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Mycotoxins are secondary metabolites of fungi that contaminate agriculture products. Their release in the environment can cause severe damage to human health. Aptasensors are compact analytical devices that are intended for the fast and reliable detection of various species able to specifically interact with aptamers attached to the transducer surface. In this review, assembly of electrochemical and surface plasmon resonance (SPR) aptasensors are considered with emphasis on the mechanism of signal generation. Moreover, the properties of mycotoxins and the aptamers selected for their recognition are briefly considered. The analytical performance of bio-sensors developed within last three years makes it possible to determine mycotoxin residues in water and agriculture/food products on the levels below their maximal admissible concentrations. Requirements for the development of sample treatment and future trends in aptasensors are also discussed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Funding: T.K. acknowledges funding by the subsidy allocated to Kazan Federal University for the state assignment in the sphere of scientific activities (grant No 0671–2020−0063). T.H. acknowledges funding from the Science Grant Agency VEGA, project No.: 1/0419/20.

Carbon nanomaterials offer unique opportunities for the assembling of electrochemical aptasensors due to their high electroconductivity, redox activity, compatibility with biochemical receptors and broad possibilities of functionalization and combination with other auxiliary reagents. In this review, the progress in the development of electrochemical aptasensors based on carbon nanomaterials in 2016–2020 is considered with particular emphasis on the role of carbon materials in aptamer immobilization and signal generation. The synthesis and properties of carbon nanotubes, graphene materials, carbon nitride, carbon black particles and fullerene are described and their implementation in the electrochemical biosensors are summarized. Examples of electrochemical aptasensors are classified in accordance with the content of the surface layer and signal measurement mode. In conclusion, the drawbacks and future prospects of carbon nanomaterials’ application in electrochemical aptasensors are briefly discussed. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. R.S. acknowledges support of the state subsidy in the sphere of scientific activity for Kazan Federal University (proposal No 0671-2020-0063). T.H. acknowledges funding from the Science Grant Agency VEGA, project No.: 1/0419/20.

We performed a comparative analysis of the sensitivity of aptamer-based biosensors for detection mycotoxin aflatoxin M1 (AFM1) depending on the method of immobilization of DNA aptamers and method of the detection. Label-free electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) for ferrocene labeled neutravidin layers were used for this purpose. Amino-modified DNA aptamers have been immobilized at the surface of polyamidoamine dendrimers (PAMAM) of fourth generation (G4) or biotin-modified aptamers were immobilized at the neutravidin layer chemisorbed at gold surface. In the first case the limit of detection (LOD) has been determined as 8.47 ng/L. In the second approach the LOD was similar 8.62 ng/L, which is below of allowable limits of AFM1 in milk and milk products. The aptasensors were validated in a spiked milk samples with good recovery better than 78%. Comparative analysis of the sensitivity of immuno-and aptasensors was also performed and showed comparable sensitivity. © 2018 by the authors.

© 2016 Elsevier B.V.We report the effect of various factors such as oligonucleotide sequence, buffer composition, ionic strength for optimal determination of cytochrome c (cyt c) by DNA aptamer sensors using thickness shear mode acoustics (TSM) and electrochemical methods. Up to now, several DNA aptamers specific to cyt c have been selected and used in various sensing approaches including optical, electrochemical and mass sensitive transducers. We have analyzed the response of three different aptamers immobilized via biotin-neutravidin method on a gold support by TSM technique. Using this approach we have shown that only 76-length base sequence (apt 76) exhibited specific binding to cyt c with detection limit of 0.50 ± 0.05 nM. This aptamer was then studied under different ionic conditions showing an optimal response for HEPES buffer. Apt 76 based sensor has been also examined by electrochemical methods. However due to the electroactive nature of cyt c, the response of this aptamer was less favorable in comparison with TSM. The apt 76 based sensor was tested also in spiked samples of human plasma by TSM achieving a recovery of 92 ± 6.6% for 1 nM cyt c.

© 2015 Elsevier B.V. All rights reserved. In this work we report the detection of plasmin protease by means of the thickness shear mode (TSM) acoustic method. The biorecognition element consists of a peptide substrate (PS) specific to plasmin immobilized on a piezoelectric quartz crystal electrode. After enzymatic reaction with plasmin, it cleaves a short fragment of the peptide causing increase in the resonance frequency of the piezo crystal. Plasmin was detected in the range of concentrations 1-20 nM, a target interval in which its presence presumably affects the quality of milk. The PS exhibited negligible response against to similar protease trypsin. This has been confirmed also by electrochemical detection method. Limit of detection of this acoustic transducer was found to be 0.65 nM. Formation of the sensing surface and kinetic effect of plasmin on the peptide substrate was studied by atomic force microscopy (AFM). The PS response was also validated in pretreated milk samples spiked by known concentrations of plasmin achieving an average recovery of 63 ± 0.6%.

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Oxidative damage of DNA was assessed with glassy carbon electrode (GCE) coated with electropolymerized Methylene Blue (MB). For this purpose, DNA solution was first mixed with an oxidant (Fenton reagent, H2O2 alone and in the presence of Cu(II) ions) and then placed on the polymeric film surface. After washing, the cyclic voltammogram was recorded in buffer solution and the anodic peak potential measured against that before the contact with DNA. Oxidative DNA damage resulted in remarkable decrease of the anodic peak potential which depended on the oxidant nature and incubation period. Specificity of the DNA - MB interactions was confirmed by surface plasmon resonance (SPR) measurements. Similar experiment performed with polymerized Methylene Green (MG) and Neutral Red (NR) showed lower selectivity of the response toward various sources of reactive oxygen species. The protocol of the DNA damage detection was tested on the estimation of antioxidant properties of green tea extract and red table wine.

© 2016 Elsevier B.V.Since first report on formation stable free standing bilayer lipid membranes (BLM) in 1962 by Mueller et al. [1] these systems became very popular in modeling various membrane processes at molecular level, such as ionic transport, ligand-receptor interactions or lipid-protein interactions. Despite of advantage of BLM in respect of variation in lipid composition and their modifications by receptors and proteins, the work with these systems was rather difficult due to their limited stability. The situation has been considerably improved by introduction of supported bilayer lipid membranes (sBLM) in 1980 by Thompson et al. [2] for possible applications in biosensors. Recent advances in stabilization of supported lipid membranes, appearance of novel nanomaterials such as carbon nanotubes has increased the number of publications on this topic. This review summarizes latest achievements in the field of biosensors utilizing sBLMs.

Since first report on formation stable free standing bilayer lipid membranes (BLM) in 1962 by Mueller et al. [1] these systems became very popular in modeling various membrane processes at molecular level, such as ionic transport, ligand-receptor interactions or lipid-protein interactions. Despite of advantage of BLM in respect of variation in lipid composition and their modifications by receptors and proteins, the work with these systems was rather difficult due to their limited stability. The situation has been considerably improved by introduction of supported bilayer lipid membranes (sBLM) in 1980 by Thompson et al. [2] for possible applications in biosensors. Recent advances in stabilization of supported lipid membranes, appearance of novel nanomaterials such as carbon nanotubes has increased the number of publications on this topic. This review summarizes latest achievements in the field of biosensors utilizing sBLMs. © 2016 Elsevier B.V.

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimImmunosensors for detection of proteins are of high importance for medical diagnostics. There exists continuous effort in their development using new methods of antibody immobilizations at the various surfaces including novel nanomaterials, such as carbon nanotubes, graphene, dendrimers and combination of these materials with nanoparticles of various origin. At the same time as an alternative to antibodies DNA or RNA aptamers are considered as novel receptors during last 2 decades. In contrast with antibodies aptamers are more flexible and stable, allowing various chemical modification without lost of their sensitivity. This review compares the properties of existing immuno- and aptasensors for detection human immunoglobulin E (IgE) and cellular prions (PrPC). It has been shown, that both immuno- and aptasensors are of comparable sensitivity and selectivity that depends on the method of receptor immobilization and detection.

© 2015 Elsevier B.V. DNA sensors based on oligonucleotides and aptamers immobilized using electropolymerization and layer-by-layer assembling are reviewed. The conditions of electropolymerization and the role of electrosynthesized layers are considered for polyaniline, polypyrrole, polythiophene, polyphenazines and their derivatives with particular attention to immobilization of bioreceptors and signal detection principles. The performance of DNA sensors for hybridization detection and for the determination of low-molecular intercalators and DNA damaging factors is reviewed. Besides, the composition of polyelectrolyte complexes utilizing DNA receptors are considered depending on the analyte nature and functions of polyionic components and auxiliary reagents used for surface layer coatings.

© 2015 Elsevier B.V. All rights reserved. Novel electrochemical aptasensor toward cytochrome c (Cyt c) has been developed on the base of glassy carbon electrode (GCE) modified with electropolymerized neutral red (Poly-NR) and decacarboxylated pillar[5]arene (P[5]A-COOH) bearing terminal neutral red (NR) and aminated aptamer specific to Cyt c. Addition of Cyt c resulted in decrease of the cathodic peak current of NR on cyclic voltammogram due to suppression of the electron exchange between reduced and oxidized NR forms in the surface layer. The implementation of Cyt c in the surface layer was confirmed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Depending on the content of the surface layer and assembling protocol, the limits of detection (LODs) varied from 0.02 to 1.0 nM and linear range of concentrations was within three orders of magnitude. Interfering influence of some proteins and polyethylene glycol was characterized. The aptasensors developed can find application in detection of Cyt c as apoptosis agent in blood serum. This has been partially validated in model blood serum mimicking the ionic composition of the plasma.

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Novel electrochemical DNA-sensor based on glassy carbon electrode (GCE) modified with Ag nanoparticles, Neutral red covalently attached to its surface and native DNA adsorbed on modifier coating was developed for the estimation of DNA damage on example of model system based on Fenton reagent. As was shown, the oxidation process resulted in synchronous increase of electron transfer resistance and capacitance measured by electrochemical impedance spectroscopy (EIS). The contribution of each sensor component on the signal was specified and sensitivity estimated against similar surface coatings. The shift of EIS parameters was found to be higher than that of similar biosensors reported. The DNA sensor was tested on the estimation of antioxidant capacity of green tea infusions again the results of coulometric titration with electrogenerated bromine.

© 2015 Elsevier B.V. All rights reserved. New approach of the detection of anthracycline preparations intercalating native DNA has been proposed and realized in the assembly of electrochemical sensor. Glassy carbon was covered with polyaniline obtained by electropolymerization in the presence of native DNA and oxalic acid as doping agents. As was shown by impedimetric and voltammetric measurements, the surface coating obtained showed extended pH range of electrochemical activity and retained ability to interact with specific intercalators. The incubation of the sensor with anthracycline preparations resulted in regular decrease of electron transfer resistance and suppression of redox probe current (ferricyanide anion). In optimal conditions, the detection limits of 0.01 nM doxorubicin, 0.1 nM daunorubicin and 0.2 nM idarubicin were achieved. The replacement of oxalic acid with sulfuric acid as polymerization media as well as thermal denaturation of DNA resulted in disappearance of the response. The selectivity of DNA interaction detection was higher in weakly acidic media for impedimetric measurements and in HEPES, pH 7.0, for voltammetric detection. Albumin, blood plasma electrolytes and sulfanylamides do not interfere with anthracycline measurements. The electrochemical sensor developed was tested in the determination of doxorubicin in commercial preparation with 91-93% recovery.

© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Novel electrochemical aptasensors based on glassy carbon electrodes modified with electropolymerized Neutral red and polycarboxylated macrocyclic ligands onto which the DNA aptamers were covalently attached have been developed for detection of Aflatoxin B1 (AFB1). The interaction with an analyte resulted in the decrease of the cathodic peak current of the probe measured by CV and in the increase of the electron transfer resistance determined by EIS. The limit of detection was found to be 0.1 nM for CV and 0.05 nM for EIS methods, respectively. The aptasensor makes it possible to detect AFB1 in peanuts, cashew nuts, white wine and soy sauce with a recovery of 85-100%.