Rainbow-inspired multicolor lateral flow immunoassay using multibranched platinum–rhodium-cobalt nanoparticles

Traditional lateral flow immunoassay (LFIA) using single-color labels has limitations in indistinct color change and restriction to the single-mode readout, which can hardly meet the demands of high-performance detection. Inspired by the multiple colors of the rainbow, we outline a multicolor LFIA using multibranched trimetallic platinum–rhodium-cobalt nanoparticles (PRCNPs) as signal labels to initiate multicolor conversion for diverse and multicolor readouts. The intrinsic properties of PRCNPs including their trimetallic composition, multibranched morphology, and strong absorption in the visible spectrum, confer advantages in catalytic activity, antibody utilization, and signal readout. Through the synergistic integration of the catalytic PRCNPs with the etching of gold nanorods, PRCNPs-LFIA enables multicolor readouts in a rainbow-like manner. PRCNPs-LFIA allows for qualitative analysis of acetamiprid, a widely-used neonicotinoid insecticide, at 2 ng mL−1. It also provides semi-quantitative analysis based on the discrimination of at least 10 colors. Furthermore, quantitative analysis can be conducted across multiple color spaces within the range of 0.01-10 ng mL−1, achieving a lowest detection result of 0.006 ng mL−1. The recoveries of acetamiprid in food samples detected by PRCNPs-LFIA in grayscale and multiple color space modes are 87.35%-103.59%, 85.56%-114.33%, 86.14%-114.77%, and 87.81%-112.01%, respectively, with all coefficients of variation below 15%. These results demonstrate the feasibility and accuracy of PRCNPs-LFIA in practical applications. Overall, this study illustrates the potential of multifunctional PRCNPs in the development of multicolor LFIA and broadens the biosensing strategies for point-of-care testing.