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Proceedings Paper

How safe is gamete micromanipulation by laser tweezers?
Author(s): Karsten Koenig; Bruce J. Tromberg; Yona Tadir M.D.; Michael W. Berns
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Paper Abstract

Laser tweezers, used as novel sterile micromanipulation tools of living cells, are employed in laser-assisted in vitro fertilization (IVF). For example, controlled spermatozoa transport with 1064 nm tweezers to human egg cells has been performed in European clinics in cases of male infertility. The interaction of approximately 100 mW near infrared (NIR) trapping beams at MW/cm2 intensity with human gametes results in low mean less than 2 K temperature increases and less than 100 pN trapping forces. Therefore, photothermal or photomechanical induced destructive effects appear unlikely. However, the high photon flux densities may induce simultaneous absorption of two NIR photons resulting in nonlinear interactions. These nonlinear interactions imply non-resonant two-photon excitation of endogenous cellular chromophores. In the case of less than 800 nm tweezers, UV- like damage effects may occur. The destructive effect is amplified when multimode cw lasers are used as tweezer sources due to longitudinal mode-beating effects and partial mode- locking. Spermatozoa damage within seconds using 760 nm traps due to formation of unstable ps pulses in a cw Ti:Sa ring laser is demonstrated. We recommend the use of greater than or equal to 800 nm traps for optical gamete micromanipulation. To our opinion, further basic studies on the influence of nonlinear effects of laser tweezers on human gamete are necessary.

Paper Details

Date Published: 29 April 1998
PDF: 7 pages
Proc. SPIE 3260, Optical Investigations of Cells In Vitro and In Vivo, (29 April 1998); doi: 10.1117/12.307112
Show Author Affiliations
Karsten Koenig, Friedrich-Schiller-Univ. Jena (Germany)
Bruce J. Tromberg, Beckman Laser Institute and Medical Clinic (United States)
Yona Tadir M.D., Beckman Laser Institute and Medical Clinic (United States)
Michael W. Berns, Beckman Laser Institute and Medical Clinic (United States)

Published in SPIE Proceedings Vol. 3260:
Optical Investigations of Cells In Vitro and In Vivo
Robert C. Leif; Daniel L. Farkas; Robert C. Leif; Bruce J. Tromberg, Editor(s)

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