Preparation of Molecularly Imprinted Magnetic Graphene Oxide-Gold Nanocomposite and Its Application to the Design of Electrochemical Sensor for Determination of Epinephrine

A novel copper ion enhanced electrochemical DNA biosensor for the determination of epinephrine

A novel electrochemical biosensor was developed for the detection of epinephrine (EP) by immobilizing double-strand DNA (dsDNA) bound with copper ions on a gold electrode (Cu2+/dsDNA/MCH/AuE). The electrochemical behavior of EP at Cu2+/dsDNA/MCH/AuE was examined, and the results demonstrated a significant enhancement in the electrocatalytic oxidation peak current of EP due to the formation of a stable G-Cu(II)-G sandwich structure between Cu2+ and guanine at the modified electrode. The modification process of the electrode was characterized by scanning electron microscopy, infrared spectroscopy, electrochemical impedance spectroscopy, and differential pulse voltammetry. A study on the effect of pH in phosphate buffer solution on the electrochemical oxidation of EP indicated that the catalytic oxidation process was pH-dependent. A plot of catalytic current versus EP concentration exhibited a dual-linear relationship within two ranges: 1.0-12.5 μM and 12.5-1000.0 μM, with correlation coefficients of 0.995 and 0.997, respectively. The limit of detection was determined to be 47 nM (S/N = 3). According to the calculated Hill coefficient (0.99), it can be concluded that the electrocatalytic process followed the Michaelis-Menten kinetic mechanism. The maximum catalytic current Im was 25 μA, while the apparent Michaelis-Menten constant Km was 1.425 mM. These findings indicated excellent electrocatalytic activity of the modified electrode towards oxidation of EP. The developed biosensor successfully detected EP in spiked mouse serum as well as epinephrine hydrochloride injection with high selectivity, sensitivity, stability, and accuracy.

Smart green CQD@SiO2 hybrid coated optical fiber manifesting dual versatile absorptive and MIP features towards epinephrine detection

For the first time, in this study, a novel optical fiber biosensor is proposed and developed via coating only one smart functional layer of silica-supported carbon dots realizing the concepts of both lossy mode resonance (LMR) and molecularly imprinted polymer (MIP) for epinephrine detection. The carbon quantum dots (CQDs) are prepared using a green synthesis method and then treated with a molecularly imprinted polymer (MIP) strategy. Under ultrasonic irradiation, a SiO₂ shell was stabilized on the surface of the CQDs to graft and to provide the LMR/MIP functional layer onto the curved optical fiber surface. Accurate structural and morphological characterization confirmed the carbon quantum dot agents and also the SiO₂ supporting shells on the optical fiber, while spectroscopic analysis confirms the formation of the imprinted polymer and desirable absorbance characteristics. The experimental and numerical sensing studies revealed that the proposed sensing probe allows the rapid adsorption/desorption of epinephrine to the sensing films and highly permeable coating for studying the influence of effective parameters. Under the optimal experimental conditions, the sensitivity of the proposed LMR-based optical fiber sensor is reported to be 0.37 nm μM^-1 with a correlation coefficient of 0.99. So, sensitive detection of epinephrine at a low concentration can be guaranteed with a 0.72 mM LOD.

An electrochemical sensor modified with a molecularly imprinted polymer and carbon black for 17-β-estradiol detection

The purpose of this work was to apply an electrochemical sensor modified with a molecularly imprinted polymer (MIP) and carbon black (CB) for 17β-estradiol (E2) detection in river water samples. The synthesized MIP was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).The modification of the electrode with the MIP and CB contributed to increased sensitivity, an increase of over 173% in relation to that of the bare electrode. The experimental parameters, amount of modifiers, pH and possible interfering species were evaluated. The method showed linearity from 0.10 to 23.0 μmol L^-1 and detection and quantification limits of 0.03 and 0.10 μmol L^-1, respectively. The application of the developed sensor was considered simple, resulting in a fast, low operating cost method, with recovery values between 103 and 105%.

Application progress of magnetic molecularly imprinted polymers chemical sensors in the detection of biomarkers

Specific recognition and highly sensitive detection of biomarkers play an essential role in identification, early diagnosis and prevention of many diseases. Magnetic molecularly imprinted polymers (MMIPs) have been widely used to capture biomimetic receptors for targets in various complex matrices due to their superior recognition ability, structural stability, and rapid separation characteristics, which overcome the existing deficiencies of traditional recognition elements such as antibodies, aptamers. The integration of MMIPs as recognition elements with chemical sensors opens new opportunities for the development of advanced analytical devices with improved selectivity and sensitivity, shorter analysis time, and lower cost. Recently, MMIPs-chemical sensors (MMIPs-CS) have made significant progress in detection, but many challenges and development spaces remain. Therefore, this review focuses on the research progress of the sensor based on biomarker detection and introduces the surface modification of the magnetic support material used to prepare high selective MMIPs, as well as the selective extraction of target biomarkers by MMIPs from the complex biological sample matrix. Based on the understanding of optical sensors and electrochemical sensors, the applications of MMIPs-optical sensors (MMIPs-OS) and MMIPs-electrochemical sensors (MMIPs-ECS) for biomarker detection were reviewed and discussed in detail. Moreover, it provides an overview of the challenges in this research area and the potential strategies for the rational design of high-performance MMIPs-CS, accelerating the development of multifunctional MMIPs-CS.

Highly sensitive electrochemical determination of the SARS-COV-2 antigen based on a gold/graphene imprinted poly-arginine sensor

The global COVID-19 pandemic starting at 2020 induced by the severe acute respiratory syndrome coronavirus 2 virus (SARS-CoV-2) has revealed a very pressing need for rapid, affordable and effective diagnosis for epidemic management and control. Although several commercialized analytical methods (e.g., reverse transcription polymerase chain reaction and enzyme linked immunosorbent assay) have been developed for detecting SARS-CoV-2, they are expensive and time-consuming. Most recently, low-cost molecularly imprinted polymer (MIP)-based sensors have received attention. In this study, by introducing gold/graphene (Au/Gr) nanohybrids to modify a screen-printed carbon electrode (SPCE) and using arginine as the functional monomer, a simple and highly sensitive MIP sensor was proposed to detect SARS-CoV-2 nucleocapsid protein (ncovNP). By optimizing various influencing factors, the proposed MIP sensor shows wide linear range and low detection limit for ncovNP owing to excellent electrical property and large surface of Au/Gr and specific recognition ability of MIP, revealing important potential application for the effective early diagnosis of COVID-19.

Magnetic-molecularly imprinted polymers in electrochemical sensors and biosensors

Magnetic particles, as well as molecularly imprinted polymers, have revolutionized separation and bioanalytical methodologies in the 1980s due to their wide range of applications. Today, biologically modified magnetic particles are used in many scientific and technological applications and are integrated in more than 50,000 diagnostic instruments for the detection of a huge range of analytes. However, the main drawback of this material is their stability and high cost. In this work, we review recent advances in the synthesis and characterization of hybrid molecularly imprinted polymers with magnetic properties, as a cheaper and robust alternative for the well-known biologically modified magnetic particles. The main advantages of these materials are, besides the magnetic properties, the possibility to be stored at room temperature without any loss in the activity. Among all the applications, this work reviews the direct detection of electroactive analytes based on the preconcentration by using magnetic-MIP integrated on magneto-actuated electrodes, including food safety, environmental monitoring, and clinical and pharmaceutical analysis. The main features of these electrochemical sensors, including their analytical performance, are summarized. This simple and rapid method will open the way to incorporate this material in different magneto-actuated devices with no need for extensive sample pretreatment and sophisticated instruments.

Application of magnetic nanomaterials in electroanalytical methods: A review

Magnetic nanomaterials (MNMs) have gained high attention in different fields of studies due to their ferromagnetic/superparamagnetic properties and their low toxicity and high biocompatibility. MNMs contain magnetic elements such as iron and nickel in metallic, bimetallic, metal oxide, and mixed metal oxide. In electroanalytical methods, MNMs have been applied as sorbents for sample preparation before the electrochemical detection (sorbent role), as the electrode modifier (catalytic role), and the integration of the above two roles (as both sorbent and catalytic agent). In this paper, the application of MNMs in electroanalytical methods have been classified based on the main role of the nanomaterial and discussed separately. Furthermore, catalytic activities of MNMs in electroanalytical methods such as redox electrocatalytic, nanozymes catalytic (peroxidase, catalase activity, oxidase activity, superoxide dismutase activity), catalyst gate, and nanocontainer have been discussed.

Screen-printed disposable electrodes using graphite-polyurethane composites modified with magnetite and chitosan-coated magnetite nanoparticles for voltammetric epinephrine sensing: a comparative study

Disposable screen-printed electrodes based on the use of graphite-polyurethane composites modified with magnetite nanoparticles (MNP-SPE) or chitosan-coated magnetite nanoparticles (CHMNP-SPE) are described. The MNP and CHMNP were synthetized and comparatively characterized by TEM, XRD, FTIR, and TGA/DTG. The MNP-SPE and CHMNP-SPE were characterized by SEM and EDX. After optimization of the MNP percentage in MNP-SPE, the materials were electrochemically characterized by cyclic voltammetry, EIS, and chronocoulometry. The electrodes were tested for their performance towards sensing of epinephrine (EP). The CHMNP-SPE is found to have better electrochemical responses in comparison to the MNP-SPE. This is assumed to be due to the chitosan coating which also protects the MNPs from oxidation under air and at different applied potential fields. The performances of the MNP-SPE and CHMNP-SPE were studied by DPV after optimization of equilibration time and DPV parameters. Response is linear in the 0.1-0.8 μM EP concentration range, at 0.03 V (vs. pseudo-Ag/AgCl), and the detection limit is 25 nM for the MNP-SPE. The linear response for the CHMNP-SPE was 0.1-0.6 μM, at 0.0 V (vs. pseudo-Ag/AgCl), and a LOD of 14 nM was achieved. The devices were used for the quantification of EP in synthetic urine and in cerebrospinal synthetic fluids. Recoveries from spiked samples are in the 95.6-102.2% range for the CHMNP-SPE and in the 98.3-109% range for MNP-SPE. The stability of the respective sensors was investigated and compared over a period of 5 months. The EP peak currents were found to decrease by only 4% for the CHMNP-SPE, while the MNP-SPE lost 23% of its EP peak current. Accordingly, the CHMNP-SPE was chosen as the most stable and sensitive sensor for EP. Graphical abstract Schematic figure of modification of a graphite-polyurethane screen-printed composite electrode with magnetite nanoparticles (MNPs) and chitosan-coated magnetite nanoparticles (CHMNPs) for the voltammetric determination of epinephrine (EP). Improved response of CHMNP-SPE (black voltammogram) in comparison to MNP-SPE (red voltammogram) was attributed to the protection of MNP from oxidation.

A Novel Sensitive Doxorubicin Hydrochloride Electrochemical Sensor Based on a Nickel Hexacyanoferrate/Ni-Al-LDH Modified Gold Electrode

A highly sensitive and selective electrochemical sensor has been fabricated by the electrodepositing of nickel hexacyanoferrate (NiHCF) on a Ni-Al layered double hydroxides (Ni-Al-LDH) modified Au electrode for the quantification of doxorubicin hydrochloride (DOX). The characterization of synthesized nanomaterials has been conducted by scanning electron microscopy, energy dispersive X-ray spectroscopy and electrochemical methods. The synergistic effect of NiHCF and Ni-Al-LDH not only excellently improves the performance of DOX electro-reduction, but also promotes electron transfer between DOX and the NiHCF/Ni-Al-LDH/Au sensor. The differential pulse voltammetric response of the NiHCF/Ni-Al-LDH/Au sensor shows a linear relationship with the concentration of DOX in the range of 1.0 × 10-8 - 6.2 × 10-6 mol L-1, a limit of detection of 1.9 × 10-9 mol L-1 (S/N = 3) and a sensibility of 14.71 A mol L-1 cm-2. The developed sensor exhibits good sensitivity, reproducibility, anti-interference and a long-term stability property. Furthermore, the NiHCF/Ni-Al-LDH/Au sensor has been successfully applied to determine DOX in biological samples and human blood serum samples.