title: Extended cavity laser enhanced two-photon flow cytometry.
abstract: We demonstrate enhanced sensitivity in two-photon flow cytometry with an extended cavity laser excitation source. At low power, the home-built 20-MHz oscillator was able to detect a significantly larger fraction, in either phosphate buffered saline (PBS) or whole blood, of green fluorescent protein (GFP)-expressing MCA-207 cells cross-labeled with the membrane-binding lipophilic dye DiD. A geometrical model is used to explain unique features of the signals resulting from the different spatial distribution of DiD and GFP. These unique features include sub-square law scaling of unsaturated two-photon signal, a sigmoidal sensitivity curve for detection under varying powers for cell detection thresholds as low as a single photon, and uncorrelated signal strengths in two detection channels.
authors.affiliation: University of Michigan, Center for Ultrafast Optical Science, Electrical Engineering & Computer Science Department, Ann Arbor, Michigan 48109-2099, USA. etkaczyk@umich.edu
authors.forename: Eric R
authors.initials: ER
authors.lastname: Tkaczyk
authors.forename: Alan H
authors.initials: AH
authors.lastname: Tkaczyk
authors.forename: Steve
authors.initials: S
authors.lastname: Katnik
authors.forename: Jing Yong
authors.initials: JY
authors.lastname: Ye
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Luker
authors.forename: Gary D
authors.initials: GD
authors.lastname: Luker
authors.forename: Andrzej
authors.initials: A
authors.lastname: Myc
authors.forename: James R
authors.initials: JR
authors.lastname: Baker
authors.forename: Theodore B
authors.initials: TB
authors.lastname: Norris
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005434:Flow Cytometry / Q000295:instrumentation* / Q000379:methods; D007834:Lasers; D036641:Microscopy, Fluorescence, Multiphoton / Q000295:instrumentation* / Q000379:methods; D010783:Photometry / Q000295:instrumentation*; D017785:Photons; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*