Development of a label-free electrochemical immunosensor based on carbon nanotube for rapid determination of clenbuterol

Magnetic engineering nanoparticles: Versatile tools revolutionizing biomedical applications

The use of nanoparticles has increased significantly over the past few years in a number of fields, including diagnostics, biomedicine, environmental remediation, and water treatment, generating public interest. Among various types of nanoparticles, magnetic nanoparticles (MNPs) have emerged as an essential tool for biomedical applications due to their distinct physicochemical properties compared to other nanoparticles. This review article focuses on the recent growth of MNPs and comprehensively reviews the advantages, multifunctional approaches, biomedical applications, and latest research on MNPs employed in various biomedical techniques. Biomedical applications of MNPs hold on to their ability to rapidly switch magnetic states under an external field at room temperature. Ideally, these MNPs should be highly susceptible to magnetization when the field is applied and then lose that magnetization just as quickly once the field is removed. This unique property allows MNPs to generate heat when exposed to high-frequency magnetic fields, making them valuable tools in developing treatments for hyperthermia and other heat-related illnesses. This review underscores the role of MNPs as tools that hold immense promise in transforming various aspects of healthcare, from diagnostics and imaging to therapeutic treatments, with discussion on a wide range of peer-reviewed articles published on the subject. At the conclusion of this work, challenges and potential future advances of MNPs in the biomedical field are highlighted.

Nanostructures of Prussian blue supported on activated biochar for the development of a glucose biosensor

This work emphasizes the utilization of biochar, a renewable material, as an interesting platform for anchoring redox mediators and bioreceptors in the development of economic, environmentally friendly biosensors. In this context, Fe(III) ions were preconcentrated on highly functionalized activated biochar, allowing the stable synthesis of Prussian blue nanostructures with an average size of 58.3 nm. The determination of glucose was carried out by indirectly monitoring the hydrogen peroxide generated through the enzymatic reaction, followed by its subsequent redox reaction with reduced Prussian blue (also known as Prussian white) in a typical electrochemical-chemical mechanism. The EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-Hydroxysuccinimide) pair was employed for the stable covalent immobilization of the enzyme on biochar. The biosensor demonstrated good enzyme-substrate affinity, as evidenced by the Michaelis-Menten apparent kinetic constant (4.16 mmol L-1), and analytical performance with a wide linear dynamic response range (0.05-5.0 mmol L-1), low limits of detection (0.94 μmol L-1) and quantification (3.13 μmol L-1). Additionally, reliable repeatability, reproducibility, stability, and selectivity were obtained for the detection of glucose in both real and spiked human saliva and blood serum samples.

Cu-BTC MOF/ionic liquid nanocomposite as novel catalyst to electrochemical monitoring of digoxin in pharmaceutical and environmental samples

There is no effective environmental treatment strategy that does not include monitoring for pharmaceutical compounds in environmental and biological fluids. The widespread presence of pharmaceutical-based pollutants in water sources is a significant public health concern. The treatment process relies heavily on maintaining a stable digoxin concentration in bodily fluids. Finding the correct dose for this medication appears to be crucial. In this research, an easy and high sensibility electrochemical sensor was developed to determine digoxin based on a paste electrode (CPE) that was modified with Cu-BTC MOF and ion liquid ((IL); 1-Methyl-3-Butyl-imidazolinium bromide in this case) using voltammetric methods in 0.1 M phosphate buffer solution (PBS) at pH 5.0. The sensor's selectivity was significantly increased by using Cu-BTC MOF and IL to detect digoxin. The characteristics of the electrode modifiers were evaluated by SEM, XRD and EDS techniques. The LDR was found to be 0.1-40 μM and the LOD of 0.08 μM, respectively.

Nanosensors: A smart remedy for early detection of clenbuterol contamination in food

Veterinary drugs which are primarily meant for livestock treatment have now been categorised under potential food contaminant due to its unregulated usage and abuse. Their over usage by animal workers lead to production of contaminated animal-based food products which contain veterinary drug residues. These drugs are also misused as growth promoters to enhance the muscle to fat ratio in human body. This review highlights the misuse of such a veterinary drug; Clenbuterol. In this review, we have comprehensively discussed the usage of nanosensors to detect clenbuterol in food samples. Colorimetric, fluorescent, electrochemical, SERS and electrochemiluminescence are major categories of nanosensors that have been utilized for this purpose. The mechanism through which these nanosensors detect clenbuterol have been discussed in detail. The limit of detection and recovery percentage values of each nanosensor have been compared. This review will impart significant information on various nanosensors for clenbuterol detection in real samples.

Electrochemical immuno determination of connective tissue growth factor levels on nitrogen-doped graphene

Connective tissue growth factor (CTGF) is a disease marker of rheumatoid arthritis (RA), and its rapid and sensitive detection is essential for the diagnosis of RA. In this work, a three-dimensional pore structure of alkali-activated nitrogen-doped graphene (aN-G) was used as an electrode modification material, and a label-free electrochemical immunosensor for the sensitive detection of CTGF was successfully constructed by the formation of an amide bond between amino groups in protein and carboxyl groups on the carbon surface. Under optimized conditions, the sensor achieved accurate detection of CTGF in the wide range of 0.0625 ~ 2000 pg mL^-1. It had good accuracy (95.0 ~ 100.1%), repeatability (1.2 ~ 2.2%), stability, selectivity, and a low limit of detection (0.0424 pg mL^-1, S/N = 3). The sensor was used in serum samples of patients with RA, and CTGF was also successfully detected. Based on this, the electrochemical sensor is expected to become an effective method for RA diagnosis and treatment effect evaluation.

Graphene-labeled synthetic antigen as a novel probe for enhancing sensitivity and simplicity in lateral flow immunoassay

Lateral flow immunoassay (LFIA), which combines immune-specific recognition properties with sensitive nano-signaling features, has emerged as an excellent tool for point-of-care testing (POCT) in food safety and clinical diagnosis. Exploring novel probes with a simple preparation process, improved signal intensity and good stability is conducive to the development and application of LFIA. Herein, a potent non-antibody probe, graphene-labeled synthetic antigen (G-Ag), was created for LFIA, in which graphene endowed a naked-eye visual colorimetric signal with high sensitivity, and the synthetic antigen competed with the target for binding to the antibody on the test line. During the G-Ag probe manufacturing process, only one simple mixing step was needed because graphene nanosheets presented a strong adsorption capacity toward the protein (BSA) on the synthetic antigen, significantly saving time, labor and cost. Especially, the synthetic antigen forms a fabulous probe element without the need for antibody, and thus the proposed LFIA avoids the destruction of antibody activity, and exhibits excellent sensitivity and stability. After optimization, LFIA was successfully applied to analyze clenbuterol; the lowest visually detectable concentration was 0.1 ng mL^-1, and the probe could be well-applied in pork, mutton, sausage and bacon samples, demonstrating favorable specificity and repeatability. Owing to the advantages of simplicity, non-antibody probe, sensitivity and reliability, G-Ag probe-based LFIA has application potential for small-molecule target monitoring and rapid detection.

In situ Preparation of HNbMoO6/C Nanocomposite for Sensitive Detection of Clenbuterol

In this paper, we synthesized HNbMoO₆/C composite through the calcination of octylamine-intercalated HNbMoO₆ precursor. The resulting HNbMoO₆/C composite showed some new phases of MoO₂, MoO₃, NbO₂, Nb₂O₅, and carbon, which was fully confirmed via powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) technologies. Besides, the HNbMoO₆/C hybrid was coated on glass carbon electrode to construct an electrochemical sensor for sensitive determination of clenbuterol. The electrochemical behaviors of clenbuterol on the prepared electrode were tested by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The results showed that the intercalated carbon can act as active sites to accelerate electron transfer. In addition, more exposed surface areas of the HNbMoO₆/C composite will facilitate the electrolyte to permeate. The oxidation peak current of clenbuterol was linearly related to its concentration in the range of 1.04 × 10^-5 to 7.51 × 10^-4 mol L^-1, and the determination limit was calculated to be 3.03 × 10^-6 mol L^-1 (S/N = 3). This sensor exhibits excellent stability, reproducibility, specificity, and good recoveries when applied to monitor clenbuterol in real samples.

Quick electrochemical immunoassay for hantavirus detection based on biochar platform

This work describes the first method using biochar (BC) as carbonaceous platform for immunoassay application. BC is a highly functionalized material obtained through biomass pyrolysis under controlled conditions. Due to the highly functionalized surface, covalent binding between BC and biomolecules can be performed by EDC/NHS conjugation. The application of the modified electrode was done with Hantavirus, that are etiologic agents mainly transmitted by wild rodents. Among its pathologies Hantavirus Cardiopulmonary Syndrome (HCPS) arises at Americas, caused by Hantavirus Araucária and reaches 40% lethality. The diagnostic is based on the presence of specific hantavirus nucleoprotein (Np), under viremic condition or IgG2b antibodies (Ab), during first symptoms. The results presented a device sensitivity of 5.28 μA dec^-1 and a LOD of 0.14 ng mL^-1 to the Np detection, ranging from 5.0 ng mL^-1 to 1.0 μg mL^-1, the Ab detection works as qualitative type sensor above 200 ng mL^-1. Both sensors were evaluated its selectivity and serum samples; selectivity against Gumboro disease, VP2 protein, and antibody IgG2a against Yellow fever disease (YF), respectively. So, the devices here proposed are promising tool suitable for both rodent and human hantavirus clinical surveys.

Computer-Aided Design of Molecularly Imprinted Polymers for Simultaneous Detection of Clenbuterol and Its Metabolites

Molecular imprinting technology (MIT) offers an effective technique for efficient separation and enrichment of specific analytes from complicated matrices and has been used for illicit veterinary drug detectionin recent years due to its high selectivity, good chemical stability, and simple preparation. The development of in silico-based approaches has enabled the simulation of molecularly imprinted polymers (MIPs) to facilitate the selection of imprinting conditions such as template, functional monomer, and the best suitable solvent. In this work, using density functional theory (DFT), the molecularly imprinted polymers of clenbuterol and its metabolites were designed by computer-aided at B3LYP/6-31 + G (d, p) level. Screening molecular imprinting components such as functional monomers, cross-linkers, and solvents has been achieved in the computational simulation considerations. The simulation results showed that methacrylic acid (MAA) is the best functional monomer; the optimal imprinting ratio for both clenbuterol (CLB) and its dummy template molecule of phenylephrine (PE) to functional monomer is 1:3, while the optimal imprinting ratio for the two dummy template molecules of CLB's metabolites is 1:5. Choosin gethyleneglycol dimethacrylate (EDGMA) as a crosslinker and aprotic solvents could increase the selectivity of the molecularly imprinted system. Atoms in Molecules (AIM) topology analysis was applied to investigate the template-monomer complexes bonding situation and helped to explain the nature of the reaction in the imprinting process. These theoretical predictions were also verified by the experimental results and found to be in good agreement with the computational results. The computer-simulated imprinting process compensates for the lack of clarity in the mechanism of the molecular imprinting process, and provides an important reference and direction for developing better recognition pattern towards CLB and its metabolite analytes in swine urine samples at the same time.

Development of Highly Sensitive Immunosensor for Clenbuterol Detection by Using Poly(3,4-ethylenedioxythiophene)/Graphene Oxide Modified Screen-Printed Carbon Electrode

Clenbuterol (CLB) is an antibiotic and illegal growth promoter drug that has a long half-life and easily remains as residue and contaminates the animal-based food product that leads to various health problems. In this work, electrochemical immunosensor based on poly(3,4-ethylenedioxythiophene)/graphene oxide (PEDOT/GO) modified screen-printed carbon electrode (SPCE) for CLB detection was developed for antibiotic monitoring in a food product. The modification of SPCE with PEDOT/GO as a sensor platform was performed through electropolymerization, while the electrochemical assay was accomplished while using direct competitive format in which the free CLB and clenbuterol-horseradish peroxidase (CLB-HRP) in the solution will compete to form binding with the polyclonal anti-clenbuterol antibody (Ab) immobilized onto the modified electrode surface. A linear standard CLB calibration curve with R² = 0.9619 and low limit of detection (0.196 ng mL-1) was reported. Analysis of milk samples indicated that this immunosensor was able to detect CLB in real samples and the results that were obtained were comparable with enzyme-linked immunosorbent assays (ELISA).

An improved clenbuterol detection by immunochromatographic assay with bacteria@Au composite as signal amplifier

Immunochromatographic assays (ICAs) are most frequently used for on-site rapid screening of clenbuterol. To improve sensitivity, a novel probe with bacteria as signal carriers was developed. Bacteria can load a great deal of gold nanoparticles (AuNPs) on their surface, meaning much fewer antibodies are needed to produce clearly visible results, although low concentrations of antibody could also trigger fierce competition between free analyte and the immobilized antigen. Thus, a limited number of antibodies was key to significantly improved sensitivity. Analytical conditions, including bacterial species, coupling method, and concentration, were optimized. The visual detection limit (VDL) for clenbuterol was 0.1 ng/mL, a 20-fold improvement in sensitivity compared with traditional strips. This work has opened up a new route for signal amplification and improved performance of ICAs. Furthermore, inactivated bacteria could also be environment-friendly and robust signal carriers for other biosensors.

A paper-based competitive lateral flow immunoassay for multi β-agonist residues by using a single monoclonal antibody labelled with red fluorescent nanoparticles

An ultrasensitive paper based lateral flow assay is described for rapid and simultaneous fluorometric detection of several β-agonists including clenbuterol and its chemical analogues (mabuterol, brombuterol, cimaterol, cimbuterol, bromchlorbuterol and banbuterol). A nonspecific monoclonal antibody (mAb) against clenbuterol and its analogues was prepared and employed in a competitive immunoassay where mAb conjugated to fluorescent nanoparticles and free β-agonists compete for the binding sites. This enables rapid screening for the 7 β-agonists in a single run that takes about 8 min. Detection limits for the seven β-agonists are <50 pg g⁻¹ of pork. Recoveries ranged from 69.5% to 102.4%, and relative standard deviations were ±15%. The assay was applied to the analysis of both using spiked and unspiked pork for β-agonists, and the results compare well to those obtained by HPLC-MS.

Graphical abstract

Electrochemical immunosensors - A powerful tool for analytical applications

Immunosensors are biosensors based on interactions between an antibody and antigen on a transducer surface. Either antibody or antigen can be the species immobilized on the transducer to detect antigen or antibody, respectively. Because of the strong binding forces between these biomolecules, immunosensors present high selectivity and very high sensitivity, making them very attractive for many applications in different science fields. Electrochemical immunosensors explore measurements of an electrical signal produced on an electrochemical transductor. This signal can be voltammetric, potentiometric, conductometric or impedimetric. Immunosensors utilizing electrochemical detection have been explored in several analyses since they are specific, simple, portable, and generally disposable and can carry out in situ or automated detection. This review addresses the potential of immunosensors destined for application in food and environmental analysis, and cancer biomarker diagnosis. Emphasis is given to the approaches that have been used for construction of electrochemical immunosensors. Additionally, the fundamentals of immunosensors, technology of transducers and nanomaterials and a general overview of the possible applications of electrochemical immunosensors to the food, environmental and diseases analysis fields are described.

Broad screening and identification of β-agonists in feed and animal body fluid and tissues using ultra-high performance liquid chromatography-quadrupole-orbitrap high resolution mass spectrometry combined with spectra library search

Broad screening and identification of β-agonists in feed, serum, urine, muscle and liver samples was achieved in a quick and highly sensitive manner using ultra high performance liquid chromatography-quadrupole-orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) combined with a spectra library search. Solid-phase extraction technology was employed for sample purification and enrichment. After extraction and purification, the samples were analyzed using a Q-Orbitrap high-resolution mass spectrometer under full-scan and data-dependent MS/MS mode. The acquired mass spectra were compared with an in-house library (compound library and MS/MS mass spectral library) built with TraceFinder Software which contained the M/Z of the precursor ion, chemical formula, retention time, character fragment ions and the entire MS/MS spectra of 32 β-agonist standards. Screening was achieved by comparing 5 key mass spectral results and positive matches were marked. Using the developed method, the identification results from 10 spiked samples and 238 actual samples indicated that only 2% of acquired mass spectra produced false identities. The method validation results showed that the limit of detection ranged from 0.021-3.854 μg kg(-1)and 0.015-1.198 ng mL(-1) for solid and liquid samples, respectively.

Detection of clenbuterol hydrochloride residuals in pork liver using a customized surface plasmon resonance bioanalyzer

A surface plasmon resonance (SPR) immunoassay with an immobilization of self-assembled molecular identification membrane for the detection of residual Clenbuterol Hydrochloride (CLB) in pork liver was systematically investigated and experimentally validated for its high performance. SPR immunoassay with a regular competitive inhibition assay cannot be directly verified to detect CLB residuals. In this study, the binding of Au film with mercaptopropionic acid was investigated using the known form of the strong S-Au covalent bonds formed by the chemical radical of the mercaptopropionic acid and the Au film. After that, the immunoglobulin IgG of swine (SwIgG-CLB) was bonded with the mercaptopropionic acid by covalent -CO-NH- amide bonding. The modified comprehensive analysis of how the membrane structure works was introduced together with the customized SPR bioanalyzer. In order to evaluate the performance of this biomembrane structure, the concentrations of CLB-contained solutions of 0 ng•mL^-1, 10 ng•mL^-1, 20 ng•mL^-1, 33.3 ng•mL^-1, and 40 ng•mL^-1 were prepared by adding CLB reagents into the solutions of CLB antibody (Clenbuterol Hydrochloride Antibody, CLB-Ab), successively and then the response unit (RU) was measured individually. Using the data collected from the linear CCD array, the fitting curve was established with the R-Square value of 0.9929. Correspondingly, the recovery rate ranged from 88.48% to 103.21% was experimented and the limit of detection of CLB in 1.26 ng•mL^-1 was obtained efficiently. It was concluded that the detection method associated with biomembrane properties is expected to contribute much to the determination of residual CLB in pork liver quantitatively by using the customized SPR bioanalyzer.

Rapid and sensitive determination of clenbuterol in porcine muscle and swine urine using a fluorescent probe

The feed additive Clenbuterol hydrochloric acid (CLB) is non-fluorescent, thus it is difficult to quantify through direct fluorescent method. Palmatine (PAL) can react with cucurbit[7]uril (CB[7]) to form stable complexes as a fluorescent probe. Significant quenching of the fluorescence intensity of the CB[7]-PAL complex was observed with the addition of CLB. Based on the significant quenching of the supramolecular complex fluorescence intensity, a novel spectrofluorimetric method with high convenience, selectivity and sensitivity was developed for the determination of CLB. The fluorescence quenching values (ΔF) showed good linear relationship with CLB concentrations from 0.011 μg mL(-1) to 4.2 μg mL(-1) with a detection limit 0.004 μg mL(-1). In this research, an ultrasound treatment replaced the former time-consuming shake method to form stable complexes. The proposed spectrofluorimetric method had been successfully applied to the determination of CLB in porcine muscle and swine urine with good precision and accuracy. The competing reaction and the supramolecular interaction mechanisms between the CLB and PAL as they fight for occupancy of the CB[7] cavity were studied using spectrofluorimetry, (1)H NMR, and molecular modeling calculations. Interestingly, results indicate that two stable CB[7]-CLB complexes were formed.

A new label-free strategy for a highly efficient chemiluminescence immunoassay

A new label-free chemiluminescence (CL) immunoassay method which is based on the co-immobilization of a capture antibody and horseradish peroxidase (HRP) on the Au nanoparticle–chitosan composite interface is proposed for the cheap, fast and convenient detection of proteins.

A label-free amperometric immunosensor for the detection of carcinoembryonic antigen based on novel magnetic carbon and gold nanocomposites

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of carcinoembryonic antigen (CEA).

Affinity-based biosensors in sport medicine and doping control analysis

Affinity-based biosensors (ABBs) have started to be considered in sport medicine and doping control analysis because they are cheap, easy to use and sufficiently selective analytical devices, characterized by a reversible interaction with the analyte under investigation allowing the use of the same sensor for multiple analyses. In this review we describe the main categories of substances reported in the World Anti-Doping Agency Prohibited List and how ABBs may contribute to their detection. Although several ABBs proposed in the last few years display limit of detections that are in principle matching the World Anti-Doping Agency requirements, their application in the framework of 'traditional' antidoping tests seems quite unlikely, mainly because of the still insufficient selectivity especially in the case of 'pseudo-endogenous' compounds, and on the lack of complete information regarding potential matrix effects in real samples and following their routine use. At the same time, ABBs could contribute to fill a significant information gap concerning complementary evidence that can be obtained from their use 'on the spot', as well as to preselect a risk population of individuals to be targeted for a full antidoping test; while in sport medicine they could contribute to obtaining analytical information of physiological relevance from the measurement of specific parameters or markers before, during and after physical exercise.

A novel electrochemical sensor for the analysis of β-agonists: the poly(acid chrome blue K)/graphene oxide-nafion/glassy carbon electrode

A novel modified electrode was constructed by the electro-polymerization of 4,5-dihydroxy-3-[(2-hydroxy-5-sulfophenyl)azo]-2,7-naphthalenedisulfonic acid trisodium salt (acid chrome blue K (ACBK)) at a graphene oxide (GO)-nafion modified glassy carbon electrode (GCE). The characterization of an electrochemically synthesized poly-ACBK/GO-nafion film was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques, and the results were interpreted and compared at each stage of the electrode construction. Electrochemical oxidation of eight β-agonists - clenbuterol, salbutamol, terbutaline, ractopamine, dopamine, dobutamine, adrenaline, and isoprenaline, was investigated by CV at the different electrodes. At the poly-ACBK/GO-nafion/GCE, the linear sweep voltammetry peak currents of the eight β-agonists increased linearly with their concentrations in the range of 1.0-36.0 ng mL(-1), respectively, and their corresponding limits of detection (LODs) were within the 0.58-1.46 ng mL(-1) range. This electrode showed satisfactory reproducibility and stability, and was used successfully for the quantitative analysis of clenbuterol in pork samples.