Enhancing lateral flow assay performance: Buffer additives and protein-membrane interactions

Lateral Flow Assays (LFA) have been valuable tools for point-of-care diagnostics for decades. During periods of high testing demand, as recently in the Covid-19-pandemic, it is necessary to deepen the understanding of test and control line signal intensities. This study investigates the interaction between proteins and structurally different nitrocellulose (CN) membranes and the resulting effects on signal intensity in an LFA under the influence of various buffer additives. The experiments focused on quantitative protein adsorption, protein stability, protein line printing and changes in signal intensity in a human chorionic gonadotropin (hCG)-assay. A method was established for detecting the widths and intensities of fluorescent protein lines. We were able to show that changes in signal intensity of LFAs are driven by accessibility of the antibodies, by hydrophilicity of the membrane or assisted adsorption of antibodies onto the membrane. Additionally, the inclusion of sodium chloride, polysorbate 80 and sodium dodecylbenzenesulfonate can enhance signal intensity. The method developed for protein line analysis has proven to be effective and can help to understand protein-membrane-interactions on a macroscopic level. We demonstrate that LFA-manufacturers have a range of options to fine-tune assay performance without major modifications to assay components.