title: Label-free biomedical imaging with high sensitivity by stimulated Raman scattering microscopy.
abstract: Label-free chemical contrast is highly desirable in biomedical imaging. Spontaneous Raman microscopy provides specific vibrational signatures of chemical bonds, but is often hindered by low sensitivity. Here we report a three-dimensional multiphoton vibrational imaging technique based on stimulated Raman scattering (SRS). The sensitivity of SRS imaging is significantly greater than that of spontaneous Raman microscopy, which is achieved by implementing high-frequency (megahertz) phase-sensitive detection. SRS microscopy has a major advantage over previous coherent Raman techniques in that it offers background-free and readily interpretable chemical contrast. We show a variety of biomedical applications, such as differentiating distributions of omega-3 fatty acids and saturated lipids in living cells, imaging of brain and skin tissues based on intrinsic lipid contrast, and monitoring drug delivery through the epidermis.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Christian W
authors.initials: CW
authors.lastname: Freudiger
authors.forename: Wei
authors.initials: W
authors.lastname: Min
authors.forename: Brian G
authors.initials: BG
authors.lastname: Saar
authors.forename: Sijia
authors.initials: S
authors.lastname: Lu
authors.forename: Gary R
authors.initials: GR
authors.lastname: Holtom
authors.forename: Chengwei
authors.initials: C
authors.lastname: He
authors.forename: Jason C
authors.initials: JC
authors.lastname: Tsai
authors.forename: Jing X
authors.initials: JX
authors.lastname: Kang
authors.forename: X Sunney
authors.initials: XS
authors.lastname: Xie
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003337:Corpus Callosum / Q000737:chemistry / Q000166:cytology; D004121:Dimethyl Sulfoxide / Q000008:administration & dosage / Q000493:pharmacokinetics; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D004817:Epidermis / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008055:Lipids / Q000032:analysis*; D051379:Mice; D008853:Microscopy / Q000379:methods*; D009474:Neurons / Q000648:ultrastructure; D012680:Sensitivity and Specificity; D012867:Skin / Q000737:chemistry / Q000648:ultrastructure; D013059:Spectrum Analysis, Raman; D014212:Tretinoin / Q000008:administration & dosage / Q000493:pharmacokinetics; D014801:Vitamin A / Q000032:analysis / Q000737:chemistry
chemical_list: D008055:Lipids; D014801:Vitamin A; D014212:Tretinoin; D015118:Eicosapentaenoic Acid; D004121:Dimethyl Sulfoxide