A new brain drug delivery strategy: focused ultrasound-enhanced intranasal drug delivery

Focused ultrasound-mediated blood-brain barrier opening is safe and feasible with moderately hypofractionated radiotherapy for brainstem diffuse midline glioma

BACKGROUND

Diffuse midline glioma (DMG) is a pediatric tumor with dismal prognosis. Systemic strategies have been unsuccessful and radiotherapy (RT) remains the standard-of-care. A central impediment to treatment is the blood-brain barrier (BBB), which precludes drug delivery to the central nervous system (CNS). Focused ultrasound (FUS) with microbubbles can transiently and non-invasively disrupt the BBB to enhance drug delivery. This study aimed to determine the feasibility of brainstem FUS in combination with clinical doses of RT. We hypothesized that FUS-mediated BBB-opening (BBBO) is safe and feasible with 39 Gy RT.

METHODS

To establish a safety timeline, we administered FUS to the brainstem of non-tumor bearing mice concurrent with or adjuvant to RT; our findings were validated in a syngeneic brainstem murine model of DMG receiving repeated sonication concurrent with RT. The brainstems of male B6 (Cg)-Tyrc-2J/J albino mice were intracranially injected with mouse DMG cells (PDGFB+, H3.3K27M, p53-/-). A clinical RT dose of 39 Gy in 13 fractions (39 Gy/13fx) was delivered using the Small Animal Radiation Research Platform (SARRP) or XRAD-320 irradiator. FUS was administered via a 0.5 MHz transducer, with BBBO and tumor volume monitored by magnetic resonance imaging (MRI).

RESULTS

FUS-mediated BBBO did not affect cardiorespiratory rate, motor function, or tissue integrity in non-tumor bearing mice receiving RT. Tumor-bearing mice tolerated repeated brainstem BBBO concurrent with RT. 39 Gy/13fx offered local control, though disease progression occurred 3-4 weeks post-RT.

CONCLUSION

Repeated FUS-mediated BBBO is safe and feasible concurrent with RT. In our syngeneic DMG murine model, progression occurs, serving as an ideal model for future combination testing with RT and FUS-mediated drug delivery.

Iron homeostasis and post-hemorrhagic hydrocephalus: a review

Iron physiology is regulated by a complex interplay of extracellular transport systems, coordinated transcriptional responses, and iron efflux mechanisms. Dysregulation of iron metabolism can result in defects in myelination, neurotransmitter synthesis, and neuronal maturation. In neonates, germinal matrix-intraventricular hemorrhage (GMH-IVH) causes iron overload as a result of blood breakdown in the ventricles and brain parenchyma which can lead to post-hemorrhagic hydrocephalus (PHH). However, the precise mechanisms by which GMH-IVH results in PHH remain elusive. Understanding the molecular determinants of iron homeostasis in the developing brain may lead to improved therapies. This manuscript reviews the various roles iron has in brain development, characterizes our understanding of iron transport in the developing brain, and describes potential mechanisms by which iron overload may cause PHH and brain injury. We also review novel preclinical treatments for IVH that specifically target iron. Understanding iron handling within the brain and central nervous system may provide a basis for preventative, targeted treatments for iron-mediated pathogenesis of GMH-IVH and PHH.

Nanomaterials as drug delivery agents for overcoming the blood-brain barrier: A comprehensive review

Background and Purpose

The blood-brain barrier (BBB), a critical interface of specialized endothelial cells, plays a pivotal role in regulating molecular and ion transport between the central nervous system (CNS) and systemic circulation.

Experimental Approach

This review aims to delve into the intricate architecture and functions of the BBB while addressing challenges associated with delivering therapeutics to the brain. Historical milestones and contemporary insights underscore the BBB's significance in protecting the CNS.

Key Results

Innovative approaches for enhanced drug transport include intranasal delivery exploiting olfactory and trigeminal pathways, as well as techniques like temporary BBB opening through chemicals, receptors, or focused ultrasound. These avenues hold the potential to reshape conventional drug delivery paradigms and address the limitations posed by the BBB's selectivity.

Conclusion

This review underscores the vital role of the BBB in maintaining CNS health and emphasizes the importance of effective drug delivery through this barrier. Nanoparticles emerge as promising candidates to overcome BBB limitations and potentially revolutionize the treatment of CNS disorders. As research progresses, the application of nanomaterials shows immense potential for advancing neurological therapeutics, albeit with careful consideration of safety aspects.

Mechanically manipulating glymphatic transport by ultrasound combined with microbubbles

The glymphatic system is a perivascular fluid transport system for waste clearance. Glymphatic transport is believed to be driven by the perivascular pumping effect created by the pulsation of the arterial wall caused by the cardiac cycle. Ultrasound sonication of circulating microbubbles (MBs) in the cerebral vasculature induces volumetric expansion and contraction of MBs that push and pull on the vessel wall to generate a MB pumping effect. The objective of this study was to evaluate whether glymphatic transport can be mechanically manipulated by focused ultrasound (FUS) sonication of MBs. The glymphatic pathway in intact mouse brains was studied using intranasal administration of fluorescently labeled albumin as fluid tracers, followed by FUS sonication at a deep brain target (thalamus) in the presence of intravenously injected MBs. Intracisternal magna injection, the conventional technique used in studying glymphatic transport, was employed to provide a comparative reference. Three-dimensional confocal microscopy imaging of optically cleared brain tissue revealed that FUS sonication enhanced the transport of fluorescently labeled albumin tracer in the perivascular space (PVS) along microvessels, primarily the arterioles. We also obtained evidence of FUS-enhanced penetration of the albumin tracer from the PVS into the interstitial space. This study revealed that ultrasound combined with circulating MBs could mechanically enhance glymphatic transport in the brain.

Microbubble Delivery Platform for Ultrasound-Mediated Therapy in Brain Cancers

The blood-brain barrier (BBB) is one of the most selective endothelial barriers that protect the brain and maintains homeostasis in neural microenvironments. This barrier restricts the passage of molecules into the brain, except for gaseous or extremely small hydrophobic molecules. Thus, the BBB hinders the delivery of drugs with large molecular weights for the treatment of brain cancers. Various methods have been used to deliver drugs to the brain by circumventing the BBB; however, they have limitations such as drug diversity and low delivery efficiency. To overcome this challenge, microbubbles (MBs)-based drug delivery systems have garnered a lot of interest in recent years. MBs are widely used as contrast agents and are recently being researched as a vehicle for delivering drugs, proteins, and gene complexes. The MBs are 1-10 μm in size and consist of a gas core and an organic shell, which cause physical changes, such as bubble expansion, contraction, vibration, and collapse, in response to ultrasound. The physical changes in the MBs and the resulting energy lead to biological changes in the BBB and cause the drug to penetrate it, thus enhancing the therapeutic effect. Particularly, this review describes a state-of-the-art strategy for fabricating MB-based delivery platforms and their use with ultrasound in brain cancer therapy.

Focused Ultrasound-Mediated Intranasal Brain Drug Delivery Technique (FUSIN)

The blood-brain barrier (BBB) is the major barrier for brain drug delivery and limits the treatment options for central nervous system diseases. To circumvent the BBB, we introduced the focused ultrasound-mediated intranasal brain drug delivery (FUSIN) technique. FUSIN utilizes the nasal route for direct nose-to-brain drug administration, bypassing the BBB and minimizing systemic exposure. It also uses the transcranial application of ultrasound energy focused at a targeted brain region to induce microbubble cavitation, which enhances the transport of intranasally administered agents at the FUS-targeted brain location. FUSIN is unique in that it can achieve noninvasive and localized brain drug delivery with minimized systemic toxicity. The goal of this chapter is to provide a detailed protocol for FUSIN delivery to the mouse brain.

Designing nanoformulation for the nose-to-brain delivery in Parkinson's disease: Advancements and barrier

Parkinson's disease (PD), a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons, which results in the loss of motor activity. In the management of PD, the primary aim is to increase the dopamine content in the brain either by delivering the precursors of dopamine or by inhibiting the molecules responsible for dopamine degradation. Due to the low bioavailability, a higher dosage of drugs needs to be administered repeatedly for achieving the desired therapeutic effect. This repeated high dose not only increases the severe side effects but also produces tolerance in the body. Often, direct administration of drugs fails to ameliorate the symptoms as the unmodified drugs cannot cross the blood-brain barrier (BBB). Nanotherapeutic is at the forefront of the alternative treatment against the central nervous system (CNS) disorders due to the ability to circumvents the BBB. Here, all the available treatments for PD have been discussed with their limitation. The current trends of nanotherapeutics for PD have been explored. Suitability and formulation prospects for nasal delivery have been analyzed in detail to explore new research scope. The most effective approach is the nose-to-brain delivery for targeting drugs directly to the brain. This delivery bypasses the BBB and concentrates more drugs at the target site. Thus, developments of nose-to-brain delivery of nanoformulations explicit the new scope to manage PD better. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Drug Delivery Challenges in Brain Disorders across the Blood-Brain Barrier: Novel Methods and Future Considerations for Improved Therapy

Due to the physiological and structural properties of the blood-brain barrier (BBB), the delivery of drugs to the brain poses a unique challenge in patients with central nervous system (CNS) disorders. Several strategies have been investigated to circumvent the barrier for CNS therapeutics such as in epilepsy, stroke, brain cancer and traumatic brain injury. In this review, we summarize current and novel routes of drug interventions, discuss pharmacokinetics and pharmacodynamics at the neurovascular interface, and propose additional factors that may influence drug delivery. At present, both technological and mechanistic tools are devised to assist in overcoming the BBB for more efficient and improved drug bioavailability in the treatment of clinically devastating brain disorders.

Focused ultrasound-mediated intranasal brain drug delivery technique (FUSIN)

The blood-brain barrier (BBB) is the major obstacle for brain drug delivery and limits the treatment options for central nervous system diseases. To circumvent the BBB, we introduce focused ultrasound-mediated intranasal brain drug delivery (FUSIN). FUSIN utilizes the nasal route for direct nose-to-brain drug administration, bypassing the BBB and minimizing systemic exposure to the major organs, such as heart, lung, liver, and kidney [1]. It also uses transcranial ultrasound energy focused at a targeted brain region to induce microbubble cavitation, enhancing the transport of intranasally administered agents at the FUS-targeted brain location. FUSIN is unique because it can achieve noninvasive and localized brain drug delivery with minimized systemic toxicity to other major organs. The goal of this paper is to provide a detailed protocol for FUSIN delivery to the mouse brain.•

FUSIN delivery utilizes the nose-to-brain pathway for brain drug delivery.

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FUSIN utilizes FUS combined with microbubble to significantly enhance the delivery efficiency of intranasally administered drugs to the FUS targeted brain regions.

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FUSIN achieves efficient brain delivery with minimized systemic exposure in the major organs.

Focused Ultrasound-Enhanced Delivery of Intranasally Administered Anti-Programmed Cell Death-Ligand 1 Antibody to an Intracranial Murine Glioma Model

Immune checkpoint inhibitors have great potential for the treatment of gliomas; however, their therapeutic efficacy has been partially limited by their inability to efficiently cross the blood–brain barrier (BBB). The objective of this study was to evaluate the capability of focused-ultrasound-mediated intranasal brain drug delivery (FUSIN) in achieving the locally enhanced delivery of anti-programmed cell death-ligand 1 antibody (aPD-L1) to the brain. Both non-tumor mice and mice transcranially implanted with GL261 glioma cells at the brainstem were used in this study. aPD-L1 was labeled with a near-infrared fluorescence dye (IRDye 800CW) and administered to mice through the nasal route to the brain, followed by focused ultrasound sonication in the presence of systemically injected microbubbles. FUSIN enhanced the accumulation of aPD-L1 at the FUS-targeted brainstem by an average of 4.03- and 3.74-fold compared with intranasal (IN) administration alone in the non-tumor mice and glioma mice, respectively. Immunohistochemistry staining found that aPD-L1 was mainly located within the perivascular spaces after IN delivery, while FUSIN further enhanced the penetration depth and delivery efficiency of aPD-L1 to the brain parenchyma. The delivered aPD-L1 was found to be colocalized with the tumor cells after FUSIN delivery to the brainstem glioma. These findings suggest that FUSIN is a promising technique to enhance the delivery of immune checkpoint inhibitors to gliomas.

Characterization of focused ultrasound-mediated brainstem delivery of intranasally administered agents

Focused ultrasound-mediated intranasal (FUSIN) delivery is a recently proposed technique that bypasses the blood-brain barrier to achieve noninvasive and localized brain drug delivery. The goal of this study was to characterize FUSIN drug delivery outcome in mice with regard to its dependency on several critical experimental factors, including the time interval between IN administration and FUS sonication (Tlag1), the FUS pressure, and the time for sacrificing the mice post-FUS (Tlag2). Wild-type mice were treated by FUSIN delivery of near-infrared fluorescent dye-labeled bovine serum albumin (800CW-BSA, used as a model agent). 800CW-BSA was intranasally administered to the mice in vivo, followed by intravenous injection of microbubbles and FUS sonication at the brainstem. Fluorescence imaging of ex vivo mouse brain slices was used to quantify the delivery outcomes of 800CW-BSA. Major organs, along with the nasal tissue and trigeminal nerve, were harvested to assess the biodistribution of 800CW-BSA. The delivery outcome of 800CW-BSA was the highest at the brainstem when Tlag1 was 0.5 h, which was on average 24.5-fold, 5.4-fold, and 21.6-fold higher than those of the IN only, Tlag1 = 1.5 h, and Tlag1 = 4.0 h, respectively. The FUSIN delivery outcome at the lowest pressure level, 0.43 MPa, was on average 1.8-fold and 3.7-fold higher than those at 0.56 MPa and 0.70 MPa, respectively. The mean concentration of 800CW-BSA in the brainstem after FUSIN delivery decreased from 0.5 h to 4.0 h post-FUS. The accumulation of 800CW-BSA was low in the heart, lung, spleen, kidneys, and liver, but high in the stomach and intestines. This study revealed the unique characteristics of FUSIN as a noninvasive, efficient, and localized brain drug delivery technique.

Intranasal Dexamethasone Reduces Mortality and Brain Damage in a Mouse Experimental Ischemic Stroke Model

Neuroinflammation triggered by the expression of damaged-associated molecular patterns released from dying cells plays a critical role in the pathogenesis of ischemic stroke. However, the benefits from the control of neuroinflammation in the clinical outcome have not been established. In this study, the effectiveness of intranasal, a highly efficient route to reach the central nervous system, and intraperitoneal dexamethasone administration in the treatment of neuroinflammation was evaluated in a 60-min middle cerebral artery occlusion (MCAO) model in C57BL/6 male mice. We performed a side-by-side comparison using intranasal versus intraperitoneal dexamethasone, a timecourse including immediate (0 h) or 4 or 12 h poststroke intranasal administration, as well as 4 intranasal doses of dexamethasone beginning 12 h after the MCAO versus a single dose at 12 h to identify the most effective conditions to treat neuroinflammation in MCAO mice. The best results were obtained 12 h after MCAO and when mice received a single dose of dexamethasone (0.25 mg/kg) intranasally. This treatment significantly reduced mortality, neurological deficits, infarct volume size, blood-brain barrier permeability in the somatosensory cortex, inflammatory cell infiltration, and glial activation. Our results demonstrate that a single low dose of intranasal dexamethasone has neuroprotective therapeutic effects in the MCAO model, showing a better clinical outcome than the intraperitoneal administration. Based on these results, we propose a new therapeutic approach for the treatment of the damage process that accompanies ischemic stroke.

Imaging of intranasal drug delivery to the brain

Intranasal (IN) delivery is a rapidly developing area for therapies with great potential for the treatment of central nervous system (CNS) diseases. Moreover, in vivo imaging is becoming an important part of therapy assessment, both clinically in humans and translationally in animals. IN drug delivery is an alternative to systemic administration that uses the direct anatomic pathway between the olfactory/trigeminal neuroepithelium of the nasal mucosa and the brain. Several drugs have already been approved for IN application, while others are undergoing development and testing. To better understand which imaging modalities are being used to assess IN delivery of therapeutics, we performed a literature search with the key words "Intranasal delivery" and "Imaging" and summarized these findings in the current review. While this review does not attempt to be fully comprehensive, we intend for the examples provided to allow a well-rounded picture of the imaging tools available to assess IN delivery, with an emphasis on the nose-to-brain delivery route. Examples of in vivo imaging, for both humans and animals, include magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), gamma scintigraphy and computed tomography (CT). Additionally, some in vivo optical imaging modalities, including bioluminescence and fluorescence, have been used more in experimental testing in animals. In this review, we introduce each imaging modality, how it is being utilized and outline its strengths and weaknesses, specifically in the context of IN delivery of therapeutics to the brain.

Focused ultrasound enhanced intranasal delivery of brain derived neurotrophic factor produces neurorestorative effects in a Parkinson's disease mouse model

Focused ultrasound-enhanced intranasal (IN + FUS) delivery is a noninvasive approach that utilizes the olfactory pathway to administer pharmacological agents directly to the brain, allowing for a more homogenous distribution in targeted locations compared to IN delivery alone. However, whether such a strategy has therapeutic values, especially in neurodegenerative disorders such as Parkinson’s disease (PD), remains to be established. Herein, we evaluated whether the expression of tyrosine hydroxylase (TH), the rate limiting enzyme in dopamine catalysis, could be enhanced by IN + FUS delivery of brain-derived neurotrophic factor (BDNF) in a toxin-based PD mouse model. Mice were put on the subacute dosing regimen of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), producing bilateral degeneration of the nigrostriatal pathway consistent with early-stage PD. MPTP mice then received BDNF intranasally followed by multiple unilateral FUS-induced blood-brain barrier (BBB) openings in the left basal ganglia for three consecutive weeks. Subsequently, mice were survived for two months and were evaluated morphologically and behaviorally to determine the integrity of their nigrostriatal dopaminergic pathways. Mice receiving IN + FUS had significantly increased TH immunoreactivity in the treated hemisphere compared to the untreated hemisphere while mice receiving only FUS-induced BBB opening or no treatment at all did not show any differences. Additionally, behavioral changes were only observed in the IN + FUS treated mice, indicating improved motor control function in the treated hemisphere. These findings demonstrate the robustness of the method and potential of IN + FUS for the delivery of bioactive factors for treatment of neurodegenerative disorder.

Focused ultrasound combined with microbubble-mediated intranasal delivery of gold nanoclusters to the brain

Focused ultrasound combined with microbubble-mediated intranasal delivery (FUSIN) is a new brain drug delivery technique. FUSIN utilizes the nasal route for direct nose-to-brain drug administration, thereby bypassing the blood-brain barrier (BBB) and minimizing systemic exposure. It also uses FUS-induced microbubble cavitation to enhance transport of intranasally (IN) administered agents to the FUS-targeted brain location. Previous studies have provided proof-of-concept data showing the feasibility of FUSIN to deliver dextran and the brain-derived neurotrophic factor to the caudate putamen of mouse brains. The objective of this study was to evaluate the biodistribution of IN administered gold nanoclusters (AuNCs) and assess the feasibility and short-term safety of FUSIN for the delivery of AuNCs to the brainstem. Three experiments were performed. First, the whole-body biodistribution of IN administered 64Cu-alloyed AuNCs (64Cu-AuNCs) was assessed using in vivo positron emission tomography/computed tomography (PET/CT) and verified with ex vivo gamma counting. Control mice were intravenously (IV) injected with the 64Cu-AuNCs. Second, 64Cu-AuNCs and Texas red-labeled AuNCs (TR-AuNCs) were used separately to evaluate FUSIN delivery outcome in the brain. 64Cu-AuNCs or TR-AuNCs were administered to mice through the nasal route, followed by FUS sonication at the brainstem in the presence of systemically injected microbubbles. The spatial distribution of 64Cu-AuNCs and TR-AuNCs were examined by autoradiography and fluorescence microscopy of ex vivo brain slices, respectively. Third, histological analysis was performed to evaluate any potential histological damage to the nose and brain after FUSIN treatment. The experimental results revealed that IN administration induced significantly lower 64Cu-AuNCs accumulation in the blood, lungs, liver, spleen, kidney, and heart compared with IV injection. FUSIN enhanced the delivery of 64Cu-AuNCs and TR-AuNCs at the FUS-targeted brain region compared with IN delivery alone. No histological-level tissue damage was detected in the nose, trigeminal nerve, and brain. These results suggest that FUSIN is a promising technique for noninvasive, spatially targeted, and safe delivery of nanoparticles to the brain with minimal systemic exposure.

Box-Behnken experimental design for preparation and optimization of the intranasal gels of selegiline hydrochloride

Selegiline hydrochloride (SL) is chosen as an adjunct for the control of clinical signs of Parkinsonian patients. The aim of the present work is to develop and optimize thermosensitive gels using Pluronic (F-127) for enhancing transport of SL into the brain through the nasal route. SL gels were prepared using a cold method and the Box-Behnken experimental design methodology. Drug (SL), gelling agent (F-127), and emulsifier (Propylene glycol, PG) were selected as independent variables, while the gelation temperature, gel strength, pH, gel content, and gel erosion were considered as dependent variables. For further understanding of the interaction between the various variables, contour plots and surface plots were also applied. Selected formulations, like S10 (contain 25 mg SL, 20 g F-127, and 1 g PG) and S14 (contain 50 mg SL, 18 g F-127 and 1 g PG), had a clear appearance in the sol form, with gelling temperature of the nasal gel ranging between 33 and 34, respectively. The gel strength of the formulations varied from 4.67 and 0.68 mm and the drug content was 100%. The pH of the formulations ranged between 6.71 and 7.11. Detachment force was acceptable (63.69-244.16 N/cm²) to provide prolonged adhesion. In vitro, drug release studies showed that the prepared formulations could release SL for up to 8 h. Permeation flux for the S10 gel was 0.0002 mg/min/cm². Results demonstrated that the potential use of SL gels can enhance the therapeutic effect of SL through the intranasal administration.

Focused Ultrasound Enabled Trans-Blood Brain Barrier Delivery of Gold Nanoclusters: Effect of Surface Charges and Quantification Using Positron Emission Tomography

Focused ultrasound (FUS) technology is reported to enhance the delivery of ⁶⁴ Cu-integrated ultrasmall gold nanoclusters (⁶⁴ Cu-AuNCs) across the blood-brain barrier (BBB) as measured by positron emission tomography (PET). To better define the optimal physical properties for brain delivery, ⁶⁴ Cu-AuNCs with different surface charges are synthesized and characterized. In vivo biodistribution studies are performed to compare the individual organ uptake of each type of ⁶⁴ Cu-AuNCs. Quantitative PET imaging post-FUS treatment shows site-targeted brain penetration, retention, and diffusion of the negative, neutral, and positive ⁶⁴ Cu-AuNCs. Autoradiography is performed to compare the intrabrain distribution of these nanoclusters. PET Imaging demonstrates the effective BBB opening and successful delivery of ⁶⁴ Cu-AuNCs into the brain. Of the three ⁶⁴ Cu-AuNCs investigated, the neutrally charged nanostructure performs the best and is the candidate platform for future theranostic applications in neuro-oncology.

Focused ultrasound-enabled delivery of radiolabeled nanoclusters to the pons

The goal of this study was to establish the feasibility of integrating focused ultrasound (FUS)-mediated delivery of ⁶⁴Cu-integrated gold nanoclusters (⁶⁴Cu-AuNCs) to the pons for in vivo quantification of the nanocluster brain uptake using positron emission tomography (PET) imaging. FUS was targeted at the pons for the blood-brain barrier (BBB) disruption in the presence of systemically injected microbubbles, followed by the intravenous injection of ⁶⁴Cu-AuNCs. The spatiotemporal distribution of the ⁶⁴Cu-AuNCs in the brain was quantified using in vivo microPET/CT imaging at different time points post injection. Following PET imaging, the accumulation of radioactivity in the pons was further confirmed using autoradiography and gamma counting, and the gold concentration was quantified using inductively coupled plasma-mass spectrometry (ICP-MS). We found that the noninvasive and localized BBB opening by the FUS successfully delivered the ⁶⁴Cu-AuNCs to the pons. We also demonstrated that in vivo real-time microPET/CT imaging was a reliable method for monitoring and quantifying the brain uptake of ⁶⁴Cu-AuNCs delivered by the FUS. This drug delivery platform that integrates FUS, radiolabeled nanoclusters, and PET imaging provides a new strategy for noninvasive and localized nanoparticle delivery to the pons with concurrent in vivo quantitative imaging to evaluate delivery efficiency. The long-term goal is to apply this drug delivery platform to the treatment of pontine gliomas.

Ultrasonic Neuromodulation Causes Widespread Cortical Activation via an Indirect Auditory Mechanism

Ultrasound has received widespread attention as an emerging technology for targeted, non-invasive neuromodulation based on its ability to evoke electrophysiological and motor responses in animals. However, little is known about the spatiotemporal pattern of ultrasound-induced brain activity that could drive these responses. Here, we address this question by combining focused ultrasound with wide-field optical imaging of calcium signals in transgenic mice. Surprisingly, we find cortical activity patterns consistent with indirect activation of auditory pathways rather than direct neuromodulation at the ultrasound focus. Ultrasound-induced activity is similar to that evoked by audible sound. Furthermore, both ultrasound and audible sound elicit motor responses consistent with a startle reflex, with both responses reduced by chemical deafening. These findings reveal an indirect auditory mechanism for ultrasound-induced cortical activity and movement requiring careful consideration in future development of ultrasonic neuromodulation as a tool in neuroscience research.

Focused Ultrasound-enabled Brain Tumor Liquid Biopsy

Although blood-based liquid biopsies have emerged as a promising non-invasive method to detect biomarkers in various cancers, limited progress has been made for brain tumors. One major obstacle is the blood-brain barrier (BBB), which hinders efficient passage of tumor biomarkers into the peripheral circulation. The objective of this study was to determine whether FUS in combination with microbubbles can enhance the release of biomarkers from the brain tumor to the blood circulation. Two glioblastoma tumor models (U87 and GL261), developed by intracranial injection of respective enhanced green fluorescent protein (eGFP)-transduced glioblastoma cells, were treated by FUS in the presence of systemically injected microbubbles. Effect of FUS on plasma eGFP mRNA levels was determined using quantitative polymerase chain reaction. eGFP mRNA were only detectable in the FUS-treated U87 mice and undetectable in the untreated U87 mice (maximum cycle number set to 40). This finding was replicated in GL261 mice across three different acoustic pressures. The circulating levels of eGFP mRNA were 1,500-4,800 fold higher in the FUS-treated GL261 mice than that of the untreated mice for the three acoustic pressures. This study demonstrated the feasibility of FUS-enabled brain tumor liquid biopsies in two different murine glioma models across different acoustic pressures.

Focused ultrasound-facilitated brain drug delivery using optimized nanodroplets: vaporization efficiency dictates large molecular delivery

Focused ultrasound with nanodroplets could facilitate localized drug delivery after vaporization with potentially improved in vivo stability, drug payload, and minimal interference outside of the focal zone compared with microbubbles. While the feasibility of blood-brain barrier (BBB) opening using nanodroplets has been previously reported, characterization of the associated delivery has not been achieved. It was hypothesized that the outcome of drug delivery was associated with the droplet's sensitivity to acoustic energy, and can be modulated with the boiling point of the liquid core. Therefore, in this study, octafluoropropane (OFP) and decafluorobutane (DFB) nanodroplets were used both in vitro for assessing their relative vaporization efficiency with high-speed microscopy, and in vivo for delivering molecules with a size relevant to proteins (40 kDa dextran) to the murine brain. It was found that at low pressures (300-450 kPa), OFP droplets vaporized into a greater number of microbubbles compared to DFB droplets at higher pressures (750-900 kPa) in the in vitro study. In the in vivo study, successful delivery was achieved with OFP droplets at 300 kPa and 450 kPa without evidence of cavitation damage using ¼ dosage, compared to DFB droplets at 900 kPa where histology indicated tissue damage due to inertial cavitation. In conclusion, the vaporization efficiency of nanodroplets positively impacted the amount of molecules delivered to the brain. The OFP droplets due to the higher vaporization efficiency served as better acoustic agents to deliver large molecules efficiently to the brain compared with the DFB droplets.

Intranasal delivery of dexamethasone efficiently controls LPS-induced murine neuroinflammation

Neuroinflammation is the hallmark of several infectious and neurodegenerative diseases. Synthetic glucocorticoids (GCs) are the first-line immunosuppressive drugs used for controlling neuroinflammation. A delayed diffusion of GCs molecules and the high systemic doses required for brain-specific targeting lead to severe undesirable effects, particularly when lifelong treatment is required. Therefore, there is an urgent need for improving this current therapeutic approach. The intranasal (i.n.) route is being employed increasingly for drug delivery to the brain via the olfactory system. In this study, the i.n. route is compared to the intravenous (i.v.) administration of GCs with respect to their effectiveness in controlling neuroinflammation induced experimentally by systemic lipopolysaccharide (LPS) injection. A statistically significant reduction in interleukin (IL)-6 levels in the central nervous system (CNS) in the percentage of CD45⁺ /CD11b⁺ /lymphocyte antigen 6 complex locus G6D [Ly6G⁺ and in glial fibrillary acidic protein (GFAP) immunostaining was observed in mice from the i.n.-dexamethasone (DX] group compared to control and i.v.-DX-treated animals. DX treatment did not modify the percentage of microglia and perivascular macrophages as determined by ionized calcium binding adaptor molecule 1 (Iba1) immunostaining of the cortex and hippocampus. The increased accumulation of DX in brain microvasculature in DX-i.n.-treated mice compared with controls and DX-IV-treated animals may underlie the higher effectiveness in controlling neuroinflammation. Altogether, these results indicate that IN-DX administration may offer a more efficient alternative than systemic administration to control neuroinflammation in different neuropathologies.

Treatment of Movement Disorders With Focused Ultrasound

Although the use of ultrasound as a potential therapeutic modality in the brain has been under study for several decades, relatively few neuroscientists or neurologists are familiar with this technology. Stereotactic brain lesioning had been widely used as a treatment for medically refractory patients with essential tremor (ET), Parkinson disease (PD), and dystonia but has been largely replaced by deep brain stimulation (DBS) surgery, with advantages both in safety and efficacy. However, DBS is associated with complications including intracerebral hemorrhage, infection, and hardware malfunction. The occurrence of these complications has spurred interest in less invasive stereotactic brain lesioning methods including magnetic resonance imaging–guided high intensity–focused ultrasound (FUS) surgery. Engineering advances now allow sound waves to be targeted noninvasively through the skull to a brain target. High intensities of sonic energy can create a coagulation lesion similar to that of older radiofrequency stereotactic methods, but without opening the skull, recent Food and Drug Administration approval of unilateral thalamotomy for treatment of ET. Clinical studies of stereotactic FUS for aspects of PD are underway. Moderate intensity, pulsed FUS has also demonstrated the potential to safely open the blood-brain barrier for localized delivery of therapeutics including proteins, genes, and cell-based therapy for PD and related disorders. The goal of this review is to provide basic and clinical neuroscientists with a level of understanding to interact with medical physicists, biomedical engineers, and radiologists to accelerate the application of this powerful technology to brain disease

Focused Ultrasound: An Emerging Therapeutic Modality for Neurologic Disease

Therapeutic ultrasound is only beginning to be applied to neurologic conditions, but the potential of this modality for a wide spectrum of brain applications is high. Engineering advances now allow sound waves to be targeted through the skull to a brain region selected with real time magnetic resonance imaging and thermography, using a commercial array of focused emitters. High intensities of sonic energy can create a coagulation lesion similar to that of older radiofrequency stereotactic methods, but without opening the skull. This has led to the recent Food and Drug Administration approval of focused ultrasound (FUS) thalamotomy for unilateral treatment of essential tremor. Clinical studies of stereotactic FUS for aspects of Parkinson's disease, chronic pain, and refractory psychiatric indications are underway, with promising results. Moderate-intensity FUS has the potential to safely open the blood-brain barrier for localized delivery of therapeutics, while low levels of sonic energy can be used as a form of neuromodulation.

Lipid microbubbles as a vehicle for targeted drug delivery using focused ultrasound-induced blood-brain barrier opening

Focused ultrasound in conjunction with lipid microbubbles has fully demonstrated its ability to induce non-invasive, transient, and reversible blood-brain barrier opening. This study was aimed at testing the feasibility of our lipid-coated microbubbles as a vector for targeted drug delivery in the treatment of central nervous system diseases. These microbubbles were labeled with the fluorophore 5-dodecanoylaminfluorescein. Focused ultrasound targeted mouse brains in vivo in the presence of these microbubbles for trans-blood-brain barrier delivery of 5-dodecanoylaminfluorescein. This new approach, compared to previously studies of our group, where fluorescently labeled dextrans and microbubbles were co-administered, represents an appreciable improvement in safety outcome and targeted drug delivery. This novel technique allows the delivery of 5-dodecanoylaminfluorescein at the region of interest unlike the alternative of systemic exposure. 5-dodecanoylaminfluorescein delivery was assessed by ex vivo fluorescence imaging and by in vivo transcranial passive cavitation detection. Stable and inertial cavitation doses were quantified. The cavitation dose thresholds for estimating, a priori, successful targeted drug delivery were, for the first time, identified with inertial cavitation were concluded to be necessary for successful delivery. The findings presented herein indicate the feasibility and safety of the proposed microbubble-based targeted drug delivery and that, if successful, can be predicted by cavitation detection in vivo.

New horizons for focused ultrasound (FUS) - therapeutic applications in neurodegenerative diseases

Access to the CNS and delivery of therapeutics across the blood-brain barrier remains a challenge for most treatments of major neurological diseases such as AD or PD. Focused ultrasound represents a potential approach for overcoming these barriers to treating AD and PD and perhaps other neurological diseases. Ultrasound (US) is best known for its imaging capabilities of organs in the periphery, but various arrangements of the transducers producing the acoustic signal allow the energy to be precisely focused (F) within the skull. Using FUS in combination with MRI and contrast agents further enhances accuracy by providing clear information on location. Varying the acoustic power allows FUS to be used in applications ranging from imaging, stimulation of brain circuits, to ablation of tissue. In several transgenic mouse models of AD, the use of FUS with microbubbles reduces plaque load and improves cognition and suggests the need to investigate this technology for plaque removal in AD. In PD, FUS is being explored as a way to non-invasively ablate the brain areas responsible for the tremor and dyskinesia associated with the disease, but has yet to be utilized for non-invasive delivery of putative therapeutics. The FUS approach also greatly increases the range of possible CNS therapeutics as it overcomes the issues of BBB penetration. In this review we discuss how the characteristics and various applications of FUS may advance the therapeutics available for treating or preventing neurodegenerative disorders with an emphasis on treating AD and PD.

Intranasal brain-targeted clonazepam polymeric micelles for immediate control of status epilepticus: in vitro optimization, ex vivo determination of cytotoxicity, in vivo biodistribution and pharmacodynamics studies

Clonazepam (CZ) is an anti-epileptic drug used mainly in status epilepticus (SE). The drug belongs to Class II according to BCS classification with very limited solubility and high permeability and it suffers from extensive first-pass metabolism. The aim of the present study was to develop CZ-loaded polymeric micelles (PM) for direct brain delivery allowing immediate control of SE. PM were prepared via thin film hydration (TFH) technique adopting a central composite face-centered design (CCFD). The seventeen developed formulae were evaluated in terms of entrapment efficiency (EE), particle size (PS), polydispersity index (PDI), zeta potential (ZP), and in vitro release. For evaluating the in vivo behavior of the optimized formula, both biodistrbution using ^99mTc-radiolabeled CZ and pharmacodynamics studies were done in addition to ex vivo cytotoxicty. At a drug:Pluronic® P123:Pluronic® L121 ratio of 1:20:20 (PM7), a high EE, ZP, Q8h, and a low PDI was achieved. The biodistribution studies revealed that the optimized formula had significantly higher drug targeting efficiency (DTE = 242.3%), drug targeting index (DTI = 144.25), and nose-to-brain direct transport percentage (DTP = 99.30%) and a significant prolongation of protection from seizures in comparison to the intranasally administered solution with minor histopathological changes. The declared results reveal the ability of the developed PM to be a strong potential candidate for the emergency treatment of SE.

Using High-Intensity Focused Ultrasound as a Means to Provide Targeted Drug Delivery

High-intensity focused ultrasound (HIFU)–mediated drug delivery is a relatively novel technique used to deliver drugs to a targeted location in the body. High-intensity focused ultrasound–mediated drug delivery has a broad range of applications, such as tumor therapy, treating central nervous diseases, transsclera drug delivery, and cardiovascular treatments. Targeted treatments prove to be advantageous to systemic treatments due to the reduction in the associated side effects. Thus, this literature review focuses on the various applications of HIFU-mediated drug delivery as well as the mechanism involved. This article is intended to supply the reader with a detailed description of how this technique can be used as well as describe its potential to surpass other treatment methods. Further discussion on the efficiency, limitations, and future of HIFU-mediated drug delivery is addressed. Furthermore, the gaps in the published literature, relative to this topic, are discussed. Ultimately, HIFU-mediated drug delivery is a developing technique that could provide patients with exciting treatment options.

Progress and perspectives on targeting nanoparticles for brain drug delivery

Due to the ability of the blood-brain barrier (BBB) to prevent the entry of drugs into the brain, it is a challenge to treat central nervous system disorders pharmacologically. The development of nanotechnology provides potential to overcome this problem. In this review, the barriers to brain-targeted drug delivery are reviewed, including the BBB, blood-brain tumor barrier (BBTB), and nose-to-brain barrier. Delivery strategies are focused on overcoming the BBB, directly targeting diseased cells in the brain, and dual-targeted delivery. The major concerns and perspectives on constructing brain-targeted delivery systems are discussed.

Focused ultrasound-enhanced intranasal brain delivery of brain-derived neurotrophic factor

The objective of this study was to unveil the potential mechanism of focused ultrasound (FUS)-enhanced intranasal (IN) brain drug delivery and assess its feasibility in the delivery of therapeutic molecules. Delivery outcomes of fluorescently-labeled dextrans to mouse brains by IN administration either before or after FUS sonication were compared to evaluate whether FUS enhances IN delivery by active pumping or passive diffusion. Fluorescence imaging of brain slices found that IN administration followed by FUS sonication achieved significantly higher delivery than IN administration only, while pre-treatment by FUS sonication followed by IN administration was not significantly different from IN administration only. Brain-derived neurotrophic factor (BDNF), a promising neurotrophic factor for the treatment of many central nervous system diseases, was delivered by IN followed by FUS to demonstrate the feasibility of this technique and compared with the established FUS technique where drugs are injected intravenously. Immunohistochemistry staining of BDNF revealed that FUS-enhanced IN delivery achieved similar locally enhanced delivery as the established FUS technique. This study suggested that FUS enhances IN brain drug delivery by FUS-induced active pumping of the drug and demonstrated that FUS-enhanced IN delivery is a promising technique for noninvasive and localized delivery of therapeutic molecules to the brain.

Phage Peptide Libraries As a Source of Targeted Ligands

One of the dominant trends in modern pharmacology is the creation of drugs that act directly on the lesion focus and have minimal toxicity on healthy tissues and organs. This problem is particularly acute in relation to oncologic diseases. Short tissue- and organ-specific peptides capable of delivering drugs to the affected organ or tissue are considered promising targeted agents that can be used in the diagnosis and therapy of diseases, including cancer. The review discusses in detail the technology of phage display as a method for obtaining specific targeted peptide agents and offers examples of their use in diagnostic and clinical practice.

Acoustic cavitation-based monitoring of the reversibility and permeability of ultrasound-induced blood-brain barrier opening

Cavitation events seeded by microbubbles have been previously reported to be associated with MR- or fluorescent-contrast enhancement after focused ultrasound (FUS)-induced blood-brain barrier (BBB) opening. However, it is still unknown whether bubble activity can be correlated with the reversibility (the duration of opening and the likelihood of safe reinstatement) and the permeability of opened BBB, which is critical for the clinical translation of using passive cavitation detection to monitor, predict and control the opening. In this study, the dependence of acoustic cavitation on the BBB opening duration, permeability coefficient and histological damage occurrence were thus investigated. Transcranial pulsed FUS at 1.5 MHz in the presence of systemically circulating microbubbles was applied in the mouse hippocampi (n  =  60). The stable and inertial cavitation activities were monitored during sonication. Contrast-enhanced MRI was performed immediately after sonication and every 24 h up to 6 d thereafter, to assess BBB opening, brain tissue permeability and potential edema. Histological evaluations were used to assess the occurrence of neurovascular damages. It was found that stable cavitation was well correlated with: (1) the duration of the BBB opening (r(2)  =  0.77); (2) the permeability of the opened BBB (r(2)  =  0.82); (3) the likelihood of safe opening (P  <  0.05, safe opening compared to cases of damage; P  <  0.0001, no opening compared to safe opening). The inertial cavitation dose was correlated with the resulting BBB permeability (r(2)  =  0.72). Stable cavitation was found to be more reliable than inertial cavitation at assessing the BBB opening within the pressure range used in this study. This study demonstrates that the stable cavitation response during BBB opening holds promise for predicting and controlling the restoration and pharmacokinetics of FUS-opened BBB. The stable cavitation response therefore showed great promise in predicting the BBB opening duration, enabling thus control of opening according to the drug circulation time. In addition, avoiding adverse effects in the brain and assessing the pharmacokinetics of the compounds delivered can also be achieved by monitoring and controlling the stable cavitation emissions.

Challenges and new strategies for therapeutic peptide delivery to the CNS

Therapeutic peptides represent a largely untapped resource in medicine today, especially in the central nervous system. Despite their ease of design and remarkably high target specificity, it is difficult to deliver them beyond the blood-brain barrier or into the required intracellular compartments. In addition, the instability of these peptides in vivo precludes their use to combat the symptoms of numerous neurological disorders including Alzheimer's disease and spinocerebellar ataxia. In this review, we aim to characterize recent advances in the delivery of therapeutic peptides to the central nervous system past the blood-brain barrier and discuss the advantages and disadvantages of the examined methods as well as explore new potential directions.

Intranasal Delivery of Proteins and Peptides in the Treatment of Neurodegenerative Diseases

The blood-brain barrier (BBB) is a major impediment to the therapeutic delivery of peptides and proteins to the brain. Intranasal delivery often provides a non-invasive means to bypass the BBB. Advantages of using intranasal delivery include minimizing exposure to peripheral organs and tissues, thus reducing systemic side effects. It also allows substances that typically have rapid degradation in the blood time to exert their effect. Intranasal delivery provides the ability to target proteins and peptides to specific regions of the brain when administered with substrates like cyclodextrins. In this review, we examined the use of intranasal delivery of various proteins and peptides that have implications in the treatment of neurodegenerative diseases, focusing especially on albumin, exendin/GLP-1, GALP, insulin, leptin, and PACAP. We have described their rationale for use, distribution in the brain after intranasal injection, how intranasal administration differed from other modes of delivery, and their use in clinical trials, if applicable. Intranasal delivery of drugs, peptides, and other proteins could be very useful in the future for the prevention or treatment of brain related diseases.