Quantification of bacterial cells based on autofluorescence on a microfluidic platform

Area of Science:

• Analytical Chemistry
• Biotechnology
• Microfluidics

Background:

• Bacterial quantification is crucial for pathogen detection, hygiene monitoring, and ensuring public health.
• Accurate and rapid bacterial counting methods are essential in food and pharmaceutical production.
• Current methods can be time-consuming or require labeling, necessitating simpler, faster alternatives.

Purpose of the Study:

• To develop and demonstrate a microfluidic chip for quantifying bacterial cell numbers.
• To utilize the intrinsic autofluorescence of bacterial cell lysates for detection.
• To establish a label-free, on-chip method for bacterial quantification.

Main Methods:

• Bacterial cells were lysed on-chip within a microfluidic device.
• Lysates were analyzed using laser-induced fluorescence detection under electrophoresis.
• Autofluorescence intensity was measured and correlated with cell numbers for three model pathogens.

Main Results:

• A nearly linear relationship was observed between autofluorescence intensity and bacterial cell count for Listeria monocytogenes, Salmonella Enteritidis, and Escherichia coli.
• The method successfully quantified bacterial loads from 240 to 4100 cells.
• A single fluorescence peak was detected even when analyzing mixtures of different bacterial species.

Conclusions:

• The developed microfluidic device provides a simple, fast, and label-free solution for on-chip bacterial cell quantification.
• The method leverages inherent bacterial autofluorescence, eliminating the need for external labeling agents.
• This approach holds potential for broader application across various bacterial species and diagnostic scenarios.