A self-loading microfluidic device for determining the minimum inhibitory concentration of antibiotics

Area of Science:

• Biotechnology
• Microfluidics
• Medical Diagnostics

Background:

• Accurate determination of antibiotic minimum inhibitory concentration (MIC) is crucial for effective treatment of bacterial infections.
• Existing methods for MIC determination can be time-consuming and require specialized laboratory equipment.
• There is a need for rapid, portable, and user-friendly diagnostic tools for point-of-care settings.

Purpose of the Study:

• To develop and validate a portable microfluidic device for the straightforward determination of antibiotic MIC against various bacterial pathogens.
• To demonstrate the utility of a novel degas-driven flow mechanism for sample introduction and cell isolation in microfluidic devices.
• To compare the performance of the developed microfluidic device with standard liquid broth dilution methods for MIC determination.

Main Methods:

• Fabrication of a microfluidic chip using poly(dimethylsiloxane) (PDMS) with preloaded, dried antibiotics in a chamber array.
• Utilizing vacuum-induced degassing of PDMS to actuate and meter fluid flow for introducing bacterial suspensions.
• Visual detection of bacterial growth via colorimetric change using a pH indicator, enabled by ambient light observation.

Main Results:

• The microfluidic device successfully determined the MIC of vancomycin, tetracycline, and kanamycin against common human pathogens, including E. faecalis, P. mirabilis, K. pneumoniae, and E. coli.
• MIC values obtained using the portable device were comparable to those determined by standard liquid broth dilution methods.
• The device demonstrated effective isolation of bacterial cells in individual chambers without cross-contamination, facilitated by the novel degas-driven flow system.

Conclusions:

• The developed portable microfluidic technology offers a simple, efficient, and visually-read method for antibiotic MIC determination.
• This technology has significant potential for clinical diagnostics and point-of-care medicine, enabling rapid assessment of antibiotic susceptibility.
• The innovative valve-free microfluidic chamber filling and isolation approach is applicable to a broader range of portable assay development.