title: Determination of liposome size distribution by flow cytometry.
abstract: BACKGROUND
  An essential parameter that describes the quality of liposome suspensions is the mean size, respectively the size distribution. Currently several analytical methods including laser light scattering techniques (LLST) are being employed.
  
  
  METHODS
  Here we present an alternative technique using flow cytometry (FCM) to characterize uni- and polydisperse suspensions. As model liposomes preparations containing dipalmitoylphosphatidylcholine (DPPC) were used. A constant number of particles (1,500/s) in the fluid stream and a representative number of 10,000 particles of each sample was measured. Fluorescence-labeled latex beads were measured identically, and their side scatter signals were calibrated and correlated to the results obtained with liposome vesicles.
  
  
  RESULTS
  Evaluation of the measurement and validation of the FCM results in comparison to LLST confirm the reliability of results obtained with our method. Latex beads in the range of 100-1000 nm were used for calibration to classify liposomes. Although measurement characteristics and calculation in both methods are basically different, very good agreement of the results was achieved.
  
  
  CONCLUSIONS
  Demonstration of stability, reproducibility, and reliability of results make the employment of this method acceptable for an adequate routine analysis technique.
authors.affiliation: Institute of Applied Microbiology, University of Agricultural Sciences, Vienna, Austria. K.Vorauer@iam.boku.ac.at
authors.forename: K
authors.initials: K
authors.lastname: Vorauer-Uhl
authors.forename: A
authors.initials: A
authors.lastname: Wagner
authors.forename: N
authors.initials: N
authors.lastname: Borth
authors.forename: H
authors.initials: H
authors.lastname: Katinger
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D002138:Calibration; D005434:Flow Cytometry / Q000379:methods*; D016650:Fluorescein-5-isothiocyanate; D007834:Lasers; D008081:Liposomes / Q000737:chemistry*; D008863:Microspheres; D010316:Particle Size; D015203:Reproducibility of Results; D012542:Scattering, Radiation
chemical_list: D008081:Liposomes; D015060:1,2-Dipalmitoylphosphatidylcholine; D016650:Fluorescein-5-isothiocyanate