Simultaneous Sensing of Seven Pathogenic Bacteria by Guanidine-Functionalized Upconversion Fluorescent Nanoparticles

Area of Science:

• Analytical Chemistry
• Nanotechnology
• Food Safety

Background:

• Simultaneous detection of multiple bacterial pathogens is crucial for food safety.
• Existing methods often lack the sensitivity or specificity required for comprehensive surveillance.
• Development of rapid and reliable detection systems is of significant interest.

Purpose of the Study:

• To develop a straightforward upconversion fluorescence sensing approach for simultaneous detection of seven common foodborne bacteria.
• To construct a guanidine-functionalized upconversion fluorescent nanoparticle (UCNPs@GDN) based nanosensor.
• To evaluate the nanosensor's performance in quantifying bacteria in both mixed and single cultures, as well as in real-world samples.

Main Methods:

• Fabrication of a fluorescent nanosensor using guanidine-functionalized upconversion fluorescent nanoparticles (UCNPs@GDN), tannic acid, and hydrogen peroxide.
• Utilizing the luminescence enhancement of UCNPs@GDN in the presence of bacteria for quantification.
• Testing the nanosensor's efficacy for simultaneous detection of *Escherichia coli*, *Salmonella*, *Cronobacter sakazakii*, *Shigella flexneri*, *Vibrio parahaemolyticus*, *Staphylococcus aureus*, and *Listeria monocytogenes*.

Main Results:

• The nanosensor achieved a linear detection range of 10^3 to 10^8 CFU mL^-1 for a mixture of seven bacteria.
• A low detection limit of 1.30 × 10^2 CFU mL^-1 was obtained for the bacterial mixture.
• Similar performance was observed for single bacterial detection, with acceptable recovery rates (70.0–118.2%) in real samples like water, milk, and beef.

Conclusions:

• The developed guanidine-functionalized upconversion fluorescent nanosensor provides a promising approach for rapid and simultaneous detection of multiple foodborne pathogens.
• This method demonstrates potential for effective surveillance of microbial contamination in food and water.
• The nonspecific quantification mechanism offers a versatile tool for bacterial detection.