Surfactant-Triggered Signal Enhancement for Lateral Flow Immunoassay.

Lateral flow assays (LFAs) are widely used as point-of-care testing (POCT) platforms because they meet key criteria such as low cost, ease of use, and suitability for resource-limited settings. However, their relatively low sensitivity remains a major challenge. Although various signal enhancement strategies have been reported, many of these strategies require multiple steps or complex setups, limiting their practical use. This study introduces a one-step, automated colorimetric signal enhancement platform based on the surfactant-triggered release of gold ions for in situ growth of gold nanoparticles. A surfactant-triggered release system is established by leveraging the hydrophobic properties of commercial office paper to automate signal enhancement in LFAs. Such a system enables a tunable delayed release of the enhancement solution, which can be adjusted by controlling the surfactant concentration and the number of stacked office paper layers. This configuration enables customizable enhancement and broad compatibility with various LFA platforms. Using this system, cardiac troponin I, a key biomarker of myocardial infarction, is detected with a limit of detection of 2.42 pg mL-1 within 20 min, achieving a 157-fold improvement in sensitivity compared to the unenhanced assay, with a material cost of less than $0.5 per test. This platform offers a low-cost, high-sensitivity, and user-friendly solution, demonstrating strong potential for universal POCT applications.