Ultrasound, liposomes, and drug delivery: principles for using ultrasound to control the release of drugs from liposomes

Avi Schroeder, Joseph Kost, Yechezkel Barenholz*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

404 Scopus citations

Abstract

Ultrasound is used in many medical applications, such as imaging, blood flow analysis, dentistry, liposuction, tumor and fibroid ablation, and kidney stone disruption. In the past, low frequency ultrasound (LFUS) was the main method to downsize multilamellar (micron range) vesicles into small (nano scale) unilamellar vesicles. Recently, the ability of ultrasound to induce localized and controlled drug release from liposomes, utilizing thermal and/or mechanical effects, has been shown. This review, deals with the interaction of ultrasound with liposomes, focusing mainly on the mechanical mechanism of drug release from liposomes using LFUS. The effects of liposome lipid composition and physicochemical properties, on one hand, and of LFUS parameters, on the other, on liposomal drug release, are addressed. Acoustic cavitation, in which gas bubbles oscillate and collapse in the medium, thereby introducing intense mechanical strains, increases release substantially. We suggest that the mechanism of release may involve formation and collapse of small gas nuclei in the hydrophobic region of the lipid bilayer during exposure to LFUS, thereby inducing the formation of transient pores through which drugs are released. Introducing PEG-lipopolymers to the liposome bilayer enhances responsivity to LFUS, most likely due to absorption of ultrasonic energy by the highly hydrated PEG headgroups. The presence of amphiphiles, such as phospholipids with unsaturated acyl chains, which destabilize the lipid bilayer, also increases liposome susceptibility to LFUS. Application of these principles to design highly LFUS-responsive liposomes is discussed.

Original languageEnglish
Pages (from-to)1-16
Number of pages16
JournalChemistry and Physics of Lipids
Volume162
Issue number1-2
DOIs
StatePublished - Nov 2009

Keywords

  • Cavitation
  • Cisplatin
  • Doxil
  • Doxorubicin
  • Lipid vesicle
  • Liposome
  • Low frequency ultrasound
  • PEGylation
  • Sonication

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