The colorimetric lateral flow assay (CLFA, also known as test strip) is a widely used point-of-care diagnostic technology. It has been a challenge to significantly improve the detection sensitivity of CLFA without involving additional equipment and/or compromising its simplicity. In this work, we break through the detection limit barrier of CLFA by developing a type of catalytic nanoparticles (NPs) used as labels. Specifically, the NPs were engineered by coating conventional gold NPs (AuNPs) with iridium (Ir) to form an Au-Ir core–shell structure. Such Au-Ir NPs possess ultrahigh peroxidase-like catalytic activities. A single Au-Ir NP can generate up to 107 colored molecules per second by catalyzing peroxidase substrates. The strong color signal from the catalysis ensures a high sensitivity of associated CLFA. The Au-Ir NP-based CLFA was successfully applied to the detection of two different cancer biomarkers that achieved limits of detection at the low picogram per milliliter level, hundreds of times lower than those of conventional AuNP-based CLFA.

Point-of-care (POC) tests for the diagnosis of diseases are critical to the improvement of the standard of living, especially for resource-limited areas or countries. In recent years, nanobiosensors based on noble metal nanoparticles (NM NPs) have emerged as a class of effective and versatile POC testing technology. The unique features of NM NPs ensure great performance of associated POC nanobiosensors. In particular, NM NPs offer various signal transduction principles, such as plasmonics, catalysis, photothermal effect, and so on. Significantly, the detectable signal from NM NPs can be tuned and optimized by controlling the physicochemical parameters (e.g., size, shape, and elemental composition) of NPs. In this article, we introduce the inherent merits of NM NPs that make them attractive for POC testing, discuss recent advancement of NM NPs-based POC tests, highlight their social impacts, and provide perspectives on challenges and opportunities in the field. We hope the review and insights provided in this article can inspire new fundamental and applied research in this emerging field.