Label-free photoacoustic microscopy of cytochromes

• Type of Material: Article
• Authors: Chi Zhang, Washington University; Yu Shrike Zhang, Georgia Institute of Technology; Da-Kang Yao, Washington University; Younan Xia, Emory University; Lihong V. Wang, Washington University
• Language: English
• Date: 2013-07-15
• Publisher: Society of Photo-optical Instrumentation Engineers (SPIE)
• Publication Version: Final Published Version
• Copyright Statement: © 2013 The Authors.
• Final Published Version (URL): http://dx.doi.org/10.1117/1.JBO.18.2.020504
• Title of Journal or Parent Work: Journal of Biomedical Optics
• ISSN: 1083-3668
• Volume: 18
• Issue: 2
• Start Page: 20504
• End Page: 20504
• Grant/Funding Information: This work was sponsored in part by National Institutes of Health (NIH) grants R01 EB000712, R01 EB008085, R01 CA134539, U54 CA136398, R01 CA157277, and R01 CA159959.
• Keywords: Microscopy; Optical Devices; Optical Phenomena; Fibroblasts; Animals; Mice; Microscopy, Fluorescence; Photoacoustic Techniques; Cytochromes; Cytoplasm; Skin
• Research Categories: Engineering, Biomedical

Abstract

Photoacoustic microscopy (PAM) has achieved submicron lateral resolution in showing subcellular structures; however, relatively few endogenous subcellular contrasts have so far been imaged. Given that the hemeprotein, mostly cytochromes in general cells, is optically absorbing around the Soret peak (~420 nm), we implemented labelfree PAM of cytochromes in cytoplasm for the first time. By measuring the photoacoustic spectra of the oxidized and reduced states of fibroblast lysate and fitting the difference spectrum with three types of cytochromes, we found that the three cytochromes account for more than half the optical absorption in the cell lysate at 420 nm wavelength. Fixed fibroblasts on slides were imaged by PAM at 422 and 250 nm wavelengths to reveal cytoplasms and nuclei, respectively, as confirmed by standard staining histology. PAM was also applied to label-free histology of mouse ear sections by showing cytoplasms and nuclei of various cells. PAM of cytochromes in cytoplasm is expected to be a high-throughput, label-free technique for studying live cell functions, which cannot be accomplished by conventional histology.