Copper deposition-induced efficient signal amplification for ultrasensitive lateral flow immunoassay

This work describes a novel signal amplification strategy via gold nanoparticle (AuNP)–induced copper deposition to develop a highly sensitive and accurate immunochromatographic platform. Copper deposition–assisted signal amplification (CDASA) was first evaluated on commercially HCG test strip. A lower limit of detection (LOD) over the well-known silver enhancement confirms the great potential of this new approach for the visual test strip. Under an optimal condition, an LOD of 1 pg mL−1 and a wide dynamic range from 1 pg mL−1 to 100 ng mL−1 were achieved by the CDASA with rabbit IgG as a model analyte. In terms of LOD, 2–3 orders of magnitude improvement is received by the CDASA as compared with the conventional test strip without any signal amplification. Potential of the proposed strategy for practical application is also validated by detection of Rabbit IgG in human serum, a mimic clinical sample. The CDASA renders much superiority such as a higher deposition efficiency, lower cost, and better reagent stability over the silver enhancement method. The results can be qualitative and quantitative analysis by the naked eyes and the combination of a flatbed scanner and a free imageJ respectively, eliminating any lab equipment.