Sorting by interfacial tension (SIFT): Label-free enzyme sorting using droplet microfluidics.

Area of Science:

• Biochemistry
• Microfluidics
• Chemical Engineering

Background:

• Droplet microfluidics enhances enzyme screening and sorting by encapsulating reagents in picoliter droplets.
• Enzymatic reactions often alter solution pH, a property that can be leveraged for sorting.
• Interfacial tension of droplets can be modulated by pH using specific surfactants.

Purpose of the Study:

• To develop a label-free method for high-throughput enzyme sorting using droplet microfluidics.
• To demonstrate the sorting of enzymes based on pH changes resulting from their activity.
• To introduce droplet sorting by interfacial tension (SIFT) as a novel technology for enzyme evolution.

Main Methods:

• Utilizing droplet microfluidics with a specific surfactant that makes droplet interfacial tension pH-sensitive.
• Confining droplets in a microfabricated trench to enable sorting based on interfacial tension differences.
• Tracking enzymatic reaction progress by monitoring droplet positions in a flow stream.

Main Results:

• Demonstrated successful sorting of esterase isoenzymes based on their enzymatic activity.
• Showcased the pH-sensitivity of droplet interfacial tension for sorting applications.
• Validated the label-free nature of the SIFT technology.

Conclusions:

• Droplet sorting by interfacial tension (SIFT) is a novel, label-free technology for high-throughput enzyme sorting.
• SIFT requires no active components and is suitable for enzyme screening and directed evolution.
• This method offers a scalable approach for advancing enzyme discovery and engineering.