单个体矢量性特征的固体纳米孔道分析研究

Analysis of Single-entity Anisotropy with a Solid-state Nanopore

固体纳米孔道作为一种高灵敏的单分子检测技术,由于其机械强度高、尺寸可控、易于阵列化集成等方面的显著优势,已经被广泛应用于DNA,蛋白质以及聚合物等小分子的检测.具有矢量性特征的各向异性单个体在纳米孔道中的穿孔行为对具有空间限域效应的纳米孔道离子流特征信号具有显著影响.为解析单个体矢量性特征对纳米孔道分析的影响,本工作利用氮化硅固态纳米孔道,以单个纳米金棒为各向异性的单个体模型,实时观测了其在孔道中的迁移行为.研究发现当纳米金棒穿过纳米孔道时,产生两种不同阻断程度的特征电流信号,通过对电流信号事件的解析,实时获取了具有矢量特征的金棒所导致的两种特征过孔事件;进一步,建立了离子电流模型,分别对这两种各向异性的穿孔事件机制进行了验证.

Solid-state nanopore has emerging as a promising tool for detection and analysis of single molecules due to its advantages of high stability, easy control of diameter and channel length, and the potential for integration into devices and arrays. Therefore, there are intensive studies regarding nanopore-based detection of DNAs, proteins, polymers and other small molecules. The electrochemical confined space of nanopore could efficiently convert the information in single biologi- cal molecules with anisotropy characters into measurable electrochemical signatures with high temporal resolution. The ani- sotropy characters of each analyte, due to its featured physical and chemical properties in different directions, strongly affects the translocation behavior of each single entity （single molecule, single nanoparticle, etc.）. To analyze the single-entity ani- sotropy effects on nanopore translocation, here, we employed gold nanorods （GNRs） as a model for single entities with ani- sotropy to investigate its translocation behavior through a solid-state nanopore. We performed the GNRs translocation ex- periments in I0 mmoloL-1 KC1 （pH 8） electrolyte solution with a 100 nm SiNx solid-state nanopore. The current trace of GNRs translocation through nanopores had been recorded with an ultra-sensitive current amplifier at a sampling rate of 100 kHz filtered at 5 kHz via a low-pass Bessel filter. At applied voltage of --600 mV, two types of characteristic current block- ades were observed when single GNRs translocate through the pore. We found this two types of blockades are mainly related to two translocation orientation of GNRs due to its anisotropy. The smaller current blockades are due to the GNR passing through the pore vertically while the larger current blockades are due to the GNR passing through the pore horizontally. To verify our observation of this two types of GNRs translocation events, we employed a simple model which is based on the relationship between the blockade magnitude and the exclude ion volume. The calculated current blockades of two types of GNRs translocation events agree well with the experimental values. These results illustrate that the anisotropy of single entity is an important factor that should be taken into consideration in nanopore translocation. This work will lead to a better under- standing of the translocation behavior of single entity with anisotropy in the electrochemical confined space of nanopore. Such understanding is vital to the development of the solid-state nanopore system as a useful single molecule analytical de- vice.