Nano-labeled materials as detection tags for signal amplification in immunochromatographic assay

The immunochromatographic assay (ICA) was widely used in rapid detection in many fields due to its advantages such as economy, simplicity, sensitivity, and specificity all the time. Like fluorescence, colored, magnetic nanoparticles (NPs) have become the most commonly used signal tags in ICA. As an ancient detection technology, improving the analytical sensitivity of ICA has always been a hot topic for scholars. However, its superiority in many booming rapid testing methods has become relatively weaker. But, after the outbreak of the epidemic in 2020, many researchers successively reported on the immunological assay of the epidemic, and the nucleic acid testing and vaccination are also being carried out across the country to ensure personal safety, which made this ancient test method favoured by experts and scholars again. This means that the ICA is still one of the most rapid and economical detection methods when faced with sudden virus disasters. With the increasing demand for rapid detection, improving the sensitivity or shortening the detection times of ICA based on NPs/nanomaterials has become the focus of the study. Now, it is urgently needed to research convenient, economical, and sensitive novel immunosensors to cope with unknown viruses and others based on the advantages of the ICA that immediate and rapid on-site detection. Therefore, this article briefly reviews the emerging nano-labeled particles used to improve the sensitivity of ICA in rapid detection, introduces the development of ICA in real-time detection, and summarizes the current status of their applications in immunoassay of viruses, proteins, molds, agricultural, and veterinary drugs, toxins, metabolites et al. based on three basic NPs with the excellent properties such as luminescent NPs, magnetic NPs, and colored NPs. To improve the sensitivity of ICA, we also introduce the detection limit of several types of new NPs with higher optical properties in immunoassay, the three new methods of amplifying the signal of immunoprobe, and the application of optical composite nanomaterials in ICA in recent years, hope to provide a reference for the development of new nano-labeled materials and new immunodetection methods to improve the sensitivity of immunoassay so that it can meet the increasing needs of rapid detection.