Chemiluminescent lateral flow assay based on transparent nitrocellulose membrane

Abstract

Lateral flow assays (LFA) have become increasingly important for point-of-care disease detection for low costs, portability, and rapid results. To improve chemiluminescence LFA (CL-LFA) performance, we present a way to make test (T) and control (C) line areas transparent by applying paraffin liquid to the nitrocellulose (NC) membrane without inducing structure deterioration. The transparent T and C line regions generate stronger light signals in CL-LFA compared with conventional LFA, where the NC membrane obstructs signals from inner conjugates. A tunable transparency ranging from 12.47% to 78.53% was achieved by increasing the paraffin volume and hence, reducing the light scattering among pores. Then, coating with 0.1 μL of paraffin liquid on the T and C line areas leads to a slower light attenuation constant of -1.35 lower than that of NC membrane (-1.72) when detecting 20 ng/mL of cardiac troponin I (cTnI), a key biomarker for myocardial injury. We achieved a detection limit of 0.063 ng/mL and clinical samples with cTnI levels ranging from 1 to 5.1 ng/mL were effectively distinguished, showing the validity and practicality of the device. This work offers fundamental insights into the materials used in LFA and contributes to the broader application of paper-based biosensors.

Graphical abstract