title: Engineering Signaling Aptamers That Rely on Kinetic Rather Than Equilibrium Competition.
abstract: During the past decade, aptasensors have largely been designed on the basis of the notion that ligand-modulated equilibration between aptamer conformations could be exploited for sensing. One implementation of this strategy has been to denature the aptamer with an antisense oligonucleotide, wait for dissociation of the antisense oligonucleotide, and stabilize the folded, signaling conformer with a ligand. However, there is a large kinetic barrier associated with releasing the oligonucleotide from the aptamer to again obtain an active, binding conformation. If the length of the antisense oligonucleotide is decreased to make dissociation from the aptamer more favorable, higher background signals are observed. To improve the general methodology for developing aptasensors, we have developed a novel and robust strategy for aptasensor design in which an oligonucleotide kinetically competes with the ligand for binding rather than having to be released from a stable duplex. While the oligonucleotide can induce conformational change, it initially chooses between the aptamer and a molecular beacon (MB), a process that does not require a lengthy pre-equilibration. Using an anti-ricin aptamer as a starting point, we developed a "competitive" aptasensor with a measured limit of detection (LOD) of 30 nM with an optical readout and as low as 3 nM for ricin toxin A-chain (RTA) detection on an electrochemical platform.
authors.affiliation: Institute for Cellular and Molecular Biology, Center for Systems and Synthetic Biology, and Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: Yan
authors.initials: Y
authors.lastname: Du
authors.affiliation: Institute for Cellular and Molecular Biology, Center for Systems and Synthetic Biology, and Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States.|Key Laboratory of Luminescent and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University , 400715, Chongqing, P.R. China.
authors.forename: Shu Jun
authors.initials: SJ
authors.lastname: Zhen
authors.affiliation: Institute for Cellular and Molecular Biology, Center for Systems and Synthetic Biology, and Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: Bingling
authors.initials: B
authors.lastname: Li
authors.affiliation: Institute for Cellular and Molecular Biology, Center for Systems and Synthetic Biology, and Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: Michelle
authors.initials: M
authors.lastname: Byrom
authors.affiliation: Institute for Cellular and Molecular Biology, Center for Systems and Synthetic Biology, and Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: Yu Sherry
authors.initials: YS
authors.lastname: Jiang
authors.affiliation: Institute for Cellular and Molecular Biology, Center for Systems and Synthetic Biology, and Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Ellington
mesh_terms: D052157:Aptamers, Nucleotide / Q000032:analysis* / Q000737:chemistry*; D001667:Binding, Competitive; D015374:Biosensing Techniques; D055664:Electrochemical Techniques; D007700:Kinetics; D008024:Ligands; D057230:Limit of Detection; D015335:Molecular Probes / Q000032:analysis / Q000737:chemistry; D016376:Oligonucleotides, Antisense / Q000737:chemistry*; D012276:Ricin / Q000032:analysis / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D052157:Aptamers, Nucleotide; D008024:Ligands; D015335:Molecular Probes; D016376:Oligonucleotides, Antisense; D012276:Ricin