Screen-printed Carbon Electrode Research Articles

Cerium dioxide-based nanostructures as signal nanolabels for current detection in the immunosensing determination of salivary myeloperoxidase

This work reports the first electrochemical immunoplatform involving the use of synthesized cerium dioxide nanoparticles (CeO2NPs) / multi-walled carbon nanotubes (MWCNTs) composites as signal nanolabels for the determination of salivary myeloperoxidase (MPO), one of the proteins suggested as diagnostic biomarkers of periodontitis. The immunosensing device profits the benefits of CeO2NPs in terms of fast electron transfer and the catalytic activity and prevents the CeO2NPs tendency to agglomerate by decoration over MWCNTs, also providing high sensitivity. After a thorough characterization of the CeO2NPs/MWCNTs using various techniques and optimization of the variables involved in the preparation of the immunoplatform, a sandwich-type immunoassay was implemented with specific MPO capture and biotinylated detection antibodies. The use of horseradish peroxidase-streptavidin (HRP-Strept) or CeO2NPs/MWCNTs-(HRP-Strept) as labels for the amperometric detection at screen printed carbon electrodes (SPCEs) at −0.20 V vs. Ag pseudo-reference electrode using the H2O2/hydroquinone (HQ) system, was compared. The method developed involving CeO2NPs/MWCNTs-(HRP-Strept) provided a linear calibration plot for MPO over the 1.0 to 100.0 ng mL−1 (R2 = 0.994) range with a limit of detection value of 0.40 ng mL−1. The immunoplatform was applied to the analysis of saliva from volunteers showing that the method allowed discrimination between healthy individuals and patients diagnosed with periodontitis through the determination of MPO in 1000-times diluted saliva. The obtained results agreed with those provided by an ELISA kit, this latter requiring a much longer assay time (4 h vs 2 h).

Ultrasensitive prostate cancer marker PCA3 detection with impedimetric biosensor based on specific label-free aptamers

Prostate cancer (PCa) appears among the most frequently diagnosed types of malignancies in males. Because of the high demand and increasing detection rate of early PCa, alongside the specificity limitations of the gold standard clinical tools available for the diagnosis and prognosis of prostate cancer, there is an urgent need for more reliable PCa markers and highly sensitive diagnostic tools to avoid under-treatment and over-diagnosis. PCA3, or prostate cancer antigen 3, is a potential prostate cancer biomarker that is more specific and useful for preventing unnecessary repeat biopsies, particularly in men with persistently high prostate-specific antigen indices after a negative biopsy. Additionally, an electrochemically based biosensor would prove to be a powerful diagnostic tool for PCA3 detection in urine because of its simplicity, sensitivity, and cost-effectiveness, in contrast to the more traditional PCa diagnostics that depend on blood testing. This paper aimed to design a novel and simple electrochemical impedimetric biosensor based on a label-free RNA-aptamer (CG3-PCA3) as the molecular recognition element for detecting PCA3. The proposed aptasensor for the detection of PCA3 has been developed using a screen-printed carbon electrode (SPCE) modified by gold nanoparticles (AuNPs), further improving sensitivity and allowing the immobilisation of thiolate aptamers on its surface. The findings presented here demonstrated a high sensitivity to PCA3, with a detection limit of 20 fM in artificial urine and 1 fM in buffer. These results indicate that the PCA3 aptasensor could be a promising tool for routine PCa diagnosis due to its high sensitivity and cost-effectiveness.

Thiol-based chemically modified carbon screen-printed electrode for simultaneous quantification of trace level Pb(II) and Cd(II).

Present work reports, the development of a novel electrochemical sensor based on a diazonium-coupling reaction and covalent attachment of the -NH2 group of cysteamine (Cyst) on screen-printed carbon electrode (SPCE), for simultaneous determination of Pb(II) and Cd(II). Initially, the in-situ generated 4-carboxyphenyl (4-CP) diazonium salt was electro-grafted to generate 4-CP/SPCE, followed by covalent bonding of terminal carboxylic group of 4-CP with -NH2 group of Cyst to give Cyst/4-CP/SPCE. The modified electrode showed an enhanced selectivity and sensitivity toward the quantification of Pb(II) and Cd(II) using square wave anodic stripping voltammetry (SWASV) without mutual interference. Under optimal experimental conditions, the newly designed sensor showed a wide linear range of 0.01µM to 0.7µM. The limit of detection (LOD) obtained was 0.882nM (0.09 ppb) and 0.65nM (0.134ppb) for Cd(II) and Pb(II), respectively. The modified SPCE exhibited good stability, selectivity, and reproducibility. Furthermore, the sensor was successfully applied for the determination of Pb(II) and Cd(II) ions in water samples which illustrated excellent recoveries in different spiked samples and the results were in line with the standard ICP-AES analysis.

Nitrocellulose/acrylic resin coated screen-printed carbon electrode to construct a capacitive immunosensor for anti-BSA

The capacitive immunosensor, known for its label-free simplicity, has great potential for point-of-care diagnostics. However, the interaction between insulation and recognition layers on the sensing electrode greatly affects its performance. This study introduces a pioneering dual-layer strategy, implementing a novel combination of acrylic resin (AR) and nitrocellulose (NC) coatings on screen-printed carbon electrodes (SPCEs). This innovative approach not only enhances the dielectric properties of the capacitive sensor but also streamlines the immobilization of recognizing elements. Particularly noteworthy is the superior reliability and insulation offered by the AR coating, surpassing the limitations of traditional self-assembled monolayer (SAM) modifications. This dual-layer methodology establishes a robust foundation for constructing capacitive sensors optimized specifically for liquid medium-based biosensing applications. The NC coating in this study represents a breakthrough in effectively immobilizing BSA, unraveling the capacitive response intricately linked to the quantity of adsorbed recognizing elements. The results underscore the prowess of the proposed immunosensor, showcasing a meticulously defined linear calibration curve for anti-BSA (ranging from 0 to 25 μg/ml). Additionally, specific interactions with anti-HAS and anti-TNF-α further validate the versatility and efficacy of the developed immunosensor. This work presents a streamlined and highly efficient protocol for developing label-free immunosensors for antibody determination and introduces a paradigm shift by utilizing readily available electrodes and sensing systems. The findings are poised to catalyze a significant acceleration in the advancement of biosensor technology, opening new avenues for innovative applications in point-of-care diagnostics.

Novel disposable screen-printed sensors based on copper oxide nanoparticles for sensitive voltammetric assay of antazoline

The fabrication and electroanalytical validation of a novel homemade screen-printed carbon electrode enriched with copper oxide nanoparticles (CuONPs/SPCEs) were demonstrated for sensitive and selective voltammetric determination antazoline (ANT) in eye drop solution and spiked serum samples. With a reported electrocatalytic activity, CuONPs catalyzed the oxidation of ANT at the electrode surface showing an irreversible anodic oxidation peak at 0.9 V under a diffusion-controlled electrode reaction. Based on the electroanalytical and molecular orbital calculation studies, oxidation of ANT molecule undergoes via oxidation of the aliphatic nitrogen atom within the ANT moiety. Linear calibration curves were illustrated covering the ANT concentration ranged from 0.01 to 3.819 µg mL−1 with and limit of detection 3 ng mL−1. The fabricated sensors enriched with CuONPs exhibited high fabrication and measurement reproducibility with a prolonged shelf lifetime (6 months). The electroanalytical approach presented adequate sensitivity and selectivity with a short analysis time, applying low-cost instrumentation and simple pretreatment protocol avoiding handling hazardous organic solvents. Trace ANT was monitored in the presence of different interfering species, degradation products, and xylometazoline hydrochloride (ZYL) in the co-formulated ophthalmic pharmaceutical samples. The CuONPs based voltammetric sensors were introduced as a reliable eco-friendly analytical tool for monitoring ANT in ophthalmic solutions and biological fluids with acceptable recovery values.

Cytochrome c electrochemical detection utilizing molecularly imprinted poly(3, 4-ethylenedioxythiophene) on a disposable screen printed carbon electrode

Cytochrome c (cyt c) has been found to play a function in apoptosis in cell-free models. This work presents the creation of molecularly imprinted conducting poly(3, 4-ethylenedioxythiopene) (MIPEDOT) on the surface of a screen printed carbon electrode (SPCE) for cyt c. Cyt c was imprinted by electropolymerization due to the presence of an EDOT monomer hydrophobic functional group on SPCE, using CV to obtain highly selective materials with excellent molecular recognition ability. MIPEDOT was characterized by CV, EIS, and DPV using ferricyanide/ferrocyanide as a redox probe. Further, the characterization of the sensor was accomplished using SEM for surface morphological confirmation. Using CV, the peak current measured at the potential of +1 to −1 V (vs. Ag/AgCl) is linear in the cyt c concentration range from 1 to 1200 pM, showing a remarkably low detection limit of 0.5 pM (sensitivity:0.080 μA pM). Moreover, the applicability of the approach was successfully confirmed with the detection of cyt c in biological samples (human plasma). Similarly, our research has proven a low-cost, simple, and efficient sensing platform for cyt c detection, rendering it a viable tool for the future improvement of reliable and exact non-encroaching cell death detection.

Synthesis and application of bismuth nanoparticle-loaded longan porous carbon for simultaneous electrochemical determination of Pb(II) and cd(II) in seafoods

The discarded longan shell-derived porous carbon material (LPC) served as a scaffold for synthesizing bismuth nanoparticle-loaded longan porous carbon nanocomposite (BiNPs@LPC) via a hydrothermal method. Then BiNPs@LPC was utilized to modify screen-printed carbon electrodes (SPCE) for simultaneous detection of Pb(II) and Cd(II) by square wave anodic stripping voltammetry (SWASV). The material was thoroughly characterized by scanning electron microscopy, X-ray diffraction, Raman spectra, Brunauer-Emmett-Teller analysis, electrochemical impedance spectroscopy and cyclic voltammetry. BiNPs@LPC exhibited abundant porous structures, high surface area, and numerous active sites, which could improve significantly response sensitivity. Under optimal conditions, the peak currents of Pb(II) and Cd(II) exhibited favorable linear relationships with the concentration within a range of 0.1–150 μg L−1, with detection limits (S/N = 3) of 0.02 μg L−1 and 0.03 μg L−1, respectively. BiNPs@LPC/SPCE demonstrated remarkable selectivity, stability and repeatability. The proposed method was successfully applied for the detection of Pb(II) and Cd(II) in seafoods achieving satisfying recovery of 97.8%–108.3% and 96.7%–106.4%. These excellent test properties were coupled with convenience for batch preparation of the modified electrodes, highlighting its potential for practical applications in heavy metal detection of real samples.

CeO2 nanoparticles modified screen-printed carbon electrode: Electrochemical sensing platform for sulfite determination in water samples

In the present work, the CeO2 nanoparticles (CeO2 NPs) were prepared by hydrothermal method and the crystal structure and morphology analysis were studied by using a series of characterizations. Then, the screen-printed carbon electrode (SPCE) modified with CeO2 NPs was employed to develop a simple and novel sensor for sulfite determination in water samples. The CeO2 NPs/SPCE showed significant current response for sulfite oxidation. The use of the developed sensor with differential pulse voltammetry (DPV) method provides a wide linear range for sulfite determination (0.08–870.0 µM) with a low limit of detection (LOD) (0.023 µM). Finally, the results determination of sulfite in water samples showed good recoveries between 96.7% and 102.7% with a relative standard deviation (RSD) less than 3.6%.

Reagent-Free Lactate Detection Using Prussian Blue and Electropolymerized-Molecularly Imprinted Polymers-Based Electrochemical Biosensors.

Sweat lactate, a promising biomarker for assessing physical performance and health conditions, calls for noninvasive, convenient, and affordable detection methods. This study leverages molecularly imprinted polymers (MIPs) as a synthetic biorecognition element for lactate detection due to their affordability and high stability. Traditional MIPs-based electrochemical sensors often require external redox probes such as ferricyanide/ferrocyanide in the solution to signal the binding between analytes and MIPs, which restricts their applicability. To address this, our study introduces an innovative approach utilizing a layer of Prussian blue (PB) nanoparticles as the internal redox probe on screen-printed carbon electrodes (SPCE), followed by a layer of electropolymerized MIP (eMIP) for molecular recognition, enabling reagent-free lactate detection. The real-time growth of eMIP and the processes of template elution and lactate rebinding were examined and validated using electrochemical surface plasmon resonance (EC-SPR) spectroscopy. The sensor's performance was thoroughly investigated using Differential Pulsed Voltammetry (DPV) and Electrochemical Impedance Spectroscopy (EIS) with samples spiked in 0.1 M KCl solution and artificial sweat. The developed sensors demonstrated a fast and selective response to lactate, detecting concentrations from 1 to 35 mM with a Limit of Detection (LOD) of 0.20 mM, defined by a signal-to-noise ratio of 3 in the DPV measurements. They also exhibited excellent reproducibility, reusability, and a shelf life of up to 10 months under ambient conditions. These eMIP/PB/SPCE-based lactate sensors show considerable potential as point-of-care (POC) devices for sweat lactate detection, and the technology could be adapted for reagent-free detection of a broad spectrum of molecules.

Bifunctional colloid based on anchoring reactions in-situ modified electrodes: For electrochemical sensing and HER

In this study, a bifunctional [PtCl6]2−-GO colloidal material was prepared by anchoring [PtCl6]2− by abundant oxygen-containing functional groups in protonated graphene oxide. Two modification strategies, surface overcoating and electrochemical in situ deposition, were adopted to modify the screen-printed carbon electrode (SPCE), foam electrodes (CuF, NiF), respectively, and Pt-rGO, which uniformly covered the electrode surface, was obtained by a simple onestep of reducing [PtCl6]2−-GO. The effectiveness of the modified materials and electrode modification strategies prepared was validated by tinidazole electrochemical detection and hydrogen evolution reaction (HER). The results indicated that the Pt-rGO modified SPCE possessed lower LOD and higher sensitivity for the detection. Furthermore, as for HER, optimized Pt-rGO-modified NiF and CuF required only 26 mV and 76 mV overpotentials in alkaline and acidic solutions, respectively, to obtain current densities of 10 mA cm−2. This was largely ascribed to the synergistic interaction between platinum and rGO, with the synthesized platinum-rGO displaying stronger active sites and higher intrinsic activity. In particular, Pt, which acts as an active center, could offer part of its electron to H2O and adjacent reduced graphene oxide sites, thus promoting strong electrical connections and efficient HER kinetics.

Copper ferrite nanoparticles anchored laser-induced graphene as novel nanoenzyme for the electrochemical catalyzing and sensing of β-estradiol in serum

β-estradiol is one of the most active hormones in steroids, and it plays a vital role in the human reproductive and non-reproductive systems. Compared with other methods for detecting β-estradiol, electrochemical biosensors are economical, simple, sensitive, and rapid. Herein, spinel copper ferrite nanoparticles and laser-induced graphene (LIG) were employed to functionalize screen-printed carbon electrodes (SPCE) for the first time, and it demonstrated that they have a synergistic effect on the catalysis of β-estradiol. Differential pulse voltammetry (DPV) was used to detect the changes in the peak current generated by the oxidation of β-estradiol. The nanoparticles were characterized by Fourier infrared spectroscopy, transmission electron microscope, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), and X-ray Diffraction (XRD), and the composition elements and morphology of the nanoparticles were explained. The linear range of β-estradiol detected by this method is 0.1 ∼ 100 μM, R2 = 0.9992, and the detection limit is 3 nM. The sensor has good selectivity, reproducibility, repeatability, stability, and anti-interference performance. In rat serum, the recovery of the sensor at 100, 10, and 1 μM β-estradiol was 105 % ∼ 110 %, with relative standard deviations of 2.3 % ∼ 4.0 % (N = 3). This study shows that the sensor can be applied to detect actual samples and has potential application value for female reproductive-related diseases.

Graphene quantum dots (GQDs)-modified screen-printed electrode for the determination of cannabidiol (CBD) in hemp seeds flour

In this work, the development of a graphene quantum dots (GQDs)-modified screen-printed carbon (SPCE) electrode for the determination of cannabidiol (CBD), a cannabinoid present in the Cannabis L. Sativa (hemp) plant, is reported. This cannabinoid is non-intoxicating and non-psychoactive, thus CBD-containing drugs as well as CBD-containing foods, are now on the market in many countries due to their health-beneficial effects and pharmacological activities. Because of the increasing interest in analyzing CBD in these real samples, we analyzed here a sample of hemp flour that was used for testing the developed CBD electrochemical sensor. Preliminary work devoted to optimizing the analysis conditions, allowed to development of a GQDs-modified electrode with promising characteristics for the simple screening of CBD. The electroanalytical tests for CBD detection showed a sensitivity of 0.98 μAμM-1 cm−2, which is increased by 2-folder compared to bare SPCE, and a limit of detection (LOD) equal to 0.277 μM. The developed GQDs/SPCE sensor and the analysis procedure were then applied for the CBD analysis in a hemp seeds flour sample. Based on the results obtained, the advantages/disadvantages evidenced by operating with the developed electrochemical sensor in the analysis of CBD in real samples were discussed.

Enhanced detection of lysergic acid diethylamide using Ehrlich reagent and screen-printed electrodes: A hybrid method for application in forensic analysis

In forensic investigations, the presumptive identification of illicit substances, such as Lysergic Acid Diethylamide (LSD), is crucial. While the Ehrlich's colorimetric reagent (EHR) is commonly employed for LSD detection, producing a characteristic colour change, its lack of selectivity often leads to false-positive or misinterpreted results. Addressing this, we propose a novel method combining electrochemical detection with EHR, enhancing selectivity for LSD’s preliminary identification in forensic samples. This method utilizes a screen-printed carbon electrode (carbon-SPE) in a pH 12 phosphate buffer. We observed two irreversible oxidation processes for LSD at Epa= +0.35 V (Ox1) and + 0.65 V (Ox2), and for EHR at + 0.62 V and + 0.83 V (vs Ag/AgCl). The LSD + EHR combination displayed three distinct irreversible oxidation processes at + 0.35 V, +0.66 V, and + 0.86 V. This approach provides three analytical responses for LSD identification: (1) colour change post-EHR test; (2) voltammetric detection of LSD’s two oxidation processes on carbon-SPE; (3) decreased peak current of LSD at Ox1 post-reaction after EHR. Additionally, our method facilitates LSD quantification, exhibiting a low limit of detection (LOD) of 0.69 μmol/L, and consistent electrochemical responses (RSD < 3.0 %) using the same or different carbon-SPEs. Interference studies with other illicit drugs underscored the method’s reliability and selectivity in LSD detection. Moreover, addition-recovery studies on real seized samples approached 100 %, and LSD identification was corroborated by QTOF-LC/MS analyses. Therefore, combining voltammetry with carbon-SPE and EHR offers significant potential for a rapid, simple, and selective LSD screening test in forensic analysis.

Functionalization of Carbon Electrode Surface Using Polyaniline and Gold Nanoparticles for Protein Immobilization

This study presents a screen-printed carbon electrode surface functionalization to immobilize proteins. The process involves the deposition of gold nanoparticles on the carbon electrode and subsequent surface modification to immobilize bovine serum albumin–fluorescein isothiocyanate conjugate (BSA-FITC). A combination of conducting polymer and gold nanoparticles was employed to enhance the electrode contact area and current transmission. The electrode surface morphology and properties were evaluated by scanning electron microscopy (SEM) and Raman spectroscopy, showing the porous polyaniline (PANI) film has been formed on the carbon electrode surface with the network of dendritic nanofibers. Gold nanoparticles were evenly distributed on the PANI film to form a nanocomposite material layer on the carbon electrode. The observed size of these gold nanoparticles was significantly smaller than those on the electrode without a PANI film. Additionally, the current transmission of this composite material layer has been verified by cyclic voltammetry (CV). The results show that the amplitude of the redox peak was doubled compared to the bare carbon electrode and gold nanoparticle-only deposited electrode. Moreover, the success of the process was verified by fluorescence and cyclic voltammetry. The fluorescent green color observed under the microscope indicated that BSA-FITC was on the electrode surface. The change of CV signal after each step verified the formation of a new layer on the electrode surface. These results are anticipated to play an important role in developing high-sensitivity immunosensors in the future.

Portable wireless electrochemical sensing of breviscapine using core-shell ZIFs-derived Co nanoparticles embedded in N-doped carbon nanotube polyhedra-modified electrode.

Acore-shell ZIF-67@ZIF-8-derived Co nanoparticles embedded in N-doped carbon nanotube polyhedra (Co/C-NCNP) hybrid nanostructure was preparedby a pyrolysis method. The synthesized Co/C-NCNP was modified on the screen-printed carbon electrode and used for the portable wireless sensitive determination of breviscapine (BVC) by differential pulse voltammetry. The Co/C-NCNP had a large surface area and excellent catalytic activity with increasing Co sites to combine with BVC for selective determination, which led to the improvement of the sensitivity of the electrochemical sensor. Under optimized conditions, the constructed sensor had linear ranges from 0.15 to 20.0µmol/L and 20.0 to 100.0µmol/L with the limit of detection of 0.014µmol/L (3S0/S). The sensor was successfully applied to BVC tablet sample analysis with satisfactory results. This work provided the potential applications of zeolitic imidazolate framework-derived nanomaterials in the fabrication of electrochemical sensors for the sensitive detection of drug samples.

Electrospun EU/HPMC nanofibers decorated by ZIF-8 nanoparticle as the advanced electrochemical biosensor modifier for sensitive and selective detection of c-MET cancer biomarker in human plasma sample

This research presents a selective and sensitive electrochemical biosensor for the detection of the mesenchymal–epithelial transition factor (c-MET). The biosensing is based on a modification of the SPCE (screen-printed carbon electrode) with the electrospun nanofiber containing eudragit (EU), hydroxypropyl methylcellulose (HPMC), and Zeolite imidazolate frameworks (ZIF-8) nanoparticles. EU/HPMC/ZIF-8 nanofibers have presented a high capability of electron transfer, and more active surface area than bare SPCE due to synergistic effects between EU, HPMC, and ZIF-8. On the other hand, EU/HPMC nanofibers provided high porosity, flexible structures, high specific surface area, and good mechanical strength. The presence of ZIF-8 nanoparticles improved the immobilization of anti-c-MET on the modified SPCE and also resulted in increasing the conductivity. By c-MET incubation on the modified SPCE, c-MET was connected to anti-c-MET, and consequently the electrochemical signal of [Fe(CN)6]3-/4- as the anion redox probe was reduced. In order to investigate the structural and morphological characteristics and elemental composition of electrospun nanofibers, various characterization methods including FE-SEM, XRD, FTIR, and EDS were used. Under optimum conditions with a working potential range −0.3−0.6 V (vs. Ag/AgCl), linear range (LR), correlation coefficient (R2), sensitivity, and limit of detection (LOD) were acquired at 100 fg/mL-100 ng/mL, 0.9985, 53.28 μA/cm2.dec, and 1.28 fg/mL, respectively. Moreover, the mentioned biosensor was investigated in a human plasma sample to determine c-MET and showed ideal results including reproducibility, stability, and good selectivity against other proteins.

Uricase conjugated nanostructured NiFe2O4/rGO modified flexible screen-printed carbon electrode based interface for long-range electrochemical determination of uric acid

Uric acid (UA) is a biomarker linked with gout and kidney stones that is harmful to the human body. Thus, this study explores the detection of UA using the differential pulse voltammetry (DPV) method. Initially synthesizing a highly active Nickel ferrite/reduced graphene oxide (NiFe2O4/rGO) nanocomposite ferrite material by simple surfactant-free low-temperature hydrothermal approach. The as-synthesized material was studied using various spectroscopic and microscopic techniques. The bioelectrode was fabricated on a screen-printed carbon electrode (SPCE), and the as-prepared Uricase/NiFe2O4/rGO/SPCE demonstrated improved electrochemical oxidation peak current (Ipa). While its electrochemical biosensing performance towards various UA concentrations shows a wide linear range from 5 to 900 μM, with a lower limit of detection (21·9 μM), high sensitivity (1·05×10−4 mA/μM cm2), good selectivity (RSD < 5·7 %), excellent stability, and repeatability. In addition, the fabricated bioelectrode was also explored to quantify the amount of UA in bovine serum albumin (BSA) real spiked samples. Hence, the proposed biosensor has potential applications in point-of-care-treatment of numerous disorders related to UA metabolism.

An Electroanalytical Enzymeless α-Fe2O3-ZnO Hybrid Nanostructure-Based Sensor for Sensitive Quantification of Nitrite Ions.

Nitrite monitoring serves as a fundamental practice for protecting public health, preserving environmental quality, ensuring food safety, maintaining industrial safety standards, and optimizing agricultural practices. Although many nitrite sensing methods have been recently developed, the quantification of nitrite remains challenging due to sensitivity and selectivity limitations. In this context, we present the fabrication of enzymeless iron oxide nanoparticle-modified zinc oxide nanorod (α-Fe2O3-ZnO NR) hybrid nanostructure-based nitrite sensor fabrication. The α-Fe2O3-ZnO NR hybrid nanostructure was synthesized using a two-step hydrothermal method and characterized in detail utilizing x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). These analyses confirm the successful synthesis of an α-Fe2O3-ZnO NR hybrid nanostructure, highlighting its morphology, purity, crystallinity, and elemental constituents. The α-Fe2O3-ZnO NR hybrid nanostructure was used to modify the SPCE (screen-printed carbon electrode) for enzymeless nitrite sensor fabrication. The voltammetric methods (i.e., cyclic voltammetry (CV) and differential pulse voltammetry (DPV)) were employed to explore the electrochemical characteristics of α-Fe2O3-ZnO NR/SPCE sensors for nitrite. Upon examination of the sensor's electrochemical behavior across a range of nitrite concentrations (0 to 500 µM), it is evident that the α-Fe2O3-ZnO NR hybrid nanostructure shows an increased response with increasing nitrite concentration. The sensor demonstrates a linear response to nitrite concentrations up to 400 µM, a remarkable sensitivity of 18.10 µA µM-1 cm-2, and a notably low detection threshold of 0.16 µM. Furthermore, its exceptional selectivity, stability, and reproducibility make it an ideal tool for accurately measuring nitrite levels in serum, yielding reliable outcomes. This advancement heralds a significant step forward in the field of environmental monitoring, offering a potent solution for the precise assessment of nitrite pollution.

Impedimetric sensor based on molecularly imprinted polythionine from deep eutectic solvent for epinephrine determination

Deep eutectic solvents have obtained growing interest in analytical chemistry due to opportunities related the green chemistry paradigm, i.e., substitution of organic solvents, application of nontoxic ingredients and minimal quantities of wastes formed in their synthesis and usage. In this work, the advantages of deep eutectic solvents were shown in the development of electrochemical sensor for epinephrine determination. Polythionine molecularly imprinted with epinephrine (PTNMIP) was electrodeposited from natural deep eutectic solvent (NADES) consisted of citric acid, glucose, and water in 1:1:6 molar ratio and tested with standard solutions of epinephrine, pharmaceutical preparations, and artificial samples of biological liquids. Only one drop (100 µL) of the monomer dissolved in NADES was applied for sensor preparation on the platform of screen-printed carbon electrode. Electropolymerization was performed by multiple scanning of the potential. The formation of molecular imprints was confirmed by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). After the template removal, the charge transfer resistance of the surface layer depended on the epinephrine concentration in the range from 100 nM to 316 µM (limit of detection 50 nM). Selectivity of the signal was confirmed against serotonin and norepinephrine commonly present in biological liquids. Sensor was successfully tested for the determination of epinephrine in spiked solutions mimicking influence of the plasma electrolytes, serum proteins, and in real saliva samples. The recoveries calculated for 10 μM epinephrine ranged from 98.3 to 102.6%. Insignificant influence of the additives and stabilizers present in medications was eliminated by sample dilution. Impedimetric sensor developed showed good opportunities for further application in clinical diagnostics, pharmacokinetics studies and medication manufacture control.

Synthesis and characterization of a nanostructure conductive copolymer based on polyaniline and polylactic acid as an effective substrate in proteins impedimetric biosensing.

Despite of all the developments in DNA microarray technology, there is not sufficient knowledge about protein abundance or their function in processes such as proteolysis, phosphorylation. Therefore, there is a significant need for direct detection and quantification of proteins, especially in processes such as proteomics, drug design and disease prediction. The present work introduce the new generation of polymeric substrate based on polyaniline and, polylactic acid, which it was used for impedimetric sensor in detection of proteins in particular for bovine serum albumin (BSA). In this copolymerization, the polylactic acid-block-polyaniline copolymer (PLA-b-PANI) was synthesized to attach polylactic acid and polyaniline using epichlorohydrin as a coupling agent. The structure of synthesized compounds in all steps, were confirmed by FT-IR and, 1H-NMR. The thermal properties and, morphology were analyzed by DSC, TGA, and, SEM. Also the electrochemical characteristics of fabricated PLA-b-PANI electrode were investigated by Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The results demonstrated that morphology of the PLA-b-PANI is sphere shape nanoparticles with dimension less than 100 nanometer diameters and, reasonable thermal properties. PLA-b-PANI was used to modify a screen-printed carbon electrode (SPCE) to fabricate a BSA impedimetric sensor. In order to increase the performance of the proposed impedimetric sensor, optimization of incubation time, pH and amount of PLA-b-PANI were investigated. The results show that the impedimetric sensor has the highest response when the electrode surface is covered with 5 microliters of PLA-b-PANI, and is incubated in BSA solution with pH 6.5 for 5 min. Impedimetric results showed that the PLA-b-PANI has excellent properties in reducing the charge transfer resistance and increasing the electron charge transfer rate. The final impedimetric sensor exhibited good repeatability, reproducibility, and chemical stability within the linear concentration range of 0.1-20 μg L-1 of BSA, and a detection limit of 0.05 μg L-1.