title: Impedimetric aptasensor with femtomolar sensitivity based on the enlargement of surface-charged gold nanoparticles.
abstract: A simple and ultrasensitive label-free electrochemical impedimetric aptasensor for thrombin based on the cascaded signal amplification was reported. The sandwich system of aptamer/thrombin/aptamer-functionalized Au nanoparticles (Apt-AuNPs) was fabricated as the sensing platform. The change of the interfacial feature of the electrode was characterized by electrochemical impedance analysis with the redox probe [Fe(CN)(6)](3-/4-). For improving detection sensitivity, the three-level cascaded impedimetric signal amplification was developed: (1) Apt-AuNPs as the first-level signal enhancer; (2) the steric-hindrance between the enlarged Apt-AuNPs as the second-level signal amplification; (3) the electrostatic-repulsion between sodium dodecylsulfate (SDS) stabilized Apt-AuNPs and the redox probe [Fe(CN)(6)](3-/4-) as the third-level signal amplification. Enlargement of Apt-AuNPs integrated with negatively charged surfactant (SDS) capping could not only improve the detection sensitivity of the impedimetric aptasensor for thrombin but also present a simple and general signal-amplification model for impedimetric sensor. The aptasensor based on the enlargement of negatively charged Apt-AuNPs showed an increased response of the electron-transfer resistance to the increase of thrombin concentration through a wide detection range from 100 fM to 100 nM. The linear detection range was 0.05-35 nM, and thrombin was easily detectable to a concentration of 100 fM. The aptasensor also has good selectivity and reproducibility.
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Deng
authors.forename: Jinhua
authors.initials: J
authors.lastname: Chen
authors.forename: Zhou
authors.initials: Z
authors.lastname: Nie
authors.forename: Mengdong
authors.initials: M
authors.lastname: Wang
authors.forename: Xiaochen
authors.initials: X
authors.lastname: Chu
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Chen
authors.forename: Xilin
authors.initials: X
authors.lastname: Xiao
authors.forename: Chunyang
authors.initials: C
authors.lastname: Lei
authors.forename: Shouzhuo
authors.initials: S
authors.lastname: Yao
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D015374:Biosensing Techniques; D004566:Electrodes; D004579:Electron Transport; D005290:Ferric Compounds / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013499:Surface Properties
chemical_list: D052157:Aptamers, Nucleotide; D005290:Ferric Compounds; C081676:thrombin aptamer; D006046:Gold