Nature-inspired nanozymes as signal markers for in-situ signal amplification strategy: A portable dual-colorimetric immunochromatographic analysis based on smartphone.

Owing to the lack of a universal descriptor to predict the nanozymes as signal markers (SM) of immunochromatographic analysis (ICA), the present exploitation of nanozymes as SM heavily relies on trial-and-error strategies, which obstructs the rational design of nanozymes with monoclonal antibodies (mAbs) recognition activity. Herein, inspired by the structure of the active center of natural multi-iron peroxidases and polyphenol-protein interactions, a rational design of an artificial peroxidase with mAbs recognition activity by utilizing gallic acid (GA) to chelate with multivalent iron was successfully proposed by utilizing gallic acid (GA) to chelate with multivalent iron. The most essential features of peroxidase-like Fe-GA nanozymes (FGN) were investigated, showing high catalytic performance and good stability. Subsequently, FGN was employed as SM for mAbs in ICA, which played the following triple roles in the ICA sensor: (i) the direct recognizer of mAbs; (ii) the generator of original colorimetric signal; (iii) the generator of catalytic in-suit amplification colorimetric signal. To make the ICA more portable, we have employed a smartphone and principal component analysis (PCA) to assist this on-site detection. As a proof-of-concept, clenbuterol (CLL) was analyzed by the proposed nanozymes-mediated dual-colorimetric ICA based on a smartphone. Notably, the proposed dual-colorimetric ICA exhibits high analytical performance for the quantification of CLL in the detection range of 0-6 ng mL-1 with a limit of detection (LOD) as low as 0.172 ng mL-1. Meanwhile, the proposed dual-colorimetric ICA exhibits remarkable feasibility and was successfully employed for the detection of CLL in pork and chicken matrixes.