Photothermal lateral flow assays for food contaminant detection: Principles, nanoprobes, and emerging detection strategies

Abstract

Lateral flow assays (LFAs) are adaptable and extensively utilized analytical instruments for detecting food risks, environmental pollutants, and disease-associated biomarkers. However, conventional colorimetric lateral flow assays are constrained by low sensitivity and specificity. Practical challenges such as the hook effect, narrow dynamic range, and subjective visual interpretation hinder the reliability of results. Additionally, matrix interferences from food components can obscure color development, complicating detection. This review elucidates the advances in photothermal LFAs for detecting food contaminants, emphasizing their ability to overcome the limitations of conventional colorimetric methods. The underlying principle and widely accepted light-to-heat conversion mechanisms are introduced, while the superior performance of photothermal LFAs in the sensitive detection of trace-level food hazards is highlighted. The crucial components of photothermal LFAs, including photothermal nanomaterials (Au nanocomposites and their derived nano-assemblies, polymer-decorated nanomaterials, flexible nanosheets) and photothermal readers (thermal imagers and smartphone-integrated portable readers), are summarized. Various analytical modalities of photothermal-derived platforms are shown, encompassing single-readout, colorimetric/photothermal dual-readout, and multiple-readout detection. The utilization of photothermal LFAs for identifying diverse pollutants in food matrices is clarified, highlighting its relevance in food safety. Despite their advantages, photothermal LFAs still require specialized instrumentation, which may increase costs and complexity. Signal readout challenges, such as calibration issues and temperature sensitivity, can also impact accuracy, particularly under varying environmental conditions. Nevertheless, continuous advancements in new photothermal nanomaterials and economical signal readers are anticipated to render photothermal LFAs commercially viable, facilitating their adoption as alternate ways for ensuring food safety.