Development of lateral flow immunoassay strip for salicylic acid detection in human plasma

• A rapid on-site LFIA strip was developed for salicylic acid detection. • The LFIA strip is highly sensitive, enabling visual detection limit of 50 ng/mL. • Results reliably match ic-ELISA, making it ideal for emergency and primary care. Salicylic acid (SA), the primary active metabolite of aspirin, is widely used in clinical practice for its antipyretic and analgesic effects. However, excessive use can cause poisoning, increase the body’s metabolic burden and potentially become life-threatening. To overcome the limitations of current detection methods—such as complex and time-consuming procedures, reliance on sophisticated instruments, and the need for trained operators—this study developed a rapid, on-site alternative. A highly specific monoclonal antibody against SA was produced using 5-aminosalicylic acid as a hapten, exhibiting high affinity with an IC₅₀ of 198.59 ng/mL. Based on this antibody, a lateral flow immunoassay strip was established, offering a visual detection limit of 50 ng/mL and a cut-off value of 1000 ng/mL for semi-quantitative analysis. Meanwhile, the results obtained from SA determination using strips showed good consistency with indirect competitive enzyme-linked immunosorbent assay, with recovery rates ranging from 97.28% to 105.81%. This strip provides a simple, efficient tool for rapid screening of SA poisoning at point-of-care settings, including emergency departments and primary healthcare facilities, demonstrating strong potential for practical use.