title: Ultrasensitive photoelectrochemical immunoassay for CA19-9 detection based on CdSe@ZnS quantum dots sensitized TiO2NWs/Au hybrid structure amplified by quenching effect of Ab2@V(2+) conjugates.
abstract: 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 (V(2+)) molecules were labeled on signal CA19-9 antibodies (Ab2) to form Ab2@V(2+) 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@V(2+) conjugates could significantly decrease the photocurrent detection signal because of strong electron-withdrawing property of V(2+) coupled with evident steric hindrance of Ab2. Thanks to synergy effect of TiO2NWs/Au/CdSe@ZnS sensitized structure and quenching effect of Ab2@V(2+) conjugates, the well-established photoelectrochemical immunoassay exhibited a low detection limit of 0.0039 U/mL with a wide linear range from 0.01 U/mL to 200 U/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.
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, Collaborative Innovation Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, Collaborative Innovation Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China.
authors.forename: Gao-Chao
authors.initials: GC
authors.lastname: Fan
authors.affiliation: Chemistry Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: E S
authors.initials: ES
authors.lastname: Abdel-Halim
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, Collaborative Innovation Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China; School of Chemistry and Life Science, Nanjing University Jinling College, Nanjing 210089, PR China. Electronic address: jrzhang@nju.edu.cn.
authors.forename: Jian-Rong
authors.initials: JR
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, Collaborative Innovation Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China. Electronic address: jjzhu@nju.edu.cn.
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Zhu
mesh_terms: D015295:Antigens, Tumor-Associated, Carbohydrate / Q000032:analysis* / Q000276:immunology; D019187:Cadmium Compounds / Q000737:chemistry; D003217:Conductometry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry; D007118:Immunoassay / Q000295:instrumentation*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D058726:Nanoconjugates / Q000737:chemistry / Q000648:ultrastructure; D053770:Nanowires / Q000737:chemistry* / Q000648:ultrastructure; D010777:Photochemistry / Q000295:instrumentation; D045663:Quantum Dots; D015203:Reproducibility of Results; D018036:Selenium Compounds / Q000737:chemistry; D012680:Sensitivity and Specificity; D014025:Titanium / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D015295:Antigens, Tumor-Associated, Carbohydrate; D019187:Cadmium Compounds; D058726:Nanoconjugates; D018036:Selenium Compounds; D017967:Zinc Compounds; C578959:carbohydrate antigen 199, human; C009495:titanium dioxide; D006046:Gold; C058667:cadmium selenide; D014025:Titanium; C044696:zinc selenide
keywords: CA 19-9; Immunoassay; Photoelectrochemistry; Quenching effect; Synergy effect