title: Transient state imaging for microenvironmental monitoring by laser scanning microscopy.
abstract: Photoinduced transient dark states are exhibited by practically all common fluorophores. These relatively long-lived states are very sensitive to the local environment and thus highly attractive for microenvironmental imaging purposes. However, because of methodological constraints, their sensitivity has to date been very sparsely exploited. Here, a concept based on spatio-temporal modulation of the excitation intensity is presented that can image these states via their photodynamic fingerprints. With the use of a standard laser scanning microscope, it unites the outstanding environmental sensitivity of the transient state parameters with the high sensitivity of the fluorescence readout and is easily implemented. For demonstration, triplet state images of liposomes with different internal environments were generated. These images provide an example of how local environmental differences can be resolved, which are not clearly distinguishable via other fluorescence parameters. Having minor instrumental and sample constraints the concept can be foreseen to provide several new, useful, and independent fluorescence-based parameters in biomolecular imaging.
authors.affiliation: Department of Applied Physics, Experimental Biomolecular Physics, Royal Institute of Technology, SE-106 91 Stockholm, Sweden.
authors.forename: Tor
authors.initials: T
authors.lastname: Sandén
authors.forename: Gustav
authors.initials: G
authors.lastname: Persson
authors.forename: Jerker
authors.initials: J
authors.lastname: Widengren
mesh_terms: D003952:Diagnostic Imaging; D005456:Fluorescent Dyes / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted; D008081:Liposomes / Q000737:chemistry*; D018613:Microscopy, Confocal
chemical_list: D005456:Fluorescent Dyes; D008081:Liposomes