Electrochemical Immunosensor Using p-Aminophenol Redox Cycling by Hydrazine Combined with a Low Background Current

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• 作者：Jagotamoy Das ; Kyungmin Jo ; Jae Wook Lee ; Haesik Yang
• 刊名：Analytical Chemistry
• 出版年：2007
• 出版时间：April 1, 2007
• 年：2007
• 卷：79
• 期：7
• 页码：2790 - 2796
• 全文大小：345K
• 年卷期：v.79,no.7(April 1, 2007)
• ISSN：1520-6882

文摘

Signal amplification and noise reduction are crucial forobtaining low detection limits in biosensors. Here, wepresent an electrochemical immunosensor in which thesignal amplification is achieved using p-aminophenol (AP)redox cycling by hydrazine, and the noise level is reducedby implementing a low background current. The redoxcycling is obtained in a simple one-electrode, one-enzymeformat. In a sandwich-type heterogeneous immunosensorfor mouse IgG, an alkaline phosphatase label convertsp-aminophenyl phosphate into AP for 10 min. Thisgenerated AP is electrooxidized at an indium tin oxide(ITO) electrode modified with a partially ferrocenyl-tethered dendrimer (Fc-D). The oxidized product, p-quinone imine (QI), is reduced back to AP by hydrazine,and then AP is electrooxidized again to QI, resulting inredox cycling. Moreover, hydrazine protects AP fromoxidation by air, enabling long incubation times. The smallamount of ferrocene in a 0.5% Fc-D-modified ITO electrode, where 0.5% represents the ratio of ferrocene groupsto dendrimer amines, results in a low background current,and this electrode exhibits high electron-mediating activityfor AP oxidation. Moreover, there is insignificant hydrazine electrooxidation on this electrode, which also resultsin a low background current. The detection limit of theimmunosensor using a 0.5% Fc-D-modified electrode is2 orders of magnitude lower than that of a 20% Fc-D-modified electrode (10 pg/mL vs 1 ng/mL). Furthermore,the presence of hydrazine reduces the detection limit byan additional 2 orders of magnitude (100 fg/mL vs 10pg/mL). These results indicate that the occurrence ofredox cycling combined with a low background currentyields an electrochemical immunosensor with a very lowdetection limit (100 fg/mL). Mouse IgG could be detectedat concentrations ranging from 100 fg/mL to 100 g/mL(i.e., 9 orders of magnitude) in a single assay.