Detection of pathogenic Salmonella with nanobiosensors

Abstract

Rapid detection methods are needed to identify pathogenic Salmonella spp. in food products to protect against outbreaks of salmonellosis. The objective of this study was to explore the feasibility of using quantum dot nanoparticles to rapidly detect pathogenic Salmonella. Selective detection was achieved with anti-Salmonella polyclonal antibodies immobilized by streptavidin–biotin binding or covalent binding to the quantum dot surface. Superparamagnetic particles were used to separate and concentrate cells from each sample. A portable fluorometer was developed to measure fluorescence signals from quantum dot nanoparticles adhered to Salmonella in the samples. The fluorometer was composed of a 415 nm UV LED, a bifurcated fiber, optical filters, and a silicon photomultiplier. Detection sensitivity was evaluated with serially diluted Salmonella typhimurium in phosphate-buffered saline containing 1% bovine serum albumin (PBS–BSA) or food extracts. Fluorescence of the nanobiosensor increased with increasing concentrations of bacteria. Salmonella detection limits were 1.4 × 10³ CFU mL⁻¹ in PBS–BSA and 4 × 10³ CFU mL⁻¹ in food extracts.