Single cell level detection of Escherichia coli in microfluidic device

Area of Science:

• Biotechnology
• Microfluidics
• Biosensing

Background:

• Accurate detection of Escherichia coli (E. coli) is crucial for public health and food safety.
• Traditional methods for E. coli detection can be time-consuming and require extensive sample preparation.
• Microfluidic devices offer potential for rapid, sensitive, and portable bacterial detection.

Purpose of the Study:

• To develop and validate a microfluidic device for the sensitive detection of E. coli K-12.
• To utilize latex immunoagglutination coupled with optical fiber sensing for bacterial quantification.
• To assess the impact of washing steps on detection limits and specificity.

Main Methods:

• A Y-channel polydimethylsiloxane (PDMS) microfluidic device was employed.
• Latex immunoagglutination assay using polystyrene particles conjugated with anti-E. coli antibodies.
• Optical fiber monitoring of 45-degree forward light scattering to quantify agglutination.
• Comparison of detection limits with and without phosphate-buffered saline (PBS) washing steps.

Main Results:

• The microfluidic device successfully detected E. coli K-12 without pre-treatments like cell lysis or culturing.
• Detection limits were <10 CFU/mL without PBS washing (including non-viable cells and free antigens) and <40 CFU/mL with PBS washing (viable cells only).
• Optical fiber sensing quantified the increase in light scattering due to immunoagglutination.

Conclusions:

• The developed microfluidic device provides a sensitive and rapid method for E. coli K-12 detection.
• The system demonstrates the potential for distinguishing between viable and non-viable bacterial cells through washing protocols.
• This approach holds promise for point-of-care diagnostics and environmental monitoring applications.