Phenotyping and Selection of Cells Using Mass Spectrometry and a Microfluidic Droplet Printer

Area of Science:

• Biotechnology
• Analytical Chemistry
• Microfluidics

Background:

• High-throughput screening is crucial in biotechnology for cell-based assays.
• Current methods often rely on fluorescent readouts, limiting label-free analysis.
• Droplet microfluidics offers potential for high-throughput screening but requires advanced detection methods.

Purpose of the Study:

• To develop an integrated system for label-free cell phenotyping and selection using droplet microfluidics.
• To enable online analysis and capture of cell-containing droplets for downstream applications.
• To demonstrate the system's capability in analyzing and sorting microbial cells based on chemical profiles.

Main Methods:

• Integration of droplet electrospray ionization-mass spectrometry (ESI-MS) with a microfluidic voltage-mediated droplet printer.
• Splitting of cell-containing droplets for simultaneous MS analysis and printing onto agar.
• Utilizing a sheath-flow ESI source for MS analysis and a microfluidic printer for droplet deposition.
• Mapping of printed microbial colonies back to their corresponding ESI-MS signals with high accuracy.

Main Results:

• Achieved 94-99% accuracy in mapping microbial colonies to their droplet ESI-MS signals without carryover.
• Demonstrated stable system operation at infusion rates of 0.4-1.2 droplets/s.
• Successfully phenotyped and selected an engineered Escherichia coli variant for l-lysine production.

Conclusions:

• The developed system provides a powerful tool for label-free, high-throughput cell analysis and selection.
• This technology has potential applications in synthetic biology, enzyme engineering, and microbial strain development.
• Enables screening of cell colonies for chemical composition and subsequent collection for further processing.