Ultrasound-sensitizing nanoparticle complex for overcoming the blood-brain barrier: an effective drug delivery system

Background: Crossing the blood--brain barrier (BBB) is crucial for drug delivery to the brain and for treatment of brain tumors, such as glioblastoma, the most common of all primary malignant brain tumors. Microbubble (MB) is oscillated and destroyed by controlling ultrasound (US) parameters. This oscillation and destruction of MB can open the BBB transiently, and a drug can be delivered to the brain. Materials and methods: For testing the efficiency of delivery to the brain, we synthesized a US-sensitizing nanoparticle (NP) complex via chemically binding MBs and NPs for the BBB opening, including near-infrared dye-incorporated albumin nanoparticles (NIR-Alb NPs) for fluorescence detection. Results: The human-derived, biocompatible NIR-Alb NPs did not show significant cytotoxicity to 500 [micro]g/mL for 3 days in four human glioma cell lines. In an in vivo animal study, some US parameters were investigated to determine optimal conditions. The optimized US conditions were applied in a U87MG orthotopic mouse model. We found that the fluorescence intensity in the brain was 1.5 times higher than in the control group. Conclusion: Our US-sensitizing NP complex and US technique could become one of the critical technologies for drug delivery to the brain. Keywords: blood--brain barrier, ultrasound, nanoparticle, microbubble, complex, drug delivery