A novel nonenzymatic hydrogen peroxide amperometric sensor based on AgNp@GNR nanocomposites modified screen-printed carbon electrode

Enhancing electrochemical sensing through the use of functionalized graphene composites as nanozymes

Graphene-based nanozymes possess inherent nanomaterial properties that offer not only a simple substitute for enzymes but also a versatile platform capable of bonding with complex biochemical environments. The current review discusses the replacement of enzymes in developing biosensors with nanozymes. Functionalization of graphene-based materials with various nanoparticles can enhance their nanozymatic properties. Graphene oxide functionalization has been shown to yield graphene-based nanozymes that closely mimic several natural enzymes. This review provides an overview of the classification, current state-of-the-art development, synthesis routes, and types of functionalized graphene-based nanozymes for the design of electrochemical sensors. Furthermore, it includes a summary of the application of functionalized graphene-based nanozymes for constructing electrochemical sensors for pollutants, drugs, and various water and food samples. Challenges related to nanozymes as electrocatalytic materials are discussed, along with potential solutions and approaches for addressing these shortcomings.

Ligand influence in electrocatalytic properties of Cu(II) triazole complexes for hydrogen peroxide detection in aqueous media

In this work, electrocatalytic changes of Cu(II) triazole complexes (Cu(L)₂) resulting from inductive effects were evaluated to fabricate a sensor for hydrogen peroxide (H₂O₂) determination. Three copper(II) complexes with electronically differentiated ligands were synthesized by slow diffusion method and characterized by X-ray crystallography, Fourier transformed infrared (FTIR), UV-Vis, scanning electron microscopy (SEM) and voltammetry cyclic (CV). Cu(LOMe)2/GC, Cu(LBr)2/GC and Cu(LNO2)2/GC sensors were then prepared. Under optimal conditions (pH = 11), the optimal sensor presented a response at -0.5 V, good linear range of 1-32 μM, reproducibility (1.7%), repeatability (1.2%), LOD of 0.0246 μM (S/N = 5), LOQ of 0.0747 μM (S/N = 5) and selectivity. Additionally, Cu(LNO2)2/GC sensor has been successfully applied in commercial substances, such as mouthwash, milk and tea.

Electrochemical Determination of Morphine in Urine Samples by Tailoring FeWO4/CPE Sensor

Morphine (MORPH) is natural alkaloid and mainly used as a pain reliever. Its monitoring in human body fluids is crucial for modern medicine. In this paper, we have developed an electrochemical sensor for submicromolar detection of MORPH. The sensor is based on modified carbon paste electrode (CPE) by investigating the Fe_xW_1-xO₄ ratio in iron tungstate (FeWO₄), as well as the ratio of this material in CPE. For the first time, the effect of the iron-tungsten ratio in terms of achieving the best possible electrochemical characteristics for the detection of an important molecule for humans was examined. Morphological and electrochemical characteristics of materials were studied. The best results were obtained using Fe₁W₃ and 7.5% of modifier in CPE. For MORPH detection, square wave voltammetry (SWV) was optimized. Under the optimized conditions, Fe₁W₃@CPE resulted in limit of detection (LOD) of the method of 0.58 µM and limit of quantification (LOQ) of 1.94 µM. The linear operating range between 5 and 85 µM of MORPH in the Britton-Robinson buffer solution (BRBS) at pH 8 as supporting electrolyte was obtained. The Fe₁W₃@CPE sensor resulted in good selectivity and excellent repeatability with relative standard deviation (RSD) and was applied in real-world samples of human urine. Application for direct MORPH detection, without tedious sample pretreatment procedures, suggests that developed electrochemical sensor has appeared to be a suitable competitor for efficient, precise, and accurate monitoring of the MORPH in biological fluids.

EDTA derived graphene supported porous cobalt hexacyanoferrate nanospheres as a highly electroactive nanocomposite for hydrogen peroxide sensing

Developed a highly electroactive graphene and porous cobalt hexacyanoferrate nanosphere (Gr/P-CoHCF-NSPs) composite for H2O2 sensing by using EDTA chelation strategy.

Highly Sensitive Amperometric Detection of Hydrogen Peroxide in Saliva Based on N-Doped Graphene Nanoribbons and MnO2 Modified Carbon Paste Electrodes

Four different graphene-based nanomaterials (htGO, N-htGO, htGONR, and N-htGONR) were synthesized, characterized, and used as a modifier of carbon paste electrode (CPE) in order to produce a reliable, precise, and highly sensitive non-enzymatic amperometric hydrogen peroxide sensor for complex matrices. CPE, with their robustness, reliability, and ease of modification, present a convenient starting point for the development of new sensors. Modification of CPE was optimized by systematically changing the type and concentration of materials in the modifier and studying the prepared electrode surface by cyclic voltammetry. N-htGONR in combination with manganese dioxide (1:1 ratio) proved to be the most appropriate material for detection of hydrogen peroxide in pharmaceutical and saliva matrices. The developed sensor exhibited a wide linear range (1.0–300 µM) and an excellent limit of detection (0.08 µM) and reproducibility, as well as high sensitivity and stability. The sensor was successfully applied to real sample analysis, where the recovery values for a commercially obtained pharmaceutical product were between 94.3% and 98.0%. Saliva samples of a user of the pharmaceutical product were also successfully analyzed.

The Interaction between DNA and Three Intercalating Anthracyclines Using Electrochemical DNA Nanobiosensor Based on Metal Nanoparticles Modified Screen-Printed Electrode

The screen-printed electrodes have gained increasing importance due to their advantages, such as robustness, portability, and easy handling. The manuscript presents the investigation of the interaction between double-strand deoxyribonucleic acid (dsDNA) and three anthracyclines: epirubicin (EPI), idarubicin (IDA), and doxorubicin (DOX) by differential pulse voltammetry on metal nanoparticles modified by screen-printed electrodes. In order to investigate the interaction, the voltammetric signals of dsDNA electroactive bases were used as an indicator. The effect of various metal nanomaterials on the signals of guanine and adenine was evaluated. Moreover, dsDNA/PtNPs/AgNPs/SPE (platinum nanoparticles/silver nanoparticles/screen-printed electrodes) was designed for anthracyclines–dsDNA interaction studies since the layer-by-layer modification strategy of metal nanoparticles increases the surface area. Using the signal of multi-layer calf thymus (ct)-dsDNA, the within-day reproducibility results (RSD%) for guanine and adenine peak currents were found as 0.58% and 0.73%, respectively, and the between-day reproducibility results (RSD%) for guanine and adenine peak currents were found as 1.04% and 1.26%, respectively. The effect of binding time and concentration of three anthracyclines on voltammetric signals of dsDNA bases were also evaluated. The response was examined in the range of 0.3–1.3 ppm EPI, 0.1–1.0 ppm IDA and DOX concentration on dsDNA/PtNPs/AgNPs/SPE. Electrochemical studies proposed that the interaction mechanism between three anthracyclines and dsDNA was an intercalation mode.

2D/3D Copper-Based Metal-Organic Frameworks for Electrochemical Detection of Hydrogen Peroxide

Metal-organic frameworks (MOFs) have been extensively used as modified materials of electrochemical sensors in the food industry and agricultural system. In this work, two kinds of copper-based MOFs (Cu-MOFs) with a two dimensional (2D) sheet-like structure and three dimensional (3D) octahedral structure for H2O2 detection were synthesized and compared. The synthesized 2D and 3D Cu-MOFs were modified on the glassy carbon electrode to fabricate electrochemical sensors, respectively. The sensor with 3D Cu-MOF modification (HKUST-1/GCE) presented better electrocatalytic performance than the 2D Cu-MOF modified sensor in H2O2 reduction. Under optimal conditions, the prepared sensor displayed two wide linear ranges of 2 μM-3 mM and 3-25 mM and a low detection limit of 0.68 μM. In addition, the 3D Cu-MOF sensor exhibited good selectivity and stability. Furthermore, the prepared HKUST-1/GCE was used for the detection of H2O2 in milk samples with a high recovery rate, indicating great potential and applicability for the detection of substances in food samples. This work provides a convenient, practical, and low-cost route for analysis and extends the application range of MOFs in the food industry, agricultural and environmental systems, and even in the medical field.

Application of an electrochemical sensor using copper oxide nanoparticles/polyalizarin yellow R nanocomposite for hydrogen peroxide

In this study, copper oxide nanoparticles (CuONPs) were prepared by a simple chemical method and then characterized by scanning electron microscope (SEM). A novel electrochemical sensor for hydrogen peroxide (H₂O₂) analysis was prepared by immobilizing copper oxide nanoparticles and polyalizarin yellow R (PYAR) on bare glassy carbon electrode (PAYR/CuONPs/GCE). The electrocatalytical behavior of the proposed electrochemical sensor was also studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Based on the results, the PAYR/CuONP nanocomposite had significant electrocatalytic oxidation and reduction properties for the detection and determination of H₂O₂. Some parameters such as linear range, sensitivity, and detection limit for reduction peak were obtained as 0.1-140 μM, 1.4154 μA cm^-2 μM^-1, and 0.03 μM, respectively, by the DPV technique. Some advantages of this electrode were having widespread linear range, low detection limit, and, most importantly, ability in simultaneous oxidation and reduction of H₂O₂ at two applied potentials.

A novel electrochemical lung cancer biomarker cytokeratin 19 fragment antigen 21-1 immunosensor based on Si3N4/MoS2 incorporated MWCNTs and core-shell type magnetic nanoparticles

Lung cancer is one of deadliest and most life threatening cancer types. Cytokeratin 19 fragment antigen 21-1 (CYFRA 21-1) is a significant biomarker for the diagnosis of non-small cell lung cancer (NSCLC). Due to these reasons, a novel electrochemical immunosensor based on a silicon nitride (Si3N4)-molybdenum disulfide (MoS2) composite on multi-walled carbon nanotubes (Si3N4/MoS2-MWCNTs) as an electrochemical sensor platform and core-shell type magnetic mesoporous silica nanoparticles@gold nanoparticles (MMSNs@AuNPs) as a signal amplifier was presented for CYFRA21-1 detection in this study. Capture antibody (Ab1) immobilization on a Si3N4/MoS2-MWCNT modified glassy carbon electrode (Si3N4/MoS2-MWCNTs/GCE) was firstly successfully performed by stable electrostatic/ionic interactions between the -NH2 groups of the capture antibody and the polar groups of Si3N4/MoS2. Then, specific antibody-antigen interactions between the electrochemical sensor platform and the signal amplifier formed a novel voltammetric CYFRA21-1 immunosensor. The prepared composite materials and electrochemical sensor surfaces were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A linearity range of 0.01-1.0 pg mL-1 and a low detection limit (LOD) of 2.00 fg mL-1 were also obtained for analytical applications. Thus, the proposed immunosensor based on Si3N4/MoS2-MWCNTs and MMSNs@AuNPs has great potential for medical diagnosis of lung cancer.

Novel voltammetric tumor necrosis factor-alpha (TNF-α) immunosensor based on gold nanoparticles involved in thiol-functionalized multi-walled carbon nanotubes and bimetallic Ni/Cu-MOFs

TNF-α, as a pro-inflammatory cytokine, regulates some physiological and pathological courses. TNF-α level increases in some important diseases such as cancer, arthritis, and diabetes. In addition, it displays an important function in Alzheimer's and cardiovascular diseases. Herein, a novel, sensitive, and selective voltammetric TNF-α immunosensor was prepared by using gold nanoparticles involved in thiol-functionalized multi-walled carbon nanotubes (AuNPs/S-MWCNTs) as sensor platform and bimetallic Ni/Cu-MOFs as sensor amplification. Firstly, the sensor platform was developed on glassy carbon electrode (GCE) surface by using mixture of thiol-functionalized MWCNTs (S-MWCNTs) and AuNPs. Then, capture TNF-α antibodies were conjugated to sensor platform by amino-gold affinity. After capture TNF-α antibodies' immobilization, a new-type voltammetric TNF-α immunosensor was developed by immune reaction between AuNPs/S-MWCNTs immobilized with primer TNF-α antibodies and bimetallic Ni/Cu-MOFs conjugated with seconder TNF-α antibodies. The prepared TNF-α immunosensor was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) method, x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), thermogravimetric analysis, Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). A linearity range of 0.01-1.0 pg mL^-1 and a low detection limit of 2.00 fg mL^-1 were also obtained for analytical applications.

Amperometric galectin-3 immunosensor-based gold nanoparticle-functionalized graphitic carbon nitride nanosheets and core-shell Ti-MOF@COFs composites

Antigen galectin-3 (GL-3), a member of β-galactoside proteins indicates cardiac fibrosis and is a significant biomarker for monitoring heart failure risk and death risk. In this study, a novel sensitive amperometric method for antigen GL-3 detection is developed based on gold nanoparticle-functionalized graphitic carbon nitride nanosheets (g-C₃N₄@Au NPs) as the sensor platform and Ti-based metal organic framework (Ti-MOF, NH₂-MIL-125)@covalent organic frameworks (COFs) composite for the signal amplification. The Ti-MOF@COF composite not only facilitates the penetration of antibody proteins into pore channels, but also the highly stable antigen-antibody interactions. The prepared sensor platform and signal amplification material are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) method, X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The amperometric technique is utilized to achieve antigen GL-3 detection in plasma samples. The immunosensor demonstrates a wide linearity range (0.0001-20.0 ng mL^-1) and a low detection limit (0.025 pg mL^-1). Finally, the prepared immunosensor shows high stability and selectivity under optimum conditions.