An electrical immuno-sandwich assay utilizing an electrokinetic-based streaming current method for signal transduction is proposed. The method records the changes in streaming current, first when a target molecule binds to the capture probes immobilized on the inner surface of a silica micro-capillary, and then when the detection probes interact with the bound target molecules on the surface. The difference in signals in these two steps constitute the response of the assay, which offers better target selectivity and a linear concentration dependent response for a target concentration within the range 0.2–100 nM. The proof of concept is demonstrated by detecting different concentrations of Immunoglobulin G (IgG) in both phosphate buffered saline (PBS) and spiked in E. coli cell lysate. A superior target specificity for the sandwich assay compared to the corresponding direct assay is demonstrated along with a limit of detection of 90 pM in PBS. The prospect of improving the detection sensitivity was theoretically analysed, which indicated that the charge contrast between the target and the detection probe plays a crucial role in determining the signal. This aspect was then experimentally validated by modulating the zeta potential of the detection probe by conjugating negatively charged DNA oligonucleotides. The length of the conjugated DNA was varied from 5 to 30 nucleotides, altering the zeta potential of the detection probe from −9.3 ± 0.8 mV to −20.1 ± 0.9 mV. The measurements showed a clear and consistent enhancement of detection signal as a function of DNA lengths. The results presented here conclusively demonstrate the role of electric charge in detection sensitivity as well as the prospect for further improvement. The study therefore is a step forward in developing highly selective and sensitive electrokinetic assays for possible application in clinical investigations.

提出了一种利用基于电流的电流流方法进行信号转导的电免疫夹心法。该方法首先记录目标分子与固定在硅胶微毛细管内表面上的捕获探针结合，然后当检测探针与表面上结合的目标分子相互作用时，记录流动电流的变化。这两个步骤中信号的差异构成了测定的响应，对于0.2-100 nM范围内的目标浓度，它提供了更好的目标选择性和线性浓度依赖性响应。通过在磷酸盐缓冲液（PBS）和掺入大肠杆菌的两种溶液中检测不同浓度的免疫球蛋白G（IgG）来证明概念验证。细胞裂解物。与相应的直接测定相比，三明治测定具有更高的靶标特异性，并且在PBS中的检出限为90 pM。从理论上分析了提高检测灵敏度的前景，这表明靶标和检测探针之间的电荷对比度在确定信号中起着至关重要的作用。然后通过缀合带负电的DNA寡核苷酸来调节检测探针的ζ电位，从而通过实验验证了该方面。缀合的DNA的长度从5到30个核苷酸不等，检测探针的Zeta电位从-9.3±0.8 mV变为-20.1±0.9 mV。测量结果表明，检测信号明显而一致地增强了DNA长度。此处给出的结果最终证明了电荷在检测灵敏度中的作用以及进一步改进的前景。因此，这项研究是开发高度选择性和灵敏的电动分析方法的一步，可用于临床研究。