Glassy Carbon Electrode Electromodification in the Presence of Organic Monomers: Electropolymerization versus Activation

Enhanced simultaneous voltammetric detection of lead, copper, and mercury using a MIL-101(Cr)-(COOH)2@MWCNTs modified glassy carbon electrode

BACKGROUND

Electrochemical methods, particularly those utilizing sensors, offer distinct advantages over classical analytical methods. They are cost-effective, compatible with mass fabrication, suitable for remote sensing, and can be designed as handheld analyzers. In this context, MIL-101(Cr)-(COOH)₂@MWCNTs was utilized for the first time as a modifier for GCE for the sensitive voltammetric detection of Pb(II), Cu(II), and Hg(II). The surface characteristics of the composite were examined using SEM, EDX, XRD, FTIR, and N₂ adsorption/desorption isotherms. The electrochemical behavior of the modified electrode was investigated using differential pulse anodic stripping voltammetry (DPASV).

RESULTS

The DPAS voltammograms of the composite modified electrode are characterized by a remarkable increase in the oxidation peak currents for Pb, Cu, and Hg, indicating that MIL-101(Cr)-(COOH)₂@MWCNTs composite significantly enhances the electrocatalytic response towards the oxidation of the studied heavy metals. The impact of various parameters, such as accumulation potential, accumulation time, amount of MOF, composite thickness, and supporting electrolyte concentration on the developed sensor's response, were investigated. The analytical performances were also investigated using DPASV. The optimized MIL-101(Cr)-(COOH)₂@MWCNTs/GCE-based sensor exhibited a linear range of 0.11-15.4 μM, 0.11-20.1 μM, and 0.06-20.1 μM, and lower limits of detection (LOD) of 0.08 μM, 0.09 μM, and 0.04 μM for Pb(II), Cu(II), and Hg(II), respectively.

SIGNIFICANCE

This study introduces a novel MIL-101(Cr)-(COOH)₂@MWCNTs composite-modified GCE, offering exceptional sensitivity, selectivity, and repeatability for detecting Pb(II), Cu(II), and Hg(II). With broad analytical ranges, low detection limits, and successful application in real water samples, the work demonstrates significant potential for environmental heavy metal monitoring and pollution control.

Green and cost-effective voltammetric assay based on activated glassy carbon electrode for determination of the plant growth regulator methyl jasmonate

A green, cost-effective, and efficient square-wave voltammetric (SWV) assay based on an electrochemically activated glassy carbon electrode (aGCE) for the determination of the plant growth regulator methyl jasmonate (MeJA) was developed. The activation was performed by anodization in 0.1 mol L-1 NaOH by 5 cyclic voltammetric measurements in the potential range of 0-2 V at a scan rate of 100 mV s-1. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) were applied to analyze the difference between the bare GCE and the aGCE in terms of their electrochemical properties. The functionalization of the GCE surface by oxygen-containing groups not only creates new active sites but also improves electron transfer dynamics and electrocatalytic activity. The SWV procedure displays a wide linear response from 0.1 to 50.0 μmol L-1, a low LOD = 0.027 μmol L-1, and LOQ = 0.097 μmol L-1. The aGCE was successfully applied to MeJA analysis in Phaseolus coccineus leaf extracts.

Development of a magnetic α-Fe2O3/Fe3O4 heterogeneous nanorod-based electrochemical biosensing platform for HPV16 E7 oncoprotein detection

The prevention, diagnosis and treatment of cancer have always been the focus of medical research. In this study, a label-free, rapid, simple, sensitive, and specific method for the detection of HPV16 E7 oncoprotein was developed. The electrochemical biosensor platform was constructed by magnetic self-assembly of α-Fe2O3/Fe3O4@Au nanocomposites onto the surface of magnetic glass carbon electrode (MGCE), and the nanocomposite was connected to aptamer through AuS bond to construct a probe to capture HPV16 E7. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were applied to verify the performance of the constructed biosensor. The condition optimization and performance analysis were carried out by differential pulse voltammetry (DPV). Under optimal conditions, the biosensor exhibited a strong linearity between current value and the logarithm of HPV16 E7 oncoprotein concentration in the range of 10 pg/mL - 0.1 μg/mL, with a limit of detection (LOD) of 159 fg/mL and a limit of quantification (LOQ) of 530 fg/mL, and it also revealed excellent reproducibility, long-term stability, and anti-interference ability. In a word, the biosensor would contribute to the early diagnosis of oncoprotein HPV16 E7 and had promising application prospects.

Electrochemical Synthesis of Molecularly Imprinted Polymers for L-Tyrosine Detection

L-Tyrosine (L-Tyr), a critical amino acid whose aberrant levels impact melanin and dopamine levels in human body while also increasing insulin resistance thereby increasing the risk of type 2 diabetes. The objective of this study was to detect the amount of L-Tyr in human fluids by tailored electrochemical synthesis of well adhered, homogenous and thin molecularly imprinted polymers (MIPs) by the electro-polymerization of pyrrole on glassy carbon electrode modified functionalized multi-walled carbon nanotubes. The key benefits of this procedure over previous imprinting techniques were the elimination of expensive materials like Au and tedious multi-step synthesis, for L-Tyr detection using a handheld potentiostat. The developed particles were characterized using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope, Chronoamperometry, and Cyclic Voltammetry. With strong reproducibility and stability, this optimized approach provides a rapid and effective method of preparing and sensing MIPs for the target analyte with a broad linear range of [Formula: see text] to [Formula: see text]. The Limit of Detection and Limit of Quantification were [Formula: see text] and [Formula: see text], respectively. The engineered sensor was validated for quantifying the concentrations of L-Tyr in human blood and serum samples, yielding satisfactory recovery and can be expanded in future to detect analytes simultaneous.

Fabrication of an affordable and sensitive corticosteroid-binding globulin immunosensor based on electrodeposited gold nanoparticles modified glassy carbon electrode

Herein, we fabricated an ultrasensitive electrochemical immunosensor for the quantitative detection of corticosteroid-binding globulin (CBG). CBG is a protein that regulates glucocorticoid levels and is an important biomarker for inflammation. A decrease in CBG levels is a key biomarker for inflammatory diseases, such as septic shock. To enhance the electrochemical performance and provide a large surface area for anti-CBG immobilization, we functionalized the glassy carbon electrode surface with AuNPs. Electrochemical characterization methods including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to examine the construction of the fabricated immunosensor. The electrochemical signal demonstrated a remarkable sensitivity to the CBG antigen, with a detection range from 0.01 to 100 μg/mL and a limit of detection of 0.012 μg/mL, making it suitable for both clinical and research applications. This label-free immunosensor offers significant advantages, including high sensitivity, low detection limits and excellent selectivity, making it a promising tool for detecting CBG in complex biological samples. Its potential applications include early disease diagnosis, treatment monitoring and studying CBG-related physiological processes.

Subtle adjustment of the cyclic potential on electro-activated glassy carbon electrodes for sensitive sensing of methyl parathion

Facile electro-activated glassy carbon electrodes (e-GCEs), which are prepared in electrolyte solution with a certain potential for a few seconds, have been verified to improve analytical performance toward not a few electro-active molecules recently. Nevertheless, how and why the potential plays an important role is not clear, and has even not received enough consideration. In this paper, we found that the mode and the range of applied potential significantly impacted the sensitivity of methyl parathion (MP), which is a typical pesticide with the electro-active group of -NO2. Compared with constant potential, the e-GCE with cyclic potential provided a much more stable baseline during MP detection. Additionally, the electro-oxidation peak current of MP at around -0.1 V on it was higher than another changeable potential (constant current). What's more interesting, with cyclic potential for 50 segments from -2 to 1.5 V, the peak current value increased by 30 times in comparison with a bare GCE, but only 2 times from -2 to 1 V. Then after systematic investigation including structures of the electrode surface and functional groups, we speculated that the produced group of O-CO in the process of activation and remaining groups of C-O and CO on the bare GCE surface are beneficial for adsorbing MP molecules leading to enhanced peak current. Employing the proposed e-GCE, the limit of detection of MP reached 0.015 μM and the reproducibility was perfect. This work elucidates the potent impact of electro-activation potential parameters on electroanalysis behaviors.

Label-free and ultrasensitive electrochemical transferrin detection biosensor based on a glassy carbon electrode and gold nanoparticles

In this study, we developed a label-free and ultrasensitive electrochemical biosensor for the detection of transferrin (Tf), an important serum biomarker of atransferrinemia. The biosensor was fabricated by using glassy carbon electrode (GCE) and modified with gold nanoparticles (AuNPs) via electroless deposition. The electrochemical characteristics of the GCE-AuNPs biosensors were characterized using cyclic voltammetry and electrochemical impedance spectroscopy analysis. Differential pulse voltammetry was used for quantitative evaluation of the Tf-antigen by recording the increase in the anodic peak current of GCE-AuNPs biosensor. The GCE-AuNPs biosensor demonstrates superior sensing performance for Tf-antigen fortified in buffer, with a wide linear range of 0.1 to 5000 μg/mL and a limit of detection of 0.18 μg/mL. The studied GCE-AuNPs biosensor showed excellent sensitivity, selectivity, long-term storage stability and simple sensing steps without pretreatment of clinical samples. This GCE-AuNPs biosensor indicates great potential for developing a Tf detection platform, which would be helpful in the early diagnosis of atransferrinemia. The developed GCE-AuNPs biosensor holds great potential in biomedical research related to point of care for the early diagnosis and monitoring of diseases associated with aberrant serum transferrin levels. These findings suggest that the GCE-AuNPs biosensor has great potential for detecting other serum biomarkers.

Green and cost-effective voltammetric assay for spiramycin based on activated glassy carbon electrode and its applications to urine and milk samples

A simple, cost-effective, and efficient differential pulse voltammetric (DPV) assay for monitoring spiramycin adipate (SPA) in its dosage forms, urine, and milk samples at an activated glassy carbon electrode (GCE) was developed. GCE was electrochemically activated by anodization at a high positive voltage (2.5 V). The activated glassy carbon electrode (AGCE) was surface characterized, optimized, and utilized for the electrochemical assay of SPA. The electrochemical behavior of the AGCEs was investigated using cyclic voltammetry (CV) which shows a remarkable increase in the anodic peak of SPA in comparison with GCE. This behavior reflects a remarkable increase in the electrocatalytic oxidation of SPA at AGCE. The impacts of various parameters such as scan rate, accumulation time, and pH were investigated. The analytical performance of the activated glassy carbon electrodes was studied utilizing DPV. Under optimum conditions, the oxidation peak current exhibited two linear ranges of 80 nm to 0.8 μM and 0.85-300 μM with a lower limit of detection (LOD) of 20 nM. The developed assay exhibited high sensitivity, excellent repeatability, and good selectivity. Additionally, the developed SPA-sensitive modified GCE was successfully applied for SPA assay in its pharmaceutical dosage form and diluted biological fluids as well, with satisfactory recovery results which correlated well with the results obtained using spectrophotometry.

Significance of an Electrochemical Sensor and Nanocomposites: Toward the Electrocatalytic Detection of Neurotransmitters and Their Importance within the Physiological System

A prominent neurotransmitter (NT), dopamine (DA), is a chemical messenger that transmits signals between one neuron to the next to pass on a signal to and from the central nervous system (CNS). The imbalanced concentration of DA may cause numerous neurological sicknesses and syndromes, for example, Parkinson's disease (PD) and schizophrenia. There are many types of NTs in the brain, including epinephrine, norepinephrine (NE), serotonin, and glutamate. Electrochemical sensors have offered a creative direction to biomedical analysis and testing. Researches are in progress to improve the performance of sensors and develop new protocols for sensor design. This review article focuses on the area of sensor growth to discover the applicability of polymers and metallic particles and composite materials as tools in electrochemical sensor surface incorporation. Electrochemical sensors have attracted the attention of researchers as they possess high sensitivity, quick reaction rate, good controllability, and instantaneous detection. Efficient complex materials provide considerable benefits for biological detection as they have exclusive chemical and physical properties. Due to distinctive electrocatalytic characteristics, metallic nanoparticles add fascinating traits to materials that depend on the material's morphology and size. Herein, we have collected much information on NTs and their importance within the physiological system. Furthermore, the electrochemical sensors and corresponding techniques (such as voltammetric, amperometry, impedance, and chronoamperometry) and the different types of electrodes' roles in the analysis of NTs are discussed. Furthermore, other methods for detecting NTs include optical and microdialysis methods. Finally, we show the advantages and disadvantages of different techniques and conclude remarks with future perspectives.

Efficient Entrapment of Alpha-Synuclein Biotinylated Antibody in KCC-1-NH-CS2 and Application for the Sensitive Diagnosis of Parkinson's Using Recognition of Biomarker: An Innovative Electrochemical Label-Free Immunosensor for the Biomedical Analysis of Neurodegenerative Diseases

The early detection of Parkinson's disease (PD) is a critical issue in terms of efficiency. Alpha-synuclein (α-Syn) is a biomarker in PD checks. Alpha-synuclein (α-syn) is the major constituent of Lewy bodies and a pathogenic hallmark of all synucleinopathies, including PDs, dementia with Lewy bodies, and multiple system atrophy. In this study, KCC-1-NH-CS₂ was conjugated with biotinylated Ab and entrapped in P(β-CD) polymer cavities. Using this approach, a novel electrochemical label-free immunosensor was designed for the quantification of α-syn in real human samples. For this purpose, the glassy carbon electrode electropolymerized with P(β-CD) biopolymer provided an excellent matrix for entrapping of KCC-1-NH-CS₂ loaded with the biotinylated antibody of α-syn. Using the chronoamperometric technique, the proposed immunosensor shows a suitable range of 0.02 to 64 ng/mL for the determination of α-syn. Additionally, a low limit of quantification of the engineered biosensor was obtained at 0.02 ng/mL. The developed immunosensor's adequate stability, sensitivity, and selectivity, together with its ease of manufacture, make it a promising diagnostic technique for further research. This study also will pave the way for further applications of the synergetic effect of β-CD and KCC-1-NH-CS₂ for biomedical analysis in the near future.

Activated Glassy Carbon Electrode as an Electrochemical Sensing Platform for the Determination of 4-Nitrophenol and Dopamine in Real Samples

Glassy carbon electrode (GCE) was electrochemically activated using a repetitive cyclic voltammetric technique to develop an activated glassy carbon electrode (AGCE). The developed AGCE was optimized and utilized for the electrochemical assay of 4-nitrophenol (4-NP) and dopamine (DA). Cyclic voltammetry (CV) was employed to investigate the electrochemical behavior of the AGCE. Compared to the bare GCE, the developed AGCE exhibits a significant increase in redox peak currents of 4-NP and DA, which indicates that the AGCE significantly improves the electrocatalytic reduction of 4-NP and oxidation of DA. The electrochemical signature of the activation process could be directly associated with the formation of oxygen-containing surface functional groups (OxSFGs), which are the main reason for the improved electron transfer ability and the enhancement of the electrocatalytic activity of the AGCE. The effects of various parameters on the voltammetric responses of the AGCE toward 4-NP and DA were studied and optimized, including the pH, scan rate, and accumulation time. Differential pulse voltammetry (DPV) was also utilized to investigate the analytical performance of the AGCE sensing platform. The optimized AGCE exhibited linear responses over the concentration ranges of 0.04-65 μM and 65-370 μM toward 4-NP with a lower limit of detection (LOD) of 0.02 μM (S/N = 3). Additionally, the AGCE exhibited a linear responses over the concentration ranges of 0.02-1.0 and 1.0-100 μM toward DA with a lower limit of detection (LOD) of 0.01 μM (S/N = 3). Moreover, the developed AGCE-based 4-NP and DA sensors are distinguished by their high sensitivity, excellent selectivity, and repeatability. The developed sensors were successfully applied for the determination of 4-NP and DA in real samples with satisfactory recovery results.

Plasmon-Boosted Cu-Doped TiO2 Oxygen Vacancy-Rich Luminol Electrochemiluminescence for Highly Sensitive Detection of Alkaline Phosphatase

In this study, an effective oxygen vacancy (O_v)-involved luminol-dissolved oxygen (O₂) electrochemiluminescence (luminol-DO ECL) system was developed and exploited for ECL sensing applications through significant plasmon enhancement of the O_v-involved weak luminol-DO ECL signals by the combined use of Cu-doped TiO₂ oxygen vacancy and a Au@SiO₂ nanomembrane. The results disclosed that the ECL response of the corresponding system could be synergistically boosted, and the plausible underlying mechanism has been discussed. Furthermore, for the first time, the developed system has been successfully applied for the highly sensitive detection of alkaline phosphatase with a low limit of detection of 0.005 U/L, with an excellent linear range from 0.005 to 10 U/L, as well as good stability and reproducibility.

Integrated hand-held electrochemical sensor for multicomponent detection in urine

Electrochemical sensors have shown great advantage and application potential in point-of-care testing (POCT) related scenarios. However, some fatal problems plague its widespread utilization, which include the susceptibility of sensors to interference in real samples (e.g. pH), the contradiction between the limited objects detectable for most sensors and the requirement of multi-target analysis in most cases, and the complicated procedures in sensor preparation as well as in routine use. This paper contributed a tip-like electrochemical sensor prototype. By integrated with a commercial pipettor, it fulfilled semi-automatic assay procedure of sampling, detection and rinsing, thus saving operational time and manual work. The tip sensor owns the property of simple fabrication and is free from any modification of extra bio/chem materials. Moreover, built on multiple electrochemical signal outputs including open circuit potential, peak current and potential of specific electrochemical reaction, this work established a novel multi-component sensing strategy, wherein detection of uric acid (UA), urea and pH in urine samples was realized by using one single working electrode. The detection range for the above targets is 5.0~600 μM for UA, 4.0~8.0 for pH and 0.5~7.0 mM for urea with the detection limits (S/N = 3) of 0.05 μM for UA and 5.4 μM for urea, and the sensitivity of pH assay is 73 mV/pH. Notably, as variation of sample pH has impact on electrochemical analysis, the pH-related parameter was introduced for calibration to diminish such interference. The developed tip sensor and the novel sensing strategy may open a new window for electrochemical technology and broaden its application in POCT.

Sensitive identification of silibinin as anticancer drug in human plasma samples using poly (β-CD)-AgNPs: A new platform towards efficient clinical pharmacotherapy

Silibinin is effective in significantly inhibiting the growth of cancer cells which shown significant anti-neoplastic effects in a variety of in vitro and in vivo cancer models, including skin, breast, lung, colon, bladder, prostate and kidney carcinomas. So, development of a new method to its biomedical analysis in clinical samples in highly demanded. In this study, an innovative electroanalysis method for the accurate, sensitive and rapid recognition of silibinin in human plasma samples was proposed and validated. The sensing platform was designed using silver nanoparticles (AgNPs) dispersed on the polymeric layer of β-cyclodextrin (β-CD). AgNPs with cubic shape providing a large effective surface area for β-CD electropolymerization. So, a layer with high electron conductivity boosting the detection electrochemical signals. Also, poly(β-CD) providing an efficient substrate with cavities to interact with silibinin and its oxidation. Differential pulse voltammetry technique was conducted to measure silibinin concentration in human real samples. Under optimized conditions, proposed sensor indicated linear relationship between the anodic peak current and concentration of silibinin in the range of 0.0103-10.3 µM on the standard and human plasma samples. Based on obtained results, proposed sensor is an efficient platform to efficient therapy of cancer based on recognition of silibinin in clinical samples.

Laser-Induced Carbon Electrodes in a Three-Dimensionally Printed Flow Reactor for Detecting Lead Ions

Nowadays, heavy metal pollution has attracted wide attention. Many electrochemical methods have been developed to detect heavy metal ions. The electrode surface usually needs to be modified, and the process is complicated. Herein, we demonstrate the fabrication of electrodes by direct laser sintering on commercial polymer films. The prepared porous carbon electrodes can be used directly without any modification. The electrodes were fixed in a 3D-printed flow reactor, which led to very little analyte required during the detection process. The velocities of the analyte under stirring and flowing conditions were simulated numerically. The results prove that flow detection is more conducive to improving detection sensitivity. The limit of detection is about 0.0330 mg/L for Pb²⁺. Moreover, the electrode has been proved to have good repeatability and stability.