title: The influence of bile salts on the response of liposomes to ultrasound.
abstract: BACKGROUND
  Triggering drug release from delivery vehicles with ultrasound has potential applications in targeted drug delivery. It was hypothesized that the addition of bile salts would increase the sensitivity of liposomes to ultrasound through creation of defects.
  
  
  OBJECTIVE
  The aim of this study was to investigate whether incorporating bile salts into liposomes would lead to differential effects on their response to low and high frequency ultrasound.
  
  
  METHODS
  Cholate, chenodeoxycholate, ursodeoxycholate, glycocholate and taurocholate were the selected bile salts. Response to ultrasound was characterized by measuring the release of carboxyfluorescein (CF).
  
  
  RESULTS
  At 30 kHz ultrasound, taurocholate containing liposomes were most responsive and released 70% (± 2) CF after 30 seconds of sonication. Compared to this, liposomes that did not contain bile salts released just 7% (± 2). At 1.1 MHz ultrasound, all liposome formulations were unresponsive. To increase the response of liposomes at 1.1 MHz ultrasound, a combination of membrane destabilizers were added to DSPC liposomes. DOPE, a hexagonal phase lipid was used in combination with taurocholate. Surprisingly, liposomes containing DOPE and taurocholate were more resistant to 1.1 MHz ultrasound than ones containing only DOPE.
  
  
  CONCLUSIONS
  This suggests that the sensitivity of liposomes towards ultrasound may not simply be defined by a single membrane component but instead depends on the interaction between constituting lipid components. Furthermore, strategies other than membrane destabilization may be required to sensitize liposomes towards high frequency ultrasound.
  
  
  CONCLUSIONS
  Bile salts may be used to increase or decrease the sensitivity of liposomes to low frequency ultrasound.
authors.affiliation: a School of Pharmacy, University of Otago , Dunedin , New Zealand and.
authors.forename: Himang
authors.initials: H
authors.lastname: Mujoo
authors.affiliation: b Department of Anatomy , The Brain Health Research Centre, University of Otago , Dunedin , New Zealand.
authors.forename: John N J
authors.initials: JN
authors.lastname: Reynolds
authors.affiliation: a School of Pharmacy, University of Otago , Dunedin , New Zealand and.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Tucker
mesh_terms: D001647:Bile Acids and Salts / Q000737:chemistry*; D005452:Fluoresceins / Q000032:analysis; D008081:Liposomes / Q000737:chemistry*; D000069453:Ultrasonic Waves
chemical_list: D001647:Bile Acids and Salts; D005452:Fluoresceins; D008081:Liposomes; C024098:6-carboxyfluorescein
keywords: Destabilization; nanotechnology; sonosensitive; sustained release; targeting