SPECTROSCOPY, IMAGING, OTHER TECHNIQUES |
Quantitative characterization of biological liquids for
third-harmonic generation microscopy
Delphine Débarre 1 and Emmanuel Beaurepaire 1*
1 CNRS - Ecole Polytechnique
* To whom correspondence should be addressed. E-mail: emmanuel.beaurepaire{at}polytechnique.edu.
Submitted on August 17, 2006
Revised on October 3, 2006
Accepted on 6 October 2006
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Abstract |
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Third-harmonic generation (THG) provides images of unstained biological samples based on spatial variations in third-order nonlinear susceptibility, refractive index, and dispersion. In this study, we establish quantitative values for the third-order nonlinear susceptibilities of several solvents (water, ethanol, glycerol), physiological aqueous (ions, amino-acids, polypeptides, bovine serum albumin, glucose) and lipid (triglycerydes, cholesterol) solutions as a function of solute concentration in the 1.05 µm-1.25 µm excitation range. We use these data in conjunction with imaging experiments to show that THG imaging around 1.2 µm lacks specificity and sensitivity to detect physiological ion concentration changes, and that non-aqueous structures such as lipid bodies provide a more robust source of signal. Finally we illustrate the impact of index-matching liquids in THG images. These data provide a basis for interpreting biological THG images and for developing additional applications.
Key Words:
Lipid droplets, Multiphoton microscopy, Third-harmonic generation microscopy, Third-order nonlinear susceptibility measurements
