A novel ternary composite of hemin-graphene-Au nanorods (H-RGO-Au NRs) with high electrocatalytic activity was synthesized by a simple method. And this ternary composite was firstly used in construction of electrochemiluminescence (ECL) immunosensor due to its double-quenching effect of quantum dots (QDs). Based on the high electrocatalytic activity of ternary complexes for the reduction of H 2 O 2 which acted as the coreactant of QDs-based ECL, as a result, the ECL intensity of QDs decreased. Besides, due to the ECL resonance energy transfer (ECL-RET) strategy between the large amount of Au nanorods (Au NRs) on the ternary composite surface and the CdS:Eu QDs, the ECL intensity of QDs was further quenched. Based on the double-quenching effect, a novel ultrasensitive ECL immunoassay method for detection of carcinoembryonic antigen (CEA) which is used as a model biomarker analyte was proposed. The designed immunoassay method showed a linear range from 0.01 pg mL −1 to 1.0 ng mL −1 with a detection limit of 0.01 pg mL −1 . The method showing low detection limit, good stability and acceptable fabrication reproducibility, provided a new approach for ECL immunoassay sensing and significant prospect for practical application.
Jiu-Jun Yang,Jun-Tao Cao,Yu-Ling Wang,Hui Wang,Yan-Ming Liu,Shu-Hui Ma
A new and simple sandwich-like electrochemiluminescence (ECL) aptasensor for carcinoembryonic antigen (CEA) assay was fabricated based on the dual quenching effect from hemin-graphene (H-rGO) nanosheet and enzymatic biocatalytic precipitation (BCP) on the Au-CdS nanocomposites-based ECL system. In this aptasensor platform, flower-like spherical Au-CdS nanocomposites were used as ECL luminophores and exhibit a strong ECL signal. The rGO nanosheet was used as a supporter to immobilize hemin molecules via π-π stacking interactions. Due to the steric hindrance and quenching effect of rGO, the ECL intensity decreased by the construction of the sandwich “CEA aptamer I (NH 2 -DNA)-CEA-aptamer II” (H-rGO-aptamer II) mode. In the process of BCP, the ECL intensity further decreased because the hemin with intrinsic peroxidase-like catalytic activity could oxidize the 4-chloro-1-naphthol (4-CN) to produce an insoluble precipitation on the sensor. Using this dual quenching strategy, the prepared aptasensor exhibits a linear range from 0.8 pg/mL to 4 ng/mL and a detection limit of 0.28 pg/mL. This ECL aptasensor has simple design and undemanding in operation and was utilized to determine the content of CEA in complex samples with recoveries of 95.0% to 115.8%. Moreover, no any chemical modification of aptamer was required, suggesting that the proposed ECL aptasensor could be applied for the detection of diverse proteins just by altering the aptamer sequence.
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