The use of cationic microbubbles to improve ultrasound-targeted gene delivery to the ischemic myocardium.

We synthesized a cationic microbubble (CMB) with the aim of enhancing its DNA-carrying capacity to improve targeted gene transfection of the ischemic heart for cardiac regeneration. We previously reported that ultrasound-targeted microbubble destruction (UTMD) employing the commercial Definity microbubble (MB) successfully transfected genes into rodent hearts, but the transfection efficiency was modest. We synthesized a CMB and compared its DNA-carrying capacity and reporter gene transfection efficiency with the Definity MB. The CMB bound 70% more plasmid DNA than the Definity MB. UTMD-mediated gene delivery with the CMB enhanced both transfection efficiency and gene expression. In vivo studies assessed the ability of the CMB to deliver the therapeutic AKT gene to the ischemic rat myocardium and evaluated the effects on apoptosis, angiogenesis, and cardiac function. AKT transfection with the CMB reduced infarct size (p < 0.05), increased infarct thickness (p < 0.05), reduced apoptosis (p < 0.05), increased vascular density (p < 0.05), and improved cardiac perfusion and function (p < 0.05) compared to the Definity MB. Delivery of AKT with the CMB resulted in greater cardiac functional improvements compared to the Definity MB. UTMD therapy with this CMB provides an efficient platform for the targeted delivery of factors required to regenerate the ischemic heart and preserve cardiac function.