Focused ultrasound-induced blood-brain barrier opening for non-viral, non-invasive, and targeted gene delivery

Focused ultrasound (FUS) exposure in the presence of microbubbles can temporally open the blood-brain barrier (BBB) and is an emerging technique for non-invasive brain therapeutic agent delivery. Given the potential to deliver large molecules into the CNS via this technique, we propose a reliable strategy to synergistically apply FUS-BBB opening for the non-invasive and targeted delivery of non-viral genes into the CNS for therapeutic purpose. In this study, we developed a gene-liposome system, in which the liposomes are designed to carry plasmid DNA (pDNA, containing luciferase reporter gene) to form a liposomal-plasmid DNA (LpDNA) complex. Pulsed FUS exposure was delivered to induce BBB opening (500-kHz, burst length = 10 ms, 1% duty cycle, PRF = 1 Hz). The longitudinal expression of luciferase was quantitated via an in vivo imaging system (IVIS). The reporter gene expression level was confirmed via immunoblotting, and histological staining was used to identify transfected cells via fluorescent microscopy. In a comparison of gene transduction efficiency, the LpDNA system showed better cell transduction than the pDNA system. With longitudinal observation of IVIS monitoring, animals with FUS treatment showed significant promotion of LpDNA release into the CNS and demonstrated enhanced expression of genes upon sonication with FUS-BBB opening, while both the luciferase and GDNF protein expression were successfully measured via Western blotting. The gene expression peak was observed at day 2, and the gene expression level was up to 5-fold higher than that in the untreated hemisphere (compared to a 1-fold increase in the direct-inject positive-control group). The transfection efficiency was also found to be LpDNA dose-dependent, where higher payloads of pDNA resulted in a higher transfection rate. Immunoblotting and histological staining confirmed the expression of reporter genes in glial cells as well as astrocytes. This study suggests that IV administration of LpDNA in combination with FUS-BBB opening can provide effective gene delivery and expression in the CNS, demonstrating the potential to achieve non-invasive and targeted gene delivery for treatment of CNS diseases.