Dynamic Study of Blood–Brain Barrier Closure after its Disruption using Ultrasound: A Quantitative Analysis

Delivery of therapeutic or diagnostic agents to the brain is majorly hindered by the blood–brain barrier (BBB). Recently, many studies have demonstrated local and transient disruption of the BBB using low power ultrasound sonication combined with intravascular microbubbles. However, BBB opening and closure mechanisms are poorly understood, especially the maximum gap that may be safely generated between endothelial cells and the duration of opening of the BBB. Here, we studied BBB opening and closure under magnetic resonance (MR) guidance in a rat model. First, MR contrast agents (CA) of different hydrodynamic diameters (1 to 65 nm) were employed to estimate the largest molecular size permissible across the cerebral tissues. Second, to estimate the duration of the BBB opening, the CA were injected at various times post-BBB disruption (12 minutes to 24 hours). A T1 mapping strategy was developed to assess CA concentration at the ultrasound (US) focal point. Based on our experimental data and BBB closure modeling, a calibration curve was obtained to compute the half closure time as a function of CA hydrodynamic diameter. These findings and the model provide an invaluable basis for optimal design and delivery of nanoparticles to the brain.

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Opening of the blood-brain barrier with an unfocused ultrasound device in rabbits

Journal of Neurosurgery ◽

10.3171/2013.5.jns122374 ◽

2013 ◽

Vol 119 (4) ◽

pp. 887-898 ◽

Cited By ~ 31

Author(s):

Kevin Beccaria ◽

Michael Canney ◽

Lauriane Goldwirt ◽

Christine Fernandez ◽

Clovis Adam ◽

...

Keyword(s):

Adverse Effects ◽

Blood Brain Barrier ◽

Ultrasonic Transducer ◽

Brain Barrier ◽

Single Element ◽

Blood Brain ◽

The Us ◽

The Brain ◽

Bbb Opening

Object The blood-brain barrier (BBB) is a major impediment to the intracerebral diffusion of drugs used in the treatment of gliomas. Previous studies have demonstrated that pulsed focused ultrasound (US) in conjunction with a microbubble contrast agent can be used to open the BBB. To apply the US-induced opening of the BBB in clinical practice, the authors designed an innovative unfocused US device that can be implanted in the skull and used to transiently and repeatedly open the BBB during a standard chemotherapy protocol. The goal of this preliminary work was to study the opening of the BBB induced by the authors' small unfocused US transducer and to evaluate the effects of the sonications on brain parenchyma. Methods Craniectomy was performed in 16 healthy New Zealand White rabbits; epidural application of a single-element planar ultrasonic transducer operating at 1 MHz was then used with a pulse-repetition frequency of 1 Hz, pulse lengths of 10–35 msec, in situ acoustic pressure levels of 0.3–0.8 MPa, and sonication for 60–120 seconds. SonoVue was intravenously injected during the US applications, and opening of the BBB was determined by detecting extravasation of Evans blue dye (EBD) in brain tissues, quantitative measurement of EBD with UV-visible spectrophotometry, and contrast enhancement after Gd injection in 4.7-T MRI. A histological study was performed to determine adverse effects. Results An opening of the BBB was observed over a large extent of the US beam in the brain corresponding to in situ pressures of greater than 0.2 MPa. The BBB opening observed was highly significant for both EBD (p < 0.01) and MRI Gd enhancement (p < 0.0001). The BBB opening was associated with minor adverse effects that included perivascular red blood cell extravasations that were less than 150 μm in size and not visible on MR images. Moderate edema was visible on FLAIR sequences and limited to the extent of the sonication field. Conclusions The results demonstrate that the BBB can be opened in large areas of the brain in rabbits with lowpower, pulsed, and unfocused US with limited damage to healthy tissue.

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The Size of Blood–Brain Barrier Opening Induced by Focused Ultrasound is Dictated by the Acoustic Pressure

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.2014.71 ◽

2014 ◽

Vol 34 (7) ◽

pp. 1197-1204 ◽

Cited By ~ 105

Author(s):

Hong Chen ◽

Elisa E Konofagou

Keyword(s):

Blood Brain Barrier ◽

Focused Ultrasound ◽

Acoustic Pressure ◽

Ex Vivo ◽

Brain Barrier ◽

Hydrodynamic Diameter ◽

Molecular Weights ◽

Blood Brain ◽

Cavitation Detection ◽

Bbb Opening

Focused ultrasound (FUS) in combination with microbubbles (MBs) has been successfully used in the delivery of various-size therapeutic agents across the blood–brain barrier (BBB). This study revealed that FUS-induced BBB opening size, defined by the size of the largest molecule that can permeate through the BBB, can be controlled by the acoustic pressure as dictated by cavitational mechanisms. Focused ultrasound was applied onto the mouse hippocampus in the presence of systemically administered MBs for trans-BBB delivery of fluorescently labeled dextrans with molecular weights 3 to 2,000 kDa (hydrodynamic diameter: 2.3 to 54.4 nm). The dextran delivery outcomes were evaluated using ex vivo fluorescence imaging. Cavitation detection was employed to monitor the MB cavitation activity associated with the delivery of these agents. It was found that the BBB opening size was smaller than 3 kDa (2.3 nm) at 0.31 MPa, up to 70 kDa (10.2 nm) at 0.51 MPa, and up to 2,000 kDa (54.4 nm) at 0.84 MPa. Relatively smaller opening size (up to 70 kDa) was achieved with stable cavitation only; however, inertial cavitation was associated with relatively larger BBB opening size (above 500 kDa). These findings indicate that the BBB opening size can be controlled by the acoustic pressure and predicted using cavitation detection.

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Claudin-5 binder enhances focused ultrasound-mediated opening in an in vitro blood-brain barrier model

10.1101/2021.08.01.454692 ◽

2021 ◽

Author(s):

Ratneswary Sutharsan ◽

Liyu Chen ◽

Jonathan LF Lee ◽

Esteban Cruz ◽

Tishila Palliyaguru ◽

...

Keyword(s):

Cell Line ◽

Blood Brain Barrier ◽

Focused Ultrasound ◽

Brain Barrier ◽

Sodium Fluorescein ◽

General Strategy ◽

Blood Brain ◽

Barrier Opening ◽

The Brain ◽

Bbb Opening

Rationale: The blood-brain barrier (BBB) while functioning as a gatekeeper of the brain, impedes cerebral drug delivery. An emerging technology to overcome this limitation is focused ultrasound (FUS). When FUS interacts with intravenously injected microbubbles (FUS+MB), the BBB opens, transiently allowing the access of therapeutic agents into the brain. However, the ultrasound parameters need to be tightly tuned: when the acoustic pressure is too low there is no opening, and when it is too high, bleeds can occur. We therefore asked whether BBB permeability can be increased by combining FUS+MB with a second modality such that in a clinical setting lower acoustic pressures could be potentially used. Methods: Given that FUS achieves BBB opening by the disruption of tight junction (TJ) proteins such as claudin-5 of brain endothelial cells, we generated a stable MDCK II cell line (eGFP-hCldn5-MDCK II) that expresses fluorescently tagged human claudin-5. Two claudin-5 binders, mC5C2 (a peptide) and cCPEm (a truncated form of an enterotoxin), that have been reported previously to weaken the barrier, were synthesized and assessed for their abilities to enhance the permeability of cellular monolayers. We then performed a comparative analysis of single and combination treatments. Results: We successfully generated a novel cell line that formed functional monolayers as validated by an increased transendothelial electrical resistance (TEER) reading and a low (< 0.2%) permeability to sodium fluorescein (376 Da). We found that the binders exerted a time- and concentration-dependent effect on BBB opening when incubated over an extended period, whereas FUS+MB caused a rapid barrier opening followed by recovery after 12 hours within the tested pressure range. Importantly, preincubation with cCPEm prior to FUS+MB treatment resulted in greater barrier opening compared to either FUS+MB or cCPEm alone as measured by reduced TEER values and an increased permeability to fluorescently labelled 40 kDa dextran (FD40). Conclusion: The data suggest that pre-incubation with clinically suitable binders to TJ proteins may be a general strategy to facilitate safer and more effective ultrasound-mediated BBB opening in cellular and animal systems and potentially also for the treatment of human diseases of the brain.

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Ultrasound-induced opening of the blood-brain barrier to enhance temozolomide and irinotecan delivery: an experimental study in rabbits

Journal of Neurosurgery ◽

10.3171/2015.4.jns142893 ◽

2016 ◽

Vol 124 (6) ◽

pp. 1602-1610 ◽

Cited By ~ 24

Author(s):

Kevin Beccaria ◽

Michael Canney ◽

Lauriane Goldwirt ◽

Christine Fernandez ◽

Julie Piquet ◽

...

Keyword(s):

Blood Brain Barrier ◽

Ultrasound Contrast Agent ◽

Ultra Performance Liquid Chromatography ◽

Brain Barrier ◽

Control Group ◽

Tumor Treatment ◽

Blood Brain ◽

Ultrasound Sonication ◽

Bbb Opening

OBJECT The blood-brain barrier (BBB) limits the intracerebral penetration of drugs and brain tumor treatment efficacy. The effect of ultrasound-induced BBB opening on the intracerebral concentration of temozolomide (TMZ) and irinotecan (CPT-11) was assessed. METHODS This study was performed using 34 healthy New Zealand rabbits. Half had unilateral BBB opening, and half served as controls. Sonications were performed by pulsing a 1.05-MHz planar ultrasound transducer with a duty cycle of 2.5% and an in situ acoustic pressure level of 0.6 MPa after injection of a microbubble ultrasound contrast agent. Drugs were injected either 5 minutes before (ChemoPreUS) or 15 minutes after (ChemoPostUS) the ultrasound sonication. The plasma and intracerebral concentrations of both drugs were quantified using ultra-performance liquid chromatography. RESULTS The mean intracerebral tissue-to-plasma drug concentration ratio in the control hemispheres was 34% for TMZ and 2% for CPT-11. After BBB opening, these values increased by up to 21% for TMZ and up to 178% for CPT-11. Intracerebral concentrations of drugs were enhanced in regions where the BBB was opened compared with the contralateral hemisphere (p < 0.01 and p < 0.0001 for CPT-11, p = 0.02 and p = 0.03 for TMZ, in ChemoPreUS and ChemoPostUS, respectively) and compared with the control group (p < 0.001 and p < 0.0001 for CPT-11, p < 0.01 and p = 0.02 for TMZ, in ChemoPreUS and ChemoPostUS, respectively). The intracerebral distribution of drugs was heterogeneous, depending on the distance from the ultrasound source. CONCLUSIONS Ultrasound-induced opening of the BBB significantly enhances the intracerebral concentration of both TMZ and CPT-11 in rabbits.

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THER-11. PEPTIDE-MEDIATED PERMEABILIZATION OF THE BLOOD-BRAIN BARRIER IMPROVES DRUG DELIVERY TO BRAIN METASTASIS

Neuro-Oncology Advances ◽

10.1093/noajnl/vdz014.054 ◽

2019 ◽

Vol 1 (Supplement_1) ◽

pp. i13-i13

Author(s):

Synnøve Nymark Aasen ◽

Heidi Espedal ◽

Christopher Holte ◽

Olivier Keunen ◽

Tine Veronika Karlsen ◽

...

Keyword(s):

Drug Delivery ◽

Blood Brain Barrier ◽

Plasma Membranes ◽

Combined Treatment ◽

Brain Barrier ◽

Therapeutic Window ◽

Dce Mri ◽

Blood Brain ◽

The Brain ◽

Bbb Opening

Abstract BACKGROUND: Melanoma patients have a high risk of developing brain metastases, which is associated with a poor prognosis. The blood-brain barrier (BBB) inhibits sufficient drug delivery into metastatic lesions. We investigated the ability of a synthetic peptide (K16ApoE) to permeabilize the BBB for more effective drug treatment. METHODS: DCE-MRI was performed to study the therapeutic window of BBB opening facilitated by K16ApoE. In vivoand in vitroassays were used to determine K16ApoE toxicity and also to obtain mechanistic insight into its action on the BBB. The therapeutic impact of K16ApoE on melanoma metastases was determined together with dabrafenib, which is otherwise known not to cross an intact BBB. RESULTS: DCE-MRI exhibited an effective K16ApoE-mediated BBB opening for up to 1h. Mechanistic studies displayed a dose-dependent effect of K16ApoE caused by induction of endocytosis. At higher concentrations, the peptide also showed unspecific disturbances on plasma membranes. Combined treatment with K16ApoE and dabrafenib reduced the brain metastatic burden in mice compared to dabrafenib. We also showed by PET/CT that the peptide facilitated the delivery of compounds up to 150 kDa into the brain. CONCLUSIONS: We demonstrate a transient opening of the BBB, caused by K16ApoE, that facilitates improved drug-delivery into the brain. This improves the efficacy of drugs that otherwise do not cross the intact BBB.

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The Transport of Leucine and Aminocyclopentanecarboxylate across the Intact, Energy-Depleted Rat Blood—Brain Barrier

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.1989.33 ◽

1989 ◽

Vol 9 (2) ◽

pp. 226-233 ◽

Cited By ~ 7

Author(s):

J. Greenwood ◽

A. S. Hazell ◽

O. E. Pratt

Keyword(s):

Amino Acid ◽

Blood Brain Barrier ◽

Molecular Size ◽

Brain Barrier ◽

Large Neutral Amino Acid ◽

Blood Brain ◽

Order Of Magnitude ◽

The Central Nervous System ◽

The Brain

The transport across the blood-brain barrier of the large neutral amino acid leucine and the nonmetabolised aminocyclopentanecarboxylate (ACPC), of similar molecular size, was studied in the perfused, energy-depleted rat brain. It was found that when both leucine and ACPC were perfused for periods of up to 10 min their accumulation in the brain increased in a linear fashion. The ratio of perfusate radioactivity per milliliter and tissue radioactivity per gram (Rt/Rp) rose to above unity for both leucine and ACPC, indicating continued uptake against a concentration gradient of the radiolabel within the CNS. When the effect of increasing the concentration of the amino acid upon its influx into the brain was studied, it was found that under these conditions the kinetics of transport for both leucine and ACPC were of a similar order of magnitude to those reported previously in vivo. The values for the Michaelis constant for transport ( Km), maximum rate of transport ( Vmax), and the constant for the apparently linear, nonsaturable component ( Kd) for leucine into the cerebrum were 84.5 ± 29.0 μ M, 45.5 ± 1.5 nmole/min/g, and 2.62 ± 0.15 μl/min/g, respectively, and for ACPC 381 ± 64 μ M, 54.0 ± 1.5 nmole/min/g and 0.35 ± 0.10 μl/min/g, respectively. Comparing this data with previously reported values it is suggested that the transport of leucine into the central nervous system from a perfusate or bolus where no other competing amino acids are present, is flow dependent. Furthermore, ACPC enters the brain almost entirely by a carrier-mediated process, with little or no nonsaturable influx despite a similar oil/water partition coefficient as leucine.

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Consistent opening of the blood brain barrier using focused ultrasound with constant intravenous infusion of microbubble agent

Scientific Reports ◽

10.1038/s41598-020-73312-9 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Norman A. Lapin ◽

Kirt Gill ◽

Bhavya R. Shah ◽

Rajiv Chopra

Keyword(s):

Blood Brain Barrier ◽

Focused Ultrasound ◽

Brain Barrier ◽

Mri Contrast ◽

Intravenous Injections ◽

Blood Brain ◽

Target Sites ◽

The Brain ◽

Microbubble Agent ◽

Bbb Opening

Abstract The blood brain barrier (BBB) is a major obstacle to the delivery of therapeutics to the brain. Focused ultrasound (FUS) in combination with microbubbles can non-invasively open the BBB in a targeted manner. Bolus intravenous injections of microbubbles are standard practice, but dynamic influx and clearance mechanisms prevent delivery of a uniform dose with time. When multiple targets are selected for sonication in a single treatment, uniform serum concentrations of microbubbles are important for consistent BBB opening. Herein, we show that bubble infusions were able to achieve consistent BBB opening at multiple target sites. FUS exposures were conducted with different Definity microbubble concentrations at various acoustic pressures. To quantify the effects of infusion on BBB opening, we calculated the MRI contrast enhancement rate. When infusions were performed at rates of 7.2 µl microbubbles/kg/min or below, we were able to obtain consistent BBB opening without injury at all pressures. However, when infusion rates exceeded 20 µl/kg/min, signs of injury occurred at pressures from 0.39 to 0.56 MPa. When compared to bolus injections, a bubble infusion offers a more controlled and consistent approach to multi-target BBB disruption.

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Impact of Drug Size on Brain Tumor and Brain Parenchyma Delivery after a Blood–Brain Barrier Disruption

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.2014.14 ◽

2014 ◽

Vol 34 (5) ◽

pp. 820-826 ◽

Cited By ~ 12

Author(s):

Marie Blanchette ◽

Luc Tremblay ◽

Martin Lepage ◽

David Fortin

Keyword(s):

Blood Brain Barrier ◽

Time Window ◽

Molecular Size ◽

Brain Parenchyma ◽

Brain Barrier ◽

Blood Brain Barrier Disruption ◽

Blood Brain ◽

Brain Barrier Disruption ◽

Cas A ◽

The Brain

Drug delivery to the brain is influenced by the blood–brain barrier (BBB) and blood–tumor barrier (BTB) to an extent that is still debated in neuro-oncology. In this paper, we studied the delivery across the BTB and the BBB of compounds with different molecular sizes in normal and glioma-bearing rats. Studies were performed at baseline as well as after an osmotic BBB disruption (BBBD) using dynamic contrast-enhanced magnetic resonance imaging and two T1, contrast agents (CAs), Magnevist (743 Da) and Gadomer (17,000 Da). More specifically, we determined the time window for the BBB permeability, the distribution and we calculated the brain exposure to the CAs. A different pattern of accumulation and distribution at baseline as well as after a BBBD procedure was observed for both agents, which is consistent with their different molecular size and weight. Baseline tumor exposure was threefold higher for Magnevist compared with Gadomer, whereas postBBBD tumor exposure was twofold higher for Magnevist. Our study clearly showed that the time window and the extent of delivery across the intact, as well as permeabilized BTB and BBB are influenced by drug size.

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Ligand and Structure-based Modeling of Passive Diffusion through the Blood-Brain Barrier

Current Medicinal Chemistry ◽

10.2174/0929867324666171106163742 ◽

2018 ◽

Vol 25 (9) ◽

pp. 1073-1089 ◽

Cited By ~ 1

Author(s):

Santiago Vilar ◽

Eduardo Sobarzo-Sanchez ◽

Lourdes Santana ◽

Eugenio Uriarte

Keyword(s):

Blood Brain Barrier ◽

In Silico ◽

Passive Diffusion ◽

Brain Barrier ◽

Barrier Permeability ◽

Blood Brain Barrier Permeability ◽

Blood Brain ◽

Brain Barrier Permeability ◽

Different Types ◽

The Brain

Background: Blood-brain barrier transport is an important process to be considered in drug candidates. The blood-brain barrier protects the brain from toxicological agents and, therefore, also establishes a restrictive mechanism for the delivery of drugs into the brain. Although there are different and complex mechanisms implicated in drug transport, in this review we focused on the prediction of passive diffusion through the blood-brain barrier. Methods: We elaborated on ligand-based and structure-based models that have been described to predict the blood-brain barrier permeability. Results: Multiple 2D and 3D QSPR/QSAR models and integrative approaches have been published to establish quantitative and qualitative relationships with the blood-brain barrier permeability. We explained different types of descriptors that correlate with passive diffusion along with data analysis methods. Moreover, we discussed the applicability of other types of molecular structure-based simulations, such as molecular dynamics, and their implications in the prediction of passive diffusion. Challenges and limitations of experimental measurements of permeability and in silico predictive methods were also described. Conclusion: Improvements in the prediction of blood-brain barrier permeability from different types of in silico models are crucial to optimize the process of Central Nervous System drug discovery and development.

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Liposomes: Novel Drug Delivery Approach for Targeting Parkinson’s Disease

Current Pharmaceutical Design ◽

10.2174/1381612826666200128145124 ◽

2020 ◽

Vol 26 (37) ◽

pp. 4721-4737 ◽

Cited By ~ 4

Author(s):

Bhumika Kumar ◽

Mukesh Pandey ◽

Faheem H. Pottoo ◽

Faizana Fayaz ◽

Anjali Sharma ◽

...

Keyword(s):

Parkinson’S Disease ◽

Drug Delivery ◽

Parkinson's Disease ◽

Side Effects ◽

Blood Brain Barrier ◽

Brain Barrier ◽

Brain Targeting ◽

Neural Cells ◽

Blood Brain ◽

The Brain

Parkinson’s disease is one of the most severe progressive neurodegenerative disorders, having a mortifying effect on the health of millions of people around the globe. The neural cells producing dopamine in the substantia nigra of the brain die out. This leads to symptoms like hypokinesia, rigidity, bradykinesia, and rest tremor. Parkinsonism cannot be cured, but the symptoms can be reduced with the intervention of medicinal drugs, surgical treatments, and physical therapies. Delivering drugs to the brain for treating Parkinson’s disease is very challenging. The blood-brain barrier acts as a highly selective semi-permeable barrier, which refrains the drug from reaching the brain. Conventional drug delivery systems used for Parkinson’s disease do not readily cross the blood barrier and further lead to several side-effects. Recent advancements in drug delivery technologies have facilitated drug delivery to the brain without flooding the bloodstream and by directly targeting the neurons. In the era of Nanotherapeutics, liposomes are an efficient drug delivery option for brain targeting. Liposomes facilitate the passage of drugs across the blood-brain barrier, enhances the efficacy of the drugs, and minimize the side effects related to it. The review aims at providing a broad updated view of the liposomes, which can be used for targeting Parkinson’s disease.

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