Two-orders of magnitude improvement detection limit of lateral flow assays using isotachophoresis

TL;DR

This paper demonstrates that using isotachophoresis (ITP) can enhance lateral flow immunoassays, achieving up to 400-fold lower detection limits and enabling their use for more sensitive diagnostic applications.

Contribution

The study introduces ITP as a preconcentration method to significantly improve the detection limits of lateral flow assays, bridging the gap with lab-based immunoassays.

Findings

ITP improves LF assay detection limit by 400-fold in 90 seconds.

ITP enhances target extraction efficiency up to 30%.

ITP-LF achieves detection sensitivity comparable to ELISA.

Abstract

Lateral flow (LF) immunoassays are one of the most prevalent point-of-care (POC) diagnostics due to their simplicity, low cost, and robust operation. A common criticism of LF tests is that they have poor detection limits compared to analytical techniques, like ELISA, which confines their application as a diagnostic tool. The low detection limit of LF assays and associated long equilibration times is due to kinetically limited surface reactions that result from low target concentrations. Here we use isotachophoresis (ITP), a powerful electrokinetic preconcentration and separation technique, to focus target analytes into a thin band and transport them to the LF capture line resulting is a dramatic increase in the surface reaction rate and equilibrium binding. We show that ITP is able to improve limit of detection (LOD) of LF assays by 400-fold for 90 second assay time and by 160-fold for a longer 5 minutes time scale. ITP-enhanced LF (ITP-LF) also shows up to 30% target extraction from 100 uL of the sample, while conventional LF captures less than 1% of the target. ITP improves LF assay LOD to the level of some lab based immunoassays, such as ELISA, and may provide sufficient analytical sensitivity for application to a broader range of analytes and diseases that require higher sensitivity and lower detection limits.