Integrating lateral flow device with controllable gold in situ growth for sensitive detection of staphylococcal enterotoxin A in milk

Gold nanoparticle-based lateral flow immunoassays (AuNP-LFIA) are widely used for pathogen monitoring to prevent foodborne illness outbreaks. However, conventional AuNP-LFIA exhibits poor sensitivity and limited quantitative capacity due to the low colorimetric signal intensity of AuNPs. Herein, we introduced a lowbackground gold in situ growth (GISG) strategy by lowering the pH of the growth solution to weaken the reducibility of hydroxylamine, thereby enhancing the sensitivity of AuNP-LFIA. Additionally, we developed a universal and manufacturable lateral flow device to streamline the GISG process. We applied this device to detect staphylococcal enterotoxin A (SEA), an exotoxin produced by Staphylococcus aureus. Under optimal conditions, the proposed device demonstrated superior practicality and excellent sensitivity for SEA detection, achieving a detection limit of 0.061 ng/mL with the total detection time of 37 min, showing 311 times more sensitive than the unamplified AuNP-LFIA. Furthermore, SEA detection in milk samples showed a strong correlation (R-2 = 0.8845) with results obtained from a conventional ELISA kit. Therefore, this promising LFIA device offers a novel strategy with high sensitivity and practicality for in-field detection of Staphylococcus aureus and can be easily adapted for screening other foodborne pathogens.