In electrochemical immunoassays, great breakthroughs have been made in ultrasensitive detection of tumor markers by amplifying signals with coreaction accelerators. Herein, carbon nitrides with nitrogen vacancies (CNNVs) are proposed as emitter, due to the introduction of nitrogen vacancies this emitter has better ECL efficiency, the phenomena of interface electron transfer and electrode passivation are improved. At the same time, it can also promote the electrochemical reduction of coreactant, making it an attractive and potential emitter. The electrode was modified with Ag-Ti 3 C 2 MXene. It not only accelerates electron transfer and increases the effective working area of the electrode, but also acts as a coreaction accelerator to promote the electrochemical reduction of the coreactant K 2 S 2 O 8 , resulting in a strong ECL signal. The immunosensor showed a good linear relationship in the range of 10 −5 -100 ng/mL with a detection limit of 0.36 fg/mL. In addition, the excellent properties of good specificity and ultra-high stability provide an effective method for ultra-sensitive immunoassays.
Chao Liu,Jing Dong,Geoffrey I.N. Waterhouse,Ziqiang Cheng,Shiyun Ai
A sensitive sandwich-type electrochemical immunosensor was developed for the detection of avian leukosis virus subgroup J (ALV-J), which benefitted from multiple signal amplification involving graphene-perylene-3,4,9,10-tetracarboxylic acid nanocomposites (GR-PTCA), nanocellulose-Au NP composites (NC-Au) and the alkaline phosphatase (ALP) catalytic reaction . GR-PTCA nanocomposites on glassy carbon electrodes served as the immunosensor platform. Due to their excellent electrical conductivity and abundant polycarboxylic sites, the GR-PTCA nanocomposites allowed fast electron transfer and good immobilization of primary antibodies, thereby affording a strong immunosensor signal in the presence of ALV-J. The detected signal could be further amplified by the introduction of NC-Au composites as a carrier of secondary antibodies (Ab 2 ) and by harnessing the catalytic properties of Au and ALP. Under optimized testing conditions, the electrochemical immunosensor displayed excellent analytical performance for the detection of ALV-J, showing a linear current response from 10 2.08 to 10 4.0 TCID 50 /mL (TCID 50 : 50% tissue culture infective dose) with a low detection limit of 10 1.98 TCID 50 /mL (S/N = 3). In addition to high sensitivity, the immunosensor showed very good selectivity, reproducibility and operational stability, demonstrating potential application for the quantitative detection of ALV-J in clinical diagnosis.
A new strategy for signal amplification was introduced in a label-free amperometric immunoassay platform. Improvements in the signal occurred following the oxidation of glucose by glucose oxidase and catalysis by polythionine of the produced H 2 O 2 from the previous oxidation reaction. In addition, a multifunctional conductive hydrogel, polypyrrole-polythionine-gold with glucose oxidase , was synthesised with a one-pot method using pyrrole and thionine as monomers, ammonium persulfate and HAuCl 4 as co-oxidant agents, and glucose oxidase as the doping agent. Combined with the hydrogel, a label-free amperometric immunoassay for the tumour marker neuron-specific enolase (NSE) was obtained. If operated at 0 V (vs. Ag/AgCl), the sensor exhibited a wide liner range from 100 ng mL −1 to 1 pg mL −1 and ultralow detection limit of 0.65 pg mL −1 (S/N = 3). The presented method was further used for the analysis of human serum samples and showed good consistency with detection results from an electrochemiluminescence immunoassay.
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