School of Chemistry and Biological Engineering, Changsha University of Science & Technology, Changsha 410110, China.
Molecules. 2018 Oct 18;23(10):2688. doi: 10.3390/molecules23102688.
Human epidermal growth factor receptor 2 (HER2) is a key tumor marker for several common and deadly cancers. It is of great importance to develop efficient detection methods for its over-expression. In this work, an electrochemical impedance spectroscopy (EIS) method adjustable by anionic porphyrin for HER2 gene detection has been proposed, based on the impedance difference between multi-walled carbon nanotubes (MWCNTs) and DNA. The interesting finding herein is that with the addition of anionic porphyrin, i.e., meso-tetra(4-sulfophenyl)-porphyrin (TSPP), the impedance value obtained at a glass carbon electrode (GCE) modified with MWCNTs and a single stranded DNA (ssDNA), the probe DNA that might be assembled tightly onto MWCNTs through π-π stacking interaction, gets a slight decrease; however, the impedance value from a GCE modified with MWCNTs and a double stranded DNA (dsDNA), the hybrid of the probe DNA with a target DNA, which might be assembled loosely onto MWCNTs for the screening effect of phosphate backbones in dsDNA, gets an obvious decrease. The reason may be that on the one hand, being rich in negative sulfonate groups, TSPP will try to push DNA far away from CNTs surface due to its strong electrostatic repulsion towards DNA; on the other hand, rich in planar phenyl or pyrrole rings, TSPP will compete with DNA for the surface of CNTs since it can also be assembled onto CNTs through conjugative interactions. In this way, the "loosely assembled" dsDNA will be repelled by this anionic porphyrin and released off CNTs surface much more than the "tightly assembled" ssDNA, leading to a bigger difference in the impedance value between dsDNA and ssDNA. Thus, through the amplification effect of TSPP on the impedance difference, the perfectly matched target DNA could be easily determined by EIS without any label. Under the optimized experimental conditions, this electrochemical sensor shows an excellent linear response to target DNA in a concentration range of 2.0 × 10⁻2.0 × 10 M with a limit of detection (LOD) of 6.34 × 10 M (S/N = 3). This abnormally sensitive electrochemical sensing performance resulting from anionic porphyrin for DNA sequences specific to HER2 gene will offer considerable promise for tumor diagnosis and treatment.
人表皮生长因子受体 2（HER2）是几种常见致命癌症的关键肿瘤标志物。开发针对其过表达的高效检测方法非常重要。在这项工作中，基于多壁碳纳米管（MWCNTs）和 DNA 之间的阻抗差异，提出了一种可通过阴离子卟啉调节的电化学阻抗谱（EIS）方法，用于 HER2 基因检测。这里有趣的发现是，随着阴离子卟啉，即间四（4-磺苯基）-卟啉（TSPP）的加入，在玻璃碳电极（GCE）上修饰的 MWCNTs 和单链 DNA（ssDNA）上获得的阻抗值略有降低，探针 DNA 可能通过π-π堆积相互作用紧密组装到 MWCNTs 上；然而，在 GCE 上修饰的 MWCNTs 和双链 DNA（dsDNA）上的阻抗值，即探针 DNA 与靶 DNA 的杂交物，可能由于 dsDNA 中磷酸骨架的筛选作用而松散地组装到 MWCNTs 上，会明显降低。原因可能是一方面，TSPP 富含负磺酸盐基团，由于其对 DNA 的强烈静电排斥作用，它会试图将 DNA 从 CNTs 表面推开；另一方面，TSPP 富含平面苯基或吡咯环，由于它也可以通过共轭相互作用组装到 CNTs 上，因此它会与 DNA 竞争 CNTs 的表面。通过这种方式，带负电荷的卟啉会排斥这种“松散组装”的 dsDNA，并使其从 CNTs 表面释放出来，远远超过“紧密组装”的 ssDNA，从而导致 dsDNA 和 ssDNA 之间的阻抗值差异更大。因此，通过 TSPP 对阻抗差异的放大作用，无需任何标记即可通过 EIS 轻松确定完全匹配的靶 DNA。在优化的实验条件下，该电化学传感器对靶 DNA 在 2.0×10-2.0×10 M 浓度范围内表现出优异的线性响应，检测限（LOD）为 6.34×10 M（S/N=3）。这种源于对 HER2 基因特定 DNA 序列的阴离子卟啉的异常灵敏的电化学传感性能，为肿瘤诊断和治疗提供了很大的希望。
