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Proceedings Paper

Two-photon excitation in living cells induced by low-power cw laser beams
Author(s): Karsten Koenig; Tatjana B. Krasieva; Yagang Liu; Michael W. Berns; Bruce J. Tromberg
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Paper Abstract

We demonstrate multi-photon excitation in optically-trapped living cells. Intracellular non-resonant two-photon excitation of endogenous and exogenous chromophores was induced by CW near infrared (NIR) trapping beams of 105 mW power. In the case of fluorescent chromophores, detection of NIR-excited visible fluorescence was achieved by imaging and spectroscopy methods. Trap-induced, two-photon excited fluorescence was employed as a novel diagnostic method to monitor intracellular redox state and cell vitality of single motile spermatozoa and Chinese hamster ovary cells. We found, that nonlinear absorption of NIR photons <800 nm may lead to oxidative stress and severe cell damage. Biological response was amplified in multimode CW lasers due to longitudinal mode-beating and partial mode- locking. As a result, we recommend the use of longwavelength-NIR, single-frequency traps ("optical tweezers") for micromanipulation of vital cells.

Paper Details

Date Published: 10 May 1996
PDF: 8 pages
Proc. SPIE 2678, Optical Diagnostics of Living Cells and Biofluids, (10 May 1996); doi: 10.1117/12.239503
Show Author Affiliations
Karsten Koenig, Friedrich Schiller Univ. and Institute of Molecular Biotechnology (Germany)
Tatjana B. Krasieva, Beckman Laser Institute and Medical Clinic (United States)
Yagang Liu, Beckman Laser Institute and Medical Clinic (United States)
Michael W. Berns, Beckman Laser Institute and Medical Clinic (United States)
Bruce J. Tromberg, Beckman Laser Institute and Medical Clinic (United States)

Published in SPIE Proceedings Vol. 2678:
Optical Diagnostics of Living Cells and Biofluids
Daniel L. Farkas; Robert C. Leif; Alexander V. Priezzhev; Toshimitsu Asakura; Bruce J. Tromberg, Editor(s)

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