Self-oxygenating nanozyme-based biosensor for rapid detection of Salmonella typhimurium

We have developed a mannose biosensor that utilizes self-oxygenating catalytic nanozymes for rapid detection of Salmonella typhimurium. The mannose-functionalized manganese Prussian blue analogue (Man-MPN) serves dual functions: (1) Specific bacterial capture through FimH-mannose affinity (validated by TEM and zeta potential analysis), eliminating antibody dependency; (2) Self-sustaining oxidase-mimic catalysis that utilizes dissolved O₂ to oxidize 3, 3', 5, 5'-tetramethylbenzidine (TMB), generating blue oxidized TMB (oxTMB) signals without exogenous H₂O₂, where the Mn³⁺/Mn²⁺ redox cycling, as reported for analogous manganese-based catalysts, likely maintains continuous oxygen activation from ambient air to form an autocatalytic loop. This "capture-signaling" synergistic mechanism achieves detection within 15 min across 10³-10⁷ CFU/mL (LOD = 10³ CFU/mL), with catalytic enhancement improving sensitivity 10-fold versus conventional strips. Testing in spiked food matrices demonstrates recovery rates of 83.22 %-109.49 % for orange juice, milk, and chicken samples. Cross-reactivity remains below 5 % against seven foodborne pathogens (S. aureus, L. monocytogenes, etc.), while the H₂O₂-independent system maintains >90 % activity after 20-day storage. This self-oxygenating nanocapture platform provides a stable, cost-effective solution for on-site food safety monitoring.