Background: 

Site specific vascular gene delivery is a much needed therapeutic tool. We combined standard ultrasonic microbubble technology with magnetic nanoparticle enhanced gene transfer to enable systemic application and local vascular gene transfer in vivo.

Methods: 

Vascular gene expression was optically assessed in the dorsal skin fold chamber of C57BL/6 mice by intravital microscopy 48–72h after intra-arterial application of magnetic microbubbles (MMB) carrying pDNA encoding dsRed (2.4 mg pDNA/g body weight) and magnetic field (MF) (B=1023mT, 5min) and ultrasound (US) (1MHz, 2W/cm², DC50%, 30sec) exposure. Magnetic nanoparticle (MNP) amounts were analysed by magnetic relaxometry.

Results: 

Microbubbles readily associated with positively charged MNP and pDNA (n=3) in vitro. These complexes circulated in the vascular system for up to 30min after injection. Local MF and US exposure of the skin fold tissue after injection of pDNA coated MMB resulted in a tenfold enhanced MNP amount in the target tissue (p<0.001, n=3). Accordingly, local dsRed gene expression was enhanced over sixtyfold as compared to the conventional microbubble technique (p<0.01, n=12). Noticeably, no expression of dsRed was observed in other vascular beds, as shown by intravital microscopy of the vessels of the cremaster muscle (n=5).

Conclusion: 

These results demonstrate that microbubbles can be successfully coated with MNP and pDNA. These compounds can be targeted with high precision to a specific sitein vivothereby enhancing local vascular gene delivery significantly. Thus, this technology may improve targeted gene delivery in the vascular system.