We describe a label-free electrochemical immunosensor for the carcinoembryonic antigen (CEA). It is based on a nanocomposite consisting of electrochemically reduced graphene oxide, gold nanoparticles (AuNPs), and poly(indole-6-carboxylic acid). Coupled to nanoparticle-amplification techniques and modified with ionic liquid (IL), this immunoassay shows high sensitivity and good selectivity for CEA. At the best working voltage of 0.95 V (vs. Ag/AgCl), the lower detection limit is 0.02 ng·mL?1, and the response to CEA is linear in the range from 0.02 to 90 ng·mL?1. The method was applied to the determination of CEA in spiked serum samples and gave recoveries in the range from 98.5 % to 102 %.
Graphical abstract A label-free electrochemical immunosensor was fabricated for the carcinoembryonic antigen (CEA) with a detection limit of 0.02 ng·mL?1. It is based on a nanocomposite consisting of electrochemically reduced graphene oxide (erGO), gold nanoparticles (Au NP), and poly(indole-6-carboxylic acid) (PICA).
CdSe:Eu nanocrystals were successfully synthesized and characterized by transmission electron microscopy, X-ray powder diffraction, and X-ray photoelectric spectroscopy. The CdSe:Eu nanocrystals showed enhanced green electrochemiluminescence (ECL) intensity when compared to pure CdSe nanocrystals. Further, the nanocrystals were used to design an ECL immunosensor for the detection of carcinoembryonic antigen (CEA) that has a linear response over the 1.0 fg·mL?1 to 100 ng·mL?1 CEA concentration range with a 0.4 fg·mL?1 detection limit. The assay was applied to the determination of CEA in human serum samples.
Graphical abstract Schematic of the assay: GCE-glassy-carbon electrode, Ab- Antibody, BSA- Bovine serum albumin, Ag- Antigen. CdSe:Eu nanocrystals were used to design an ECL immunosensor for the detection of carcinoembryonic antigen.
Diphenyl diselenide was immobilized on chitosan loaded with magnetite (Fe3O4) nanoparticles to give an efficient and cost-effective nanosorbent for the preconcentration of Pb(II), Cd(II), Ni(II) and Cu(II) ions by using effervescent salt-assisted dispersive magnetic micro solid-phase extraction (EA-DM-μSPE). The metal ions were desorbed from the sorbent with 3M nitric acid and then quantified via microflame AAS. The main parameters affecting the extraction were optimized using a one-at-a-time method. Under optimum condition, the limits of detection, linear dynamic ranges, and relative standard deviations (for n?=?3) are as following: Pb(II): 2.0 ng·mL?1; 6.3–900 ng·mL?1; 1.5%. Cd(II): 0.15 ng·mL?1; 0.7–85 ng·mL?1, 3.2%; Ni(II): 1.6 ng·mL?1,.6.0–600. ng·mL?1, 4.1%; Cu(II): 1.2 ng·mL?1, 3.0–300 ng·mL?1, 2.2%. The nanosorbent can be reused at least 4 times.
Graphical abstract Fe3O4-chitosan composite was modified with diphenyl diselenide as a sorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction.
The authors describe a voltammetric immunosensor with antibody immobilized on a glassy carbon electrode (GCE) modified with N-doped graphene (N-GS), electrodeposited gold nanoparticles (AuNPs) and chitosan (Chit). The preparation is simple and the thickness of the electrodeposited films can be well controlled. Due to the specific advantages of N-GS, AuNPs and Chit, the electrode has a large specific surface, improved conductivity, high stability. A new label-free immunosensor for the model antigen (alpha fetoprotein, AFP) detection was then designed by employing N-GS-AuNP-Chit as the antibody immobilization and signal amplification platform. Differential pulse voltammetry and electrochemical impedance spectroscopy were used for the characterization of the stepwise assembly process. Under the optimized conditions, at a typical working potential of +0.20 V (vs. SCE), and by using hexacyanoferrate as an electrochemical probe, the immunosensor has a detection limit as low as 1.6 pg mL?1 and a linear analytical range that extends from 5 pg mL?1 to 50 ng mL?1. AFP was quantified in spiked human serum samples with acceptable precision.
Graphical Abstract Schematic of sensitive and effective label-free electrochemical immunosensor for the detection of AFP based on N-GS-AuNP-Chit as signal amplification matrix.
The family of zearalenones (ZENs) represents a major group of mycotoxins with estrogenic activity. They are produced by Fusarium fungi and cause adverse effects on human health and animal production. The authors describe here a label-free amperometric immunosensor for the direct determination of ZENs. A glassy carbon electrode (GCE) was first modified with polyethyleneimine-functionalized multi-walled carbon nanotubes. Next, gold and platinum nanoparticles (AuPt-NPs) were electro-deposited. This process strongly increased the surface area for capturing a large amount of antibodies and enhanced the electrochemical performance. In a final step, monoclonal antibody against zearalenone was orientedly immobilized on the electrode, this followed by surface blocking with BSA. The resulting biosensor was applied to the voltammetry determination of ZENs, best at a working voltage of 0.18 V (vs SCE). Under optimized conditions, the method displays a wide linear range that extends from 0.005 to 50 ng mL?1, with a limit of detection of 1.5 pg mL?1 (at an S/N ratio of 3). The assay is highly reproducible and selective, and therefore provides a sensitive and convenient tool for determination of such mycotoxins.
Graphical abstract An amperometric immunosensor for the direct determination of ZENs has been developed by immobilizing anti-ZEN monoclonal antibody on multi-walled carbon nanotubest hat were deposited, along with gold and platinum nanoparticles, on a glassy carbon electrode modified with Staphylococcus protein A.
The authors report on a disposable sensor for the differential pulse anodic stripping voltammetric (DPASV) determination of the ions Zn(II), Pb(II) and Cu(II). Simultaneous detection is accomplished by using a screen-printed carbon electrode (SPCE) co-modified with an in-situ plated bismuth (Bi)) film and gold nanoparticles (AuNPs). The synergistic effect of the Bi film, and the large surface and good electrical conductivity of the AuNPs strongly assist in the co-deposition of the three ions. Four well-defined and fully separated anodic stripping peaks, at 540 mV for Zn(II), 50 mV for Pb(II), 140 mV for Bi(III) and 295 mV for Cu(II), all vs. Ag/AgCl, can be seen. The modified SPCE was characterized by scanning electron microscopy, X-ray diffraction, cyclic voltammetry and electrochemical impedance spectroscopy. Under the optimized conditions, the sensor has a good response to these ions. The detection limits (at an S/N ratio of 3) are 50 ng·L?1 for Zn(II), 20 ng·L?1 for Pb(II), and 30 ng·L?1 for Cu(II). The method was applied to the determination of the 3 ions in spiked lake water samples.
Graphical abstract Schematic of screen-printed carbon electrode (SPCE) co-modified with a bismuth film and gold nanoparticles for electrochemical simultaneous determination of Zn(II), Pb(II) and Cu(II) by differential pulse anodic stripping voltammetric (DPASV).
A dual-responsive sandwich-type immunosensor is described for the detection of interleukin 6 (IL-6) by combining electrochemiluminescent (ECL) and electrochemical (EC) detection based on the use of two kinds of TiO2 mesocrystal nanoarchitectures. A composite was prepared from TiO2 (anatase) mesocages (AMCs) and a carboxy-terminated ionic liquid (CTIL) and then placed on a glassy carbon electrode (GCE). In the next step, the ECL probe Ru(bpy)3(II) and antibody against IL-6 (Ab1) were immobilized on the GCE. Octahedral anatase TiO2 mesocrystals (OAMs) served as the matrix for immobilizing acid phosphatase (ACP) and secondary antibody (Ab2) labeled with horseradish peroxidase (HRP) to form a bioconjugate of type Ab2-HRP/ACP/OAMs. It was self-assembled on the GCE by immunobinding. 1-Naphthol, which is produced in-situ on the surface of the GCE due to the hydrolysis of added 1-naphthyl phosphate by ACP, is oxidized by HRP in the presence of added H2O2. This results in an electrochemical signal (typically measured at 0.4 V vs. Ag/AgCl) that increases linearly in the 10 fg·mL?1 to 90 ng·mL?1 IL-6 concentration range with a detection limit of 0.32 fg·mL?1. Secondly, the oxidation product of 1-naphthol quenches the ECL emission of Ru(bpy)32+. This leads to a decrease in ECL intensity which is linear in the 10 ag·mL?1 to 90 ng·mL?1 concentration range, with a detection limit of 3.5 ag·mL?1. The method exhibits satisfying selectivity and good reproducibility which demonstrates its potential in clinical testing and diagnosis.
Graphical abstract A dual-responsive sandwich-type immunosensor was fabricated for the detection of interleukin 6 by combining electrochemiluminescence and electrochemical detection based on the use of two kinds of TiO2 mesocrystal nanoarchitectures.
A magnetic sorbent was fabricated by coating the magnetized graphene oxide with polystyrene (PS) to obtain a sorbent of the type GO-Fe3O4@PS. The chemical composition and morphology of the sorbent were characterized. The sorbent was employed for the enrichment of polycyclic aromatic hydrocarbons (PAHs) from water samples. Various parameters affecting the enrichment were investigated. The PAHs were then quantified by gas chromatography with flame ionization detection. Linear responses were found in the range of 0.03–100 ng mL?1 for naphthalene and 2-methylnaphthalene, and of 0.01–100 ng mL?1 for fluorene and anthracene. The detection limits (at an S/N ratio of 3) range between 3 and 10 pg mL?1. The relative standard deviations (RSDs) for five replicates at three concentration levels (0.05, 5 and 50 ng mL?1) of analytes ranged from 4.9 to 7.4%. The method was applied to the analysis of spiked real water samples. Relative recoveries are between 95.8 and 99.5%, and RSD% are <8.4%.
Graphical abstract A magnetic sorbent was fabricated by polystyrene coated on the magnetic graphene oxide for the extraction and preconcentration of PAHs in water samples prior to their determination by gas chromatography with flame ionization detection.
The authors describe a sandwich-type electrochemical immunoassay for sensitive determination of the carcinoembryonic antigen (CEA). It is based on the use of iridium nanoparticles (Ir NPs) acting as electrochemical signal amplifier on the surface of a glassy carbon electrode. At first, polydopamine-reduced graphene oxide (PDA-rGO) was employed to immobilize primary antibody (Ab1) against CEA. Secondly, Ir-NPs were used as a support for the immobilization of secondary antibody (Ab2) to afford signal labels. The large surface area of PDA-rGO and the excellent electro-oxidative H2O2-sensing properties of Ir NPs result in a sensitive assay for CEA. Operated best at a working voltage of ?0.6 V (vs. SCE), the assay has a linear range that extends from 0.5 pg?mL?1 to 5 ng·mL?1, and the lower detection limit is 0.23 pg?mL?1. The immunosensor displays satisfactory reproducibility and stability, thus demonstrating a reliable immunoassay strategy for tumor biomarkers. It was applied to the determination of CEA in spiked serum samples.
Graphical abstract Schematic of an amperometric sandwich immunoassay for the carcinoembryonic antigen using a glassy carbon electrode modified with polydopamine, reduced graphene oxide and iridium nanoparticles
CdTe quantum dots (QDs) were integrated with polyethyleneimine-coated carbon dots (PEI-CDs) to form a dually emitting probe for heparin. The red fluorescence of the CdTe QDs is quenched by the PEI-CDs due to electrostatic interactions. In the presence of heparin, the blue fluorescence of PEI-CDs remains unaffected, while its quenching effect on the fluorescence of CdTe QDs is strongly reduced. A ratiometric fluorometric assay was worked out. The ratio of the fluorescences at 595 and 436 nm serves as the analytical signal. Response is linear in the concentration range of 50–600 ng·mL?1 (0.1–1.2 U·mL?1) of heparin. The limit of detection is 20 ng·mL?1 (0.04 U·mL?1). This makes the method a valuable tool for heparin monitoring during postoperative and long-term care. This assay is relatively free from the interference by other analogues which commonly co-exist with heparin in samples, and it is more robust than single-wavelength based assays.
Graphical abstract In the presence of heparin, the fluorescence of polyethyleneimine-coated carbon dots (PEI-CDs) at 436 nm remains unaffected, while its quenching effect on the fluorescence of CdTe at 595 nm is strongly reduced.
The authors describe an electrochemical sensor for the breast cancer marker α-lactalbumin (αLA). It is based on the use of printed single-walled carbon nanotube (SWCNT) electrodes that were modified with polycatechol. Impedance-derived electrochemical capacitance spectroscopy (ECS) is applied for detection at an applied potential of ?0.14 V vs. Ag/AgCl reference electrode. The electrode was prepared in a two-step process. First, a dispersion of SWCNTs was drop-cast onto the surface of a poly(ethylene terephthalate) substrate to act as the working electrode. Next, catechol was electrochemically polymerized on the SWCNTs, prior to the immobilization of lysozyme. The strong interaction between lysozyme and αLA induced changes in the redox capacitance which are detected by ECS. The latter shows the device to be capable of detecting αLA in the 20 to 80 ng·mL?1 concentration range. The limit of detection is 9.7 ng·mL?1 at an S/N ratio of 3. The device was used to detect αLA in human blood serum with good recovery results.
Graphical abstract A sensitive biosensor for αLA was prepared by modifying SWCNT electrode with polycatechol and lysozyme. The electrochemical capacitance spectroscopy was used for the first time to selectively detect αLA in the blood in the range from 20 to 80 ng·mL?1.
This article describes an electrochemical immunosensor for rapid determination of Salmonella pullorum and Salmonella gallinarum. The first step in the preparation of the immunosensor involves the electrodeposition of gold nanoparticles used for capturing antibody and enhancing signals. In order to generate a benign microenvironment for the antibody, the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate was used to modify the surface of a screen-printed carbon electrode (SPCE). The single steps of modification were monitored via cyclic voltammetry and electrochemical impedance spectroscopy. Based on these findings, a sandwich immunoassay was worked out for the two Salmonella species by immobilizing the respective unlabeled antibodies on the SPCE. Following exposure to the analytes, secondary antibody (labeled with HRP) is added to form the sandwich. After adding hydrogen peroxide and thionine, the latter is oxidized and its signal measured via CV. A linear response to the Salmonella species is obtained in the 104 to 109 cfu · mL−1 concentration range, and the detection limits are 3.0 × 103 cfu · mL−1 for both species (at an SNR of 3). This assay is sensitive, highly specific, acceptably accurate and reproducible. Given its low detection limit, it represents a promising tool for the detection of S. pullorum, S. gallinarum, and - conceivably - of other food-borne pathogens by exchanging the antibody.
We describe an electrochemical sandwich assay based on a screen-printed carbon electrode, gold nanoparticles and ILs and capable of detecting Salmonella pullorum and Salmonella gallinarum. The preparation is outlined in the Schematic.
A conductive hydrogel acting as a redox-active species was synthesized by crosslinking phytic acid as a ligand and lead(II) as the metal ion. The resulting gelatine-like material displays excellent redox activity and facilitates the transport of electrons and ions. Gold nanoparticles were electrochemically deposited on the hydrogel film, and antibody against cytokeratin antigen was immobilized thereon. An amperometric immunosensor for cytokeratin antigen 21–1 (CYFRA21-1), a kind of biomarker of lung cancer, was obtained by deposition of the composite on a glassy carbon electrode. If operated at ? 0.58 V (vs. Ag/AgCl), the sensor exhibits a linear detection range that extends from 50 fg mL?1 to 100 ng mL?1 CYFRA21-1, and a 38 fg mL?1 detection limit (at a signal to noise ratio of 3). The quantitation of CYFRA21-1 in (spiked) human serum samples showed satisfactory accuracy compared to an ELISA.
Graphical abstract A conductive hydrogel acting as a redox-active species was synthesized by crosslinking phytic acid as a ligand and lead(II) as the metal ion, which was used to fabricate an ultrasensitive label-free amperometric immunosensor for tumor marker.
Tungsten disulfide (WS2) nanosheets were obtained by exfoliating WS2 bulk crystals in N-methylpyrrolidone by ultrasonication. Gold nanoparticles (GNPs) were synthesized by in-situ ultrasonication of sodium citrate and HAuCl4 while fabricating the WS2 nanosheets. In this way, the GNPs were self-assembled on WS2 nanosheets to form a GNPs/WS2 nanocomposite through interaction between sulfur and gold atoms. The photoelectrochemical response of WS2 nanosheets is significantly enhanced after integration of the GNPs. The GNPs/WS2 nanocomposite was coated onto a glassy carbon electrode (GCE) to construct a sensing interface which then was modified with an antibody against the carcinoembryonic antigen (CEA) to obtain a photoelectrochemical immunosensor for CEA. Under optimized conditions, the decline in relative photocurrent is linearly related to the logarithm of the CEA concentration in the range from 0.001 to 40 ng mL?1. The detection limit is 0.5 pg mL?1 (at S/N =?3). The assay is sensitive, selective, stable and reproducible. It was applied to the determination of CEA in clinical serum samples.
Graphical abstract Schematic presentation of the fabrication of Au/WS2 nanocomposites by in-situ ultrasonication and the procedure for the CEA photoelectrochemical immunosensor preparation, and the photocurrent response towards the carcinoembryonic antigen.
The authors describe an immunoassay for the determination of carcinoembryonic antigen (CEA) tumor markers by depositing a polydopamine-Pb(II) nanocomposite on the surface of a glassy carbon electrode. The nanocomposite acts as a redox system that displays a large specific surface and provides a strong current signal at ?0.464 V (vs. Ag/AgCl). After the deposition of PDA-Pb2+ on glassy carbon electrode, the electrode was additionally coated with a chitosan-gold nanocomposite. The immunoassay platform was obtained by immobilization of antibodies against carcinoembryonic antigens by using glutaraldehyde and blocking with bovine albumin. Owing to its large surface, good electrical conductivity and powerful current response, the immunoassay has a wide linear range that extends from 1 fg·mL?1 to 100 ng·mL?1, with a detection limit as low as 0.26 fg·mL?1. The results obtained with this immunoassay when determining CEAs in human serum were found to be consistent with those obtained by ELISAs.
Graphical abstract Schematic of an ultrasensitive electrochemical immunosensor for the carcinoembryonic antigen. It is based on a glassy carbon electrode modified with a polydopamine-Pb(II) nanocomposite acting as a signal-inherent substrate.
The authors describe an immunochromatographic test for the rapid detection of cardiac dysfunction by quantifying the cardiac markers troponin I (TnI), fatty acid binding protein (FABP), and C-reactive protein (CPR) in serum. The dynamics of the formation of the immuno-complexes between antibodies (labeled with gold nanoparticles) and analytes (biomarkers) during immunochromatography was studied, and requirements are specified in terms of membrane carriers and reaction medium that are necessary to detect these biomarkers with their varying intracellular localizations and physical and chemical properties. The test can be performed within 10 min and enables TnI to be determined in concentrations of ≥?1.0 ng mL?1, FABP in concentrations of ≥?3.8 ng mL?1, and CPR in concentrations of ≥?600 ng mL?1. The results of the new test system correlated well with those obtained by ELISAs as used in cardiodiagnostics. It is emphasized here that simultaneous control of several myocardial biomarkers provides more information on the dynamics and development of the pathological process and enables more effective therapeutic decisions.
Graphical abstract An immunochromatographic test system for rapid diagnostics of cardiac dysfunctions was developed. In 10 min it provides detection of two biomarker of acute myocardial infarction, namely «rapid» one, fatty acid binding protein and «slow» one, troponin I and also inflammation biomarker, C-reactive protein.
Electrochemical sandwich immunoassay strategies involving the use of carboxyl-functionalized magnetic microbeads (cMBs) and magnetic nanoparticles (cMNPs) have been evaluated and compared. The proteolytically cleaved soluble tyrosine kinase receptor sAXL was used as the target analyte. Antibodies against AXL were covalently immobilized on cMBs or cMNPs. Immunobinding of AXL was detected by means of a secondary biotinylated antibody and a streptavidin-horseradish peroxidase conjugate. The electrochemical transduction was accomplished by capturing the cMBs or cMNPs bearing the immunoconjugates onto screen-printed carbon electrodes (SPCEs) by using a small magnet. The amperometric response was measured at ?0.20 V (vs the silver pseudo-reference electrode of the SPCE) upon the addition of H2O2 in the presence of hydroquinone as the redox mediator. The calibration plots for AXL extended up to 7.5 ng mL?1 when cMBs were used for the preparation of the immunosensor and up to 40 ng mL?1 in the case of using cMNPs. The respective slope values were 158 (cMBs) and 43 nA mL ng?1 (cMNPs), while the achieved LODs were 74 (cMBs) and 75 pg mL?1 (cMNPs). Although the immunosensors prepared with cMBs provided a shorter range of linearity, they exhibited a 3.7-times larger sensitivity than those constructed with cMNPs. The successful application of the new strategies was demonstrated for the determination of the endogenous content of sAXL in real human serum samples (a cut-off value of 71 ng mL?1 have been established for patients with risk of heart failure). The immunosensors constructed using cMBs or cMNPs can be advanta geously compared, in terms of sensitivity and fabrication time, with the only immunosensor for AXL previously reported. In addition, these new immunosensors took approximately half time than ELISA to perform the assay.
Graphical abstract Comparative evaluation of the performance of amperometric immunosensors for tyrosine kinase receptor AXL determination using carboxyl-modified magnetic microparticles (cMBs) and nanoparticles (cMNPs) and application to the determination of the endogeneous concentration in real human serum samples.
The authors describe a voltammetric immunoassay for the carcinoembryonic antigen (CEA). A GCE was modified by electrodeposition of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with tannic acid (TA). Subsequently, four-armed poly(ethylene glycol) (PEG) was assembled onto the modified surface through hydrogen bonding. The fabrication steps were characterized by scanning electron microscopy, energy dispersive spectroscopy, fourier transform infrared spectroscopy, contact angle measurements, electrochemical impedance spectroscopy and differential pulse voltammetry. The PEG/TA-PEDOT surface is shown be super-hydrophilic and to possess anti-fouling capability. Antibody against CEA was then covalently immobilized on the electrode. By using hexacyanoferrate as an electrochemical probe and at a working potential of 0.18 V vs SCE, the amperometric response is linear in the 10 ag·mL?1 to 1.0 ng·mL?1 CEA concentration range, and the detection limit is as low as 4.8 ag·mL?1 (at an S/N ratio of 3). The assay was applied to the quantification of CEA in 1:10 diluted human serum samples. Recoveries ranged from 103.7 to 108.7%, and relative standard deviations from 2.9 to 4.8%.
Graphical abstract Schematic of an electrochemical immunosensor for the carcinoembryonic antigen (CEA). It is based on the use of tannic acid (TA) and poly(ethylene glycol) (PEG), both deposited on a glassy carbon electrode (GCE), and using hexacyanoferrate as the electrochemical probe. The sensor has a wide linear range and a 4.8 ag·mL?1 detection limit.
The authors describe a fluorometric assay for ochratoxin A (OTA) that is based on the use of graphene oxide and RNase H-aided amplification. On addition of OTA, cAPT is replaced from the APT/cAPT hybridization complex and then hybridizes with RNA labeled with a fluorophore at the 5′-end. Eventually, the fluorophore is released by RNase H cleavage. As the concentration of OTA increases, more cAPTs are displaced, this leading to fluorescence enhancement (best measured at excitation/emission wavelengths of 495/515 nm). This RNase H-assisted cycle response results in strong signal amplification. The limit of detection, calculated on the basis of a signal to noise ratio of 3, is 0.08 ng·mL?1. Response is linear in the 0.08–200 ng·mL?1 OTA concentration range. The method is highly selective for OTA over ochratoxin B and aflatoxin B1. It was applied to the determination of OTA in red wine samples spiked at levels of 1, 7, and 50 ng·mL?1, and the recoveries ranged from 90.9 to 112%.
A polydopamine-based molecularly imprinted polymer was deposited on the surface of magnetite (ferroferric oxide) nanoparticles (Fe3O4@PDA MIPs) and is shown to be an efficient and fairly specific sorbent for the extraction of various ochratoxins. The MIPs were characterized by IR spectroscopy and transmission electron microscopy. The adsorption capacities, evaluated through the langmuir adsorption isotherm model, are 1.8, 0.23 and 0.17 mg·g?1 for ochratoxin A, ochratoxin B and ochratoxin C, respectively. Parameters such as the amount of magnetic MIPs, pH value, time for ultrasonication, elution solvent and volume were optimized. Following desorption from the MIP with acetonitrile, the ochratoxins were quantified by HPLC with fluorometric detection. Under optimal experimental conditions, the calibration plots are linear in the range of 0.01–1.0 ng·mL?1 of OTA, 0.02–2.0 ng·mL?1 of OTB, and 0.002–0.2 ng·mL?1 of OTC. The LODs are between 1.8 and 18 pg·mL?1, and the recoveries from spiked samples are 71.0% - 88.5%, with RSDs of 2.3–3.8% in case of rice and wine samples. The MIPs can be re-used for at least 7 times.
Graphical abstract Schematic of the preparation of a magnetic molecularly imprinted polymer based on self-polymerization of dopamine in weakly alkaline solution. Ochratoxins are recognized owing to homologous cavities in the MIPs, and quantified by HPLC after desorption with acetonitrile.
