Label-Free DNA Sensor by Boron-Doped Diamond Electrode Using an ac Impedimetric Approach

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• 作者：Jian Weng ; Jianfeng Zhang ; Hui Li ; Liping Sun ; Chenghong Lin ; Qiqing Zhang
• 刊名：Analytical Chemistry
• 出版年：2008
• 出版时间：September 15, 2008
• 年：2008
• 卷：80
• 期：18
• 页码：7075-7083
• 全文大小：181K
• 年卷期：v.80,no.18(September 15, 2008)
• ISSN：1520-6882

文摘

An electrochemical biosensor using a boron-doped diamond (BDD) electrode is described for differentiating between gene sequences according to DNA hybridization events using an ac impedimetric approach. BDD electrodes were dipped into a 1% solution of polyethylenimine (PEI) to adsorb a thin layer of positively charged PEI on the surface of BDD, then PEI-modified BDD electrodes were used to immobilize negatively charged single-stranded PCR fragments from Exon 7 of human p53 gene. Alternating current impedimetric measurements were first performed on these systems in phosphate buffered saline (PBS) and then upon exposure to single-stranded DNA (ssDNA). When the ssDNA-immobilized BDD electrode and solution ssDNA were completely complementary, a large drop in impedance was measured. Complementary DNA could be clearly detected at concentrations down to 10⁻¹⁹ g mL⁻¹ at a fixed frequency (10 Hz). Higher concentrations of DNA gave faster hybridization with saturation occurring at levels above 1.0 pg mL^−1. Responses were much lower upon exposure to noncDNA, even at higher concentrations. The results show it is possible to directly detect target DNA at a fixed frequency and without additional labeling.