ABSTRACT
Bubbles for ultrasound applications generally consist of a poorly water-soluble gas and a shell of surfactants, lipids, polymers or proteins. The physicochemical properties of lipid-stabilized microbubbles depend on both the gas inside the bubbles and the lipid covering the bubbles. Bubbles in an ultrasound field will be affected by the oscillating compressional wave of the ultrasound. Bubble oscillation creates microstreaming around the bubbles that can affect a nearby cell membrane by shear forces on the membrane. Gene delivery has also been examined by co-injection of plasmid DNA with bubbles and combined with ultrasound exposure with the purpose of increasing the gene expression locally. Various drug carrier particles have been developed to improve the efficacy of drugs. The nanoparticles that has been mostly combined with bubbles and ultrasound exposure are liposomes. Liposomes are vesicles consisting of one or several lipid bilayers encapsulating a liquid core.
