title: Near infrared two-photon excitation cross-sections of voltage-sensitive dyes.
abstract: Microscopy based on voltage-sensitive dyes has proven effective for revealing spatio-temporal patterns of neuronal activity in vivo and in vitro. Two-photon microscopy using voltage-sensitive dyes offers the possibility of wide-field visualization of membrane potential on sub-cellular length scales, hundreds of microns below the tissue surface. Very little information is available, however, about the utility of voltage-sensitive dyes for two-photon imaging purposes. Here we report on measurements of two-photon fluorescence excitation cross-sections for nine voltage-sensitive dyes in a solvent, octanol, intended to simulate the membrane environment. Ultrashort light pulses from a Ti:sapphire laser were used for excitation from 790 to 960 nm, and fluorescein dye was used as a calibration standard. Overall, dyes RH795, RH421, RH414, di-8-ANEPPS, and di-8-ANEPPDHQ had the largest two-photon excitation cross-sections ( approximately 15 x 10(-50)cm4 s photon(-1)) in this wavelength region and are therefore potentially useful for two-photon microscopy. Interestingly, di-8-ANEPPDHQ, a chimera constructed from the potentiometric dyes RH795 and di-8-ANEPPS, exhibited larger cross-sections than either of its constituents.
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104, USA. aafisher@physics.upenn.edu
authors.forename: Jonathan A N
authors.initials: JA
authors.lastname: Fisher
authors.forename: Brian M
authors.initials: BM
authors.lastname: Salzberg
authors.forename: Arjun G
authors.initials: AG
authors.lastname: Yodh
mesh_terms: D000818:Animals; D005456:Fluorescent Dyes / Q000378:metabolism*; D018613:Microscopy, Confocal; D009474:Neurons / Q000378:metabolism*; D017785:Photons; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013194:Staining and Labeling
chemical_list: D005456:Fluorescent Dyes