Nucleic acid-responsive DNA functionalized Fe3O4@Zr-MOF/GOx colorimetric probe for ultrasensitive detection of Salmonella typhimurium

Salmonella typhimurium ( S. typhimurium ) contamination has become the main source of foodborne diseases and has substantial effects on human well-being. Herein, we present a nucleic acid-responsive colorimetric biosensor for ultrasensitive detection of S. typhimurium , integrating a multifunctional Fe 3 O 4 @Zr-MOF/GOx nanoprobe with exponential amplification reaction (EXPAR). The system integrates glucose oxidase (GOx) encapsulated within a Zr-based metal-organic framework (Zr-MOF) modified with magnetic Fe 3 O 4 nanoparticles. In the presence of S. typhimurium , the EXPAR reaction is triggered, and the controlled release of GOx is achieved by DNA strand displacement. The detection mechanism leverages GOx-catalyzed glucose oxidation to generate H 2 O 2 , which oxidizes 3,3’,5,5’-tetramethylbenzidine (TMB) for colorimetric signal readout. The biosensor demonstrates high specificity for S. typhimurium , with a detection limit of 2.26 CFU mL⁻¹ , and practical applicability in spiked milk samples, achieving recoveries of 89.6–111.5 %. The strategy employing stimuli-responsive DNA/MOF composites demonstrated significant potential in food quality monitoring and analysis.