title: PolyA-tailed and fluorophore-labeled aptamer-gold nanoparticle conjugate for fluorescence turn-on bioassay using iodide-induced ligand displacement.
abstract: Depending on the strong affinity of polyA sequence to gold (or silver) surface, applicability of polyA-tailed DNA-gold (or silver) nanoparticle conjugates in homogeneous and heterogeneous protein assays was first demonstrated. Interestingly, when using polyA-tailed, fluophore-labeled DNA-AuNP conjugate, it was found that iodide and thiosulfate anions could act as the ligand displacing reagent to detach polyA-tailed DNA strands from AuNP surface and simultaneously activate the AuNP-quenched fluorophores by destroying the polyA-AuNP interaction via a divide-and-conquer strategy. Based on this new discovery, we have developed a novel, cost-effective and sandwich-type fluorescence turn-on aptasensor for highly sensitive and specific thrombin detection, what took advantage of aptamer-conjugated magnetic beads (apt-MBs) for protein capture and separation, and iodide-induced fluorescence recovery of activatable polyA-based AuNP probes through ligand displacement for fluorescence turn-on detection. This proposed aptasensor could detect thrombin specifically with a detection limit as low as 89pM, which was better than or comparable to many existing fluorescent thrombin assays. Importantly, employment of such polyA-based AuNP conjugate not only avoids the use of thiolated oligonucleotides and thiol-containing displacing reagents, but also offers new possibilities for fabricating convenient and cost-effective bioanalytical applications.
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, China.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, China. Electronic address: xudanke@nju.edu.cn.
authors.forename: Danke
authors.initials: D
authors.lastname: Xu
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D007454:Iodides / Q000737:chemistry; D008024:Ligands; D057230:Limit of Detection; D053768:Metal Nanoparticles / Q000737:chemistry*; D011061:Poly A / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013917:Thrombin / Q000032:analysis*
chemical_list: D052157:Aptamers, Nucleotide; D005456:Fluorescent Dyes; D007454:Iodides; D008024:Ligands; C081676:thrombin aptamer; D011061:Poly A; D006046:Gold; D013917:Thrombin
keywords: Fluorescence; Gold nanoparticles; Iodide; Ligand displacement; PolyA-tailed aptamer; Thrombin aptasensor