title: The shape/morphology balance: a study of stealth liposomes via fractal analysis and drug encapsulation.
abstract: OBJECTIVE
  Fractal analysis was used as a tool in order to study the morphological characteristics of PEGylated liposomes. We report on the morphological characteristics of stealth liposomes composed of DPPC and DPPE-PEG 3000 in two dispersion media using fractal analysis.
  
  
  METHODS
  Light scattering techniques were used in order to elucidate the size, the morphology and the surface charge of PEGylated liposomes as a function of PEGylated lipid concentration and temperature. Fluorescence spectroscopy studies revealed a microenvironment of low polarity inside the liposomal membranes.
  
  
  RESULTS
  All formulations were found to retain their physicochemical characteristics for at least 3 weeks. The hydrodynamic radii (Rh) of stealth liposomes were stable in the process of heating up to 50°C; while the fractal dimension values (df) which correspond to their morphology, have been changed during heating. Hence, these results are a first indication of the presence of a heterogeneous microdomain structure of the stealth liposomal system. The amphiphilic drug indomethacin (IND) was successfully encapsulated within the liposomes and led to an increased size of stealth liposomes, while the morphology of liposomal vectors changed significantly at the highest molar ratio of PEGylated lipid.
  
  
  CONCLUSIONS
  We can state that this approach can promote a new analytical concept based on the morphological characteristics and quantify the shape of drug carriers complementary to that of the conventional analytical techniques.
authors.affiliation: Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Athens, Panepistimioupolis Zografou, 157 71, Athens, Greece.
authors.forename: Natassa
authors.initials: N
authors.lastname: Pippa
authors.forename: Faidra
authors.initials: F
authors.lastname: Psarommati
authors.forename: Stergios
authors.initials: S
authors.lastname: Pispas
authors.forename: Costas
authors.initials: C
authors.lastname: Demetzos
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000031:analogs & derivatives* / Q000737:chemistry; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage*; D017709:Fractals; D007213:Indomethacin / Q000008:administration & dosage*; D008081:Liposomes / Q000737:chemistry*; D010316:Particle Size; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; C102564:DPPE-PEG2000; D008081:Liposomes; D010714:Phosphatidylethanolamines; D015060:1,2-Dipalmitoylphosphatidylcholine; C081581:colfosceril palmitate; D011092:Polyethylene Glycols; D007213:Indomethacin