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BACKGROUND Malaria is a disease that affects many tropical and subtropical countries, including Brazil. The use of tests for malaria detection is one of the fundamental strategies recommended by the World Health Organization for the control and eradication of the disease. The lack of diagnostic tests leads to an increase in transmission and non-reporting cases. OBJECTIVES This work described an electrochemical immunosensor for detecting Plasmodium vivax lactate dehydrogenase antigen (Ag-PvLDH). METHODS The device has developed by immobilising egg yolk IgY antibodies (Ab-PvLDH) on a gold electrode surface using cysteamine as linker. The immunosensor fabrication was followed by differential pulse voltammetry, and contact angle measurements were performed to characterise the modified gold electrode surface. FINDINGS The results for Ag-PvLDH determination exhibit a linear response at 10-50 µg mL-1 concentration range, with a limit of detection of 455 ng mL-1. The excellent selectivity of the device was confirmed. MAIN CONCLUSIONS The developed immunosensor showed a good performance, therefore, it can be considered an alternative test to detect malaria caused by P. vivax.
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A competitive electrochemical immunosensor based on the nano-composite material immobilization and enzymatic amplification was designed for detection of microcystin-LR. Gold nanoparticles/carboxylated multi-walled carbon nanotubes (AuNPs/c-MWCNTs) composite film, which formed by electrodepositing of AuNPs on the C-MWCNTs modified glassy carbon electrode,was used for the immobilization of the antibody of microcystin-LR (anti-MCLR). Horseradish peroxidase (HRP) was introduced onto the nanocomposite interface by HRP blocked sensing interface and specific capture of antibody with target. It could be employed to catalyze the reduction of H2O2, and to block the possible remaining active sites as well. A competitive immunoreaction between antigen and MCLR-HRP was used for target analysis. In the presence of H2O2and hydroquinone (HQ),MCLR could be indirectly detected with differential pulse voltammetry (DPV) method by determining the reduction current of HQ. Under the optimal conditions, the proposed immunosensor exhibited wide linear ranges in the concentration ranges of 0.1-100.0 μg/L, with a detection limit of 0.038 μg/L (S/N = 3,n=8). The immunosensor showed good specificity, stability and sensitivity. It was used to determine MCLR in real water samples with the recoveries of 72.9%-117.3%.
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Objective Todesign a novel impedimetric immunosensor basedon AgI mimic enzyme nanomaterial for detecting carcinoembryonic antigen (CEA) in serum with high sensitivity. Methods A novil chitosan modified AgI (CS-AgI) nanomaterial was synthesized and was characterized by transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FTIR). Then by utilizing CS-AgI labeled CEA antibody as tags, we prepared a novel impedimetric immunosensor on the gold electrode using the sandwich-type immunoassay. The electrochemical propertiesof the prepared impedimetric immunosensor were observed by electrochemical workstation and the concentration of CEA in sample was quantitatively analyzed. Results The synthesized CS-AgI nanoparticles were spherical in shape, with the particle size being 100 nm; the particles were employed to construct immunosensor as signal markers. The immunosensor had an excellent electrochemical performance in detection of CEA under PBS base solution of pH = 7, and its AC impedance response increased with the increase of the logarithm of CEA concentration, exhibiting a good linear relationship in the range of 0. 1ng/mL to 80ng/mL (r = 0.996), with a detection limkof 0. 05 ng/mL. Conclusion Based on AgI mimic enzyme nanomaterial, the impedance immunosensor prepared in this study shows a high sensitivity in detecting CEA; meanwhile, t has acceptable selectivity, repeatability and stability, providing an experimental evidence for early diagnosis and treatment of cancer.
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@#An ultrasensitive electrochemical immunosensor modified with graphene and dienestrol(DE)was developed for the detection of dienestrol through indirect competition with K3Fe(CN)6 acting as the redox probes. The results revealed that under optimized conditions a calibration for DE was obtained with a linear range of 500-5 000 ng/mL and the detection limit was up to 0. 2 ng/mL, showing that the proposed electrochemical immunosensor had excellent sensitivity and wide detection range. The immunosensor was examined in real samples for the analysis of DE. A good recovery in the range of 83. 8%-97. 7% was obtained in pork samples.
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Objective To develop a new type of electrochemical immunosensor for the detection of ochratoxin A (OTA ) . Methods Double layers of self‐assembly immunosensor for the detection of OTA were constructed based on the composite single‐walled carbon nanotubes(SWNTs)/chitosan(CS) membrane immobilized on glassy carbon electrode(GC) .Scanning electron mi‐croscopy(SEM) ,square wave voltammetry and cyclic voltammetry were used to analyze the characterization of the sensor ,then its specificity for detection was studied .Results SWNTs/CS composit membrane could increase the sensitivity of OTA detection sig‐nificantly ,and effectively distinguish the different types of mycotoxins .Conclusion The electrochemical immunosensor developed in the study is easy to operate and could detect OTA rapidly with good specificity and low detection limit .
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Objective To construct an electrochemical immunosensor for ultrasensitive determination of myeloperoxidase (MPO) .Methods The electrochemical immunosensor for M PO was prepared by modifying the electrode using Au-graphitized me-soporous carbon nanoparticles(AuNPs@ GMCs) hybrid and immobilizing MPO antibodies onto the glass carbon electrode surface . The effect of experimental parameters on the immunosensor and results comparison with ELISA were investigated .Results The immunosensor was sensitive to M PO with a linear relationship between 2 .000 and 300 .000 ng/mL and a correlation coefficient of 0 .999 ;the detection limit was 0 .5 ng/mL .The correlation coefficient of two methods was 0 .983 .Conclusion The immunosensor can be used for ultrasensitive detection of MPO .
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Objective To expand the application of electrochemical immunosensor during deleting aflatoxin B1 in foods and feeds through analyzing impacts of the time of antibody incubation and sample preparation .Methods T he double self-assembly immu-nosensor combined with aflatoxin B1 and carboxylated single-walled carbon nanotubes (SWNTs) was characterized by cyclic volta-mmetry and impacts of the time of antibody incubation and sample preparation methods were investigated .Results The signal in-creased gradually following the increasing time of antibody incubation and reached a plateau at 90 min and sample preparation meth-ods showed a comparatively large impact on results .Additionally ,the crude extractions purified through removing interfering com-pounds by immunoaffinity column could effectively eliminate the interference effects of sample matrix .Conclusion Deleting aflatox-in B1 by electrochemical immunosensor is characterized by various features ,such as fast ,simple and low detection limits .The pres-ent study shows that stability of the electrochemical immunosensor is affected by the time of antibody incubation and sample prepa-ration .
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Carbon nanotubes/Au nanoparticles ( CNT/AuNP ) composite film was fabricated on glassy carbon electrode ( GCE) by first dropping CNTs on the electrode surface and then electrodeposition of AuNPs by multi-potential step. The antibody of microcystin-( leucine-arginine ) ( anti-MCLR ) was immobilized on the modified electrode surface through adsorption on AuNPs. Subsequently, bovine serum albumin ( BSA) was used to block the non-specific adsorption to obtain the immunosensor for MCLR assay. The immunosensor could effectively capture MCLR by the specific immunoreaction between the electrode surface-confined antibody and MCLR, followed by the attachment of the anti-MCLR HRP-labeled to form a sandwich-type system. The analysis of MCLR was performed based on the catalytic reaction of HRP toward the oxidation of hydroquinone ( QH2 ) by H2 O2 . Under the optimal experimental conditions, the peak current response increased linearly with the concentration of MCLR in the range of 0 . 50-12 μg/L with a detection limit of 0. 30 μg/L (S/N=3). The developed immunosensor was used to determine MCLR in real water samples, and the recoveries of standard addition experiments were in the range of 93 . 0%-108 . 5%, with the relative standard deviation of 3 . 8%-5 . 0%.