Bogomolova A, Komarova E, Reber K, Gerasimov T, Yavuz O, Bhatt S, Aldissi M
Fractal Systems Inc., 108 Fourth Street, Belleair Beach, Florida 33786, USA.
Anal Chem. 2009 May 15;81(10):3944-9. doi: 10.1021/ac9002358.
Electrochemical impedance spectroscopy (EIS) measurement, performed in the presence of a redox agent, is a convenient method to measure molecular interactions of electrochemically inactive compounds taking place on the electrode surface. High sensitivity of the method, being highly advantageous, can be also associated with nonspecific impedance changes that could be easily mistaken for specific interactions. Therefore, it is necessary to be aware of all possible causes and perform parallel control experiments to rule them out. We present the results obtained during the early stages of aptamer-based sensor development, utilizing a model system of human alpha thrombin interacting with a thiolated DNA aptamer, immobilized on gold electrodes. EIS measurements took place in the presence of iron ferrocyanides. In addition to known method limitations, that is, inability to discriminate between specific and nonspecific binding (both causing impedance increase), we have found other factors leading to nonspecific impedance changes, such as: (i) initial electrode contamination; (ii) repetitive measurements; (iii) additional cyclic voltammetry (CV) or differential pulse voltammetry (DPV) measurements; and (iv) additional incubations in the buffer between measurements, which have never been discussed before. We suggest ways to overcome the method limitations.
在氧化还原试剂存在的情况下进行的电化学阻抗谱（EIS）测量，是一种测量电极表面发生的电化学惰性化合物分子相互作用的便捷方法。该方法的高灵敏度虽然具有很大优势，但也可能与非特异性阻抗变化相关，这些变化很容易被误认为是特异性相互作用。因此，有必要了解所有可能的原因并进行平行对照实验以排除它们。我们展示了在基于适配体的传感器开发早期阶段获得的结果，该研究利用了人α凝血酶与固定在金电极上的硫醇化DNA适配体相互作用的模型系统。EIS测量是在铁氰化亚铁存在的情况下进行的。除了已知的方法局限性，即无法区分特异性和非特异性结合（两者都会导致阻抗增加）之外，我们还发现了其他导致非特异性阻抗变化的因素，例如：（i）初始电极污染；（ii）重复测量；（iii）额外的循环伏安法（CV）或差分脉冲伏安法（DPV）测量；以及（iv）测量之间在缓冲液中的额外孵育，这些因素以前从未被讨论过。我们提出了克服该方法局限性的方法。
