title: Temperature-sensitive nonionic vesicles prepared from Span 80 (sorbitan monooleate).
abstract: Different types of nonionic vesicles were prepared from commercial Span 80 (also called sorbitan monooleate), as an inexpensive, biocompatible alternative to conventional phospholipid-based vesicles (liposomes). The vesicles were characterized by different techniques and comparison was made with vesicles formed from POPC (1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine) or DOPC (1,2-dioleoyl- sn-glycero-3-phosphocholine). Dynamic light scattering measurements, electron microscopy analyses, and two types of fusion assays indicate that Span 80 vesicles are stable for at least 7 days at 4 or 25 degrees C, while storage at 42 degrees C causes irreversible vesicle fusion. This indicates that Span 80 vesicles are thermoresponsive with vesicle fusion occurring at elevated temperature. This property may be related to headgroup dehydration and is certainly not directly linked to the phase transition temperature (Tm) of the vesicles, since the Tm is below -30 degrees C, as determined by differential scanning calorimetry (DSC). The measured Tm value for Span 80 vesicles is lower than in the case of DOPC or POPC, correlating with a higher fluidity of Span 80 vesicles as compared to POPC or DOPC vesicles, as determined with DPH (1,6-diphenyl-1,3,5-hexatriene) as fluorescent membrane probe. High fluidity correlates with increased leakage of entrapped water-soluble dye molecules. Addition of cholesterol and soybean phosphatidylcholine lowers the extent of leakage, allowing a tuning of the bilayer permeability.
authors: Department of Applied Chemistry, Faculty of Engineering, Ehime University, Matsuyama, Japan. kato@eng.ehime-u.ac.jp
authors: Keiichi
authors: K
authors: Kato
authors: Peter
authors: P
authors: Walde
authors: Norio
authors: N
authors: Koine
authors: Sosaku
authors: S
authors: Ichikawa
authors: Takashi
authors: T
authors: Ishikawa
authors: Ryo
authors: R
authors: Nagahama
authors: Takehiko
authors: T
authors: Ishihara
authors: Tetsuya
authors: T
authors: Tsujii
authors: Masachika
authors: M
authors: Shudou
authors: Yousuke
authors: Y
authors: Omokawa
authors: Takashi
authors: T
authors: Kuroiwa
mesh_terms: D002152:Calorimetry, Differential Scanning; D002851:Chromatography, High Pressure Liquid; D020285:Cryoelectron Microscopy; D006601:Hexoses / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D010713:Phosphatidylcholines / Q000737:chemistry; D012680:Sensitivity and Specificity; D013696:Temperature
chemical_list: D006601:Hexoses; D007477:Ions; D010713:Phosphatidylcholines; C018665:sorbitan monooleate