We monitored cell viability and damage under femtosecond laser irradiation using aser weezers Raman pectroscopy
(LTRS) which is becoming a powerful tool for the analysis of biological materials. Femtosecond lasers are more
frequently used as a light source for optical tweezers since they enable nonlinear optical phenomena such as two-photon
absorption or second harmonic generation trapping. Femtosecond laser optical trapping similar to thee CW laser optical
trapping except that optical damage can be easily induced due to extremely high peak power of femtosecond pulses. We
monitored the Raman signal changes as a marker for optical damage. We used red blood cell (RBC) as a target sample
and first used the CW laser beams to trap the RBC from the bottom of the chamber. After the trapped RBC is moved to a
desired depth, we switched the laser mode to mode-locked mode and monitored the Raman signals as a function of the
laser irradiation time. It was observed that the Raman shift at 1543 cm-1 may be a good marker for optical damage both
for CW and femtosecond laser trapping.
We constructed a high-speed laser line-scanning confocal microscope (LSCM) using He-Ne laser (633 nm), a line CCD
camera, and an acousto-optic deflector (AOD). The line scanner consists of an AOD and a cylindrical lens, which create
a line focus sweeping over the sample. The line scanner generates two-dimensional confocal images (512× 512 pixel
image) up to 191 frames per second with no mechanically-moving parts. This system is configured as an inverted
microscope for imaging biological organisms or tissues. Images of various biological samples were obtained including
rabbit cornea, onion cells, mouse melanoma tumor cells (B16BL6), and human breast tumor cells (BT-20). The frame
rate may be further improved up to over 700 frames per second when the image size is reduced (512×128 pixel image).
This system may be useful for analyzing fast phenomena during biological and chemical interactions and for imaging 3D
structures rapidly.
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