Overview

Prospects and developments incell and embryo laser nanosurgeryVikram 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 thedevelopments that have occurred within the last several years in the fields of celland embryo nanosurgery. Each of the individual studies presented in this reviewclearly demonstrates the nondestructiveness of fs laser pulses, which are used toalter both cellular and subcellular sites within simple cells and more complicatedmulticompartmental embryos. The ability to manipulate these model systemsnoninvasively makes applied fs laser pulses an invaluable tool for developmentalbiologists, geneticists, cryobiologists, and zoologists. We are beginning to seethe integration of this tool into life sciences, establishing its status amongmolecular and genetic cell manipulation methods. More importantly, severalstudies demonstrating the versatility of applied fs laser pulses have establishednew collaborations among physicists, engineers, and biologists with the commonintent of solving biological problems. 2008 John Wiley & Sons, Inc. Wiley Interdiscipl. Rev. Nanomed. Nanobiotechnol. 2009 1 11–25

Several studies have reported the application offemtosecond (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 (700–900nm) delivering a sub-10 fs to 250 fs pulse at arepetition rate of 76 MHz to 1 kHz. The fs laserpulses were coupled to a high numerical aperture (NA)microscope objective, NA = 0.95–1.4, and localizedto cellular and subcellular sites. Beam dwell timesranged from milliseconds to seconds and pulseenergies delivered to the sample were 0.03 to severalnanojoules per pulse (nJ/pulse). Model systems thathave been used in fs laser pulse mediated nanosurgeryinclude human metaphase chromosomes,4 Chinesehamster and canine kidney epithelial cells,1,2 plantchloroplasts,5 mitochondria in endothelial and HeLacells,6,7 yeast microtubules,8 the actin cytoskeletonin fixed 3T3 fibroblast and bovine endothelialcells,6,9 hamster ovary cells,10,17 Caenorhabditiselegans,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.ca1Department of Electrical and Computer Engineering, University ofAlberta, Edmonton, Alberta, Canada

DOI: 10.1002/wnan.029

biological systems, intrachromosonal dissections,4

membrane surgery,1 cell isolation,1 cytoskeletal andmicrotubule ablation,6,8,9 knockdown of plastids,5

laser axotomy of neurons,11 intravascular disruptionof microvessels,13 cellular delivery of exogenous DNA,carbohydrates and quantum dots2,3,17 and the surgicalablation of Drosophila16 and zebrafish embryos3,15

have been demonstrated. In this paper, we present areview of current developments in fs laser mediatednanosurgery of cells and embryos with emphasis onthe fs laser as a tool able to induce ablation withhigh spatial resolution and with minimal transferof thermal and mechanical stresses to the materialinvestigated.

LASER INTERACTION WITH

BIOLOGICAL MATERIALS

Features that distinguish fs laser pulses from longerpulse durations (i.e., nanosecond pulses) include theability to localize cellular disruption to a sub-micronresolution, the low threshold energy needed to elicitablation and the lower conversion of energy intoshockwaves and cavitation bubbles, which are adverseside effects known to increase the spatial extentof cellular damage.18–22 When fs laser pulses arefocused 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 Wi ley & Sons, Inc. 11