Nanocatalyst-based assay using DNA-conjugated Au nanoparticles for electrochemical DNA detection.
Compared to enzymes, Au nanocatalysts show better long-term stability and are more easily prepared. Au nanoparticles (AuNPs) are used as catalytic labels to achieve ultrasensitive DNA detection via fast catalytic reactions. In addition, magnetic beads (MBs) are employed to permit low nonspecific binding of DNA-conjugated AuNPs and to minimize the electrocatalytic current of AuNPs as well as to take advantage of easy magnetic separation. In a sandwich-type electrochemical sensor, capture-probe-conjugated MBs and an indium-tin oxide electrode modified with a partially ferrocene-modified dendrimer act as the target-binding surface and the signal-generating surface, respectively. A thiolated detection-probe-conjugated AuNP exhibits a high level of unblocked active sites and permits the easy access of p-nitrophenol and NaBH 4 to these sites. Electroactive p-aminophenol is generated at these sites and is then electrooxidized to p-quinoneimine at the electrode. The p-aminophenol redox cycling by NaBH 4 offers large signal amplification. The nonspecific binding of detection-probe-conjugated AuNPs is lowered by washing DNA-linked MB-AuNP assemblies with a formamide-containing solution, and the electrocatalytic oxidation of NaBH 4 by AuNPs is minimized because long-range electron transfer between the electrode and the AuNPs bound to MBs is not feasible. The high signal amplification and low background current enable the detection of 1 fM target DNA.
Selvaraju
Thangavelu
T
Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 609-735, Korea.
Das
Jagotamoy
J
Jo
Kyungmin
K
Kwon
Kiyeon
K
Huh
Chan-Hwa
CH
Kim
Tae Kyu
TK
Yang
Haesik
H
D001665:Binding Sites; D002384:Catalysis; D004247:DNA / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D008280:Magnetics; D008956:Models, Chemical; D053758:Nanoparticles / Q000032:analysis*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013438:Sulfhydryl Compounds; D013997:Time Factors
D013438:Sulfhydryl Compounds; D006046:Gold; D004247:DNA; D010100:Oxygen