title: Three-Dimensional Holographic Refractive-Index Measurement of Continuously Flowing Cells in a Microfluidic Channel.
abstract: Refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, RI contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving parts approach that provides three-dimensional refractive index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate RI maps of the samples from the measured spectra. Using this method, we demonstrate label-free 3-D imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass and density of these cells from the measured 3-D refractive index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, promises as a quantitative tool for stain-free characterization of large number of cells.
authors.affiliation: Laser Biomedical Research Center, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Yongjin
authors.initials: Y
authors.lastname: Sung
authors.affiliation: Laser Biomedical Research Center, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Niyom
authors.initials: N
authors.lastname: Lue
authors.affiliation: BioMEMS Resource Center, Massachusetts General Hospital, and Harvard Medical School, Charlestown, MA, USA.
authors.forename: Bashar
authors.initials: B
authors.lastname: Hamza
authors.affiliation: BioMEMS Resource Center, Massachusetts General Hospital, and Harvard Medical School, Charlestown, MA, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Martel
authors.affiliation: BioMEMS Resource Center, Massachusetts General Hospital, and Harvard Medical School, Charlestown, MA, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Irimia
authors.affiliation: Laser Biomedical Research Center, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Ramachandra R
authors.initials: RR
authors.lastname: Dasari
authors.affiliation: Department of Physics, Korea University, Seoul, Korea.
authors.forename: Wonshik
authors.initials: W
authors.lastname: Choi
authors.affiliation: Laser Biomedical Research Center, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Zahid
authors.initials: Z
authors.lastname: Yaqoob
authors.affiliation: Laser Biomedical Research Center, Massachusetts Institute of Technology, Cambridge, MA, USA ; Department of Mechanical Engineering and Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: So