The development of a simple, rapid and sensitive method for foodborne pathogens is essential to ensure public health safety. Existing methods, such as culture-based techniques and polymerase chain reaction (PCR), often face challenges in terms of time-consuming, labor-intensive, and require extensive sample preparation and amplification, which makes them impractical for rapid or on-site pathogen detection. Herein, a competitive mechanism-driven electrochemiluminescence (ECL) aptasensor was constructed for Salmonella typhimurium (S. typhimurium) detection without nucleic acid extraction and amplification. To boost the ECL signal of luminol-H₂O₂ systems, in-situ anchoring of Pt nanoclusters on mesoporous Mn₃O₄ nanoparticles (Pt NCs@M-Mn₃O₄) used as the nanoconfinement co-reactor. Benefitting from the restricted mesoporous structure, Pt NCs@M-Mn₃O₄ provided a unique microenvironment for the enrichment of H₂O₂. Furthermore, the interfacial interaction could activate the electronic transfer between active species of Pt NCs and M-Mn₃O₄, enabling a synergistic catalytic effect on ROS generation to effectively boost the ECL emission of luminol. The proposed ECL aptasensor had a linear concentration from 2 × 10¹ to 2 × 10⁶ CFU/mL with limit of detection of 8 CFU/mL of S. typhimurium. Furthermore, the method showed high anti-interference ability. Especially, satisfactory recovery values in spiked-actual samples were obtained, thereby demonstrating great potential for sensitive and reliable detection of S. typhimurium in various environments.

Salmonella Typhimurium (S. Typhimurium) is an important foodborne pathogen, its harm is mainly reflected in high pathogenicity, clinical manifestations, and drug resistance. The detection technology for this pathogen is gradually shifting from traditional methods to rapid and highly sensitive molecular biological methods. In order to solve the sensitivity and specificity of Salmonella detection, we built a fluorescent biosensor with an antibody-target-aptamer sandwich structure based on immune recognition and aptamer technology for quantitative detection of S. Typhimurium. By integrating the heterogeneous recognition mode composed of antibody and aptamer with isothermal hybridization chain reaction (HCR), this approach enables highly specific detection of Salmonella while significantly enhancing detection sensitivity through signal amplification. In the HCR hairpin structure, site-specific labeling of the fluorophore and quencher enables fluorescence signal generation via fluorescence resonance energy transfer (FRET), thereby achieving efficient optical signal output. The results show that the proposed enzyme-free heterogeneous recognition mode sensor has a detection limit of 9 CFU/mL and a 10-10⁴ CFU/mL detection range under optimized conditions. It also has good detection performance in milk and drinking water, which are common sources of S. Typhimurium contamination.

In this study, an aptamer-functionalized magnetic bead-based fluorescence sensor for the detection of Cronobacter sakazakii in milk powder using hybridization chain reaction (HCR) amplification was constructed. First, the sequence HP, combining a trigger sequence and an aptamer sequence which complement each other to form a stable secondary structure, and the hairpin sequences H1 and H2 were cleverly designed. Then, aptamer-functionalized magnetic beads were prepared by pentanediol reaction and avidin-biotin reaction. C. sakazakii was incubated with the aptamer magnetic beads. The aptamer sequence in HP recognized the target, causing conformational change of HP to expose its trigger sequence. The chain assembly of H1 and H2 was triggered by HCR to produce long double-stranded DNA, and the fluorescent dye SYBR Green I (SG) bound to the long double strands of HCR products by intercalation and slot binding. Finally, graphene oxide (GO) was added to adsorb free H1, H2 and SG on its surface via π-π stacking, so the fluorescence signal was quenched. However, the HCR products could not be adsorbed on the surface of GO, so SG binding to the HCR product emitted a strong fluorescence signal dependent on the target concentration, thus allowing quantitative detection of C. sakazakii. The detection limit of this method was 2 CFU/mL for pure culture and 8 CFU/g for milk powder. It gave results for milk powder samples in good agreement with those obtained by the traditional microbial culture method. This method has the advantages of no requirement for DNA extraction, fast operation, high stability, specificity and sensitivity, so it provides a potential method for the on-site rapid detection of C. sakazakii.