Enhancement of lateral flow assay performance by electromagnetic relocation of reporter particles

Lateral flow assays (LFAs) are a widely-used point-of care diagnostic format, but suffer from limited analytical sensitivity, especially when read by eye. It has recently been reported that LFA performance can be improved by using magnetic reporter particles and an external magnetic field applied at the test line. The mechanism of sensitivity/performance enhancement was suggested to be concentration/retardation of reporter particles at the test line. Here we demonstrate an additional mechanism of particle relocation where reporter particles from the lower depths of the translucent LFA strip relocate to more-visible locations nearer to the top surface, producing a more visible signal. With a magnetic field we observed an improvement in sensitivity of human chorionic gonadotropin (hCG) detection from 1.25 ng/mL to 0.31 ng/mL. We also observed an increase of the color intensity per particle in test lines when the magnetic field was present.

侧向流层析检测（Lateral flow assays, LFAs）是一类应用广泛的即时诊断技术，但存在分析灵敏度有限的缺陷，尤其在目视读取结果时更为明显。近期有研究表明，借助磁性报告粒子并在检测线位置施加外部磁场，可改善LFAs的检测性能。此前研究提出，灵敏度与性能提升的机制在于报告粒子在检测线处的富集与滞留。本文中我们证实了一种额外的粒子重定位机制：当施加磁场时，半透明层析试纸条深层的报告粒子可重定位至更贴近试纸条上表面的可视区域，从而生成更显著的检测信号。通过施加磁场，我们将人绒毛膜促性腺激素（human chorionic gonadotropin, hCG）的检测灵敏度从1.25 ng/mL提升至0.31 ng/mL。此外，我们还观察到，在磁场存在的条件下，检测线处的单粒子颜色强度有所提升。