd·s/m2 stimuli. Reproducible ERGs were recorded in the majority of infants for the weaker stimuli (with detectable ERGs in 20/28, 25/28, and 27/28 at 3, 6, and 12 cd·s/m2, respectively). Flicker ERG amplitudes increased with increasing stimulus strength, with peak times concurrently decreasing slightly.ConclusionFlicker ERG recording is feasible and reliably recorded in sleeping neonates through closed eyelids using skin electrodes and without mydriasis. Flicker ERG amplitude decreases for lower luminance flicker but remains detectable for 3 cd·s/m2 flicker in the majority of healthy term-born neonates. These data provide a basis to study retinal function in premature infants using this protocol.

Capacitive nanobiosensing of β-1,4-galactosyltransferase-V colorectal cancer biomarker

β-1,4-GalT-V is an enzyme with glycosyltransferase activity that glycosylates proteins and synthesizes the lactosylceramide sphingolipid in the Golgi apparatus. Colorectal cancer (CRC) tumor cells produce these biomolecules in high concentrations concerning normal cells, releasing them into the blood serum. Hence, β-1,4-GalT-V glycoprotein has emerged as a promising CRC biomarker, and its detection opens opportunities for the diagnosis/prognosis of CRC. We report the first capacitive nanobiosensor for the detection of β-1,4-GalT-V based on disposable screen-printed carbon electrodes (SPCEs) nanostructured with gold nanorods (AuNRs) and the Prussian blue (PrB) redox-active compound. AuNRs increased the SPCE surface area for antibody immobilization by physical adsorption and promoted the deposition of PrB onto the SPCE surface. Antibody-glycoprotein molecular biorecognition event onto the SPCE/AuNRs/PrB surface perturbed the PrB redox density-of-states and hence redox capacitance (Cμ̅). We found that changes in the inverse of Cμ̅ correlated well with the increasing concentrations of β-1,4-GalT-V in the linear range from 50 to 400 fM with a sensitivity of 1.5 µF fM-1 cm-2 and a limit of detection of 20 fM. The nanobiosensor detected the β-1,4-GalT-V glycoprotein from raw human serum samples with high specificity, ultrasensitivity, and reagentless label-free electrochemical transduction. The nanobiosensor could be applied as a CRC diagnosis/prognosis tool in a decentralized setting, with minimal patient sample manipulation and rapid response.

Sulfur-doped Graphene-coated Graphite Foil as Disposable Electrodes for Electrochemical Sensing

Sulfur-doped Graphene-coated Graphite Foil as Disposable Electrodes for Electrochemical Sensing

Azure A embedded in carbon dots as NADH electrocatalyst: Development of a glutamate electrochemical biosensor

Carbon nanodots modified with azure A (AA-CDs) have been synthesized and applied as redox mediator of bioelectrocatalytic reactions. A deep characterization of AA-CDs nanomaterial has been carried out, proving the covalent attachment of azure A molecules into the carbon dots nanostructure. Disposable screen-printed carbon electrodes (SPCE) have been modified with AA-CDs, through the action of chitosan polymer (Chit-AA-CDs/SPCE). The Chit-AA-CDs/SPCE electrocatalytic activity towards the oxidation of NADH has been proved, obtaining excellent results regarding the low oxidation potential achieved (−0.15 V vs. Ag) and low detection and quantification limits (LOD and LOQ) for NADH, 16 and 53 µM, respectively. The developed electrochemical platform has been applied for the construction of a glutamate biosensor by immobilizing L-glutamic dehydrogenase (GLDH/Chit-AA-CDs/SPCE). The morphology of GLDH/Chit-AA-CDs/SPCE platform was analysed by AFM at each different step of the electrode modification process. The resulting biosensing platform is capable of detect NADH enzymatically generated by GLDH in the presence of glutamate and NAD+. Good analytical parameters were obtained for glutamate analysis using GLDH/Chit-AA-CDs/SPCE, as LOD and LOQ of 3.3 and 11 µM, respectively. The biosensor has been successfully applied to the analysis of food and biological samples.

ЦЕНТИЛЬНЫЙ МЕТОД В ХАРАКТЕРИСТИКЕ АНТРОПОМЕТРИЧЕСКИХ И БИОИМПЕДАНСОМЕТРИЧЕСКИХ ПАРАМЕТРОВ ЮНОШЕЙ ЯКУТИИ

Assessing the level of physical development of individual population groups is necessary for the formation of a personalized approach in medicine. The purpose of the study was to develop centile tables on anthropometric and bioimpedance parameters of young men in the Sakha Republic (Yakutia). The young men of the Yakut ethnicity aged 17-21 years were examined; under the age classification of human ontogenesis, they belonged to the youth age period. Anthropometric measurements were carried out according to the classical method of V.V. Bunak. The length and weight of the body, the girths of the chest, waist and buttocks are determined. Absolute and relative values of the main components of the body were determined by bioimpedance measurement (BIA). The analyzer of body composition and balance of water sectors of the body ABC – 01 “Medass” was used. Measurements were carried out according to a standard four-electrode scheme with the attachment of disposable electrodes (Shiller Biotabs® with Ag/AgCl coating) in the area of the wrist and ankle joints. The obtained material was processed by the method of variation statistics using the SPSS 17.0 application software package. To assess the distribution of anthropometric and bioimpedance indicators of young men in Yakutia in percentage terms, a centile analysis was carried out. The cents P5, P10, P25, P75, P90, P95 were applied. The study revealed regional peculiarities of overall dimensions and body composition of young Yakut men. Lower indicators of body weight, fat mass, active cell mass and musculoskeletal mass of Yakuts were established in comparison with the data of young men from other regions of Russia. Centile tables of parameters of body length and weight, girth dimensions of the chest, waist and buttocks, body mass index, bioimpedance indicators of fat mass, active cell mass, musculoskeletal mass, lean mass of Yakut boys were developed. These tables allow us to assess the level of physical development of young Yakut men for the formation of a personalized approach in medicine. The results obtained can be used in conducting comparative analyses with the indicators of young men living in other regions.

Raman spectroelectrochemical determination of clopyralid in tap water

Clopyralid is a common herbicide used all around the world that can be dissolved in the rain stream and accumulate in underground water with the potential threat of reaching drinking water. Many methodologies have been proposed to perform quantitative analysis of this compound but, to this day, no Raman detection of clopyralid has been carried out. Here, a novel methodology to quantify clopyralid, based on Electrochemical Surface Oxidation-Enhanced Raman Scattering (EC-SOERS), is developed, using disposable silver screen-printed electrodes as substrate. The optimization of the electrolytic media is carried out, searching for the conditions where a maximum Raman enhancement is obtained. Moreover, a study about the effect of various interfering compounds, which could be present in water, on the clopyralid Raman response is performed. The results demonstrate that the presented methodology allows the determination of clopyralid in the micromolar range in tap water without any purification or preconcentration step, requiring few minutes to perform the measurement of each sample.

A green route for lignin-derived graphene electrodes: A disposable platform for electrochemical biosensors

The tremendous growth of disposable electrode-based portable devices for point-of-care testing requires mass production of disposable electrodes in a low-cost and sustainable manner. Here, we demonstrate a green route for the conversion of biomass lignin, patterning, and reduction of the lignin-derived graphene electrodes by sequential laser lithography, water lift-off and sodium borohydride (NaBH4) treatment, and their use for electrochemical lactate biosensors. Energy-saving and localized laser lithography converted the aromatic ring-rich lignin into porous laser-induced graphene (LIG). The conductivity and attachment of the LIG to the substrate were optimized in a factorial experiment with laser power and scan speed as variables. Characterization results revealed the conversion of partial heteroatoms (e.g., Na, S, O) into granular inorganic compounds on the LIG surface under laser treatment. Water was used as an eco-friendly solvent for the patterning of the LIG (P-LIG) by a lift-off process, where the inorganic residues and un-reacted lignin were dissolved, exposing the macro-/micro-pores in the P-LIG. NaBH4 induced a reduction of the P-LIG (P-rLIG) resulting in improved electrochemical kinetics with lower charge transfer resistance (27.3 Ω) compared to the LIG (248.1 Ω) and the P-LIG (61.4 Ω). The porous P-rLIG served as a 3D electrode for the deposition of Prussian blue and lactate oxidase for disposable electrochemical lactate biosensors, delivering a good analytical performance towards lactate detection with a linear range up to 16 mM and a high sensitivity (1.21 μA mM−1). These lignin-derived disposable electrodes, utilizing renewable resources together with low-energy consumption fabrication and patterning, may contribute to the sustainable manufacturing of biosensors for point-of-care and point-of-use applications.

Development of New Simple Compositions of Silver Inks for the Preparation of Pseudo-Reference Electrodes.

Silver materials are known to present excellent properties, such as high electrical and thermal conductivity as well as chemical stability. Silver-based inks have drawn a lot of attention for being compatible with various substrates, which can be used in the production uniform and stable pseudo-reference electrodes with low curing temperatures. Furthermore, the interest in the use of disposable electrodes has been increasing due to the low cost and the possibility of their use in point-of-care and point-of-need situations. Thus, in this work, two new inks were developed using Ag as conductive material and colorless polymers (nail polish (NP) and shellac (SL)), and applied to different substrates (screen-printed electrodes, acetate sheets, and 3D-printed electrodes) to verify the performance of the proposed inks. Measurements attained with open circuit potential (OCP) attested to the stability of the potential of the pseudo-reference proposed for 1 h. Analytical curves for β-estradiol were also obtained using the devices prepared with the proposed inks as pseudo-references electrodes, which presented satisfactory results concerning the potential stability (RSD < 2.6%). These inks are simple to prepare and present great alternatives for the development of pseudo-reference electrodes useful in the construction of disposable electrochemical systems.

Optimization of electrochemical analysis for signal amplification in gold nanoparticle-probed immunoassays

Biosensing systems with integrated nanomaterials have revolutionized technological advancements in recent decades. Gold nanoparticles (AuNPs) in particular have been widely used in electrochemical sensors owing to their stability and unique characteristics. Previously, we developed biosensors that utilize the redox activity of AuNPs. In recent years, unique advances have been made by combination with other nanomaterials. However, information regarding the optimal electrochemical measurement conditions and the relationship between the electrode surface and AuNPs remain unknown. In this study, we quantitatively determined kinetic parameters such as the diffusion coefficient and electron transfer rate in the redox reaction of AuNPs on disposable screen-printed electrodes. Furthermore, the relationship between the addition of antibodies and blocking agents and the decrease in the determined parameters could be deduced. This is useful for the determination of the fine balance between the sensitivity and specificity. Limits of detection (LOD) were obtained as 5.0 fmol/L (M) for AuNPs on a bare electrode, 0.1 pM for AuNPs on an antibody-modified electrodes, and 9.3 pM for AuNPs after immunoassay, allowing discussion of the given principle limits and actual biosensor performance. Under optimal conditions, the electrochemical biosensor achieved nearly two-fold signal amplification using a reduction current after AuNPs oxidation. These findings will allow the investigation of the kinetics of AuNPs on electrodes consisting of different materials to further elucidate the framework for improved sensitivity.

Modification of BIOFISH 300 HIS for Determination of Histamine in Fish and Fish Products: AOAC Performance Tested MethodSM 051604.

The BIOFISH 300 HIS method for the quantification of histamine in fish and fish products was validated by the AOAC Research Institute and granted Performance Tested MethodSM certification in 2016. The method is based on the use of an electrochemical reader (BIOFISH 300 device) together with disposable gold electrodes (Biotest) modified with a specific enzyme that oxidizes the histamine molecules and produces a detectable and quantifiable electric current signal. It was validated for raw fish (tuna, mackerel, sardine, and anchovy), cooked fish (tuna), canned fish (tuna in water, tuna in oil, mackerel in tomato sauce, and pickled sardine), and salted fish (canned salted anchovy). The validated ranges were 30-150 mg/kg histamine for canned salted anchovy and 10-200 mg/kg histamine for all other matrices. The objective of the present report is to validate some method modifications, namely the use of a new reader (BIOFISH 3000), the inclusion of new quantification ranges, new matrixes in the certified claims, a histamine reference solution (Verifying Solution) that will enable the user to perform a system verification, and also the inclusion of the kit ASC1-10 for the elimination of ascorbic acid from sample extract. New quantification ranges can be obtained by diluting the sample appropriately into the measurement cuvette, thereby adjusting the concentration to the internal calibration range of the device. New matrixes such as fish meal, preserved salted anchovy, and fish with added ascorbic acid were validated. The new digitalized reader enables new functionalities such as the use of an intuitive app and cloud storage of the results, with no changes in the data acquisition and processing. As the use of the new reader does not imply any change at the electrochemical readout level, all assays were performed using the BIOFISH 3000 device. The method was shown to be linear in all the quantitation ranges configured. Accuracy and recovery studies over a wide range of matrixes showed that the method yields comparable results to the reference method used. Stability and product consistency testing of kit components demonstrated that the system produces accurate results when expiration dates from the manufacturer are met. All modifications made to the BIOFISH 300 HIS method, PTM 051604, have been validated satisfactorily, under criteria of the AOAC Research Institute. The use of the BIOFISH 300/3000 HIS method is ideal as a routine histamine control method for the fish industry. After a simple aqueous extraction of the sample, results are obtained in less than 3 minutes. All data generated by the new BIO3000 biosensor are sent to a web platform, allowing new functionalities to the user. All these technical capabilities represent a competitive advantage over other existing technologies.

Rapid electrochemical detection of Mycobacterium tuberculosis in sputum by measuring Ag85 activity with disposable carbon sensors

An electrochemical assay for the detection of the enzymatic activity of the antigen 85 (Ag85) tuberculosis (TB) biomarker was developed and evaluated for the qualitative detection of Mycobacterium tuberculosis in decontaminated sputum. For this purpose, the electroactive properties of both synthetic p-aminophenyl-6-O-octanoyl-3-d-glucopyranoside (p-APOG) substrate and p-aminophenyl-6-3-d-glucopyranoside (p-APG) product released after the removal of the octanoyl fatty acid by the Ag85 were investigated with disposable carbon screen-printed electrodes by cyclic voltammetry. Since specific anodic responses were obtained for the p-APOG substrate and the p-APG product, the intensity of the oxidation peak of the p-APG (E = + 0.35 V vs. Ag/AgCl) was selected as the analytical response for the detection of the Ag85 acyltransferase activity. Once the proof of concept of the Ag85 electrochemical assay was validated with a commercially-available Ag85B protein, its specificity was further assessed by analyzing pure cultures of various bacteria including tuberculous and non-tuberculous mycobacteria as well as different species found in patients' sputum. Finally, with a specificity of 78% and a sensitivity of 89%, the method was successfully compared to microscopy and culture routine tests for TB testing in 36 frozen fluidized and decontaminated sputum. This suggests that owing to its convenience, rapidity, low-cost and portability, the reported Ag85 electrochemical assay is a promising tool to screen patients for TB.

Se substituted 2D-gC3N4 modified disposable screen-printed carbon electrode substrate: A bifunctional nano-catalyst for electrochemical and absorption study of hazardous fungicide.

The indispensable usage of pesticides for the control and prevention of pests is probable and includes several types based on the problems in the crops. Among them, fungicides, are one problem-solving agent curing fungal developments. the disproportionate use of fungicides will lead to environmental deterioration and several health issues. The assessment of such fungicides is highly motivated to be detected. Under the class of two-dimensional materials, graphitic carbon nitride (GCN) with high surface area and high electrocatalytic activity was chosen as electrode material. The efficiency of GCN was improved with the subsequent substitution of selenium (Se) into the triazine ring as Se-GCN. The structural and surface analysis was done and the layered structure was proved. The electrochemical detection of CBM showed a lower detection limit at 6nM with a linear range 0.099μM-346.9μM while, the absorption studies showed a LOD of 20nM with a linear range of 0.099μM-182.09μM. The orange juice and vegetable extract samples had good recovery with CBM at Se-GCN modified disposable screen-printed electrode. The developed disposable electrode was more sensitive with 6.45μAμM-1cm2 sensitivity and highly reactive with CBM. Moreover, the developed sensor will be more effective in sensing applications to avoid the menace generated by several agents.

An electrochemical immunosensor based on graphite paper electrodes for the sensitive detection of creatine kinase in actual samples

• The electrochemical immunosensor designed very stable, low-cost and sensitive method for determination of Creatine Kinase. • CK immunosensor exhibited high analytical performance with a linear range 0.150 pg/mL and low detection limit (0.045 pg/mL). • Disposable graphite paper electrodes were firstly used to detection CK antigen for a novel biosensor system. • The optimization was performed for all fabrication steps of the electrochemical biosensor system. The enzyme creatine kinase (CK) is one of the most well-established biomarkers in cardiovascular disease. For acute myocardial infarction (AMI) diagnosis, CK has a clinical comorbidity rate of 90%. This study has developed a novel electrochemical immunosensor using disposable graphite paper electrodes (GP). The GP electrodes were modified with gold nanoparticles (AuNP) to facilitate CK detection. Afterwards, GP electrodes were covalently immobilized with 6-mercapto-1-hexanol (6-MH), resulting in self-assembled monolayers (SAMs). Then, the electrodes were formed with a 3-Glycidyloxypropyltrimethoxysilane (3-GOPE) agent. Afterwards, the electrodes were immobilized with anti-CK (antibody creatine kinase) protein. In the final immobilization step, BSA (bovine serum albumin) protein was used to block non-covalent interactions. All parameters of the proposed immunosensor were optimized, including concentrations and incubation times. Analytical characteristics such as square wave voltammetry, linear determination range, repeatability, reproducibility, and regeneration of biosensors were determined. All characterization steps were monitored by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV). Moreover, the single frequency impedance (SFI) technique interacted with anti-CK and CK antigens. Furthermore, the proposed immunosensor was characterized using scanning electron microscopy (SEM). The proposed immunosensor exhibited a wide detection range (0.1–50 pg mL −1 ), and low limit of detection (LOD), and a low limit of quantification (LOQ); 0.045 pg mL −1 and 0.171 pg mL −1 , respectively. Finally, the developed biosensor was tried in an actual blood sample, which showed it could be utilized in clinical applications.

Electrochemical and physicochemical degradability evaluation of printed flexible carbon electrodes in seawater

• Sustainable printed electrodes using a graphite paste (G-PE) were fabricated. • Study of the G-PEs against commercial silver and carbon SPEs (Ag- and C-SPEs). • Enhanced electrochemical stability in seawater by using carbon-based electrodes. • Excellent degradability and dispersibility of G-PEs against C- and Ag-SPEs. • The G-PEs are a promising sustainable alternative for disposable electrodes. The environmental impact of metals and non-degradable plastics in printed electrodes has highlighted the need of employing sustainable materials in environmental monitoring. In this work, we developed a new sustainable graphite-based paste (G-PE) printed on a bioderived and biodegradable polyhydroxybutyrate polyhydroxyvalerate substrate for tap water and seawater monitoring. We compared its performance against two standard screen-printed electrodes (SPEs) fabricated using commercial silver and carbon pastes (Ag-SPEs and C-SPEs) printed on a polyvinyl chloride substrate. The Ag-SPEs exhibited the lowest sheet resistance ( R S = 0.053 Ω/sq), however they were also less reliable as silver oxidised and reacted with ions present in seawater. Meanwhile, the C-SPEs and G-PE presented similar R S (26.9 and 30.1 Ω/sq, respectively), were inert in different media and showed relatively stable response during cyclic bending studies (less than 2.3% relative resistance variation for the C-SPE). Physical and chemical degradation studies of the sustainable G-PE in seawater demonstrated relatively quick ultrasound induced dissolution (less than5 min) while the SPEs did not dissolve even after 30 min of sonication, highlighting the suitability of this new, eco-friendly G-PE for single use or short-term water quality monitoring applications.

Disposable Electrochemical Biosensor Based on the Inhibition of Alkaline Phosphatase Encapsulated in Acrylamide Hydrogels.

The present work describes the development of an easy-to-use portable electrochemical biosensor based on alkaline phosphatase (ALP) as a recognition element, which has been immobilized in acrylamide-based hydrogels prepared through a green protocol over disposable screen-printed electrodes. To carry out the electrochemical transduction, an electroinactive substrate (hydroquinone diphosphate) was used in the presence of the enzyme and then it was hydrolyzed to an electroactive species (hydroquinone). The activity of the protein within the matrix was determined voltammetrically. Due to the adhesive properties of the hydrogel, this was easily deposited on the surface of the electrodes, greatly increasing the sensitivity of the biosensor. The device was optimized to allow the determination of phosphate ion, a competitive inhibitor of ALP, in aqueous media. Our study provides a proof-of-concept demonstrating the potential use of the developed biosensor for in situ, real-time measurement of water pollutants that act as ALP inhibitors.

Electrochemical study and forensic electroanalysis of fungicide benzovindiflupyr using disposable graphite pencil electrode

Nowadays, the use of pesticides in world agriculture is fundamental. However, it leads to an increase in the illegal sale and smuggling of these products in various parts of the world, mainly in Brazil. Therefore, the development of new analytical methods for screening and analysis of these kind of substances is a relevant issue. We present in this work, for the first time, an electrochemical study and a novel electroanalytical method for determination of fungicide benzovindiflupyr (BENZO). According to our knowledge, the electrochemical behavior of BENZO, as well as its voltammetric determination, have never been reported before. The sensors used here consisted of disposable pencil graphite electrodes (PGEs). On this electrode surface and at optimal pH, BENZO behaved according to a quasi-reversible system and showed two voltammetric peaks, one anodic at Ep = +0.59 V and another cathodic at Ep = +0.43 V. The analytical studies utilized BENZO anodic sweep and square-wave adsorptive stripping voltammetry (SWAdSV). All experimental and instrumental parameters were fully investigated and optimized. Under the best conditions, a calibration plot was obtained in the concentration range from 0.10 to 12.5 μmol L−1. The limits of detection (LOD) and quantification (LOQ) achieved were 0.023 and 0.076 μmol L−1, respectively. An electrochemical mechanism for BENZO oxidation was also proposed. The method developed here was successfully employed for the qualitative and quantitative forensic analysis of BENZO in smuggled products, showing good accuracy (recoveries ca. 104%) and precision (relative standard deviation < 5%). These data attest the potential for use of this method in forensic area.

Determination of Paracetamol on Electrochemically Reduced Graphene Oxide-Antimony Nanocomposite Modified Pencil Graphite Electrode Using Adsorptive Stripping Differential Pulse Voltammetry.

A simple, highly sensitive, accurate, and low-cost electrochemical sensor was developed for the determination of over-the-counter painkiller, paracetamol (PC). The enhanced sensing capabilities of the developed sensor were fabricated by the single-step modification of disposable pencil graphite electrodes (PGEs) with the simultaneous electrochemical reduction in graphene oxide and antimony (II) salts. For this purpose, an electrochemically reduced graphene oxide–antimony nanoparticle (ERGO-SbNP) nanocomposite material was prepared by trapping metallic nanoparticles between individual graphene sheets in the modification of PGEs. Structural characterization by FTIR and Raman spectroscopy was employed to confirm the presence of oxygen functional groups and defects in the conjugated carbon-based structure of GO. Morphological differences between the modified PGEs were confirmed by HRTEM and HRSEM for the presence of nanoparticles. The modified electrodes were further electrochemically characterized using CV and EIS. The electrooxidation of PC on an ERGO-SbNPs-PGE was achieved by adsorptive stripping differential pulse voltametric analysis in 0.1 mol·L−1 phosphate buffer solution at pH = 7.0. The optimum current response was used to record a detection limit of 0.057 µmol·L−1 for PC. The electrochemical sensor was further used in real sample analysis for a commercially available pharmaceutical tablet (500 mg PC), for which the percentage recovery was between 99.4% and 100.8%.