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Proceedings Paper

Micromanipulation and physiological monitoring of cells using two-photon excited fluorescence in cw laser tweezers
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Paper Abstract

We report the observation of two-photon fluorescence excitation and cell confinement, simultaneously, in a continuous-wave (cw) single-beam gradient force optical trap, and demonstrate its use as an in-situ probe to study the physiological state of an optically confined cell sample. At the wavelength of 1064 nm, a single focused gaussian laser beam is used to simultaneously confine, and excite visible fluorescence from, a human sperm cell that has been tagged with propidium iodide, a exogenous fluorescent dye that functions as a viability assay of cellular physiological state. The intensity at the dye peak emission wavelength of 620 nm exhibits a near-square-law dependence on incident trapping beam photon laser power, a behavior consistent with a two-photon absorption process. In addition, for a sperm cell held stationary in the optical tweezers for a period of several minutes at a constant trapping power, red fluorescence emission was observed to increase the time, indicating that the cell has gradually transitioned between a live and dead state. Two-photon excited fluorescence was also observed in Chinese hamster ovary cells that were confined by cw laser tweezers and stained with either propidium iodide or Snarf, a pH-sensitive dye probe. These results suggest that, for samples suitably tagged with fluorescent probes and vital stains, optical tweezers can be used to generate their own in-situ diagnostic optical probes of cellular viability or induced photodamage, via two-photon processes.

Paper Details

Date Published: 10 May 1996
PDF: 7 pages
Proc. SPIE 2678, Optical Diagnostics of Living Cells and Biofluids, (10 May 1996); doi: 10.1117/12.239506
Show Author Affiliations
Gregory J. Sonek, 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 and Univ. of California (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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