1. Overview
Prospects and developments in
cell and embryo laser nanosurgery
Vikram Kohli∗ and Abdulhakem Y. Elezzabi1
Recently, there has been increasing interest in the application of femtosecond (fs)
laser pulses to the study of cells, tissues and embryos. This review explores the
developments that have occurred within the last several years in the fields of cell
and embryo nanosurgery. Each of the individual studies presented in this review
clearly demonstrates the nondestructiveness of fs laser pulses, which are used to
alter both cellular and subcellular sites within simple cells and more complicated
multicompartmental embryos. The ability to manipulate these model systems
noninvasively makes applied fs laser pulses an invaluable tool for developmental
biologists, geneticists, cryobiologists, and zoologists. We are beginning to see
the integration of this tool into life sciences, establishing its status among
molecular and genetic cell manipulation methods. More importantly, several
studies demonstrating the versatility of applied fs laser pulses have established
new collaborations among physicists, engineers, and biologists with the common
intent of solving biological problems.
© 2008 John Wiley & Sons, Inc. Wiley Interdiscipl. Rev. Nanomed. Nanobiotechnol. 2009 1 11–25
Several studies have reported the application of
femtosecond (fs) laser pulses as a precise scalpel
tool for performing cellular surgery.1–17
In each study,
fs laser pulses were produced from a titanium sapphire
(Ti:Sapphire) laser oscillator or amplifier (700–900
nm) delivering a sub-10 fs to 250 fs pulse at a
repetition rate of 76 MHz to 1 kHz. The fs laser
pulses were coupled to a high numerical aperture (NA)
microscope objective, NA = 0.95–1.4, and localized
to cellular and subcellular sites. Beam dwell times
ranged from milliseconds to seconds and pulse
energies delivered to the sample were 0.03 to several
nanojoules per pulse (nJ/pulse). Model systems that
have been used in fs laser pulse mediated nanosurgery
include human metaphase chromosomes,4 Chinese
hamster and canine kidney epithelial cells,1,2 plant
chloroplasts,5
mitochondria in endothelial and HeLa
cells,6,7
yeast microtubules,8
the actin cytoskeleton
in fixed 3T3 fibroblast and bovine endothelial
cells,6,9
hamster ovary cells,10,17
Caenorhabditis
elegans,11,12 Drosophila melanogaster,16 Sprague-
Dawley rats and Danio rerio (zebrafish).13 Using these
∗
Correspondence to: Vikram Kohli, University of Alberta, Edmon-
ton, Alberta, Canada.
E-mail: vkohli@ece.ualberta.ca
1Department of Electrical and Computer Engineering, University of
Alberta, Edmonton, Alberta, Canada
DOI: 10.1002/wnan.029
biological systems, intrachromosonal dissections,4
membrane surgery,1
cell isolation,1
cytoskeletal and
microtubule ablation,6,8,9 knockdown of plastids,5
laser axotomy of neurons,11
intravascular disruption
of microvessels,13 cellular delivery of exogenous DNA,
carbohydrates and quantum dots2,3,17
and the surgical
ablation of Drosophila16
and zebrafish embryos3,15
have been demonstrated. In this paper, we present a
review of current developments in fs laser mediated
nanosurgery of cells and embryos with emphasis on
the fs laser as a tool able to induce ablation with
high spatial resolution and with minimal transfer
of thermal and mechanical stresses to the material
investigated.
LASER INTERACTION WITH
BIOLOGICAL MATERIALS
Features that distinguish fs laser pulses from longer
pulse durations (i.e., nanosecond pulses) include the
ability to localize cellular disruption to a sub-micron
resolution, the low threshold energy needed to elicit
ablation and the lower conversion of energy into
shockwaves and cavitation bubbles, which are adverse
side effects known to increase the spatial extent
of cellular damage.18–22
When fs laser pulses are
focused to a high peak intensity of 1011
–1013
W/cm2
,
optical breakdown occurs, resulting in the ablation of
Volume 1, January/February 2009 © 2008 John Wiley & Sons, Inc. 11