Functionalized AgFeO₂ Particles as Fluorescent Platforms for the Detection of Salmonella spp

Rapid and accurate pathogen detection remains a major challenge in public health, particularly in food safety and biomedical diagnostics. Here, we present a highly sensitive biosensing platform based on silver ferrite (AgFeO₂) nanoparticles functionalized with 3-mercaptopropionic acid (3-MPA) and single-stranded DNA (ssDNA). The sensor enables ultrafast detection, with signal saturation reached in under 10 min, and achieves an analytical limit of detection (LoD) of 73 pmol L^-1 for Salmonella spp. DNA sequences. The platform also exhibits excellent selectivity, clearly distinguishing fully complementary targets from sequences containing base mismatches. Its versatility is further enhanced by the incorporation of SYBR Green I dye, enabling dual fluorescence-based detection and on-off sensing of double-stranded DNA (dsDNA). By combining high sensitivity, selectivity, and operational simplicity, the AgFeO₂@MPA/ssDNA biosensor demonstrates strong potential for applications in biotechnology, diagnostics, and food safety, with performance comparable to state-of-the-art biosensing technologies.