This is supported by correlation of the uptake of a dye with cellular deformation and membrane changes as assessed by scanning electron microscopy, membrane electrophysiology and atomic force microscopy [10–12]. Following pore formation, nonspecific uptake of extracellular molecules can occur, the membrane is repaired, and molecules are, therefore, retained within cells. Mammalian cells have been shown to repair Inhibitors,research,lifescience,medical pores of up to ~1000μm2 within

a short period [13], in a manner resembling the kinetics of membrane repair after mechanical wounding, and Ca2+ levels are thought to promote this response [14, 15]. Figure 1 Sonoporation mechanisms for therapeutic delivery. (a) Sonoporation for drug delivery. Drugs can be delivered by sonoporation. Microbubbles with drug attached to the surface or enclosed within the particle travel in capillaries. Upon Inhibitors,research,lifescience,medical US exposure MBs rupture, … 3. Echogenic Nanoparticles In this paper, nanoparticles (NPs) are defined as molecules ranging in size from 1nm to 1μm and that are able to form a separate phase in aqueous suspension. Echogenic NPs are defined as NPs containing either atmospheric air or gas to form “nanobubbles” Inhibitors,research,lifescience,medical that can be used for drug and gene delivery when US is applied. In most medical applications, NPs typically

are in suspension and can be classified into micelles, nanoemulsions, and suspensions of solid nanoparticles (Figure 2). Most of them have been tested for US-mediated

gene delivery. Figure 2 Various nanoparticles (not to scale) that may be used in ultrasound-enhanced drug and gene delivery. (a) Inhibitors,research,lifescience,medical Micelle (nonpolymeric) composed of amphiphilic surfactants. (b) Polymeric micelle composed of amphiphilic block copolymers. (c) Nanoemulsion consisting … 3.1. Nanoparticles Used for Gene Delivery 3.1.1. Lipid-Based Nanoparticles Complexing of cationic lipids and DNA plasmids (lipofection) is efficient at transfection of various cell lines and several lipid Inhibitors,research,lifescience,medical combinations are available commercially. However, there has been little combination of US with lipofection, possibly because early studies using ultrasound and gas bubbles showed that the addition of the chemical structure contrast agents enhanced transfection of naked DNA MTMR9 much more than traditional transfection by lipofection, which is mediated through endocytosis and pinocytosis mechanisms [16]. The incubation time of lipofection from transfection to gene expression is also slower compared to that with naked DNA and contrast agents [17]. Of the few studies that combined US and lipofection, one example highlights the challenges of this method. For example, brain tumor cell transfection using 2MHz pulsed US for 1min and Lipofectamine condensed with plasmids coding for green fluorescent protein (GFP) produced no change in transfection efficiency compared to conventional lipofection alone [18].