Performance improvement of lateral flow assay using heterogeneous nitrocellulose membrane with nonuniform pore size

Lateral flow assay (LFA) has found widespread applications in point-of-care diagnostics over the past decades. Its detection sensitivity is dependent on the properties of paper itself (e.g., porous microstructure of nitrocellulose membrane), however, the effect remains unknown. Existing mathematical models for LFA have not been proved to predict the variation trends of detection performance with different specifications of nitrocellulose membrane. To address this, we developed a mathematical model coupling the macroscopic capillary flow and the binding reaction on the internal pore surface to illustrate the complex interaction among the convection, diffusion, and binding reaction with different nitrocellulose membranes. The model was experimentally validated by implementing nucleic acid detection on LFA. The simulated results suggest that due to the trade-off between the reagent transport and the reactive surface area, there is an optimal average pore size of the nitrocellulose membrane to achieve the highest detection sensitivity. Additionally, a heterogeneous pore distribution design (i.e., smaller pore diameter at the test line region and larger pore diameter for the rest region) of the nitrocellulose membrane was proposed to provide a faster detection with improved sensitivity. The numerical model would be a practical tool for the material selection and optimization of LFA.