Perovskite Quantum Dot/Mesoporous Silica Nanoparticles Loaded with Osmium Nanozymes for Fluorescent and Colorimetric Dual-Mode Lateral Flow Immunoassay of <i>Salmonella enterica</i> <i>Serovar Typhimurium</i>

In view of foodborne pathogens posing a huge threat to public health, the development of sensitive and time-sensitive detection methods for foodborne pathogens is of great significance. In this work, osmium nanozyme was innovatively assembled on perovskite quantum dot-embedded mesoporous silica nanoparticles to form a fluorescent (FL) and catalytic colorimetric (CL) PQD/MSN@Os nanolabel of dual-mode lateral flow immunoassay (LFIA) for sensitive and reliable detection of Salmonella enterica serovar Typhimurium (S. Typhimurium). Nanoscale PQD/MSN@Os showed stable green fluorescence, as well as excellent peroxidase-like activity with Michaelis–Menten constants of 0.36 and 2.36 mM for H2O2 and TMB, respectively. Anti-S. Typhimurium antibody-modified PQD/MSN@Os nanolabel could capture S. Typhimurium and be immobilized by a monoclonal antibody on the LFIA strip, presenting “turn-on” green FL and blue CL signals. Notably, PQD/MSN@Os-LFIA can determinate S. Typhimurium within 12 min and exhibited the qualitative naked-eye limits of detection (LODs) of 103 CFU/mL. The quantitative linear detection ranges of FL-LFIA and CL-LFIA mode were 103–107 CFU/mL and 103–108 CFU/mL with LODs of 9.79 × 102 and 6.96 × 102 CFU/mL, respectively. Moreover, the recoveries of S. Typhimurium spiked in orange juice and milk were 83.1–110.9%, with coefficients of variation ranging from 1.1 to 9.4% for PQD/MSN@Os-LFIA. These results indicated the proposed dual-mode PQD/MSN@Os-LFIA as a highly sensitive and specific sensing platform, exhibiting great potential for the rapid detection of foodborne pathogens.