Targeted gene transfer to the brain via the delivery of brain-penetrating DNA nanoparticles with focused ultrasound

Abstract

Gene therapy holds promise for the treatment of many pathologies of the central nervous system (CNS), including brain tumors and neurodegenerative diseases. However, the delivery of systemically administered gene carriers to the CNS is hindered by both the blood-brain barrier (BBB) and the nanoporous and electrostatically charged brain extracelluar matrix (ECM), which acts as a steric and adhesive barrier. We have previously shown that these physiological barriers may be overcome by, respectively, opening the BBB with MR image-guided focused ultrasound (FUS) and microbubbles and using highly compact “brain penetrating” nanoparticles (BPN) coated with a dense polyethylene glycol corona that prevents adhesion to ECM components. Here, we tested whether this combined approach could be utilized to deliver systemically administered DNA-bearing BPN (DNA-BPN) across the BBB and mediate localized, robust, and sustained transgene expression in the rat brain. Systemically administered DNA-BPN delivered through the BBB with FUS led to dose-dependent transgene expression only in the FUS-treated region that was evident as early as 24 h post administration and lasted for at least 28 days. In the FUS-treated region ~42% of all cells, including neurons and astrocytes, were transfected, while less than 6% were transfected in the contralateral non-FUS treated hemisphere. Importantly, this was achieved without any sign of toxicity or astrocyte activation. We conclude that the image-guided delivery of DNA-BPN with FUS and microbubbles constitutes a safe and non-invasive strategy for targeted gene therapy to the brain.

MR image-guided delivery of cisplatin-loaded brain-penetrating nanoparticles to invasive glioma with focused ultrasound

“…We previously determined [22,32] that 0.6 MPa was sufficient to produce significant enhancements in BPN delivery across the BBB in normal tissue, and we demonstrated here that 0.6 MPa significantly increased BPN delivery across the BTB in both the 9L and F98 glioma models. However, presumably abnormal tumor vasculature [30] and parenchyma [61] combined with the aggressive nature of the F98 tumor model [28,29,61] required the use of slightly higher pressure to achieve a treatment effect.…”

“…Furthermore, local administration techniques are highly invasive and associated with significant risks [1,55], particularly for therapeutics that require multiple treatments. MRgFUS is the only treatment modality capable of producing non-invasive, localized, reversible BBB disruption [19,21,22,32,56,57] and has been shown to increase the delivery of therapeutics across the BTB as well [17,58–60]. In agreement with this body of work, as well as our previous work [22,32], we show here that MRgFUS significantly increases both the total delivery and distribution of BPN within the tumor parenchyma and surrounding normal tissue in both the 9L and F98 glioma models.…”

“…However, it should be noted that these transfected cells were several fold less aggressive than wild-type F98 cells, most likely due to increased immunogenicity. Additional strategies could be employed to improve the efficacy of MRgFUS-mediated delivery of BPN, including utilizing BPNs loaded with other chemotherapeutics [74,75], immunotherapeutics [76,77], or plasmids [22,25,78–80]. Finally, to maintain treatment consistency both within and between the FUSlo+CDDP-BPN and FUShi+CDDP-BPN groups, we always used a 3×3 sonication grid for FUS-mediated BPN delivery, independent of whether this treatment volume matched the size of the F98 tumor being treated.…”

“…Together, these factors generate what is now commonly referred to as the “blood-tumor barrier” (BTB). Transcranial MR-guided focused ultrasound (MRgFUS) is currently the only treatment modality capable of achieving safe, non-invasive, reversible BBB and BTB disruption in a targeted manner [17–22]. …”

Closed-loop control of targeted ultrasound drug delivery across the blood–brain/tumor barriers in a rat glioma model

“…BBBD, the subject of the current study, reversibly opens the blood-brain barrier (BBB) enabling the delivery of even large-molecule therapeutics to the central nervous system and offers great potential for treating multiple neurological disorders. This technology has been demonstrated in rodent (11)(12)(13)(14)(15)(16) and nonhuman primate (17,18) models, and clinical trials are underway (19,20).…”