Sensitivity enhancement of lateral flow assay by embedding cotton threads in paper

Lateral flow assays (LFAs) have been extensively used as point-of-care testing platforms because they are inexpensive, portable, simple, and rapid, which particularly improve their availability in resource-poor settings. However, the poor sensitivity of LFAs restricts their further applications. Herein, we proposed a novel and simple method to enhance the detection sensitivity of LFAs by embedding cotton thread-based barriers into paper and further integrating them into strips to decrease the flow rate of sample and extend the reaction time. The number and hydrophilicity of the embedded cotton threads were sequentially optimized. The flow rate of liquid in cotton thread-embedded LFAs was mathematically simulated using a circuit-like model and the simulation results are consistent with the experimental results. With using human immunodeficiency virus nucleic acid as a model target, the cotton thread-embedded LFAs presented a fourfold enhancement in detection sensitivity compared to that of the unmodified LFAs. The strategy of embedding cotton threads into paper possesses great potential for fabricating other paper-based microfluidic devices in the future.