title: "Signal-on" photoelectrochemical sensing strategy based on target-dependent aptamer conformational conversion for selective detection of lead(II) ion.
abstract: A "signal-on" photoelectrochemical sensing strategy for selective determination of Pb(2+) is designed on the basis of the combination of Pb(2+)-induced conformational conversion, the amplified effect of reduced graphene oxide (RGO) and resonance energy transfer between CdS quantum dots (QDs) and gold nanoparticles (AuNPs). The RGO/CdS/aptamer platform is constructed via a stepwise modification method, and characterized by electrochemical impedance spectroscopy. In the absence of Pb(2+), the AuNP-labeled DNA, as a signal quenching element, can be introduced by hybridization with aptamer on the surface of sensing platform, which quenches the photocurrent of QDs via an energy transfer process. Upon addition of Pb(2+), the aptamer is induced into a G-quadruplex structure, which can greatly hinder the hybridization between aptamer and AuNP-labeled DNA due to the competitive occupation of binding sites and steric effect, leading to the recovery of photocurrent. Under optimized conditions, this "signal-on" photoelectrochemical biosensor shows a linear relationship between photocurrent variation and the logarithm of Pb(2+) concentration in the range of 0.1-50 nM with a detection limit of 0.05 nM. Meanwhile, it also exhibits good selectivity for Pb(2+) over other interfering ions, and is successfully applied to the detection of Pb(2+) in environmental water samples. By substituting the aptamers with other sequences, this proposed strategy could be conveniently extended to detect different targets as versatile photoelectrochemical devices.
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University , Nanjing 210093, People's Republic of China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zang
authors.forename: Jianping
authors.initials: J
authors.lastname: Lei
authors.forename: Qing
authors.initials: Q
authors.lastname: Hao
authors.forename: Huangxian
authors.initials: H
authors.lastname: Ju
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D019187:Cadmium Compounds / Q000737:chemistry; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods; D031541:Fluorescence Resonance Energy Transfer / Q000295:instrumentation / Q000379:methods; D006108:Graphite / Q000737:chemistry; D007854:Lead / Q000032:analysis*; D045663:Quantum Dots / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry
chemical_list: D052157:Aptamers, Nucleotide; D019187:Cadmium Compounds; D013440:Sulfides; C034939:cadmium sulfide; D007854:Lead; D006108:Graphite
keywords: aptamer; biosensors; detection; photoelectrochemistry; quantum dots; resonance energy transfer