title: Fluorescent liposomes as contrast agents for in vivo optical imaging of edemas in mice.
abstract: This study assesses if specially designed fluorescent liposomes can be used as contrast agent for near-infrared fluorescence (NIRF) optical imaging of cultured macrophages in vitro and for NIRF imaging of inflammatory processes, like edema, in an in vivo mouse model. Fluorescent liposomes are prepared by the film hydration and extrusion method using cholesterol, L-phosphatidylcholine, and the NIR fluorescent dye DY-676-C(18) ester. Photon correlation spectroscopy and flow cytometry reveal that fluorescent liposomes are structurally stable for up to 133 days. Distinct uptake/labeling of cultured murine J774 macrophages is demonstrated by confocal laser scanning microscopy (CLSM), flow cytometry, and macroscopic NIRF imaging system at wavelengths >670 nm. Moreover, CLSM analysis reveals fluorescence signals within intracellular compartments. Ear edema is induced in mice (n = 16) by subcutaneous injection of zymosan A. Whole-body NIRF imaging is performed after intravenous injection (0-24 h) of fluorescent liposomes (55 nmol dye per kg body weight). Distinctly higher fluorescence intensities (1613.6 +/- 61.7 a.u.) are detected at inflamed areas of diseased mice as compared to controls (892.8 +/- 19.4 a.u.). Furthermore, cell isolated from ear lavage reveals the presence of labeled F4/80 positive tissue macrophages. Taken together, the results indicate both that mouse macrophages labeled with fluorescent liposomes can be detected in vitro with fluoro-optical methods and that in vivo optical imaging of inflammatory processes with fluorescent liposomes as contrast agent is feasible. Possibly, early stages of other inflammatory diseases could also be detected by the proposed diagnostic tool in the long term.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Jena FZL, Erlanger Allee 101, 07747 Jena, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Deissler
authors.forename: Ronny
authors.initials: R
authors.lastname: Rüger
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Frank
authors.forename: Alfred
authors.initials: A
authors.lastname: Fahr
authors.forename: Werner A
authors.initials: WA
authors.lastname: Kaiser
authors.forename: Ingrid
authors.initials: I
authors.lastname: Hilger
mesh_terms: D000818:Animals; D002460:Cell Line; D003287:Contrast Media; D004195:Disease Models, Animal; D004487:Edema / Q000175:diagnosis* / Q000473:pathology; D005456:Fluorescent Dyes; D008081:Liposomes; D008264:Macrophages; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018613:Microscopy, Confocal
chemical_list: D003287:Contrast Media; D005456:Fluorescent Dyes; D008081:Liposomes