High-throughput sorting and analysis of human sperm with a ring-shaped laser trap

Area of Science:

• Biophysics
• Reproductive Biology
• Cellular Mechanics

Background:

• Sperm motility is crucial for fertility research.
• Existing single-spot laser tweezers offer limited throughput and sorting capabilities for sperm analysis.
• High laser power and inability to dynamically monitor sperm behavior are limitations of current methods.

Purpose of the Study:

• To develop a high-throughput, multi-level sperm sorting method using optical trapping.
• To enable in-situ sorting based on sperm motility and chemotaxis.
• To investigate sperm behavior and energetics under controlled laser irradiation.

Main Methods:

• A continuous 3-D ring-shaped laser trap was designed and implemented.
• The trap allows for parallel sorting of tens to hundreds of sperm per ring.
• Low to medium velocity human sperm are manipulated using optical gradient force.

Main Results:

• The ring-shaped trap achieves high-throughput sperm sorting based on motility and chemotaxis.
• Lower laser power (tens of milliWatts) is sufficient compared to previous methods.
• Sperm trajectories are altered, allowing for dynamic monitoring and analysis of laser-induced effects.

Conclusions:

• This novel optical trapping system represents the first demonstration of parallel sperm sorting by motility.
• The method offers a gentler and more quantitative approach to study sperm energetics and behavior.
• Potential applications extend to motility and bio-tropism studies of other self-propelled cells like algae and bacteria.