Plasma-mediated ablation: an optical tool for submicrometer surgery on neuronal and vascular systems

Abstract

Plasma-mediated ablation makes use of high energy laser pulses to ionize molecules within the first few femtoseconds of the pulse. This process leads to a submicrometer-sized bubble of plasma that can ablate tissue with negligible heat transfer and collateral damage to neighboring tissue. We review the physics of plasma-mediated ablation and its use as a tool to generate targeted insults at the subcellular level to neurons and blood vessels deep within nervous tissue. Illustrative examples from axon regeneration and microvascular research illustrate the utility of this tool. We further discuss the use of ablation as an integral part of automated histology.The classic application of light microscopy to studies in physiology is observational; the illumination is too weak to affect the preparation. Yet the focused illumination in light microscopy can be strong enough to influence the chemical and physical structure of the sample and thus constitutes a means to manipulate living preparations. At the level of molecular studies, optical tweezers allow the application of forces and torques to individual molecules attached to dielectric microspheres [1,2]. At the level of subcellular organelles, photo-switching of fluorescent labels can toggle molecules between active and inactive states [3,4], while photo-activation of ions and small molecules provide a means to alter the chemical milieu within diffraction-limited volumes [5]. At the level of cells, photoswitching of bound ligands can lead to agonist binding [6], while light-activated membrane channels and pumps provide a means to change the electrical potential across cell membranes [7] Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. [8,9]. This last application is the subject of this review. NIH Public Access Principles and practice of plasma-mediated ablationPulsed laser systems easily achieve the high instantaneous peak powers necessary to induce nonlinear absorption, while maintaining sufficiently low average powers to avoid linear heating of the sample. This enables nonlinear imaging of biological structure and function [10], including two-photon laser scanning microscopy [11][12][13], second [14][15][16] and third harmonic [17][18][19][20][21][22] imaging, and coherent anti-stokes Raman spectroscopy [23,24]. The critical issue, especially for in vivo imaging, is that the nonlinear absorption allows excitation to occur only in the focus volume so that all excited molecules are a potential source of signal. Thus optical sectioning is performed solely by the excitation beam. Fluorescently labeled cells deep below th...

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“…There are several good discussions of laser microsurgery with different laser systems 3,[5][6][7][8][9][10][11] . Femtosecond IR lasers are the "gold standard" for subcellular laser ablation 12 and convenient if associated with an imaging facility, but they are often too costly for individual users.…”

“…Put in the ND4 and ND8 filter in intermediate module. 10. Image the target slide with your CLSM, Spinning disk, or CCD camera system.…”

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Pulsetrain-burst mode, ultrafast-laser interactions with 3D viable cell cultures as a model for soft biological tissues

“…Unlike long-pulse (i.e., >1 μs laser-pulse duration) laser ablation, which relies on linear absorption into endogenous chromophores (e.g., water), tissue ablation with ultrafast-laser pulses is plasma-mediated [12], offering submicrometer-scale precision [15], applicable over a broad range of tissues of varying optical and mechanical properties. Moreover, the collateral damage (e.g., cracking, charring) from ultrafast-laser ablation is small compared to most long-pulsed laser surgeries.…”