PAMAM dendrimer-enhanced DNA biosensors based on electrochemical impedance spectroscopy.
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.
Zhu
Ningning
N
Department of Chemistry, Shanghai Normal University, Shanghai 200234, China. zhunn@shnu.edu.cn
Gao
Huan
H
Gu
Yunfeng
Y
Xu
Qin
Q
He
Pingang
P
Fang
Yuzhi
Y
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*
D050091:Dendrimers; C104700:PAMAM Starburst; D011073:Polyamines; D004247:DNA