Development of a portable dropper-based biosensor for rapid and cost-effective detection of Salmonella typhimurium in food samples

Background

Foodborne pathogens such as Salmonella typhimurium continue to pose a major threat to public health worldwide. Rapid and reliable on-site screening is crucial to preventing foodborne outbreaks, yet conventional methods such as culture, PCR, and ELISA are time-consuming, require bulky instruments, and lack portability. These limitations are especially problematic in decentralized or resource-limited settings. Current diagnostic tools are inadequate for addressing the need for fast, low-cost, and equipment-free pathogen detection in complex food matrices. Therefore, there is an urgent demand for portable biosensing platforms capable of delivering sensitive and specific results directly at the point-of-need. (94)

Results

We developed a dropper-based biosensor that integrates sample mixing, magnetic separation, and nanozyme-based colorimetric detection within a disposable plastic dropper. The assay involves aspirating the food sample, antibody-functionalized magnetic beads, and Au@Pt nanozymes into the dropper, followed by repeated manual squeezing for incubation. A static magnetic field isolates bead–bacteria–nanozyme complexes from unbound reagents. Upon addition of TMB substrate, a visible color change is triggered by the nanozyme, which can be quantified using a smartphone. Under optimal conditions, the biosensor achieved a linear detection range from 5 × 10¹ to 5 × 10⁶ CFU/mL and a detection limit of 16 CFU/mL. The entire workflow is completed within 40 min. Specificity studies confirmed no cross-reactivity with non-target bacteria, and the platform demonstrated consistent performance in spiked milk, juice, and chicken meat samples, validating its robustness in diverse food matrices. (143)

Significance

This study presents a portable and affordable tool for rapid pathogen screening, requiring no instruments or professional training. The integration of manual operation, magnetic separation, and smartphone readout offers a practical solution for food safety monitoring in field or low-resource environments. This work advances point-of-care biosensing by offering a simplified yet effective approach to detect Salmonella typhimurium with high sensitivity, specificity, and operational ease. (66)