title: In vivo imaging of endogenous enzyme activities using luminescent 1,2-dioxetane compounds.
abstract: BACKGROUND
  Here we present a non-invasive imaging method for visualizing endogenous enzyme activities in living animals. This optical imaging method is based on an energy transfer principle termed chemically initiated electron exchange luminescence (CIEEL). The light energy is provided by enzymatic activation of metastable 1,2-dioxetane substrates, whose protective groups are removed by hydrolytic enzymes such as β-galactosidase and alkaline phosphatase. In the presence of a nearby fluorescent recipient, the chemical energy within the activated substrate is then transferred via formation of a charge-transfer complex with the fluorophore, a mechanism closely related to glow stick chemistry.
  
  
  RESULTS
  Efficient CIEEL energy transfer requires close proximity between the trigger enzyme and the fluorescent recipient. Using cells stained with fluorescent dialkylcarbocyanines as the energy recipients, we demonstrated CIEEL imaging of cellular β-galactosidase or alkaline phosphatase activity. In living animals, we used a similar approach to non-invasively image alkaline phosphatase activity in the peritoneal cavity.
  
  
  CONCLUSIONS
  In this report, we provide proof-of-concept for CIEEL imaging of in vivo enzymatic activity. In addition, we demonstrate the use of CIEEL energy transfer for visualizing elevated alkaline phosphatase activity associated with tissue inflammation in living animals.
authors.affiliation: Lurie Family Imaging Center, Dana-Farber Cancer Institute, 450 Brookline Avenue, Boston, MA, 02215, USA. jct223@gmail.com.|Current address: PerkinElmer Inc, 68 Elm Street, Hopkinton, MA, 01748, USA. jct223@gmail.com.
authors.forename: Jen-Chieh
authors.initials: JC
authors.lastname: Tseng
authors.affiliation: Columbia University Medical Center, 3959 Broadway, New York, NY, 10032, USA.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Kung
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D003952:Diagnostic Imaging; D004734:Energy Metabolism; D045325:HCT116 Cells; D006571:Heterocyclic Compounds / Q000737:chemistry* / Q000494:pharmacology; D006573:Heterocyclic Compounds, 1-Ring; D006801:Humans; D008027:Light; D049449:Luminescence; D051379:Mice; D001616:beta-Galactosidase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D006571:Heterocyclic Compounds; D006573:Heterocyclic Compounds, 1-Ring; C079142:1,2-dioxetane; D000469:Alkaline Phosphatase; D001616:beta-Galactosidase