Ultrasound-mediated delivery of brain-penetrating nanoparticles across the blood-tumor barrier

The intact blood-brain barrier (BBB) presents a major obstacle for drug delivery to the brain. In addition, both high interstitial pressure and a nanoporous electrostatically charged tissue composition, produce a “blood-tumor barrier” (BTB), further complicating the treatment of diseases like glioblastoma. Focused ultrasound (FUS) in conjunction with microbubbles (MB) has been shown to cause reversible, localized disruption of the BBB. Incorporating MR guidance with FUS offers the ability to exquisitely target the BBB disruption to specific regions of the brain, thereby permitting drug delivery in a highly localized manner. This work examines the ability of MR guided FUS to deliver highly specialized brain-penetrating nanoparticles (NP) across both the BBB and the BTB in tumor-bearing rats. NPs were 60 nm in diameter and covered with an exceptionally dense brush layer of PEG to permit excellent diffusion through brain tissue. Initial studies utilized fluorescent polystyrene tracer particles to measure NP delivery and inform dosing of cisplatin-loaded biodegradable NPs.