Defect-rich intermetallic Pt3Sn nanocrystals as colorimetric signal amplifiers for sensitive immunochromatographic detection of early-stage bacterial contamination.

Early detection of pathogenic bacterial infections is crucial for mitigating risks, yet conventional assays face limited adoption due to their dependence on laborious protocols, specialized instruments/personnel, and slow turnaround times. While colorimetric lateral flow immunoassays (CLFIA) offer an efficient and convenient alternative, their sensitivity remains insufficient for detecting early-stage bacterial contamination primarily constrained by inadequate colorimetric signal intensity. Here, we integrate defect-rich intermetallic Pt3Sn nanocrystals (D-Pt3Sn NCs) as colorimetric signal amplifiers to develop an enzyme-accelerated signal enhancement (EASE)-based CLFIA for the detection of early-stage bacterial contamination. D-Pt3Sn NCs exhibit enhanced peroxidase-like activity than Pt3Sn NCs without surface depressions, and superior tolerance and stability under extreme environments relative to natural horseradish peroxidase. Upon integration with the EASE-based CLFIA platform, D-Pt3Sn NCs enable sensitive immunochromatographic analysis of Escherichia coli O157:H7 (E. coli O157:H7) with a visual detection sensitivity of 10 CFU/mL. Besides, proof-of-concept assays for detecting E. coli O157:H7 in cabbage and beef samples validate the anti-matrix interference capability and practicality of this platform. Overall, defect-rich intermetallic nanocrystals hold promise as versatile catalytic colorimetric signal amplifiers, enabling highly-sensitive immunochromatographic detection of trace-level analytes in complex matrices.