Utilizing the Thermostability of Nanozymes for Joule Heating to Remove Background Peroxidase Activities in Lateral Flow Assays

Lateral flow assays (LFAs) are essential for point-of-care testing. The use of peroxidase-mimicking nanozymes as catalytic labels is an actively developing direction in LFA, primarily focused on enhancing sensitivity. However, endogenous peroxidases, naturally present in various samples, can interfere with nanozyme signal amplification, leading to a high background signal and making visual detection more challenging. The issue of endogenous peroxidases is particularly significant for LFAs as wash-free biosensors. In this study, we showcase the remarkable thermostability of nanozymes in contrast to enzymes, applied to the analytically relevant use of lateral flow assays for the detection of aflatoxin B1. By employing Joule heating in a portable battery-powered device, the test strips were rapidly heated to 75-80 °C after completing the conventional LFA process. This heating caused thermal denaturation of endogenous peroxidases without affecting the Au@Pt nanozymes. As a result, substrate oxidation on the test strip was carried out solely by the Au@Pt nanozymes, which reduced background noise and improved the limit of detection by a factor of 3.5 compared to the assay without heating.