Selvaraju Thangavelu, Das Jagotamoy, Jo Kyungmin, Kwon Kiyeon, Huh Chan-Hwa, Kim Tae Kyu, Yang Haesik
Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 609-735, Korea.
Langmuir. 2008 Sep 2;24(17):9883-8. doi: 10.1021/la801828a. Epub 2008 Aug 9.
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.
与酶相比，金纳米催化剂具有更好的长期稳定性，且制备更容易。金纳米颗粒（AuNPs）被用作催化标记物，通过快速催化反应实现超灵敏的DNA检测。此外，磁珠（MBs）用于使与DNA结合的AuNPs具有低非特异性结合，并使AuNPs的电催化电流最小化，同时利用其易于磁分离的特性。在三明治型电化学传感器中，与捕获探针结合的MBs和用部分二茂铁修饰的树枝状聚合物修饰的氧化铟锡电极分别作为目标结合表面和信号产生表面。与硫醇化检测探针结合的AuNP表现出高水平的未被阻断的活性位点，并使对硝基苯酚和硼氢化钠易于接近这些位点。在这些位点产生电活性对氨基酚，然后在电极上被电氧化为对醌亚胺。硼氢化钠对氨基酚的氧化还原循环提供了大的信号放大。通过用含甲酰胺的溶液洗涤与DNA连接的MB-AuNP组装体，降低了与检测探针结合的AuNPs的非特异性结合，并且由于电极与结合到MBs上的AuNPs之间的长程电子转移不可行，AuNPs对硼氢化钠的电催化氧化被最小化。高信号放大和低背景电流使得能够检测1 fM的目标DNA。
