title: PAMAM dendrimer-enhanced DNA biosensors based on electrochemical impedance spectroscopy.
abstract: A novel, simple and sensitive DNA biosensor based on DNA-poly(amidoamine) (PAMAM) dendrimer nanoconjugates was developed by using the electrochemical impedance spectroscopy (EIS) technique. In this context, the assay relies on the hybridization of the single-stranded DNA (ssDNA) probe covalently conjugated on a mercaptoacetic acid self-assembled monolayer on gold electrodes, with the generation 4.5 (G-4.5) PAMAM-target DNA complex in solution. Once the double-stranded DNA (dsDNA) formed on the gold electrodes, G-4.5 PAMAM bearing carboxyls on the periphery was anchored on the hybrids; the changes of interfacial electron-transfer resistance (R(et)) of the electrodes were measured using an Fe(CN)(6)(3-/4-) redox probe by electrochemical impedance spectroscopy. The results showed that only a complementary sequence could form a dsDNA-PAMAM with the DNA-PAMAM probe and give an obviously enlarged R(et) value. The non-complementary and three-base mismatched sequence exhibited negligible impedance change compared with the blank measurement (the blank measurement means: ssDNA probe-modified gold electrode was directly measured by EIS). The unique spherical structure combining with more negative charges on the G-4.5 PAMAM periphery anchored on the hybrids could significantly amplify the hybridization signal (R(et) value), and the detection limit for measuring the full complementary sequence is down to pM level.
authors.affiliation: Department of Chemistry, Shanghai Normal University, Shanghai 200234, China. zhunn@shnu.edu.cn
authors.forename: Ningning
authors.initials: N
authors.lastname: Zhu
authors.forename: Huan
authors.initials: H
authors.lastname: Gao
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Gu
authors.forename: Qin
authors.initials: Q
authors.lastname: Xu
authors.forename: Pingang
authors.initials: P
authors.lastname: He
authors.forename: Yuzhi
authors.initials: Y
authors.lastname: Fang
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D004247:DNA / Q000032:analysis*; D050091:Dendrimers; D017097:Electric Impedance; D055664:Electrochemical Techniques / Q000379:methods*; D011073:Polyamines / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D050091:Dendrimers; C104700:PAMAM Starburst; D011073:Polyamines; D004247:DNA