Ultrasensitive photoelectrochemical immunoassay for CA19-9 detection based on CdSe@ZnS quantum dots sensitized TiO2NWs/Au hybrid structure amplified by quenching effect of Ab2@V2+ conjugates
2016
Zhu, Hua | Fan, Gao-Chao | Abdel-Halim, E.S. | Zhang, Jian-Rong | Zhu, Jun-Jie
A novel, enhanced photoelectrochemical immunoassay was established for sensitive and specific detection of carbohydrate antigen 19-9 (CA19-9, Ag). In this protocol, TiO2 nanowires (TiO2NWs) were first decorated with Au nanoparticles to form TiO2NWs/Au hybrid structure, and then coated with CdSe@ZnS quantum dots (QDs) via the layer-by-layer method, producing TiO2NWs/Au/CdSe@ZnS sensitized structure, which was employed as the photoelectrochemical matrix to immobilize capture CA19-9 antibodies (Ab1); whereas, bipyridinium (V²⁺) molecules were labeled on signal CA19-9 antibodies (Ab2) to form Ab2@V²⁺ conjugates, which were used as signal amplification elements. The TiO2NWs/Au/CdSe@ZnS sensitized structure could adequately absorb light energy and dramatically depress electron–hole recombination, resulting in evidently enhanced photocurrent intensity of the immunosensing electrode. While target Ag were detected, the Ab2@V²⁺ conjugates could significantly decrease the photocurrent detection signal because of strong electron-withdrawing property of V²⁺ coupled with evident steric hindrance of Ab2. Thanks to synergy effect of TiO2NWs/Au/CdSe@ZnS sensitized structure and quenching effect of Ab2@V²⁺ conjugates, the well-established photoelectrochemical immunoassay exhibited a low detection limit of 0.0039U/mL with a wide linear range from 0.01U/mL to 200U/mL for target Ag detection. This proposed photoelectrochemical protocol also showed good reproducibility, specificity and stability, and might be applied to detect other important biomarkers.
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