Dr. Eric O. Potma, Ph.D.
School of Physical Sciences
University of California
Irvine, CA 92697, United States
Phone: +1 (949) 824-9942
One of the challenges in biological imaging is to efficiently probe molecular targets, while maintaining sample integrity and ensuring that other off-target molecules remain optically unresponsive. Vibrational excitation of molecules is a natural choice to achieve such chemically selective contrast, as it allows nondestructive and label-free imaging of biological samples.
Coherent Raman scattering (CRS) microscopy is a form of optical imaging based on vibrational contrast. The technique, in the form coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) excitation schemes, has gained popularity as a label-free imaging tool in biology and material sciences. As a biomedical imaging method, CRS continues to make an impact in the fields of lipid metabolism and lipid disease. Besides the quantitative detection of lipids in tissues, CRS microscopy also enables the detection of water, protein and nucleic acids in tissues, in addition to topically applied drugs.
In this lecture we will zoom into the basics of the CRS interaction and how it can be used as a probe in an optical microscope. The physics behind CRS will be explained in an intuitive yet thorough fashion, an overview recent CRS imaging applications in biology will be given, and a critical look into the future will be provided.
Figure Caption: Gallery of CRS images. (a) SRS image of a meibomian gland at the symmetric CH2 stretch of 2850 cm-1 (single frequency) (b) Principal component analysis (PCA) of spectral SRS image in the range 2750–3100 cm-1. Different colors correspond to pixels with different vibrational spectra. (c) Principal component analysis (PCA) of spectral image of a human lung cancer cell (range 2750–3100 cm-1). (d) Vertex component analysis (VCA) of a spectral SRS image of an atherosclerotic plaque from macaque aorta human (range 2750 – 3100 cm-1). (d) VCA of a spectral SRS image of mouse muscle fibers (range 2750–3100 cm-1). (d) VCA of a spectral SRS image a human lung cancer cell (range 2750–3100 cm-1).
A. Alfonso-García, R. Mittal, E. S. Lee, and E. O. Potma, “Biological imaging with coherent Raman scattering microscopy: a tutorial,” J. Biomed. Opt. 19, 071407 (2014). doi:10.1117/1.JBO.19.7.071407