Differential Pulse Voltammetry Measurements Research Articles

Electrochemical Nanosensor for the Simultaneous Determination of Anticancer Drugs Epirubicin and Topotecan Using UiO-66-NH2/GO Nanocomposite Modified Electrode

In this work, UiO-66-NH2/GO nanocomposite was prepared using a simple solvothermal technique, and its structure and morphology were characterized using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). An enhanced electrochemical sensor for the detection of epirubicin (EP) was proposed, which utilized a UiO-66-NH2/GO nanocomposite-modified screen-printed graphite electrode (UiO-66-NH2/GO/SPGE). The prepared UiO-66-NH2/GO nanocomposite improved the electrochemical performance of the SPGE towards the redox reaction of EP. Under optimized experimental conditions, this sensor demonstrates a remarkable limit of detection (LOD) of 0.003 µM and a linear dynamic range from 0.008 to 200.0 µM, providing a highly capable platform for sensing EP. Furthermore, the simultaneous electro-catalytic oxidation of EP and topotecan (TP) was investigated at the UiO-66-NH2/GO/SPGE surface utilizing differential pulse voltammetry (DPV). DPV measurements revealed the presence of two distinct oxidation peaks of EP and TP, with a peak potential separation of 200 mV. Finally, the UiO-66-NH2/GO/SPGE sensor was successfully utilized for the quantitative analysis of EP and TP in pharmaceutical injection, yielding highly satisfactory results.

Determination of imatinib as anticancer drug in serum and urine samples by electrochemical technique using a chitosan/graphene oxide modified electrode

The purpose of this work was to construct an electrochemical sensor for the detection of imatinib. It was based on a modified glassy carbon electrode (chitosan/rGO/GCE) that was a reduced graphene oxide nanocomposite. By employing a straightforward drop-casting technique, the rGO/chitosan composite was applied to the GCE surface. The XRD, FT-IR, and FE-SEM structural studies verified that graphene oxide was successfully reduced and that the rGO/chitosan nanocomposite was formed. The synergistic effect of rGO and chitosan boosted electron transfer kinetics and facilitated the oxidation reaction of imatinib on the electrode surface, according to electrochemical experiments, which indicated the chitosan/rGO/GCE's sensitive, selective, and stable response to imatinib. The findings showed sensitivity of 0.16502 μA/μM, detection limit value of 7.3 nM, and a wide and stable linear range of 1–300 µM. Differential pulse voltammetry measurements were performed on prepared human serum and urine samples to evaluate the applicability of chitosan/rGO/GCE for imatinib detection in real samples. For the prepared genuine samples, the chitosan/rGO/GCE showed good recoveries ranging from 95.00% to 99.20% with a relative standard deviation of 3.10–4.49%. These findings showed that imatinib in a variety of genuine samples may be accurately analyzed using the chitosan/rGO/GCE.

Computational aptamer design for spike glycoprotein (S) (SARS CoV-2) detection with an electrochemical aptasensor

A new bioinformatic platform (APTERION) was used to design in a short time and with high specificity an aptamer for the detection of the spike protein, a structural protein of SARS-CoV-2 virus, responsible for the COVID-19 pandemic. The aptamer concentration on the carbon electrode surface was optimized using static contact angle and fluorescence method, while specificity was tested using differential pulse voltammetry (DPV) associated to carbon screen-printed electrodes. The data obtained demonstrated the good features of the aptamer which could be used to create a rapid method for the detection of SARS-CoV-2 virus. In fact, it is specific for spike also when tested against bovine serum albumin and lysozyme, competitor proteins if saliva is used as sample to test for the virus presence. Spectrofluorometric characterization allowed to measure the amount of aptamer present on the carbon electrode surface, while DPV measurements proved the affinity of the aptamer towards the spike protein and gave quantitative results. The acquired data allowed to conclude that the APTERION bioinformatic platform is a good method for aptamer design for rapidity and specificity.Key points• Spike protein detection using an electrochemical biosensor• Aptamer characterization by contact angle and fluorescent measurements on electrode surface• Computational design of specific aptamers to speed up the aptameric sequence time

Highly Sensitive Wearable Sensor Based on (001)-Orientated TiO2 for Real-Time Electrochemical Detection of Dopamine, Tyrosine, and Paracetamol.

The concentration of dopamine (DA) and tyrosine (Tyr) reflects the condition of patients with Parkinson's disease, whereas moderate paracetamol (PA) can help relieve their pain. Therefore, real-time measurements of these bioanalytes have important clinical implications for patients with Parkinson's disease. However, previous sensors suffer from either limited sensitivity or complex fabrication and integration processes. This work introduces a simple and cost-effective method to prepare high-quality, flexible titanium dioxide (TiO2 ) thin films with highly reactive (001)-facets. The as-fabricated TiO2 film supported by a carbon cloth electrode (i.e., TiO2 -CC) allows excellent electrochemical specificity and sensitivity to DA (1.390µAµM-1 cm-2 ), Tyr (0.126µAµM-1 cm-2 ), and PA (0.0841µAµM-1 cm-2 ). More importantly, accurate DA concentration in varied pH conditions can be obtained by decoupling them within a single differential pulse voltammetry measurement without additional sensing units. The TiO2 -CC electrochemical sensor can be integrated into a smart diaper to detect the trace amount of DA or an integrated skin-interfaced patch with microfluidic sampling and wireless transmission units for real-time detection of the sweat Try and PA concentration. The wearable sensor based on TiO2 -CC prepared by facile manufacturing methods holds great potential in the daily health monitoring and care of patients with neurological disorders.

Electrochemically assisted DNA and thioaromatic assembly as sensing and antifouling interface for food allergens.

Food allergies have become a global issue and are estimated to affect approximately 220 million people worldwide. Allergy to peanuts can easily become life-threatening and induce anaphylactic reactions. Mislabeling and cross-contamination during food processing can occur in the frame of world population growth and pose a serious health issue. As the mandatory allergen list is not uniform worldwide, the development of routine analytical strategies with high specificity and sensitivity is a demanding task to aid in the rapid identification of allergenic foods. In this work, an electrochemical aptasensor for Ara h1 peanut allergen was developed by immobilizing the specific aptamer by the inserting method. First, a layer of p-aminothiophenol (p-ATP) was immobilized on the gold surface of screen-printed electrodes (GSPE) to improve the aptamer insertion and reduce the fouling effects at the electrode surface. The grafting of the p-ATP and Ara h1 aptamer on the GSPE surface was monitored by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The resulting disposable aptasensor allowed for indirect electrochemical detection of Ara h1 protein in the presence of 5 mM ferro/ferricyanide as a redox probe. The electrochemical response upon aptamer-target interaction was monitored in the concentration range 1-250 nM, and two limits of detection in the nanomolar range were estimated based on DPV (2.78 nM Ara h1) and EIS (0.82 nM Ara h1) measurements. The aptasensor was successfully applied to real sample analysis.

Ultrasensitive detection of ornidazole–antibiotic drug residues in water using NiMOFs functionalized MWCNT modified electrode

Nitroimidazole-based drugs are widely used as an antibiotic for the treatment of anaerobic bacterial and parasite illnesses. The widespread use of these drugs in animal feed and the consequent environmental pollution have become significant concerns in recent years. Simple, sensitive, and rapid detection of the antibody in various real samples is demanding research interest. Herein, we report a Nickel-metal organic framework functionalized Multiwalled Carbon nanotubes modified glassy carbon electrode (MWCNT@NiMOFs) as an ultrasensitive and rapid voltammetric sensor for the detection of ornidazole (ORDZ) in a neutral pH solution. The MWCNT@NiMOFs were prepared using a microwave-assisted solvothermal technique accompanied by an ultrasonication method. The designed MWCNT@NiMOFs offered a low charge transfer resistance (Rct) of 141 Ω along with excellent electrocatalytic activity, and high current density at the lowered cathodic peak potential (-0.62 V vs Ag/AgCl) for ORDZ detection. The surface adsorption capacity (Γs) in terms of surface excess and heterogeneous charge transfer rate constant (k0) of the MWCNT@NiMOFs were calculated to be 3.29 × 10-9 mol cm−2 and 5.33 × 10-3 cm s−1, respectively. Under an optimal working condition, differential pulse voltammetry measurements of ORDZ have shown concentration linearity in a window, 100 nm to 10 µM range with excellent sensitivity, 5.69 × 10-5A µM−1 cm−2, and detection limit, 26 nM (3.3/s). The designed MWCNT@NiMOFs offered appreciable reproducibility, and repeatability up to 30 days of storage time. The real-time quantitative evaluation of ORDZ in human urine and tap water specimens was done along with ∼ 100 % recovery values. Since the new approach is simple, selective, and separation-free, it can be extendable to a variety of real-time practical applications.

Electrospun cobalt-doped 2D-MoSe2/polypyrrole hybrid-based carbon nanofibers as electrochemical sensing platforms

A novel cobalt-doped two-dimensional molybdenum diselenide/polypyrrole hybrid-based carbon nanofiber (Co/MoSe2/PPy@CNF) was prepared using the hydrothermal method followed by electrospinning technique. The structural and morphological properties of the 2D-TMD@CNF-based hybrids were characterized through X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and transmission electron microscopy (TEM). The Co-MoSe2/PPy@CNF exhibited large surface area, porous structure, and improved active sites due to the synergistic effect of the components. The electrochemical and electrocatalytic characteristics of the 2D-TMD@CNF-modified electrodes were also investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Co/MoSe2/PPy@CNF electrode was used as an electrochemical sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) and showed enhanced catalytic activity and sensitivity. Using DPV measurements, the Co/MoSe2/PPy@CNF demonstrated wide linear ranges of 30–3212 μM for AA, 1.2–536 μM for DA, and 10–1071 μM for UA with low detection limits of 6.32, 0.45, and 0.81 μM, respectively. The developed sensor with the Co/MoSe2/PPy@CNF-modified electrode was also applied to a human urine sample and gave recoveries ranging from 94.0 to 105.5% (n = 3) for AA, DA, and UA. Furthermore, the Co/MoSe2/PPy@CNF-based sensor exhibited good selectivity and reproducibility for the detection of AA, DA, and UA.Graphical abstract

Polysaccharides derived from Ganoderma lucidum applied to the extraction chitosan and development of electrochemical sensor based on extracted chitosan and graphitic carbon nitride modified electrode for determination nitrite in food samples

The current study focused on extracting chitosan from polysaccharides generated from Ganoderma lucidum and applying it to the construction of electrochemically modified electrodes based on graphitic carbon nitride (g-C3N4) for the measurement of nitrite in water and food samples. Ganoderma Lucidum polysaccharides were isolated and characterized. The chitosan was then isolated enzymatically from the polysaccharides using a chemical technique. The isolated chitosan and g-C3N4 were used to modify a GCE (chitosan/g-C3N4/GCE). The structural investigations employing FT-IR, SEM, and XRD show that chitosan successfully interacted with g-C3N4 in the chitosan/g-C3N4 sample. Electrochemical evaluation using cycle voltammetry (CV), differential pulse voltammetry (DPV), and amperometry revealed that the chitosan/g-C3N4/GCE electrode has good sensitivity and selectivity for determining nitrite. The use of chitosan and g-C3N4 in electrode surface modification improved nitrite electro-oxidation performance by allowing for more effective adsorption and electron transport processes. DPV measurement showed that the sensor had a sensitivity of 0.12103 μA/μM, a linear range of 40 to 2000 μM, and a limit of detection of 21 nM, and amperometry measurement showed the sensor's sensitivity of 0.15487 μA/μM, linear range of 20 to 4230 μM, and an LOD of 10 nM. These findings indicated a more sensitive and wide range of sensor performance using amperometry with respect to the DPV technique. The method's validity and accuracy in determining nitrite in prepared genuine samples (water, milk, apple juice, orange juice, Aloe vera, and tomato juice) were investigated. RSD values (3.19 % to 4.75 %) and recovery values (80.00 % to 98.33 %) were found to be satisfactory. The data also revealed that there were no substantial matrix interferences, demonstrating the accuracy and applicability of the proposed approach for detecting nitrite in food samples. Therefore, the proposed sensor design has several advantages that make it a promising candidate for various applications. Its reusability, stability, wide linear range, accuracy, and low cost make it an attractive option for many industries.

Easy-to-prepare graphene-based inkjet-printed electrodes for diclofenac electrochemical sensing

Inkjet-printed electrodes (IPEs) from flexible Kapton® as substrate and easy to prepare graphene oxide (GO)-based inks (K/GO) were prepared using a standard desktop printer. Subsequently, they were submitted to a post-processing thermal treatment (K/GO_TR400) and assessed as disposable working electrodes (WEs) for diclofenac (DCF) indirect electrochemical detection at pH 7.0 (close to physiological pH value). DCF monitoring is attracting much interest, due to its classification as contaminant of emerging concern in water sources. The performance of the printed active sensor material was compared to that of thermally reduced (at 400 °C) graphene oxide (TRGO-400, in a powder form), which has been successfully used as glassy carbon electrode (GCE) modifier for the detection of DCF. This electrode worked linearly within the concentration range between 5 and 25 μM with an LOD value of 2.25 μM. Moreover, the morphology and chemical composition of the obtained IPEs were characterized by means of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) and compared with GCE/TRGO-400. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements using a miniaturized 3-electrode cell of the post-processed IPEs showed a promising electrochemical performance for DCF sensing. Thus, this study demonstrated the effective partial recovery of the valuable properties of graphene on the IPEs after the thermal treatment and the successful production of flexible and disposable electrodes for target analyte detection. Therefore, this is a promising alternative to conventional modified GCEs, as it offers a facile approach for the fabrication of cutting edge graphene-based electrodes and widens the available portfolio of electrochemical sensors towards detection of water contaminants of emerging concern.

Palladium-Copper Bimetallic Aerogel as New Modifier for Highly Sensitive Determination of Bisphenol A in Real Samples.

In this study, a bimetallic palladium-copper aerogel was synthesized and used for modification of a graphite paste electrode (Pd-Cu/GPE), allowing the sensitive determination of bisphenol A (BPA). Different techniques, such as SEM, TEM, XPS, and AFM, were used for characterization of the Pd-Cu aerogel. To elucidate the properties of the Pd-Cu/GPE, the electrochemistry methods such as differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy were used. DPV measurements were conducted in phosphate electrolyte and buffer solution (0.2 M PBS, pH 5) at a potential range from 0.4 to 0.9 V vs. Ag/AgCl. The DPVs peaks currents increased linearly with BPA concentrations in the 0.04-85 and 85-305 µM ranges, with a limit of detection of 20 nM. The modified electrode was successfully used in real samples to determine BPA, and the results were compared to the standard HPLC method. The results showed that the Pd-Cu/GPE had good selectivity, stability, and sensitivity for BPA determination.

EIS and Amperometric Analysis of Gold Nanoparticle Probes on the Immunosensor Surface

[Introduction]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. Briefly, antibody-modified AuNPs not only hold secondary antibodies to react with antigens and primary antibodies on the electrode but also supply redox signals. We specially call this biosensing method Gold-Linked Electrochemical ImmunoAssay (GLEIA). In recent years, GLEIA has evolved uniquely in 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 the decrease in the determined parameters could be deduced. This is useful for the determination of the fine balance between the sensitivity and specificity.[Experimental]Electrochemical characteristics of AuNPs were performed using the following method, where 2 µL of AuNPs solution was dropped onto the working electrode and allowed to dry spontaneously. The number of AuNPs on each electrode was calculated from the datasheet (2.6 x 1010 particles/mL, O.D. 520 =1.0), and all nanoparticles were assumed to have dried on the working electrode. To characterize the reduction current, the AuNPs on the electrode underwent a pre-oxidation process, followed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) to evaluate the reduction current. The pre-oxidation condition was set at 1.2 V for 40 s, which was considered optimal for immunoassays. To evaluate the concentration response, 2 µL of the AuNPs solution was diluted with ultrapure water and poured and allowed to dry on the working electrode, pre-oxidized in 2 M KCl solution, and DPV measurements were performed. This experiment was also performed on an antibody-modified electrode, and the differences between the modified and unmodified electrodes were established. The same DPV measurements were performed using antibody-modified AuNPs (Ab-AuNPs).For immunoassay, IgA was reacted with a secondary antibody and incubated dropwise on an electrode. After washing, electrochemical measurements were performed[Results and Discussion]We investigated the influence of the DPV parameters and electrode surface conditions on a biosensor for the redox reaction of AuNPs. CV and classical theory were used to investigate the reduction kinetics of the AuNPs’ reduction after oxidation. The diffusion coefficient and electron transfer rate, which are related to sensor performance, were significantly reduced in the presence of antibodies and blocking agents on the electrode surface. This was due to the interaction between proteins and gold ions, and the effect of the electrode surface on sensitivity was evaluated using electrochemical reaction rates. Next, the influence of the biosensor on sensitivity was examined by focusing on the pulse amplitude of the DPV, and the increase in signal current coupled to increase in pulse amplitude was confirmed. The signal of AuNPs relative to the blank sample was of particular interest. Theoretically, changing the pulse potential above 100 mV does not change the current values obtained; however, in this study, a significant difference was observed between 150 mV and 100 mV. This was presumably due to the detection of nonspecific adsorption of antibodies that could not be detected under conventional conditions, suggesting the use of a more sensitive biosensor. This study provides evidence for fabrication of an IgA sensor with an improved Limit of detection (LOD) by optimizing pulse amplitude.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 (Figure). 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. Figure 1

Synthesis and characterization of carbon dots nanoparticles for detection of ascorbic acid

Hydrothermal method has been employed for the synthesis of carbon dots (CDs) nanoparticles at 180 °C. CDs were characterized by powder x-ray diffraction (XRD), FT-IR, electron microscopy, thermo-gravimetric analysis (TGA), UV–visible and fluorescence spectroscopy. XRD results reveal the formation of CDs. Electron microscopic studies show the spherical shape of CDs without apparent aggregation. Optical absorption measurements indicate a direct bandgap of 4.6ev. The electrochemical studies were conducted for the detection of ascorbic acid (A.A.) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements.

Highly sensitive and selective detection of selenate in water samples using an enzymatic gold nanodendrite biosensor

Gold (Au) and glassy carbon electrodes have been decorated with gold nanodendrites (NDs) using galvanic replacement reactions. Modification of the ND surfaces by lipoic acid N-hydroxysuccinimide ester allows to immobilise selenate reductase to the electrode surface, rendering it selective for the catalytic reduction of selenate ([Formula: see text], Se(VI)) to selenite ([Formula: see text], Se(IV)). Electrode modifications have been characterized by electrochemical impedance spectroscopy and cyclic voltammetry (CV). For selenate detection, CV and differential pulse voltammetry measurements have been carried out in 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid buffer with pH 6.0. Under optimum conditions, the linear range for Au electrodes decorated with AuNDs was 0.3–203 µg/L Se with a limit of detection of 0.01 µg/L Se, which is a 274-fold improvement over using non-nanostructured surfaces for selenate detection. Other anions such as [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] did not interfere with the detection of selenate. The electrochemical sensor was used for the detection of selenate in three different real samples with recovery between 98.5% and 102.0%.

Insights into the Interaction of Dacarbazine and Human Serum Albumin from Electrochemical Probing

The interaction between dacarbazine (DAC) and human serum albumin (HSA) was investigated under physiological conditions using electrochemical techniques, including cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The CV results demonstrated that the oxidation of DAC on a pyrolytic graphite electrode (PGE) surface was irreversible and controlled by an adsorption-diffusion process. The addition of HSA was found to decrease the peak potential of DAC without altering the electrochemical parameters, which is likely due to the formation of an electro-inactive complex between the drug and protein, as supported by DPV and EIS measurements. Using DPV, the binding constant and stoichiometry of the complex were calculated to be 2.16 × 104 mol−1 l and 1:1, respectively. The temperature effect revealed that DAC binds to HSA through hydrophobic forces. In addition, the PGE electrode was successfully used to determine DAC in from biological samples.

Differential Pulse Voltammetric Tuning of the Screen-Printed Carbon Electrode Surface to Enhance the Electrochemical Performance and Multiplex Detection

Screen-Printed Carbon Electrode (SPCE) has shown tremendous scope for the miniaturization and commercialization of low-cost electrochemical sensors and biosensors devices. But the commercial SPCEs have a narrow potential window (PW) that limits their versatile applications for various analytes owing to the presence of some inherent redox peaks in the wider PW. In this work, we have explored the most effective and innovative electrochemical tuning of the SPCE surface using DPV (differential pulse voltammetry) for the removal of those inherent redox peaks that are responsible for narrowing the working PW. After that, the electrochemical performance of the tuned SPCE electrode was evaluated in terms of a range of electrochemical parameters including reproducibility by CV (Cyclic Voltammetry), DPV and EIS (electrochemical impedance spectroscopy) measurements using [Fe(CN)6]3−/4− as a model redox analyte. In addition, the suitability of the tuned electrode for multiple analytes detection was tested in presence of a mixture of Cd2+ (cadmium), Cu2+ (copper) and Hg2+ (Mercury) ions using CV and DPV techniques. The electrochemical analysis data show that after electrochemical DPV treatment, the SPCE surface exhibits excellent reproducibility and electrochemical performance within a wider PW minimizing their inherent drawback creating a wide scope of their precise applications in various fields.

Electrochemical Detection of ompA Gene of C. sakazakii Based on Glucose-Oxidase-Mimicking Nanotags of Gold-Nanoparticles-Doped Copper Metal-organic Frameworks.

The present work developed an electrochemical genosensor for the detection of virulence outer membrane protein A (ompA, tDNA) gene of Cronobacter sakazakii (C. sakazakii) by exploiting the excellent glucose-oxidase-mimicking activity of copper Metal-organic frameworks (Cu-MOF) doped with gold nanoparticle (AuNPs). The signal nanotags of signal probes (sDNA) that biofunctionalized AuNPs@Cu-MOF (sDNA-AuNPs@Cu-MOF) were designed using an Au-S bond. The biosensor was prepared by immobilization capture probes (cDNA) onto an electrodeposited AuNPs-modified glassy carbon electrode (GCE). AuNPs@Cu-MOF was introduced onto the surface of the GCE via a hybridization reaction between cDNA and tDNA, as well as tDNA and sDNA. Due to the enhanced oxidase-mimicking activity of AuNPs@Cu-MOF to glucose, the biosensor gave a linear range of 1.0 × 10-15 to 1.0 × 10-9 mol L-1 to tDNA with a detection limit (LOD) of 0.42 fmol L-1 under optimized conditions using differential pulse voltammetry measurement (DPV). It can be applied in the direct detection of ompA gene segments in total DNA extracts from C. sakazakii with a broad linear range of 5.4-5.4 × 105 CFU mL-1 and a LOD of 0.35 CFU mL-1. The biosensor showed good selectivity, fabricating reproducibility and storage stability, and can be used for the detection of ompA gene segments in real samples with recovery between 87.5% and 107.3%.

Simultaneous determination of ascorbic acid, dopamine, and uric acid with a highly selective and sensitive reduced graphene oxide/polypyrrole-platinum nanocomposite modified electrochemical sensor

In this article, a new method for the synthesis of reduced graphene oxide/polypyrrole-platinum (rGO/PPy-Pt) nanoparticles via microwave-assisted procedure is reported. Material characterization of the synthesized nanocomposites was carried out with X-Ray Diffraction Diffractometry (XRD), Scanning Electron Microscope (SEM), and Fourier Transform Infrared Spectrophotometer (FTIR). In addition, the electrocatalytic performance of rGO/PPy-Pt nanocomposites for the determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA) was carried out by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements. Under optimized conditions, linear calibration plots were found to be 0.8–2.1 mM, 0.03 – 1.4 mM, and 0.1–0.35 mM with corresponding detection limits of 0.12 μM, 0.071 μM, and 0.16 μM for AA, DA, and UA, respectively. In the results obtained, it was seen that the rGO/PPy-Pt bimetallic composite provided high electrocatalytic performance against AA, DA, and UA biomolecules.

Rational synthesis of alkaline earth metal vanadates: Structural origin of MgVO3 honeycomb lattice system and its electrochemical analysis for the detection of sulfadiazine

In this study, well-defined alkaline earth metal vanadates, including MgV, CaV, SrV, and BaV, are synthesized using a simple hydrothermal method, and the crystalline structure, morphology, and structural parameters of the synthesized alkaline earth metal vanadates are investigated and compared. Among the alkaline earth metal vanadates, the MgV shows the unique 3D architecture and MgVO3 hexagonal phase with space group R-3c (167) and a single crystalline phase in V4+ valence state and Mg2+ state revealing cation dimerization in 3d1 honeycomb system. Further Raman spectroscopy with Lorentzian peak fitting and X-ray photoelectron spectroscopy exhibit the phase development with a bucky-ball structure. In order to apply the unique feature, the MgV based composite with reduced graphene oxide as a co-catalyst is prepared to examine the practical application for electrochemical sensing of sulfadiazine. The differential pulse voltammetry and the amperometry i-t analysis demonstrate the superior performance of MgV/reduced graphene oxide composite for the sulfadiazine detection including a superior low limit of detection of 9 nM from the differential pulse voltammetry measurements and 3 nM from the amperometry i-t analysis as well as excellent selectivity and long-term stability. These results are attributed to the enhanced electron transfer and ion diffusion from the synergistic effect of unique MgV and reduced graphene oxide. Moreover, the MgV/reduced graphene oxide composite delivers excellent capability in the detection of sulfadiazine in real samples of human blood serum, industrial wastewater, and pharmaceutical tablet.

Enhanced Performance Electrochemical Biosensor for Detection of Prostate Cancer Biomarker PCA3 Using Specific Aptamer

In the quest for the development of accurate, reliable, and cost-effective biosensing technology for early diagnostics of prostate cancer, we describe here an electrochemical biosensor combining a simple transducing method of differential pulse voltammetry (DPV) with an RNA-based aptamer labelled with a methylene blue redox group acting as a highly specific bioreceptor to the prostate cancer biomarker PCA3. A series of DPV measurements on screen-printed gold electrodes is functionalised with a redox-labelled aptamer in solutions (either buffer or synthetic urine) containing PCA3 in a wide range of concentrations from 0.1 picomolar (pM) to 10 nanomolar (nM). In these measurements, the current peak values correlate with the concentration of PCA3 and yield a low detection limit (LDL) of 0.1 pM. Furthermore, the binding kinetics study revealed the high affinity of the aptamer to the target PCA3 with the affinity constants KD of about 3.0 × 10−8 molar. In addition, the AFM study showed the increase in the molecular layer roughness caused by the binding of PCA3, which is a large RNA molecular fragment.

Electrochemical Biosensor for the Determination of Specific Antibodies against SARS-CoV-2 Spike Protein

In this article, we report the development of an electrochemical biosensor for the determination of the SARS-CoV-2 spike protein (rS). A gold disc electrode was electrochemically modified to form the nanocrystalline gold structure on the surface. Then, it was further altered by a self-assembling monolayer based on a mixture of two alkane thiols: 11-mercaptoundecanoic acid (11-MUA) and 6-mercapto-1-hexanol (6-MCOH) (SAMmix). After activating carboxyl groups using a N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide hydrochloride and N-hydroxysuccinimide mixture, the rS protein was covalently immobilized on the top of the SAMmix. This electrode was used to design an electrochemical sensor suitable for determining antibodies against the SARS-CoV-2 rS protein (anti-rS). We assessed the association between the immobilized rS protein and the anti-rS antibody present in the blood serum of a SARS-CoV-2 infected person using three electrochemical methods: cyclic voltammetry, differential pulse voltammetry, and potential pulsed amperometry. The results demonstrated that differential pulse voltammetry and potential pulsed amperometry measurements displayed similar sensitivity. In contrast, the measurements performed by cyclic voltammetry suggest that this method is the most sensitive out of the three methods applied in this research.