Magnetic Glassy Carbon Electrode Research Articles

A green EC/ECL dual-mode biosensing platform for detection of Vibrio parahaemolyticus

Here, a green EC/ECL dual-mode biosensing platform was designed for sensitive and accurate detection of Vibrio parahaemolyticus (VP). When VP was present, Apt on Fe3O4@SiO2-cDNA/Apt was specifically bound to VP and detached to obtain Fe3O4@SiO2-cDNA. Subsequently, aDNA on Zn-TCPP@AgNPs-aDNA was hybridized with cDNA on Fe3O4@SiO2-cDNA to obtain magnetic conjugates, which were quickly collected by magnetic force and then one-step assembled onto a magnetic glassy carbon (MGCE) electrode for EC/ECL dual-mode measurement. Under the optimal experimental conditions, the detection linear range of VP was 10 ∼ 107 CFU/mL, and the detection limits (LOD) were as low as 7 CFU/mL (EC) and 3 CFU/mL (ECL), respectively, with good repeatability, storage stability and selectivity. In addition, Fe3O4@SiO2-cDNA/Apt and Zn-TCPP@AgNPs-aDNA could be regained by adding Apt into the magnetic conjugates recovered after EC/ECL test, thus the biosensing platform was regenerated with the signal still remaining up to 91.7% (EC) and 92.8% (ECL) after 10 cycles of recovery. With homogeneous recognition and good regeneration, this EC/ECL dual-mode sensing platform provides a green, simple and reliable pathway for the analysis of VP or other foodborne pathogens.

A magnetically fixed bifunctional monomer molecularly imprinted electrochemiluminescence sensor for specifically identifying thiabendazole in food

A magnetically fixed bifunctional monomer molecularly imprinted electrochemiluminescence (ECL) sensor (MIP/MMOF@g-C3N4/L-Aas/MGCE) was constructed to selective detection thiabendazole (TBZ). Fe3O4 modified by sulfonic acid group (–SO3H) acted as magnetic core to attract Co2+ to initiate the growth of ZIF-67 (MMOF). Graphitic carbon nitride nanosheets (g-C3N4) were doped into MMOF by inherent amino groups to prepare integrated magnetic ECL luminophore (MMOF@g-C3N4). MMOF@g-C3N4 was immobilized on the surface of magnetic glassy carbon electrode (MGCE) by using the superparamagnetism of Fe3O4, which enhanced the stability and reusability of ECL system. Sodium ascorbate (L-Aas) acted as co-reactant accelerators to further enhance ECL intensity. MIP prepared with TBZ as template molecule and o-phenylenediamine (oPD)/resorcinol (RS) as bifunctional monomers contained more imprinting sites, which can enhance the adsorption performance. The luminescence mechanism of magnetic ECL system was investigated, and the specific recognition mechanism of MIP recognition system was deeply explored. The linear range of the method was 1 × 10−9–5 × 10−5 mol L−1, and the detection limit was 3.77 × 10−10 mol L−1. A good recovery rate (80.08%–96.82%) was obtained in the actual sample detection, which was basically consistent with the detection results of High Performance Liquid Chromatography.

Ultrasensitive detection of PSA in human serum using Label-Free electrochemical biosensor with magnetically induced Self-Assembly based on α-Fe2O3/Fe3O4@Au nanocomposites

To achieve the goals of early diagnosis, screening, and precision medicine for prostate cancer, this research designed a label-free electrochemical biosensor by combining magnetic probes (PSAA/α-Fe2O3/Fe3O4@Au) with magnetically induced self-assembly (MISA) technology to explore the application of prostate-specific antigen (PSA) in precise detection. Magnetic α-Fe2O3/Fe3O4 nanoparticles (NPs) were constructed using a hydrothermal-calcination reduction method. Subsequently, α-Fe2O3/Fe3O4@Au nanocomposites were prepared by reducing HAuCl4 with NaBH4 at a low temperature. The self-assembly method was adopted in two steps: firstly, the sulfhydryl-modified PSA aptamer is immobilized onto the material surface using Au–S bonds; secondly, the magnetic NPs and magnetic glassy carbon electrode (MGCE) undergo self-assembly. The biosensor showed good linear response in the range of 100 fg/mL to 100 ng/mL, with a detection limit of 0.78 pg/mL (S/N = 3) under optimal conditions. Repeatability, stability, selectivity, reproducibility, and the capability to analyze real samples were also investigated. With its cost-effectiveness, operational simplicity, and speed of analysis, the biosensing system platform holds great potential as a valuable tool in clinical PSA detection for point-of-care testing (POCT).

Magnetic nanoparticles-based electrochemical aptasensor for the detection of enrofloxacin in chicken

Enrofloxacin (ENR) is widely applied in preventing and treating animal diseases and hence directly passed into animal-derived foods. Therefore, the detection of this drug in food samples must be strengthened to ensure food safety. In this work, a simple, sensitive electrochemical aptasensor for the detection of ENR was fabricated by using magnetic nanoparticles (MNPs) as carriers. The ENR aptamer was modified on the surface of MNPs to capture the ENR target or a biotin-complementary strand and then recognize streptavidin-horse radish peroxidase. Subsequently, the resulting MNPs were easily transferred onto the surface of magnetic glassy carbon electrode with the help of its integral magnet. Under optimal experimental conditions, a linear relationship between the variable of LSV current and the logarithm of ENR concentration in the range of 0.01–100 ng/mL was obtained with the limit of detection at 4.9 pg/mL. In addition, this method exhibited good stability, selectivity, reproducibility and was successfully applied in detecting ENR in spiked chicken samples with recoveries of 100.70%–108.96%. The proposed method is easy to fabricate and process; it is particularly suitable for food sample pretreatment and is beneficial in removing the interference of a complex matrix.

Construction of a label-free electrochemical biosensing system utilizing Fe3O4/α-Fe2O3@Au with magnetic-induced self-assembly for the detection of EGFR glycoprotein

A label-free electrochemical biosensing system was developed for the sensitive detection of epidermal growth factor receptor (EGFR), which was frequently overexpressed in lung cancer, breast cancer, and glioblastoma. Magnetic Fe3O4/α-Fe2O3@Au nanocomposites were utilized as the signal amplifiers and for the immobilization matrix of specific probes (ssDNA-APT) in the biosensors. The Fe3O4/α-Fe2O3@Au/ssDNA-APT biosensors were formed through Au–S binding on this matrix and were immobilized onto a magnetic glassy carbon electrode (MGCE) using magnetic-induced self-assembly. The performance of the EGFR detection system was verified using differential pulse voltammetry (DPV). The system exhibited a wide linear range from 0.1 ng/mL to 1000 ng/mL (R2 = 0.9947), with a limit of detection (LOD) of 0.18 ng/mL. Furthermore, the repeatability, stability, selectivity, and ability for real sample analysis were investigated. With its simplicity and reliability, this biosensing system has the potential to be developed as a valuable tool in clinical EGFR detection, offering a promising candidate for point-of-care (POC) testing.

Construction of electrochemical biosensor based on magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods for the sensitive detection of MUC1 mucoprotein

Magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods with the saturation magnetization of 69.5 emu/g were prepared via the hydrothermal and calcination-reduction process using β-FeOOH nanorods as precursor and galactose as the reducing agent. The average length and diameter of the nanorods were 81.6 nm and 23.9 nm, respectively. The surfaces of the heterogeneous nanorods were modified with PEI and HAuCl4, resulting in magnetic rod-like Fe3O4/α-Fe2O3@Au nanocomposites. By utilizing the Au–S effect, Apt/ssDNA hybrid double-strands were loaded onto Fe3O4/α-Fe2O3@Au nanocomposites to form Fe3O4/α-Fe2O3@Au-Apt/ssDNA biosensors capable of recognizing mucoprotein-1 (MUC1) mucoprotein. These biosensors could be magnetically assembled onto a magnetic glassy carbon electrode to create a "Turn off" type electrochemical biosensor. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) techniques were used to evaluate the detection performance. Based on the change in DPV signals, the optimal concentrations of magnetic Fe3O4/α-Fe2O3@Au nanocomposites and Apt/ssDNA double-stranded probes were 12 mg/mL and 9 μM, respectively, while the optimal incubation time was 2 h. Under these conditions, the sensor exhibited a linear detection range of 0.1 pg/mL to 1500 pg/mL (R2 = 0.9988), with a limit of detection (LOD) of 0.1 pM and a limit of quantitation (LOQ) of 0.34 pM. The biosensor demonstrated excellent performance in terms of selectivity, reproducibility (RSD = 2.9 %), and stability. When actual serum samples diluted by a factor of 20 in PBS were tested, the recovery rate ranged from 95.65 % to 103.40 %, indicating that this approach for sensitive detection of MUC1 holds promising prospects.

Electrochemical sensor for sensitive nitrite and sulfite detection in milk based on acid-treated Fe3O4@SiO2 nanoparticles

In this work, a simple electrochemical sensing platform based on acid-treated Fe3O4@SiO2 nanoparticles was successfully prepared for nitrite and sulfite detection. Fe3O4@SiO2 nanoparticles were synthesized through the sol–gel and hydrothermal methods. Fe3O4@SiO2 presented positive charges after acid treatment, which could enhance the electrostatic attraction between Fe3O4@SiO2 and nitrite and sulfite. The Fe3O4@SiO2(acid-treated) modified magnetic glassy carbon electrode (MGCE) was applied to detect nitrite and sulfite using differential pulse voltammetry and cyclic voltammetry. Under optimized conditions, the developed electrochemical sensor presented good analytical properties for nitrite and sulfite detection with detection limits of 3.33 μmol/L and 31.57 μmol/L, respectively. The good recoveries varied from 85.18% to 111.02%, with a relative standard deviation of 0.23–4.80%. Furthermore, the Fe3O4@SiO2(acid-treated) modified MGCE showed better selectivity, reproducibility, and repeatability in nitrite and sulfite detection. Therefore, this proposed electrochemical sensor provides a new method for developing a nitrite and sulfite detection sensor.

Label-free electrochemical biosensor with magnetically induced self-assembly for the detection of cancer antigen 125

Magnetically induced self-assembly technology was used to construct a label-free electrochemical biosensor based on magnetic Mg0.5Cu0.5Fe2O4-Au nanocomposites for the sensitive detection of cancer antigen 125 (CA125). To aim for this, Mg0.5Cu0.5Fe2O4 nanoparticles were first prepared via the rapid combustion process. The average diameter of the nanoparticles calcined at 800 °C with the absolute ethanol volume of 20 mL was about 169.3 nm. Then Au was used for the surface modification by NaBH4 reduction reaction approach. The magnetic glassy carbon electrode (MGCE) was modified by Mg0.5Cu0.5Fe2O4-Au via a magnetic induction self-assembly process. The reduced thiol-modified single-stranded DNA was attached to the Mg0.5Cu0.5Fe2O4-Au nanocomposites by Au-S bonds without any coupling agent. CA125 antigen was grabbed directly by its aptamer DNA due to its specific identification with the aptamer. Finally, the modified electrodes were blocked with BSA and then characterized. Finally, DPV analysis was used for CA125 detection, the novel fabricated biosensor demonstrated good detection properties for CA125 with a linear range of 5–125 U/mL and a detection limit of 4.4 U/mL. The results showed that the aptamer sensor had good specificity, repeatability, and stability. The feasibility of our sensor for the determination of CA125 was also demonstrated by measuring CA125 levels in serum using the Roche gold-standard instrument of the People’s Hospital of Danyang as the reference value. The recoveries of real serum samples were 94.65–101.71%, and RSDs were 1.26–4.65%. Moreover, the surface of the electrode could be cleaned and reused by magnetic separation, greatly reducing the cost and providing the possibility for a point-of-care test (POCT). This work demonstrated a new strategy for integrating both nanostructures and biocompatibility to build advanced cancer biomarker sensors with wide applications.

CoFe2O4 decorated graphene/C18-functionalized mesoporous silica nanocomposites prepared for magnetic enrichment and electrochemical detection of promethazine in beef

Promethazine (PHZ) is used as a sedative in veterinary medicine, and its residue can threaten the health of human. The electrochemical detection of PHZ is suitable method for application in the field. However, the traditional electroanalysis is difficult to perform directly in meat samples due to matrix interference. This work integrates magnetic solid-phase extraction and differential pulse voltammetry for highly sensitive and selective determination of PHZ in beef and beef liver for the first time. CoFe2O4/graphene coated with C18-functionalized mesoporous silica (MG@mSiO2-C18) is synthesized as dispersed magnetic adsorbent to extract PHZ. Magnetic glassy carbon electrode modified with nitrogen-doped hollow carbon microspheres (HCM) attracts the MG@mSiO2-C18 with PHZ, and directly detects the PHZ without elution procedure. MG@mSiO2-C18 can separate PHZ to avoid the interference of impurities on following detection, and also concentrate PHZ on magnetic electrode. Additionally, the electrode modification with HCM can amplify the electrochemical signal of PHZ. Finally, the integrated PHZ determination method exhibits a wide linear range from 0.08 µmol/L to 300 µmol/L with a low limit of detection of 9.8 nmol/L. The beef sample analysis presents excellent recovery, demonstrating that this protocol is promising for the rapid and onsite detection of PHZ in real meat samples

Specific Adsorption of Magnetic Fe3O4@hydroxyapatite Nanocomposites to a Hybridized Duplex for Immobilization and Label-Free Electrochemical Biosensing of MicroRNA

The unique discriminating ability of hydroxyapatite (HAP) to single- and double-stranded nucleic acid implies its potential as a biosensing material for nucleic acid analysis. Herein, a novel immobilization- and label-free electrochemical strategy has been developed for miRNA let-7a detection based on the specific adsorption of magnetic Fe3O4@hydroxyapatite (Fe3O4@HAP) to a duplex structure. Typically, the highly efficient homogeneous reaction between probe DNA (pDNA) and target miRNA let-7a produces the nucleic acid duplex, which is specifically adsorbed on the surface of Fe3O4@HAP. Thereafter, the electroactive intercalator Nile blue (NB) is introduced as the label-free signal molecule and inserts between the stacked base pairs of the pDNA–miRNA duplex. Thus, the Fe3O4@HAP bearing pDNA–miRNA and numerous intercalated NBs are adsorbed by the magnetic glassy carbon electrode, giving rise to an intense sensing signal without the need of nuclease-assisted cyclic amplification. With this advantage, the sensing system shows a wide linear range from 1.0 fM to 100 nM and a low detection limit of 0.051 fM for miRNA let-7a analysis. What is more, the synergy of the base-pairing-driven hybridization, the specific intercalation of NB to the duplex structure, and the selective adsorption of Fe3O4@HAP contribute to a high sensing specificity of the biosensing strategy. The sensing method provides a state-of-the-art strategy for the sensitive and facile bioanalysis and clinical diagnosis of miRNA.

Fascinating Immobilization-Free Electrochemical Immunosensing Strategy Based on the Cooperation of Buoyancy and Magnetism.

Rapid and accurate detection of biomolecules is of vital importance for the diagnosis of disease and for performing timely treatments. The point-of-care analysis of cancer biomarkers in the blood with low cost and easy processing is still challenging. Herein, an advanced and robust strategy, which integrates the buoyant recognition probe with the magnetic reporter probe in one solution, was first proposed for immobilization-free electrochemical immunosensing. The tumor marker of alpha fetoprotein (AFP) can be captured immune-buoyantly, and then a multifunctional magnetic reporter probe in pseudo-homogeneous solution was further captured to fulfill a sandwich-type immunoreaction. The residual magnetic reporter probe can be firmly and efficiently attracted on a magnetic glassy carbon electrode to fulfill the conversion of the target AFP amount into the residual magnetic electrochemical signal indicator. As a result, the electrochemical signal of methylene blue can accurately reflect the original level of target antigen AFP concentration. By integrating buoyancy-driven quasi-homogenous biorecognition with magnetism-mediated amplification and signal output, the proposed immobilization-free electrochemical immunosensing strategy displayed a wide range of linear response (100 fg mL-1 to 10 ng mL-1), low detection limit (14.52 fg mL-1), and good reproducibility, selectivity, and stability. The designed strategy manifests remarkable advantages including assay simplicity, rapidness, and high sensitivity owing to the in-solution instead of on-electrode biorecognition that could accelerate and improve the biorecognition efficiency. To the best of our knowledge, this is the first cooperation of buoyancy-driven biorecognition with magnetism-mediated signal output in bioanalysis, which would be attractive for rapid clinic biomedical application. Thus, this work provides a fresh perspective for convenient and favorable immobilization-free electrochemical biosensing of universal biomolecules.

Novel electrochemical sensing platform basing on di-functional stimuli-responsive imprinted polymers for simultaneous extraction and determination of metronidazole

A novel magnetic-controlled electrochemical sensor has been fabricated by combined photo-responsive surface molecular imprinted polymers (P-SMIPs) and electrochemical sensor. In particular, the P-SMIPs were obtained by living radical polymerization of photo-responsive functional monomer onto the magnetic Fe3O4 modified multi-walled carbon nanotubes nanocomposites. The magnetic glassy carbon electrode was introduced to make the anchoring and removal of P-SMIPs onto the magnetic-controlled glassy carbon electrode easy to manipulate. Driven by UV/vis light, the platform performs releasing and absorption of metronidazole basing on conformational variations of the photo-responsive monomer at the receptor sites part in the P-SMIPs. This process can be tested by the photo-responsive variations of metronidazole electrochemical signal. As the consequence, extracting of P-SMIPs sensor can be conveniently triggered by the controllable UV light intervention measure, leading to effectively improve in both analytes mass transfer rate to the receiving media and extraction efficiency. The experimental result indicated that the excellent recoveries of metronidazole were varied between 77.9% and 89.9% with RSDs ≤4.87% in the biological samples. Therefore, the P-SMIPs sensor shows satisfactory potential in reusable extractions that can be recycled several times with no significant loss of activity, and this utilization strategy can be extended to other analytes, achieving manifold applications of pharmaceutical and environmental.

Washing-free electrogenerated chemiluminescence magnetic microbiosensors based on target assistant proximity hybridization for multiple protein biomarkers

This work reports washing-free electrogenerated chemiluminescence (ECL) magnetic microbiosensors based on target assistant proximity hybridization (TAPH) for multiple protein biomarkers for the first time. As a principle-of-proof, alpha-fetoprotein (AFP) was chosen as a model analyte, and biotin-DNA1 bound streptavidin-coated magnetic microbeads (MMB@SA⋅biotin-DNA1) were designed as the universal capture MMB, while the corresponding two antibodies tagged with DNA2 or DNA3 were utilized as hybrid recognition probes, and ruthenium complex-tagged DNA4-10A was designed as a universal ECL signal probe. When the capture MMB was added into the mixture solution (containing the analyte, hybrid recognition probes, signal probe and tri-n-propylamine), biocomplexes were formed on the MMB. After the resulting MMB was efficiently brought to the surface of a magnetic glassy carbon electrode (MGCE), ECL measurement was performed without a washing step, resulting in an increase in the ECL intensity. A model for ECL measuring the second-order rate constants of hybridization reactions on MMB was derived. It was found that the rate constants for hybridization reactions on MMB in rotating mode are 1.6-fold higher than those in shaking mode, and a suitable DNA length of the signal probe can improve the signal-to-noise ratio. The washing-free ECL method was developed for the determination of AFP with a much lower detection limit (LOD) of 0.04 ng mL−1. The developed flexible strategy has been extended to determine D-dimer with an LOD of 0.1 ng mL−1 and myoglobinglobin with an LOD of 1.1 ng mL−1. This work demonstrated that the proposed strategy of ECL TAPH on MMB at MGCE is a washing-free and flexible promising strategy, and can be extended to qualify other multiple protein biomarkers in real clinical assays.

Electrochemical sensor for detecting streptomycin in milk based on label-free aptamer chain and magnetic adsorption

Exploiting a simple and sensitive sensor to efficiently detect streptomycin (STR) in milk is critical for resolving the harm caused to humans by STR residues. This study reports an electrochemical sensor using magnetic mesoporous carbon materials (MMCM) as a loaded material through magnetic adsorption immobilized on magnetic glassy carbon electrode (MGCE) and adsorbing unlabeled streptomycin aptamer (STP) as the identification element. The sensor can detect STR sensitively with a wide detection range (0.172–17.2 × 103 and 17.2 × 103 –17.2 × 105 nM) and a low detection limit of 0.015 nM. Experimental results revealed that the specific binding of STP with STR on the electrode changed the configuration of STP, thereby causing current change of differential pulse voltammetry curve. Compared with HPLC, this study provides a new method for rapid and sensitive detection of STR in milk (n = 5, 95 % confidence level, RSD＜5%).

Electrochemical sensor based on micromotor technology for detection of Ox-LDL in whole blood

Detecting the concentration of oxidized low-density lipoprotein (Ox-LDL) in whole blood is of great significance for monitoring the development of atherosclerosis. In order to simplify the complex processing steps of blood sample before the detection, an electrochemical sensor based on micromotor technology was designed, which was called magnesium (Mg)–Fe3O4@ prussian blue (PB)@ antibody of Ox-LDL (Ab)@ bovine serum albumin (BSA). The active capture of Ox-LDL in whole blood can be realized by the help of the movement of Mg microsphere with the driving force of H2. Then the captured Ox-LDL was collected on the surface of the magnetic glassy carbon electrode (MGCE) by self-made funnel device, and the content of Ox-LDL was detected by electrochemical workstation in the way of chronoamperometry (i-t). Due to the application of micromotor, the electrochemical sensor proposed in this study had good detection efficiency for Ox-LDL in whole blood with range from 1 × 10−2 μg/mL to 10 μg/mL, and the limit of detection (LOD) towards Ox-LDL was 9.80 × 10−4 μg/mL. The electrochemical sensor based on micromotor technology provides a rapid, effective, and sensitive method for the detection of Ox-LDL in whole blood.

Fabrication of biogenic iron oxide and their efficiency to detect carbofuran in vegetable samples

First time we approached green way method to synthesize iron oxide (Fe3O4) nanoparticles using aqueous extract of Artocarpus heterophyllus seeds through an environmentally friendly method. Further, as prepared Fe3O4 nanoparticles were characterized and confirmed by different analytical techniques such as Fourier transform infrared (FT-IR) spectroscopy, Raman spectrum, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectrometer (EDAX) employed to determine the functional groups, crystalline structure, size, and shape of nanoparticles. A spherical with a size of 34 nm, and highly stable iron oxide nanoparticles were obtained. Further, Fe3O4 nanoparticles have been coated on the magnetic glassy carbon electrode (Fe3O4/MGCE) and applied for the electrocatalytic oxidation of carbofuran (CF) was examined by using cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. The Fe3O4/MGCE has shown excellent catalytic activity towards CF oxidation in the concentration of 0.3 – 38.5 µM with LOD of 0.01 µM and sensitivity of 6.53 ± 0.08 µA µM−1 cm−2. Moreover, the practical applicability of the fabricated Fe3O4/MGCE has been applied for the detection of CF in different vegetable samples and the obtained results were compared with HPLC outputs.

WITHDRAWN: A facile protocol based on magnetic molecularly imprinted particles and metal ions for highly sensitive and selective sulfonamides electrochemical detection

In this work, cost-effective and highly sensitive electrochemical magnetic molecularly imprinted particles (MMIPs) sensors were proposed for indirectly detecting sulfamethazine (SMZ) and sulfamonomethoxine (SMM). MMIPs were synthesized using a sol-gel process using SMZ or SMM as a template, Fe 3 O 4 -NH 2 as a core, and tetraethoxysilane as a cross-linking agent, then the template removal. The electrochemical MMIPs sensor was prepared by a complex of metal ions and the MMIPs of rebinding the template, modified on the magnetic glassy carbon electrode surface. Here, the sulfonyl oxygen atoms, pyrimidine nitrogen, and sulfonamide nitrogen of sulfonamides can combine with metal ions by coordination, and metal ions can be used as signal probes of the electrochemical MMIPs sensor. The electrochemical MMIPs sensor was characterized by differential pulse voltammetry, and the response peak currents of metal ions re-oxidized to metal were applied to monitor sulfonamides concentration. Under the optimal conditions, the electrochemical MMIPs sensors exhibited a high sensitivity toward SMZ and SMM with detection limits of 0.068 and 0.075 ng/mL (3σ), respectively. Those developed sensors also exhibited high selectivity to detect SMZ and SMM. Moreover, the proposed electrochemical MMIPs sensors were successfully applied to determine SMZ and SMM in milk. • Electrochemical MMIPs sensor was developed based on MMIPs and metal ions. • Metal ions were used as signal probes of the developed MMIPs sensor. • The response peak currents of metal ions were used to monitor sulfonamides. • Highly sensitive detection of sulfonamides with a lower detection limit. • Sulfonamides in milk were determined successfully.

Microwave-prepared surface imprinted magnetic nanoparticles based electrochemical sensor for adsorption and determination of ketamine in sewage

Detection technology for the determination of drugs, such as ketamine (KT), in sewage is of great significance in drug inspection and criminal investigation. Herein, we propose the utilization of ketamine magnetic molecularly imprinted polymers (Fe3O4@MIPs) as a target molecule identification and concentration container coupled with magnetic glassy carbon electrode (mGCE) for KT detection in sewage. Molecular simulations were employed to evaluate the most suitable monomer and ratio of functional monomer to template. Fe3O4@MIPs were prepared using microwave-assisted synthesis and possessed a “shell-core” structure with good recognition ability, superior adsorption capacity and fast kinetics toward KT. Additionally, a novel imprinted electrochemical sensor was constructed based on the magnetism of Fe3O4@MIPs for efficient monitoring of low concentrations of KT. The morphology and properties of Fe3O4@MIPs/mGCE were effectively characterized by element mapping, transmission electron microscopy, cyclic voltammetry and square wave voltammetry. KT detection was performed by square wave voltammetry within the range of 1.0 × 10−12 and 4.0 × 10−4 mol L−1, and the limit of detection was 8.0 × 10−13 mol L−1. Furthermore, Fe3O4@MIPs/mGCE was successfully tested for KT determination in domestic sewage samples.

Electrochemical detection of aminoglycoside antibiotics residuals in milk based on magnetic molecularly imprinted particles and metal ions

This work proposed a cost-effective, simple, and highly sensitive magnetic molecularly imprinted particles (MMIPs) electrochemical sensor to indirectly detect kanamycin (KAN), tobramycin (TOB), and gentamicin (GEN). The MMIPs electrochemical sensor was prepared by a complex of metal ions and the MMIPs of rebinding the template, which modified on the magnetic glassy carbon electrode surface. Here, metal ions were used as the signal tracers and amplifiers of the MMIPs electrochemical sensor. Then the response peak currents of metal re-oxidized to metal ion was recorded by differential pulse voltammetry and used to monitor the level of aminoglycoside antibiotics. Under the optimal conditions, the MMIPs electrochemical sensors showed a high sensitivity toward KAN, TOB, and GEN with detection limits of 4.88, 1.28, and 1.07 nmol/L, respectively. Furthermore, the MMIPs electrochemical sensors showed high selectivity for determining KAN, TOB, and GEN, and they were successfully used to detect KAN, TOB, and GEN in milk.

Determination of EGFR-overexpressing tumor cells by magnetic gold-decorated graphene oxide nanocomposites based impedance sensor

This work developed an electrochemical impedance spectroscopy (EIS) sensor for detection of EGFR (epidermal growth factor receptor)-overexpressing tumor cell and preliminary estimation of EGFR expression. Here, EGFR antibodies as the specific antibodies for cancer cells were conjugated on magnetic gold-decorated graphene oxide nanocomposites, which were used to capture the EGFR-overexpressing tumor cells. The magnetically responsive tumor cells were enriched and immobilized on a magnetic glassy carbon electrode (mGCE) surface, leading to increased electron-transfer resistance (Ret) utilized for determination of cells and preliminary evaluation of EGFR expression level. This strategy enables the enrichment, fixation and detection of tumor cells to be accomplished in a facile way. An excellent linearity in the range of 2.0 × 102 − 3.0 × 105 cell mL−1 with the detection limit of 152 cell mL−1 for MDA-MB-231 cells was obtained. Investigation on the expression levels of EGFR on various types of cells was conducted. MDA-MB-231 cells showed a distinctly higher EGFR expression, compared with MHCC97-L and L02 cells, providing the possibility for the EGFR-targeted therapy of the tumors. It is expected that the proposed sensor has the potential to be applied for cancer monitoring.