Electrochemical Aptasensor For Ultrasensitive Detection Research Articles

Highly conductive AuNPs/Co-MOF nanocomposites synergistic hybridization chain reaction enzyme-free electrochemical aptasensor for ultrasensitive detection of Aflatoxin B1

Aflatoxin B1 (AFB1) is the most poisonous and carcinogenic pollutant among numerous mycotoxins, posing a serious risk to the health of humans. Herein, an electrochemical aptasensor was constructed for AFB1 detection using gold nanoparticles/cobalt-based metal–organic skeleton (AuNPs/Co-MOF) as a modifying material combined with an enzyme-free signal amplification strategy. AuNPs/Co-MOF have an extensive specific surface area and outstanding electrical conductivity, which allows for the loading of a large number of DNA strands and enhancement of the thionine (THi) redox signal, leading to a significant increase in signal response THi loaded bimetallic core–shell nanocomposites (Au@PtNPs) were synthesized as signal labels. Au@PtNPs have high catalytic activity towards THi while improving the efficiency of the loaded THi, which enables the electrochemical signal of THi to be amplified. In addition, the hybridization chain reaction (HCR) signal amplification strategies for enzyme-free amplification elicits a strong response in the electrochemical signal while ensuring sensor stability. The aptasensor has a detection range of 0.001–500 ng/mL and achieves the limit of detection (LOD) was 1.2 × 10-2 pg/mL and limit of quantification (LOQ) was 4.0 × 10-2 pg/mL under optimal experimental conditions. Therefore, applications for electrochemical aptasensors in the realm of food safety monitoring are quite promising.

Enzyme-catalyzed electrochemical aptasensor for ultrasensitive detection of soluble PD-L1 in breast cancer based on decorated covalent organic frameworks and carbon nanotubes

BackgroundSoluble programmed death-ligand 1 (sPD-L1) is critically involved in breast cancer recurrence and metastasis. However, the clinical application of highly sensitive sPD-L1 assays remains a challenge due to its low abundance in peripheral blood. To address this issue, for the first time, an enzyme-catalyzed electrochemical aptasensing platform was devised, incorporating covalent organic frameworks-gold nanoparticles-antibody-horseradish peroxidase (COFs-AuNPs-Ab-HRP) and polyethyleneimine-functionalized multiwalled carbon nanotubes (MWCNTs-PEI-AuNPs) for the highly specific and ultrasensitive detection of sPD-L1. ResultsMWCNTs-PEI-AuNPs possessed an extensive specific surface area and exhibited excellent electrical conductivity, facilitating the immobilization of aptamer and amplifying the signal. COFs modified with AuNPs not only amplified the electrical signal but also proffered a loading platform for the Ab and HRP. The favorable biocompatibility of COFs contributed to the preservation of enzyme activity and stability. HRP acted in synergy with hydrogen peroxide (H2O2) to catalyze the oxidation of hydroquinone (HQ) to benzoquinone (BQ). Subsequently, BQ underwent electrochemical reduction to HQ, inducing an enzymatic redox cycle that amplified the electrochemical signal and enhanced the sensitivity and selectivity of the detection method. The developed aptasensor displayed a liner range for sPD-L1 identification from 1 pg mL−1 to 100 ng mL−1 and the detection limit reached 0.143 pg mL−1 (S/N = 3). SignificancePaving the way for clinical application, this strategy detected differences in sPD-L1 in cell supernatants and peripheral blood of breast cancer patients with higher sensitivity compared to commercial sPD-L1 ELISA kit. This work demonstrates significant potential in offering reference information for early diagnosis and disease surveillance of breast cancer.

Modified electrochemical aptasensor for ultrasensitive detection of tetracycline: In silico and in vitro studies.

An ultrasensitive electrochemical aptasensor based on a glassy carbon electrode, modified by carbon nanofibers and carboxylated multi-walled carbon nanotubes was fabricated to detect tetracycline in food samples. The affinity of antibiotics, including kanamycin, tetracycline, ampicillin, and sulfadimethoxine toward desired sequences of aptamers and the stability of antibiotic-aptamer complexes were studied using molecular docking and molecular dynamic simulations. Moreover, the highest affinity and most stable complex were observed for tetracycline in complex with kanamycin-specific aptamer (KAP). Finally, KAP was used to develop an aptasensor. The central composite design (CCD) was used to optimize effective parameters. The biosensor achieved a wide dynamic linear range (1.0×10-17-1.0×10-5M) and a low limit of detection (2.28×10-18M) under optimized conditions using differential pulse voltammetry. Using the developed aptasensor, tetracycline residues in milk samples were determined.

A novel electrochemical aptasensor for ultrasensitive detection of herbicide prometryn based on its highly specific aptamer and Ag@Au nanoflowers

Herbicide prometryn has become a common pollutant in aquatic environments and caused adverse impacts on ecosystems. This study developed an ultrasensitive electrochemical aptasensor for prometryn based on its highly affinitive and specific aptamer and Ag@Au nanoflowers (Ag@AuNFs) for signal amplification. Firstly, this study improved the Capture-SELEX strategy to screen aptamers and obtained aptamer P60-1, which had a high affinity (Kd: 23 nM) and could distinguish prometryn from its structural analogues. Moreover, the typical stem-loop structure in aptamer P60-1 was found to be the binding pocket for prometryn. Subsequently, an electrochemical aptasensor for prometryn was established using multiwalled carbon nanotubes and reduced graphene oxide as electrode substrate, Ag@Au NFs as signal amplification element, and aptamer P60-1 as recognition element. The aptasensor had a detection range of 0.16–500 ng/mL and a detection limit of 60 pg/mL, which was much lower than those of existing detection methods. The aptasensor had high stability and good repeatability, and could specifically detecting prometryn. Furthermore, the utility of the aptasensor was validated by measuring prometryn in environmental and biological components. Therefore, this study provides a robust and ultrasensitive aptasensor for accurate detection for prometryn pollution.

A novel DNAzyme-driven walker-walkers serial amplified electrochemical aptasensor for ultrasensitive detection of cardiac troponin I

Sensitive and accurate detection of Cardiac troponin I (cTnI) plays an instrumental role in the prevention and management of acute myocardial infarction. Herein, a novel electrochemical aptasensor was designed for cTnI ultrasensitive detection based on DNAzyme-driven walker-walkers serial amplified strategy. The Au/NiCo2S4 nanocomposites, which possess excellent conductivity and a high specific surface area, were used to assemble on the modified electrode for the first time. The Hairpin probe I (HPI) and hairpin probe II (HP II) were self-assembled onto an Au/NiCo2S4 electrode surface through the interaction of Au-S bond. In the present of cTnI, the walker-walkers strategy was activated. After the hybridization between cTnI and HP I, the DNA walker shears the specific sequence of HP II and releases triggered DNA. Since the triggered DNA corresponds to the HP I complementary sequence, which could trigger multiple recycling and release DNA walkers. By the joint action of cTnI and triggered DNA, HP I was opened and released more DNA walkers. With the use of cDNA, capturing methylene blue (MB), resulting in the significant electrochemical signal in differential pulse voltammetry (DPV). The proposed strategy can effectively avoid problems of the insufficient distance or limited available driving force that general exist in unipedal DNA walkers. Under optimal conditions, the change of current was linearly related to the negative logarithm of cTnI concentration in the detection range of 0.01–60 ng/mL with a low detection limit of 0.26 pg/mL. Moreover, the proposed aptasensor was successfully applied in detection of human serum samples.

Development of an Electrochemical Aptasensor for Ultrasensitive Detection of Tetracycline in Eggs

In recent years, in order to prevent the occurrence of various diseases, the fncscrambled misuse of antibiotics is quite serious, and the residues of antibiotics such as tetracycline in eggs can also cause damage to human health. A double-stranded DNA probe modified with ferrocene was immobilized onto a gold nanoparticle modified substrate. Tetracycline was added to form a strong affinity binding between the target and the aptamer. During this process, the complementary strand was detached from the electrode surface. Therefore, the measured electrical signal attenuates with the emergence of the target. The linear response of tetracycline concentration to the signal ranged from 0.0005μM~50μM. The fabricated biosensor showed excellent selectivity. The accurate detection limit can be as low as 0.5 nm. Further, in the determination of tetracycline concentrations in water and egg samples, the fabricated biosensor showed excellent selectivity. Furthermore, the applicability of the developed sensor was demonstrated in the determination of tetracycline concentrations in egg samples. The spiking recoveries ranged from 96.18% to 102.75% which reached acceptable level. This detection sensor is simple, time-saving, selective and efficient, which can provide potential services in food production safety, environmental detection and so on.

A label-free and selective electrochemical aptasensor for ultrasensitive detection of Di(2-ethylhexyl) phthalate based on self-assembled DNA nanostructure amplification

• An electrochemical aptasensor was constructed to detect Di(2-ethylhexyl) phthalate. • The aptasensor has the advantages of easy operation, label-free and low cost. • Utilizing self-assembly of DNA nanostructures for amplifying detection signal. • The aptasensor shows wide linear range and low detection limit of 0.04 ng mL −1 . • The aptasensor shows good reproducibility and high selectivity for DEHP assay. Di(2-ethylhexyl) phthalate (DEHP) is an endocrine disrupting compound that is often used as a plasticizer and tends to migrate in the environment and accumulates in the human body causing harm to humans. Thus, a simple, label-free, enzyme-free, high selective and ultrasensitive electrochemical aptasensor has been constructed for detection of DEHP based on the self-assembly of DNA nanostructure signal amplification strategy in this paper. The DNA-junction nanostructure is made of hairpin 1 (HP1), hairpin 2 (HP2), hairpin 3 (HP3) and quarter sequence (QS). Without DEHP, the electrochemical detection response is very low. Only when the aptamer binds to the target and detaches from the electrode surface, the DNA-junction is trapped on the electrode surface, enhancing the electrochemical signal. This is because the DNA-junction nanostructure is rich in guanine, which is able to adsorb more methylene blue (MB) for the purpose of enhancing the detection signal. The linear detection range of the obtained aptasensor is 0.1 ng mL −1 to 5000 ng mL −1 and the limit detection is 0.04 ng mL −1 . Finally, the proposed aptasensor has been applied to analyze DEHP in real samples, laying the foundation for its utilization in environmental water samples and food safety.

Development of a label-free electrochemical aptasensor for ultrasensitive detection of ochratoxin A

The prevalent ochratoxin A (OTA) contamination in food has increased the urgency to develop sensitive and accurate detection methods. This study reported a conveniently fabricated label-free electrochemical (EC) aptasensor for ultrasensitive detection of OTA based on the competitive binding of OTA with its specific aptamer without any signal amplification strategy. A gold electrode (AuE) was modified with a compact layer of double-stranded DNA (dsDNA), obtained via OTA aptamer and complementary DNA (cDNA) hybridization, to act as a barrier for redox probe [Fe(CN) 6 ] 3-/4- to AuE access. This led to a high initial electron-transfer resistance (R ct ), recorded via electrochemical impedance spectroscopy (EIS). Since the aptamer displayed a higher affinity to OTA than cDNA, the added OTA triggered aptamer dissociation from AuE to form the OTA-aptamer complex, obviously decreasing the R ct . The target-induced variation in the resistance response strongly depended on the OTA concentration. Optimum conditions improved the linear relationship between R ct and the logarithm of OTA concentration in a range of 0.05–10 ng/mL with a limit of detection (LOD) of 0.05 ng/mL for OTA. Recoveries of 74.8–105% with relative standard deviations (RSDs) of 8.86–13.09% were obtained in the spiked malt samples. The Real-world detection of OTA in the actual malt samples confirmed the reliability of the convenient, cost-effective, and highly specific impedimetric aptasensor, exhibiting significant promise for extended application in food control to identify more hazardous contaminants by altering the corresponding aptamers. • A label-free electrochemical impedimetric aptasensor for OTA detection was developed. • No extra coupling medium was involved for immobilizing the aptamers. • The aptasensor achieved high sensitivity for OTA without signal amplification. • The impedimetric aptasensor succeeded in real malt samples with satisfactory recoveries. • The aptasensor can be extended to more contaminants in foods via replacing the corresponding aptamers.

Tetrahedral DNA nanostructure-enabled electrochemical aptasensor for ultrasensitive detection of fumonisin B1 with extended dynamic range

Fumonisin B1 (FB1) is common contaminant in agricultural and food products, and sensors with high sensitivity and broad dynamic range are extremely required for FB1 determination. Herein, we reported the tetrahedral DNA nanostructure (TDN)-enabled electrochemical aptasensor for FB1 detection at sub-fg mL−1 level with a dynamic range of 7-folds magnitude. TDN with side length of 5.67 nm was designed to fabricate the substrate for FB1 aptamer anchoring, aiming to achieve the controllable and stable assembly of sensing interface by tuning the assembly density of TDN; TDN at the electrode acts as the anchor for aptamer, absorption of methylene blue as signal generator. Assistant aptamer was added into the sample solution to deplete FB1, reducing the amount of free FB1, thereby extending dynamic range of sensing system. Simultaneously, the negatively-charged TDN can efficiently depress absorption of free aptamer in sample solution. In this way, the utilization of TDN helps to enable the sensor with higher sensitivity and extended dynamic range for FB1. Consequently, the developed sensor allowed a linear dynamic range of 0.500 fg mL−1~1.00 ng mL−1, while the limit of detection was offered to be 0.306 fg mL−1, which was the lowest among the available methods. The applicability of aptasensor was validated by rice sample analysis, which exhibited the comparable reliability of liquid-chromatography tandem mass spectrometry/mass spectrometry. Our work has provided an efficient sensing platform for FB1, and the strategy can be also extended to fabricate sensors for other mycotoxins.

A new electrochemical aptasensor for ultrasensitive detection of endotoxin using Fe-MOF and AgNPs decorated P-N-CNTs as signal enhanced indicator

Sensitive detection of endotoxin is especially critical in the fields of food security, therapeutics and medical science. In this work, a new sandwich-type electrochemical aptasensor was designed for ultrasensitive detection of endotoxin. For the first time, nitrogen-doped carbon nanotubes (N-CNTs) was functionalized with polydiallyldimethylammonium chloride (PDDA), forming P-N-CNTs nanocomposite. Then, Fe-based metal–organic framework (Fe-MOF) and silver nanoparticles (AgNPs) was decorated with P-N-CNTs to form the MOF/Ag-P-N-CNTs nanohybrid, which was employed as an enhanced signal indicator, not only exhibited outstanding electrochemical activity, but also could directly label with thiol-modified signal probes (TSPs) to form tracer label. Additionally, the avidin–biotin recognition system was introduced to increase the amount of biotin-modified capture probes (BCPs). Differential pulse voltammetry (DPV) was utilized to investigate the detection performances of the proposed aptasensor, which suggested a wide linear range from 1 fg/mL to 100 ng/mL with a low detection limit of 0.55 fg/mL toward endotoxin.

Electrochemical aptasensor for ultrasensitive detection of lipopolysaccharide using silver nanoparticles decorated titanium dioxide nanotube/functionalized reduced graphene oxide as a new redox nanoprobe.

Anovel and relatively simple signal-off electrochemical aptasensor was constructed for highly sensitive detection of lipopolysaccharide (LPS). For the first time, silver nanoparticles (AgNPs) decorated titanium dioxide nanotube (TNT) was conjugated with polydiallyldimethylammonium chloride (PDDA) functionalized reduced graphene oxide (rGO) to form a new nanohybrid of Ag-TNT/P-rGO. This nanohybrid with a large specific surface area exhibited excellent electrochemical activity, which not only served as the sensing platform to immobilize LPS binding aptamer (LBA) but wasalso employed as the redox probe to monitor the change of the electrochemical signal. The electrochemical signal responses were measured by cyclic voltammetry (CV) in the potential range-0.3 to 0.5V at a scan rate of 0.1V/s. The proposed aptasensor exhibited acceptable stability, reproducibility, and specificity for LPS detection with a wide linear range from 17fg/mL to 100ng/mL. Thelimit of detection (LOD) was 5fg/mL. Furthermore, the prepared aptasensor showed acceptable recovery ranging from 96% to 103%, and the RSD varied between 1.4% and 8.5% for determining LPS in real samples.Graphical abstract.

A DNAzyme-assisted triple-amplified electrochemical aptasensor for ultra-sensitive detection of T-2 toxin

Herein, an electrochemical aptasensor was constructed for ultra-sensitive determination of T-2 toxin based on Silver ion (Ag+) -dependent DNAzyme-assisted signal amplification and Gold nanoparticles/Graphene oxide @ manganese dioxide (AuNPs/MnO2@GO) nanocomposites. In the presence of Ag+, the secondary structure of the T-2 aptamer is altered via the Ag+ mediated coordination of C–Ag+–C base pairs. When T-2 toxin is added, the secondary structure of DNA is changed again, and the trapped Ag+ are released. Then, the DNAzyme could repeatedly bind and cleave methylene blue (MB)-modified substrate DNA (S-DNA) in the assistance of Ag+, which leads to a decrease in the electrochemical signal. With the optimal conditions, there is a good linear relationship between the current value and the logarithm of T-2 toxin concentration in the range from 2 fg mL−1 to 20 ng mL−1, and a detection limit of 0.107 fg mL−1 is obtained. Moreover, the proposed method was successfully applied to measure T-2 toxin in beer, thus showing great potential of this system for food safety and quality control.

Ratiometric electrochemical aptasensor for ultrasensitive detection of Ochratoxin A based on a dual signal amplification strategy: Engineering the binding of methylene blue to DNA

A novel ratiometric electrochemical aptasensor was developed for Ochratoxin A (OTA) detection based on the binding of methylene blue (MB) to DNA with a dual signal amplification strategy. The formation of dsDNA structures between ferrocene-labeled complementary DNA (Fc-cDNA), the OTA aptamer, and complementary helper DNA (hDNA) caused Fc away from the electrode, and allowed dsDNA to bind with a certain amount of MB. Here, a small oxidation current of Fc (IFc) and a large oxidation current of MB (IMB) were obtained. In the presence of OTA, its specific recognition with the aptamer induced the release of aptamer and hDNA from the electrode and subsequently the formation of hairpin structure for cDNA, which caused Fc close to the electrode and a weaker binding ability with MB. Then, an increased IFc and a decreased IMB were obtained. Based on this principle, OTA could be accurately quantified by measuring the ratiometric signal of IFc/IMB. Herein, the dual signal amplification strategy of the introduction of hDNA and the binding with MB after the OTA recognition was exploited to amplify the response signal. The obtained aptasensor showed a linear detection range from 10 pg mL−1 to 10 ng mL−1 and a detection limit of 3.3 pg mL−1. The aptasensor was successfully applied to determine OTA in wheat, and the results were validated through HPLC-MS. Furthermore, by changing the target aptamers, this strategy could be universally used for the determination of various mycotoxins, showing promising potential applications for mycotoxins monitoring in agricultural products and foods.

Fabrication of pioneering 3D sakura-shaped metal-organic coordination polymers Cu@L-Glu phenomenal for signal amplification in highly sensitive detection of zearalenone

Low molecular weight pollutants from foods have aroused global attention due to their toxicity after long-time exposure. There is an increased demand for appropriate methods to detect these pollutants in foods. In this study, a brand-new type of nano metal–organic coordination polymers (MOCPs) nanocarriers (3D sakura-shaped copper (II) ions@L-glutamic acid (L-Glu)) has been first synthesized. We herein demonstrate a facile chelated method that allows the combination of copper (II) ions and L-Glu. A series of controlled experiments have revealed that the reaction time and the ratio of reactants played the crucial roles in affecting the morphology of the final product. 3D sakura-shaped Cu@L-Glu combined with palladium-platinum nanoparticle (Pd-PtNPs) to obtain Cu@L-Glu/Pd-PtNPs acting as the signal tag, which applied in electrochemical aptasensor for ultrasensitive detection of zearalenone (ZEN). A glassy carbon electrode was first modified with spherical Au-PANI-Au nanohybrids to enhance the conductivity and immobilize more amino modified ZEN aptamer. Cu@L-Glu/Pd-PtNPs were labeled with Complementary DNA (partial matching with ZEN aptamer) to form bioconjugates for signal amplification. After the hybridization reaction of ZEN aptamer and the bioconjugates, a significant electrochemical signal from the catalysis of H2O2 by Cu@L-Glu/Pd-PtNPs can be observed. ZEN competed with bioconjugates for binding to ZEN aptamer, resulting in decreased the electrochemical signal. Chronoamperometry was applied to record the final electrochemical signals. Under optimal conditions, the electrochemical aptasensor exhibited desirable sensitive detection of ZEN with a wide linearity ranging from 1 fg/mL to 100 ng/mL and a relatively low detection limit of 0.45 fg/mL (S/N = 3). Furthermore, the proposed electrochemical aptasensor shows excellent selectivity to the ZEN in the presence of possible interfering substances, and has potential application for ZEN detection in food samples.

Copper ion-assisted gold nanoparticle aggregates for electrochemical signal amplification of lipopolysaccharide sensing

A signal amplification electrochemical aptasensor for ultrasensitive detection of lipopolysaccharide (LPS) was fabricated. The sensor was constructed with a probe of LPS aptamer and a copper ions-mediated gold nanoparticles aggregate (Cu/Au NA) as a signal amplification material. The Cu/Au NAs comprising copper ions (Cu2+) and L-cysteine modified AuNPs were fabricated by a self-assembly process. For functionalization of the electrode, the carboxylic group of a mercaptoacetic acid self-assembly layer was covalently coupled with the amine group of the aptamer. The aptamer with high specificity and affinity can effectively gather the dissociative LPS firstly, and the Cu/Au NAs were captured by anionic groups of the carbohydrate portions from LPS molecules based on the specific interactions. With the employment of the sandwich-type biosensor, the strategy can significantly amplify the electrochemical signal for determination of trace amount of LPS. The sensing performance of the electrochemical sensor was investigated by differential pulse voltammetry (DPV) and the stripping peak currents of Cu re-oxidized to Cu2+ was used to monitor the level of LPS. The electrochemical aptasensor exhibited excellent sensitivity toward LPS with a detection limit of 0.033 pg/mL (S/N = 3). The biosensor also exhibited a high specificity toward LPS in the presence of other common interfering substances and was easily regenerated. Furthermore, the fabricated biosensor showed a good practical application for LPS determination in human serum samples.

Graphene and AuNPs based electrochemical aptasensor for ultrasensitive detection of hydroxylated polychlorinated biphenyl

An electrochemical aptasensor for ultrasensitive detection of hydroxylated polychlorinated biphenyl (OH-PCB) was developed. In this work, the sulfydryl aptamer selected for OH-PCB was easily immobilized on the surface of the modified glassy carbon electrode via Au-S bond due to incorporation of gold nanoparticles/poly dimethyl diallyl ammonium chloride-graphene composite. The fabrication process of the electrochemical aptasensor was characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The peak currents obtained by differential pulse voltammetry decreased with the increasing of OH-PCB concentrations. The current responded approximately logarithmically to the OH-PCB concentration ranging from 2.9 × 10−11 M to 2.9 × 10−7 M with excellent linear correlation performance. The detection limit of OH-PCB was estimated as low as 5.3 × 10−12 M. The developed method had been successfully applied to analyzing lake water. Particularly, the method of the electrochemical aptasensor opens up a new perspective in environmental monitoring by the aptamer identification.

Fullerene-doped polyaniline as new redox nanoprobe and catalyst in electrochemical aptasensor for ultrasensitive detection of Mycobacterium tuberculosis MPT64 antigen in human serum.

Tuberculosis caused by Mycobacterium tuberculosis (MTB) is still a major threat to global public health. However, the existing methods for MTB detection are usually complicated and time consuming with unsatisfactory sensitivity and specificity. In this work, a relatively simple and ultrasensitive electrochemical aptasensor based on novel signal generation and amplification was constructed for the determination of MTB antigen MPT64. The coil-like fullerene (C60)-doped polyaniline (C60-PAn) nanohybrids with large surface area, abundant active groups and excellent electric performance were synthesized and used both as new redox nanoprobe and catalyst for the generation and amplification of electrochemical signal for the first time. Then gold nanoparticles decorated C60-PAn nanocomposites (GNPs-C60-PAn) were labeled with signal aptamer to form the tracer label. After the sandwich reaction of target MPT64 antigen between capture aptamer and the tracer label, a distinguishing detection signal of C60-PAn would be observed. Moreover, the detection signal could be enormously enhanced towards the efficient electrocatalytic oxidation of ascorbic acid based on C60-PAn, resulting in further improvement of the sensitivity. With the excellent redox and electrocatalytic activity of C60-PAn, a wide detection linear range from 0.02 to 1000pg/mL was obtained with a detection limit of 20fg/mL for MPT64. The proposed aptasensor showed high selectivity to target antigen compared with possible interfering substances. More importantly, it also exhibited excellent specificity and sensitivity for MPT64 detection in serum samples of tuberculosis patients, which provided a rapid and efficient detection method for MTB infection.

A new amplified π-shape electrochemical aptasensor for ultrasensitive detection of aflatoxin B1

There is a prompt need for determination of aflatoxin B1 (AFB1) in food products to avoid distribution and consumption of contaminated food products. In this study, an accurate electrochemical sensing strategy was presented for detection of AFB1 based on aptamer (Apt)-complementary strands of aptamer (CSs) complex which forms a π-shape structure on the surface of electrode and exonuclease I (Exo I). The presence of π-shape structure as a double-layer physical barrier allowed detection of AFB1 with high sensitivity. In the absence of AFB1, the π-shape structure remained intact, so only a weak peak current was recorded. Upon the addition of AFB1, the π-shape structure was disassembled and a strong current was recorded following the addition of Exo I. Under optimal conditions, the electrochemical signals enhanced as AFB1 concentrations increased with a dynamic range of 7–500pg/mL and a limit of detection (LOD) of 2pg/mL. The developed aptasensor was also used to analyze AFB1 spiked human serum and grape juice samples and the recoveries were 95.4–108.1%.

A novel electrochemical aptasensor for ultrasensitive detection of fluoroquinolones based on single-stranded DNA-binding protein

Determination of fluoroquinolones (FQs) in foodstuffs and environment is of great importance. In this study, a novel electrochemical sensing method was developed for rapid, highly sensitive and specific detection of FQs, based on aptamer (Apt) as molecular recognition probe, single-stranded DNA-binding protein (SSB) as a physical and negatively charged barrier for the access of redox probe ([Fe(CN)6]3−/4−) to the surface of gold electrode. The designed electrochemical aptasensor needs less than 1h for detection of ciprofloxacin. In the absence of ciprofloxacin, SSB interacts with Apt and restricts the access of redox probe to the surface of electrode, leading to a weak current signal. In the presence of target, SSB could not bind to the Apt, resulting in more access of redox probe to the surface of electrode and a strong current signal. The designed electrochemical sensor exhibited high specificity toward FQs with a limit of detection (LOD) as low as 263 pM for ciprofloxacin. Moreover, the developed sensing method was successfully applied for determination of ciprofloxacin in serum, milk and water samples with LODs of 336, 351 and 261 pM, respectively.

A novel M-shape electrochemical aptasensor for ultrasensitive detection of tetracyclines

Analytical techniques for detection and quantitation of tetracyclines in food products are greatly in demand. In this study, a novel electrochemical aptasensor was designed for ultrasensitive and selective detection of tetracyclines, based on M-shape structure of aptamer (Apt)-complementary strands of aptamer (CSs) complex, exonuclease I (Exo I) and gold electrode. The aptasensor was developed to make a noticeable electrochemical difference in the absence and presence of tetracycline. In the absence of tetracycline, the M-shape structure, which acts as a gate and barrier for the access of redox probe to the surface of gold electrode remains intact, leading to a weak electrochemical signal. Upon addition of tetracycline, Apt leaves CSs, resulting in disassembly of M-shape structure and following the addition of Exo I, a strong electrochemical signal was observed. The developed analytical assay indicated high selectivity toward tetracycline with a limit of detection (LOD) as low as 450 pM. Moreover, the designed aptasensor was effectively used for the detection of tetracycline in milk and serum samples with LODs of 740 and 710 pM, respectively.