Abstract
A label-free impedimetric immunosensor based on N, S-graphene quantum dots@Au-polyaniline (N, S-GQDs@Au-PANI) nanowires was fabricated for the quantitative detection of carcinoembryonic antigen (CEA). The N, S-GQDs and Au-PANI were synthesized by a simple hydrothermal pyrolysis and interfacial polymerization, respectively. Subsequently, 2–9 nm N, S-GQDs are successfully decorated onto 30–50 nm Au-PANI nanowires by Au-thiol linkage to serve as the bifunctional probe for amplifying the electrochemical activity as well as anchoring anti-CEA. The N, S-GQDs@Au-PANI nanowires are excellent conducting materials to accelerate the electron transfer, while the formation of CEA antibody-antigen bioconjugates after the addition of CEA significantly increase the charge transfer resistance, and subsequently provides a highly stable and label-free immunoassay platform for the impedimetric detection of CEA. The label-free immunosensor exhibits a wide linear range from 0.5 to 1000 ng mL−1 with a low detection limit of 0.01 ng mL−1. The N, S-GQDs@Au-PANI based immunosensor also shows high selectivity and stability over other cancer makers and amino acids. Moreover, this promising platform is successfully applied to the detection of CEA in human serum samples with excellent recovery of (96.0 ± 2.6)–(103 ± 3.8)%. These results clearly demonstrate a newly developed highly efficient and label-free impedimetric immunosensor for the detection of CEA using N, S-GQDs@Au-PANI nanowires as the biosensing probe, which can pave the gateway for the fabrication of high performance and robust impedimetric immunosensor to detect cancer makers in early stage of cancer diagnosis and therapy.
Highlights
Become a promising material for ultrasensitive detection of chemicals and biomolecules[13,14] have combined graphene and magnetic beads with enzyme-labelled antibody-AuNP bioconjugate for the electrochemical detection of carcinoembryonic antigen (CEA)
The regularly shaped Au-PANI nanowires are prepared by the interfacial polymerization method where aniline molecules in toluene are exposed to HAuCl4 in aqueous solution at the organic-aqueous interface to undergo the controlled polymerization
A novel and ultrasensitive label-free impedimetric immunosensor has been successfully developed for the detection of CEA using N, S-graphene quantum dots (GQDs)@Au-PANI as the biosensing platform
Summary
Become a promising material for ultrasensitive detection of chemicals and biomolecules[13,14] have combined graphene and magnetic beads with enzyme-labelled antibody-AuNP bioconjugate for the electrochemical detection of CEA. Nanostructured polyaniline (PANI) is a low-dimensional organic conductor with high surface area, which can exist in various protonated degrees ranging from the most reduced leucoemeraldine form to the half-oxidized emeraldine base form, and to the fully oxidized pernigraniline form[15,16] This property makes PANI a unique and interesting polymeric material. It gives a great advantage that the presence of uniformly distributed AuNP on the PANI surface can exhibit high electron transfer capability and increase the amount of immobilized antibodies, significantly amplifying the signal source to enhance the sensitivity of the constructed electrochemical immunosensors. The developed novel N, S-GQDs@Au-PANI nanocomposites show high sensitivity and good stability for quantitative determination of CEA in a linear range of 0.5–1000 ng mL−1 with limit of detection (LOD) of 0.01 ng mL−1, which exhibits a great potential in clinical and cancer diagnostic applications. The superior sensitivity of the developed impedimetric immunosensor is mainly attributed to the remarkable electro-conductivity of N, S-GQDs@Au-PANI, which can accelerate the electron transfer process between N, S-GQDs and electrode
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