Single cell viability and impact of heating by laser absorption

Area of Science:

• Biophysics
• Cell Biology
• Optical Tweezers

Background:

• Optical traps (tweezers, stretchers) are vital for probing cell mechanics.
• Infrared laser light in optical traps induces significant cellular heating.
• Existing viability assays lack sensitivity for short-term, single-cell heat damage.

Purpose of the Study:

• To investigate the impact of laser-induced heating on cell viability.
• To establish cell spreading as a sensitive viability marker for optical trap experiments.
• To quantify cell survival thresholds under simulated heat shock conditions.

Main Methods:

• Utilized an optical stretcher (two-beam laser trap) to induce controlled heat shocks.
• Simulated thermal stress experienced by cells during optical trap measurements.
• Assessed cell viability using cell spreading as a novel, sensitive indicator.

Main Results:

• Approximately 60% of cells survived heat shocks up to 58 ± 2°C for 0.5 seconds without vital damage.
• Cell viability was maintained in 60% of cells exposed to 48 ± 2°C for 5 seconds.
• Demonstrated the sensitivity of cell spreading as a viability marker under thermal stress.

Conclusions:

• Cell spreading is a practical and sensitive marker for assessing viability after short-term heat exposure.
• Optical trap-induced heating can be tolerated by cells within specific temperature and duration limits.
• Findings provide crucial data for optimizing optical trap experiments to minimize thermal damage to cells.