title: Cavitation microstreaming and stress fields created by microbubbles.
abstract: Cavitation microstreaming plays a role in the therapeutic action of microbubbles driven by ultrasound, such as the sonoporative and sonothrombolytic phenomena. Microscopic particle-image velocimetry experiments are presented. Results show that many different microstreaming patterns are possible around a microbubble when it is on a surface, albeit for microbubbles much larger than used in clinical practice. Each pattern is associated with a particular oscillation mode of the bubble, and changing between patterns is achieved by changing the sound frequency. Each microstreaming pattern also generates different shear stress and stretch/compression distributions in the vicinity of a bubble on a wall. Analysis of the micro-PIV results also shows that ultrasound-driven microstreaming flows around bubbles are feasible mechanisms for mixing therapeutic agents into the surrounding blood, as well as assisting sonoporative delivery of molecules across cell membranes. Patterns show significant variations around the bubble, suggesting sonoporation may be either enhanced or inhibited in different zones across a cellular surface. Thus, alternating the patterns may result in improved sonoporation and sonothrombolysis. The clear and reproducible delineation of microstreaming patterns based on driving frequency makes frequency-based pattern alternation a feasible alternative to the clinically less desirable practice of increasing sound pressure for equivalent sonoporative or sonothrombolytic effect. Surface divergence is proposed as a measure relevant to sonoporation.
authors.affiliation: Department of Mechanical Engineering, University of Melbourne, VIC 3010, Melbourne, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Collis
authors.forename: Richard
authors.initials: R
authors.lastname: Manasseh
authors.forename: Petar
authors.initials: P
authors.lastname: Liovic
authors.forename: Paul
authors.initials: P
authors.lastname: Tho
authors.forename: Andrew
authors.initials: A
authors.lastname: Ooi
authors.forename: Karolina
authors.initials: K
authors.lastname: Petkovic-Duran
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000162:Acoustics; D001812:Blood-Brain Barrier; D002462:Cell Membrane / Q000187:drug effects; D004867:Equipment Design; D045423:Microbubbles; D044085:Microfluidics / Q000295:instrumentation*; D008856:Microscopy, Fluorescence; D010316:Particle Size; D015912:Thrombolytic Therapy / Q000379:methods; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage; D014465:Ultrasonics
chemical_list: D010959:Tissue Plasminogen Activator