Label-free electrochemical detection for aptamer-based array electrodes.
An electrochemical impedance spectroscopy method of detection for aptamer-based array electrodes is reported in which the binding of aptamers immobilized on gold electrodes leads to impedance changes associated with target protein binding events. Human IgE was used as a model target protein and incubated with the aptamer-based array consisting of single-stranded DNA containing a hairpin loop. To increase the binding efficiency for proteins, a hybrid modified layer containing aptamers and cysteamine was fabricated on the photolithographic gold surface through molecular self-assembly. Atomic force microscopy analysis demonstrated that human IgE could be specifically captured by the aptamer and stand well above the self-assembled monolayer (SAM) surface. Compared to immunosensing methods using anti-human IgE antibody as the recognition element, impedance spectroscopy detection could provide higher sensitivity and better selectivity for aptamer-modified electrodes. The results of this method show good correlation for human IgE in the range of 2.5-100 nM. A detection limit of 0.1 nM (5 fmol in a 50-microL sample) was obtained, and an average of the relative standard deviation was <10%. The method herein describes the first label-free detection for arrayed electrodes utilizing electrochemical impedance spectroscopy.
Xu
Danke
D
Department of Biochemistry, Beijing Institute of Radiation Medicine, Beijing 100850, China. xudk@nic.bmi.ac.cn
Xu
Dawei
D
Yu
Xiaobo
X
Liu
Zhihong
Z
He
Wei
W
Ma
Zhenqiu
Z
D052157:Aptamers, Nucleotide / Q000032:analysis* / Q000737:chemistry*; D001483:Base Sequence; D004563:Electrochemistry; D004566:Electrodes; D006046:Gold; D006801:Humans; D007073:Immunoglobulin E / Q000737:chemistry / Q000276:immunology; D018625:Microscopy, Atomic Force; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D020411:Oligonucleotide Array Sequence Analysis / Q000295:instrumentation* / Q000379:methods*; D012996:Solutions
D052157:Aptamers, Nucleotide; D012996:Solutions; D007073:Immunoglobulin E; D006046:Gold