Sharp Branched Gold Nanostar-Based Lateral-Flow Immunoassay for Detection of Yersinia pestis

Over the past few decades, colorimetric paper-based lateral flow immunoassay (LFIA) has emerged as a versatile analytical tool for rapid point-of-care detection of infectious diseases with high simplicity and flexibility. The LFIA sensitivity is based on color visualization of the antibody-labeled nanoparticles bound with the target analytes at the test line. Therefore, the nanoparticle design is crucial for LFIA sensitivity. The traditional LFIA is based on spherical gold nanoparticles, which usually suffer from poor sensitivity because of very low optical contrast at the test line. To improve the LFIA sensitivity, we have developed an LFIA based on gold nanostars (GNSs) with different branch lengths and sharpness (GNS-1, GNS-2, and GNS-3), which possess higher optical contrast than conventional gold nanospheres (GNSPs). We have selected the bacterium Yersinia pestis as a model analyte system. The effective affinity of GNSPs and GNSs with the Y. pestis fraction 1 (F1) protein was quantitively investigated by colorimetric and optical density measurements of the test line. The results show that GNS-3, which has maximum spike length and branch sharpness, exhibits the highest analytical sensitivity based on the limit of detection of the LFIA readout compared to other GNSs and GNSPs. The detection limit of the Y. pestis F1 antigen was achieved up to 0.1 ng/mL for GNS-3, which is 100 times lower than that for the GNSP at a 1 pmol/L concentration and 10 times lower than that for the reported procedure based on traditional gold nanoparticles. Overall, our prototype LFIA platform based on a highly spiked GNS (GNS-3) exhibits high analytical sensitivity, indicating it to be a promising candidate for routine LFIA application to detect infectious diseases.