Translation of focused ultrasound for blood-brain barrier opening in glioma

Effect of Microbubble Size, Composition, and Multiple Sonication Points on Sterile Inflammatory Response in Focused Ultrasound-Mediated Blood-Brain Barrier Opening

Blood-brain barrier opening (BBBO) using focused ultrasound (FUS) and microbubbles (MBs) has emerged as a promising technique for delivering therapeutics to the brain. However, the influence of various FUS and MB parameters on BBBO and subsequent sterile inflammatory response (SIR) remains unclear. In this study, we investigated the effects of MB size and composition, as well as the number of FUS sonication points, on BBBO and SIR in an immunocompetent mouse model. Using MRI-guided MB + FUS, we targeted the striatum and assessed extravasation of an MRI contrast agent to assess BBBO and RNaseq to assess SIR. Our results revealed distinct effects of these parameters on BBBO and SIR. Specifically, at a matched microbubble volume dose (MVD), MB size did not affect the extent of BBBO, but smaller (1 μm diameter) MBs exhibited a lower classification of SIR than larger (3 or 5 μm diameter) MBs. Lipid-shelled microbubbles exhibited greater BBBO and a more pronounced SIR compared to albumin-shelled microbubbles, likely owing to the latter's poor in vivo stability. As expected, increasing the number of sonication points resulted in greater BBBO and SIR. Furthermore, correlation analysis revealed strong associations between passive cavitation detection measurements of harmonic and inertial MB echoes, BBBO, and the expression of SIR gene sets. Our findings highlight the critical role of MB and FUS parameters in modulating BBBO and subsequent SIR in the brain. These insights inform the development of targeted drug delivery strategies and the mitigation of adverse inflammatory reactions in neurological disorders.

Open-Source Throttling of CD8+ T Cells in Brain with Low-Intensity Focused Ultrasound-Guided Sequential Delivery of CXCL10, IL-2, and aPD-L1 for Glioblastoma Immunotherapy

Improving clinical immunotherapy for glioblastoma (GBM) relies on addressing the immunosuppressive tumor microenvironment (TME). Enhancing CD8+ T cell infiltration and preventing its exhaustion holds promise for effective GBM immunotherapy. Here, a low-intensity focused ultrasound (LIFU)-guided sequential delivery strategy is developed to enhance CD8+ T cells infiltration and activity in the GBM region. The sequential delivery of CXC chemokine ligand 10 (CXCL10) to recruit CD8+ T cells and interleukin-2 (IL-2) to reduce their exhaustion is termed an "open-source throttling" strategy. Consequently, up to 3.39-fold of CD8+ T cells are observed with LIFU-guided sequential delivery of CXCL10, IL-2, and anti-programmed cell death 1 ligand 1 (aPD-L1), compared to the free aPD-L1 group. The immune checkpoint inhibitors (ICIs) therapeutic efficacy is substantially enhanced by the reversed immunosuppressive TME due to the expansion of CD8+ T cells, resulting in the elimination of tumor, prolonged survival time, and long-term immune memory establishment in orthotopic GBM mice. Overall, LIFU-guided sequential cytokine and ICIs delivery offers an "open-source throttling" strategy of CD8+ T cells, which may present a promising strategy for brain-tumor immunotherapy.

Pulsed focused ultrasound alters the proteomic profile of the tumor microenvironment in a syngeneic mouse model of glioblastoma

PURPOSE

Glioblastoma (GBM), a lethal primary adult malignancy, is difficult to treat because of the restrictive nature of the blood-brain barrier (BBB), blood-tumor barrier (BTB), and the immunosuppressive tumor microenvironment (TME). Since pulsed focused ultrasound (pFUS) is currently used to improve therapeutic deliveries across these barriers, this study aims to characterize the impact of pFUS on the TME proteomics upon opening the BBB and BTB.

METHODS

We utilized MRI-guided, pFUS with ultrasound contrast microbubbles (termed 'pFUS' herein) to selectively and transiently open the BBB and BTB investigating proteomic modifications in the TME. Utilizing an orthotopically-allografted mouse GL26 GBM model (Ccr2RFP/wt - Cx3cr1GFP/wt), pFUS's effect on glioma proteomics was evaluated using a Luminex 48-plex assay.

RESULTS

pFUS treated tumors exhibited increases in pro-inflammatory cytokines, chemokines, and trophic factors (CCTFs). Proteomic changes in tumors tend to peak at 24 h after single pFUS session (1x), with levels then plateauing or declining over the subsequent 24 h. Tumors receiving three pFUS sessions (3x) showed elevated CCTFs levels peaking as early as 6 h after the third session.

CONCLUSIONS

pFUS together with microbubbles induces a sterile inflammatory response in the TME of a mouse GBM tumor. Moreover, this proinflammatory shift can be sustained and perhaps primed for more rapid responses upon multiple sessions of pFUS. These findings raise the intriguing potential that pFUS-induced BBB and BTB opening may not only be effective in facilitating the therapeutic agent delivery, but also be harnessed to modify the TME to assist immunotherapies in overcoming immune evasion in GBM.

Stimuli-Responsive Polymeric Nanocarriers Accelerate On-Demand Drug Release to Combat Glioblastoma

Glioblastoma multiforme (GBM) is a highly malignant brain tumor with a poor prognosis and limited treatment options. Drug delivery by stimuli-responsive nanocarriers holds great promise for improving the treatment modalities of GBM. At the beginning of the review, we highlighted the stimuli-active polymeric nanocarriers carrying therapies that potentially boost anti-GBM responses by employing endogenous (pH, redox, hypoxia, enzyme) or exogenous stimuli (light, ultrasonic, magnetic, temperature, radiation) as triggers for controlled drug release mainly via hydrophobic/hydrophilic transition, degradability, ionizability, etc. Modifying these nanocarriers with target ligands further enhanced their capacity to traverse the blood-brain barrier (BBB) and preferentially accumulate in glioma cells. These unique features potentially lead to more effective brain cancer treatment with minimal adverse reactions and superior therapeutic outcomes. Finally, the review summarizes the existing difficulties and future prospects in stimuli-responsive nanocarriers for treating GBM. Overall, this review offers theoretical guidelines for developing intelligent and versatile stimuli-responsive nanocarriers to facilitate precise drug delivery and treatment of GBM in clinical settings.

Research Progress on the Strategies for Crossing the Blood-Brain Barrier

Recently, the incidence of brain diseases, such as central nervous system degenerative diseases, brain tumors, and cerebrovascular diseases, has increased. However, the blood-brain barrier (BBB) limits the effective delivery of drugs to brain disease areas. Therefore, the mainstream direction of new drug development for these diseases is to engineer drugs that can better cross the BBB to exert their effects in the brain. This paper reviews the research progress and application of the main trans-BBB drug delivery strategies (receptor/transporter-mediated BBB crossing, focused ultrasound to open the BBB, adenosine agonist reversible opening of the BBB, aromatic resuscitation, transnasal administration, cell-mediated trans-BBB crossing, and viral vector system-mediated brain drug delivery). Meanwhile, the potential applications, advantages, and disadvantages of these strategies for crossing the BBB are analyzed. Finally, the future development prospects of strategies for crossing the BBB are also discussed. These strategies have potential value for treating brain diseases.

The road ahead to successful BBB opening and drug-delivery with focused ultrasound

This review delves into the innovative technology of Blood-Brain Barrier (BBB) opening with low-intensity focused ultrasound in combination with microbubbles (LIFU-MB), a promising therapeutic modality aimed at enhancing drug delivery to the central nervous system (CNS). The BBB's selective permeability, while crucial for neuroprotection, significantly hampers the efficacy of pharmacological treatments for CNS disorders. LIFU-MB emerges as a non-invasive and localized method to transiently increase BBB permeability, facilitating the delivery of therapeutic molecules. Here, we review the procedural stages of LIFU-MB interventions, including planning and preparation, sonication, evaluation, and delivery, highlighting the technological diversity and methodological challenges encountered in current clinical applications. With an emphasis on safety and efficacy, we discuss the crucial aspects of ultrasound delivery, microbubble administration, acoustic feedback monitoring and assessment of BBB permeability. Finally, we explore the critical choices for effective BBB opening with LIFU-MB, focusing on selecting therapeutic agents, optimizing delivery methods, and timing for delivery. Overcoming existing barriers to integrate this technology into clinical practice could potentially revolutionize CNS drug delivery and treatment paradigms in the near future.

Microbubble-Enhanced Focused Ultrasound for Infiltrating Gliomas

Infiltrating gliomas are challenging to treat, as the blood-brain barrier significantly impedes the success of therapeutic interventions. While some clinical trials for high-grade gliomas have shown promise, patient outcomes remain poor. Microbubble-enhanced focused ultrasound (MB-FUS) is a rapidly evolving technology with demonstrated safety and efficacy in opening the blood-brain barrier across various disease models, including infiltrating gliomas. Initially recognized for its role in augmenting drug delivery, the potential of MB-FUS to augment liquid biopsy and immunotherapy is gaining research momentum. In this review, we will highlight recent advancements in preclinical and clinical studies that utilize focused ultrasound to treat gliomas and discuss the potential future uses of image-guided precision therapy using focused ultrasound.

Recent advances of focused ultrasound induced blood-brain barrier opening for clinical applications of neurodegenerative diseases

With the aging population on the rise, neurodegenerative disorders have taken center stage as a significant health concern. The blood-brain barrier (BBB) plays an important role to maintain the stability of central nervous system, yet it poses a formidable obstacle to delivering drugs for neurodegenerative disease therapy. Various methods have been devised to confront this challenge, each carrying its own set of limitations. One particularly promising noninvasive approach involves the utilization of focused ultrasound (FUS) combined with contrast agents-microbubbles (MBs) to achieve transient and reversible BBB opening. This review provides a comprehensive exploration of the fundamental mechanisms behind FUS/MBs-mediated BBB opening and spotlights recent breakthroughs in its application for neurodegenerative diseases. Furthermore, it addresses the current challenges and presents future perspectives in this field.

Recent advances in targeted drug delivery for the treatment of glioblastoma

Glioblastoma multiforme (GBM) is one of the highly malignant brain tumors characterized by significant morbidity and mortality. Despite the recent advancements in the treatment of GBM, major challenges persist in achieving controlled drug delivery to tumors. The management of GBM poses considerable difficulties primarily due to unresolved issues in the blood-brain barrier (BBB)/blood-brain tumor barrier (BBTB) and GBM microenvironment. These factors limit the uptake of anti-cancer drugs by the tumor, thus limiting the therapeutic options. Current breakthroughs in nanotechnology provide new prospects concerning unconventional drug delivery approaches for GBM treatment. Specifically, swimming nanorobots show great potential in active targeted delivery, owing to their autonomous propulsion and improved navigation capacities across biological barriers, which further facilitate the development of GBM-targeted strategies. This review presents an overview of technological progress in different drug administration methods for GBM. Additionally, the limitations in clinical translation and future research prospects in this field are also discussed. This review aims to provide a comprehensive guideline for researchers and offer perspectives on further development of new drug delivery therapies to combat GBM.

Nanoparticles for efficient drug delivery and drug resistance in glioma: New perspectives

Gliomas are the most common primary tumors of the central nervous system, with glioblastoma multiforme (GBM) having the highest incidence, and their therapeutic efficacy depends primarily on the extent of surgical resection and the efficacy of postoperative chemotherapy. The role of the intracranial blood-brain barrier and the occurrence of the drug-resistant gene O6-methylguanine-DNA methyltransferase have greatly limited the efficacy of chemotherapeutic agents in patients with GBM and made it difficult to achieve the expected clinical response. In recent years, the rapid development of nanotechnology has brought new hope for the treatment of tumors. Nanoparticles (NPs) have shown great potential in tumor therapy due to their unique properties such as light, heat, electromagnetic effects, and passive targeting. Furthermore, NPs can effectively load chemotherapeutic drugs, significantly reduce the side effects of chemotherapeutic drugs, and improve chemotherapeutic efficacy, showing great potential in the chemotherapy of glioma. In this article, we reviewed the mechanisms of glioma drug resistance, the physicochemical properties of NPs, and recent advances in NPs in glioma chemotherapy resistance. We aimed to provide new perspectives on the clinical treatment of glioma.

Advanced tumor electric fields therapy: A review of innovative research and development and prospect of application in glioblastoma

BACKGROUND

Glioblastoma multiforme (GBM) is an aggressive malignant tumor with a high mortality rate and is the most prevalent primary intracranial tumor that remains incurable. The current standard treatment, which involves surgery along with concurrent radiotherapy and chemotherapy, only yields a survival time of 14-16 months. However, the introduction of tumor electric fields therapy (TEFT) has provided a glimmer of hope for patients with newly diagnosed and recurrent GBM, as it has been shown to extend the median survival time to 20 months. The combination of TEFT and other advanced therapies is a promising trend in the field of GBM, facilitated by advancements in medical technology.

AIMS

In this review, we provide a concise overview of the mechanism and efficacy of TEFT. In addition, we mainly discussed the innovation of TEFT and our proposed blueprint for TEFT implementation.

CONCLUSION

Tumor electric fields therapy is an effective and highly promising treatment modality for GBM. The full therapeutic potential of TEFT can be exploited by combined with other innovative technologies and treatments.

Brain delivery enabled by transient blood-brain barrier disruption induced by regadenoson: a PET imaging study

BACKGROUND

Regadenoson, an agonist of adenosine A2 receptors, enables transient blood-brain barrier (BBB) disruption. The relevance of regadenoson as a pharmacological strategy for brain delivery was investigated using in vivo PET imaging in rats.

RESEARCH DESIGN AND METHODS

Kinetic modeling of brain PET data was performed to estimate the impact of regadenoson (0.05 mg.kg-1, i.v.) on BBB permeation compared with control rats (n = 4-6 per group). Three radiolabeled compounds of different sizes, which do not cross the intact BBB, were tested.

RESULTS

Regadenoson significantly increased the BBB penetration (+116 ± 13%, p < 0.001) of [18F]2-deoxy-2-fluoro-D-sorbitol ([18F]FDS, MW = 183 Da), a small-molecule marker of BBB permeability. The magnitude of the effect was different across brain regions, with a maximum increase in the striatum. Recovery of BBB integrity was observed 30 min after regadenoson injection. Regadenoson also increased the brain penetration (+72 ± 45%, p < 0.05) of a radiolabeled nanoparticle [89Zr]AGuIX (MW = 9 kDa). However, the brain kinetics of a monoclonal antibody ([89Zr]mAb, MW = 150 kDa) remained unchanged (p > 0.05).

CONCLUSIONS

PET imaging showed the features and limitations of BBB disruption induced by regadenoson in terms of extent, regional distribution, and reversibility. Nevertheless, regadenoson enables the brain delivery of small molecules or nanoparticles in rats.

Effect of Microbubble Size, Composition and Multiple Sonication Points on Sterile Inflammatory Response in Focused Ultrasound-Mediated Blood-Brain Barrier Opening

Blood-brain barrier opening (BBBO) using focused ultrasound (FUS) and microbubbles (MBs) has emerged as a promising technique for delivering therapeutics to the brain. However, the influence of various FUS and MB parameters on BBBO and subsequent sterile inflammatory response (SIR) remains unclear. In this study, we investigated the effects of MB size and composition, as well as the number of FUS sonication points, on BBBO and SIR in an immunocompetent mouse model. Using MRI-guided MB+FUS, we targeted the striatum and assessed extravasation of an MRI contrast agent to assess BBBO and RNAseq to assess SIR. Our results revealed distinct effects of these parameters on BBBO and SIR. Specifically, at a matched microbubble volume dose (MVD), MB size did not affect the extent of BBBO, but smaller (1 μm diameter) MBs exhibited a lower classification of SIR than larger (3 or 5 μm diameter) MBs. Lipid-shelled microbubbles exhibited greater BBBO and a more pronounced SIR compared to albumin-shelled microbubbles, likely owing to the latter's poor in vivo stability. As expected, increasing the number of sonication points resulted in greater BBBO and SIR. Furthermore, correlation analysis revealed strong associations between passive cavitation detection measurements of harmonic and inertial MB echoes, BBBO and the expression of SIR gene sets. Our findings highlight the critical role of MB and FUS parameters in modulating BBBO and subsequent SIR in the brain. These insights inform the development of targeted drug delivery strategies and the mitigation of adverse inflammatory reactions in neurological disorders.

A Roadmap of CAR-T-Cell Therapy in Glioblastoma: Challenges and Future Perspectives

Glioblastoma (GBM) is the most common primary malignant brain tumor, with a median overall survival of less than 2 years and a nearly 100% mortality rate under standard therapy that consists of surgery followed by combined radiochemotherapy. Therefore, new therapeutic strategies are urgently needed. The success of chimeric antigen receptor (CAR) T cells in hematological cancers has prompted preclinical and clinical investigations into CAR-T-cell treatment for GBM. However, recent trials have not demonstrated any major success. Here, we delineate existing challenges impeding the effectiveness of CAR-T-cell therapy for GBM, encompassing the cold (immunosuppressive) microenvironment, tumor heterogeneity, T-cell exhaustion, local and systemic immunosuppression, and the immune privilege inherent to the central nervous system (CNS) parenchyma. Additionally, we deliberate on the progress made in developing next-generation CAR-T cells and novel innovative approaches, such as low-intensity pulsed focused ultrasound, aimed at surmounting current roadblocks in GBM CAR-T-cell therapy.

Nanoparticle-Based Combinational Strategies for Overcoming the Blood-Brain Barrier and Blood-Tumor Barrier

The blood-brain barrier (BBB) and blood-tumor barrier (BTB) pose substantial challenges to efficacious drug delivery for glioblastoma multiforme (GBM), a primary brain tumor with poor prognosis. Nanoparticle-based combinational strategies have emerged as promising modalities to overcome these barriers and enhance drug penetration into the brain parenchyma. This review discusses various nanoparticle-based combinatorial approaches that combine nanoparticles with cell-based drug delivery, viral drug delivery, focused ultrasound, magnetic field, and intranasal drug delivery to enhance drug permeability across the BBB and BTB. Cell-based drug delivery involves using engineered cells as carriers for nanoparticles, taking advantage of their intrinsic migratory and homing capabilities to facilitate the transport of therapeutic payloads across BBB and BTB. Viral drug delivery uses engineered viral vectors to deliver therapeutic genes or payloads to specific cells within the GBM microenvironment. Focused ultrasound, coupled with microbubbles or nanoparticles, can temporarily disrupt the BBB to increase drug permeability. Magnetic field-guided drug delivery exploits magnetic nanoparticles to facilitate targeted drug delivery under an external magnetic field. Intranasal drug delivery offers a minimally invasive avenue to bypass the BBB and deliver therapeutic agents directly to the brain via olfactory and trigeminal pathways. By combining these strategies, synergistic effects can enhance drug delivery efficiency, improve therapeutic efficacy, and reduce off-target effects. Future research should focus on optimizing nanoparticle design, exploring new combination strategies, and advancing preclinical and clinical investigations to promote the translation of nanoparticle-based combination therapies for GBM.

Glioblastoma Margin as a Diffusion Barrier Revealed by Photoactivation of Plasmonic Nanovesicles

Glioblastoma (GBM) is the most complex and lethal primary brain cancer. Adequate drug diffusion and penetration are essential for treating GBM, but how the spatial heterogeneity in GBM impacts drug diffusion and transport is poorly understood. Herein, we report a new method, photoactivation of plasmonic nanovesicles (PANO), to measure molecular diffusion in the extracellular space of GBM. By examining three genetically engineered GBM mouse models that recapitulate key clinical features including the angiogenic core and diffuse infiltration, we found that the tumor margin has the lowest diffusion coefficient (highest tortuosity) compared with the tumor core and surrounding brain tissue. Analysis of the cellular composition shows that tortuosity in the GBM is strongly correlated with neuronal loss and astrocyte activation. Our all-optical measurement reveals the heterogeneous GBM microenvironment and highlights the tumor margin as a diffusion barrier for drug transport in the brain, with implications for therapeutic delivery.

Targeting diffuse midline gliomas: The promise of focused ultrasound-mediated blood-brain barrier opening

Diffuse midline gliomas (DMGs), including diffuse intrinsic pontine glioma, have among the highest mortality rates of all childhood cancers, despite recent advancements in cancer therapeutics. This is partly because, unlike some CNS tumors, the blood-brain barrier (BBB) of DMG tumor vessels remains intact. The BBB prevents the permeation of many molecular therapies into the brain parenchyma, where the cancer cells reside. Focused ultrasound (FUS) with microbubbles has recently emerged as an innovative and exciting technology that non-invasively permeabilizes the BBB in a small focal region with millimeter precision. In this review, current treatment methods and biological barriers to treating DMGs are discussed. State-of-the-art FUS-mediated BBB opening is then examined, with a focus on the effects of various ultrasound parameters and the treatment of DMGs.

Effect of Phase-Change Nanodroplets and Ultrasound on Blood-Brain Barrier Permeability In Vitro

Phase-change nanodroplets (PCND;NDs) are emulsions with a perfluorocarbon (PFC) core that undergo acoustic vaporisation as a response to ultrasound (US). Nanodroplets change to microbubbles and cavitate while under the effect of US. This cavitation can apply forces on cell connections in biological barrier membranes, such as the blood-brain barrier (BBB), and trigger a transient and reversible increased permeability to molecules and matter. This study aims to present the preparation of lipid-based NDs and investigate their effects on the brain endothelial cell barrier in vitro. The NDs were prepared using the thin-film hydration method, followed by the PFC addition. They were characterised for size, cavitation (using a high-speed camera), and PFC encapsulation (using FTIR). The bEnd.3 (mouse brain endothelial) cells were seeded onto transwell inserts. Fluorescein with NDs and/or microbubbles were applied on the bEND3 cells and the effect of US on fluorescein permeability was measured. The Live/Dead assay was used to assess the BBB integrity after the treatments. Size and PFC content analysis indicated that the NDs were stable while stored. High-speed camera imaging confirmed that the NDs cavitate after US exposure of 0.12 MPa. The BBB cell model experiments revealed a 4-fold increase in cell membrane permeation after the combined application of US and NDs. The Live/Dead assay results indicated damage to the BBB membrane integrity, but this damage was less when compared to the one caused by microbubbles. This in vitro study shows that nanodroplets have the potential to cause BBB opening in a similar manner to microbubbles. Both cavitation agents caused damage on the endothelial cells. It appears that NDs cause less cell damage compared to microbubbles.

Improving the efficacy of anti-EGFR drugs in GBM: Where we are going?

The therapies targeting mutations of driver genes in cancer have advanced into clinical trials for a variety of tumors. In glioblastoma (GBM), epidermal growth factor receptor (EGFR) is the most commonly mutated oncogene, and targeting EGFR has been widely investigated as a promising direction. However, the results of EGFR pathway inhibitors have not been satisfactory. Limited blood-brain barrier (BBB) permeability, drug resistance, and pathway compensation mechanisms contribute to the failure of anti-EGFR therapies. This review summarizes recent research advances in EGFR-targeted therapy for GBM and provides insight into the reasons for the unsatisfactory results of EGFR-targeted therapy. By combining the results of preclinical studies with those of clinical trials, we discuss that improved drug penetration across the BBB, the use of multi-target combinations, and the development of peptidomimetic drugs under the premise of precision medicine may be promising strategies to overcome drug resistance in GBM.

The innovative design of a delivery and real-time tracer system for anti-encephalitis drugs that can penetrate the blood-brain barrier

As a "wall" between blood flow and brain cells, the blood-brain barrier (BBB) makes it really difficult for drugs to cross this barrier and work. This is particularly the case for pharmaceuticals of acute encephalitis therapies, largely excluded from the brain following systemic administration. Herein we report an advanced drug delivery system that can cross the BBB and target acute inflammation based on the controlled release of macrophage-camouflaged glow nanoparticles via a Trojan horse strategy. Benefiting from afterglow imaging that eliminates background interference and RAW 264.7 cells (RAW) with special immune homing and long-term tracking capabilities, polydopamine (PDA)-modified afterglow nanoparticles (ANPs) as near-infrared photo-responsive drug carriers in a controlled delivery system camouflaged by macrophages can penetrate the BBB by crossing the intercellular space and trigger the anti-inflammatory drug by photothermal conversion in the brain parenchyma dexamethasone (Dex) release, exhibiting good acute inflammation recognition and healing ability. APD@RAW was monitored to cross the BBB and image deep brain inflamed areas in a model of acute brain inflammation. Meanwhile, the delivered Dex mitigated the brain damage caused by inflammatory cytokines secretion (IL-6, TNF-α, and IL-1β). Overall, this drug delivery system holds excellent potential for BBB penetrating and acute encephalitis therapies.

Glioblastoma Margin as a Diffusion Barrier Revealed by Photoactivation of Plasmonic Nanovesicles

Glioblastoma (GBM) is the most complex and lethal adult primary brain cancer. Adequate drug diffusion and penetration are essential for treating GBM, but how the spatial heterogeneity in GBM impacts drug diffusion and transport is poorly understood. Herein, we report a new method, photoactivation of plasmonic nanovesicles (PANO), to measure molecular diffusion in the extracellular space of GBM. By examining three genetically engineered GBM mouse models that recapitulate key clinical features including angiogenic core and diffuse infiltration, we found that the tumor margin has the lowest diffusion coefficient (highest tortuosity) compared with the tumor core and surrounding brain tissue. Analysis of the cellular composition shows that the tortuosity in the GBM is strongly correlated with neuronal loss and astrocyte activation. Our all-optical measurement reveals the heterogeneous GBM microenvironment and highlights the tumor margin as a diffusion barrier for drug transport in the brain, with implications for therapeutic delivery.

Optical blood-brain-tumor barrier modulation expands therapeutic options for glioblastoma treatment

The treatment of glioblastoma has limited clinical progress over the past decade, partly due to the lack of effective drug delivery strategies across the blood-brain-tumor barrier. Moreover, discrepancies between preclinical and clinical outcomes demand a reliable translational platform that can precisely recapitulate the characteristics of human glioblastoma. Here we analyze the intratumoral blood-brain-tumor barrier heterogeneity in human glioblastoma and characterize two genetically engineered models in female mice that recapitulate two important glioma phenotypes, including the diffusely infiltrative tumor margin and angiogenic core. We show that pulsed laser excitation of vascular-targeted gold nanoparticles non-invasively and reversibly modulates the blood-brain-tumor barrier permeability (optoBBTB) and enhances the delivery of paclitaxel in these two models. The treatment reduces the tumor volume by 6 and 2.4-fold and prolongs the survival by 50% and 33%, respectively. Since paclitaxel does not penetrate the blood-brain-tumor barrier and is abandoned for glioblastoma treatment following its failure in early-phase clinical trials, our results raise the possibility of reevaluating a number of potent anticancer drugs by combining them with strategies to increase blood-brain-tumor barrier permeability. Our study reveals that optoBBTB significantly improves therapeutic delivery and has the potential to facilitate future drug evaluation for cancers in the central nervous system.

Targeting cerebral diseases with enhanced delivery of therapeutic proteins across the blood-brain barrier

INTRODUCTION

Cerebral diseases have been threatening public physical and psychological health in the recent years. With the existence of the blood-brain barrier (BBB), it is particularly hard for therapeutic proteins like peptides, enzymes, antibodies, etc. to enter the central nervous system (CNS) and function in diagnosis and treatment in cerebral diseases. Fortunately, the past decade has witnessed some emerging strategies of delivering macromolecular therapeutic proteins across the BBB.

AREAS COVERED

Based on the structure, functions, and substances transport mechanisms, various enhanced delivery strategies of therapeutic proteins were reviewed, categorized by molecule-mediated delivery strategies, carrier-mediated delivery strategies, and other delivery strategies.

EXPERT OPINION

As for molecule-mediated delivery strategies, development of genetic engineering technology, optimization of protein expression and purification techniques, and mature of quality control systems all help to realize large-scale production of recombinant antibodies, making it possible to apply to the clinical practice. In terms of carrier-mediated delivery strategies and others, although nano-carriers/adeno-associated virus (AAV) are also promising candidates for delivering therapeutic proteins or genes across the BBB, some issues still remain to be further investigated, including safety concerns related to applied materials, large-scale production costs, quality control standards, combination therapies with auxiliary delivery strategies like focused ultrasound, etc.

3D-Printed Microrobots: Translational Challenges

The science of microrobots is accelerating towards the creation of new functionalities for biomedical applications such as targeted delivery of agents, surgical procedures, tracking and imaging, and sensing. Using magnetic properties to control the motion of microrobots for these applications is emerging. Here, 3D printing methods are introduced for the fabrication of microrobots and their future perspectives are discussed to elucidate the path for enabling their clinical translation.

The function of histone methylation and acetylation regulators in GBM pathophysiology

Glioblastoma (GBM) is the most common and lethal primary brain malignancy and is characterized by a high degree of intra and intertumor cellular heterogeneity, a starkly immunosuppressive tumor microenvironment, and nearly universal recurrence. The application of various genomic approaches has allowed us to understand the core molecular signatures, transcriptional states, and DNA methylation patterns that define GBM. Histone posttranslational modifications (PTMs) have been shown to influence oncogenesis in a variety of malignancies, including other forms of glioma, yet comparatively less effort has been placed on understanding the transcriptional impact and regulation of histone PTMs in the context of GBM. In this review we discuss work that investigates the role of histone acetylating and methylating enzymes in GBM pathogenesis, as well as the effects of targeted inhibition of these enzymes. We then synthesize broader genomic and epigenomic approaches to understand the influence of histone PTMs on chromatin architecture and transcription within GBM and finally, explore the limitations of current research in this field before proposing future directions for this area of research.

Magnetic Targeting Nanocarriers Combined with Focusing Ultrasound for Enhanced Intracerebral Hemorrhage Therapy

Intracerebral hemorrhage (ICH) remains a significant cause of morbidity and mortality around the world, and surgery is still the most direct and effective way to remove ICH. However, the potential risks brought by surgery, such as normal brain tissue damage, post-operative infection, and difficulty in removing deep hematoma, are still the main problems in the surgical treatment of ICH. Activation of the peroxisome proliferator-activated receptor gamma (PPARγ) is reported to show a good therapeutic effect in hematoma clearance. Herein, a magnetic targeting nanocarrier loaded with a PPARγ agonist (15d-PGJ2-MNPs) is synthesized, which could be magnetically targeted and enriched in the area of the hematoma after intravenous injection. Subsequent application of focusing ultrasound (FUS) could enhance drug diffusion, which activates the PPARγ receptors on macrophages around the hematoma for better hematoma clearance. The 15d-PGJ2-MNP treatment alleviates brain injury, accelerates hematoma clearance, attenuates neuroinflammation, reduces brain edema and significantly improves the deficits in sensory and motor function and spatial learning ability in the ICH mouse model. This work proposes an effective magnetic targeting plus FUS method to treat ICH, highlighting its great potential in the treatment of hemorrhagic stroke.

Focal opening of the neuronal plasma membrane by shock-induced bubble collapse for drug delivery: a coarse-grained molecular dynamics simulation

Cell permeabilization using shock-induced bubble collapse provides an attractive choice for drug delivery systems. In this work, based on a realistically human brain plasma membrane (PM) model, we investigated the focal opening of this complex model by the jet from cavitation, focusing on the effect of characteristic membrane components, particle velocity (u_p) and bubble diameters (D). Both high levels of cholesterol and specific cerebrosides in the PM model limit the pore opening of cavitation jets. Sphingomyelin is the opposite, but has little effect due to its low content. Two adjustable parameters of u_p and D can be coupled to control the opening size. The relationship between them and the maximum pore area was provided for the first time. The maximum pore area increases with the u_p (or the impulse that is positively related to u_p) in the low-speed range, which agrees with the experimentally observed impulse determinism. However, the maximum area drops in the high-speed range. Combined with D, we proposed that the jet size determines the pore size, not the impulse. Larger bubbles that can create a larger pore in the membrane have a larger jet size, but their impulse is relatively small. Finally, the recovery simulation shows that the membrane with a small pore can be quickly recovered within 300 ps, while that with a larger pore did not recover until 2 μs. These rules from this work may be helpful to optimize the choice of shock waves for the delivery of different drugs across membranes.

CXCR4-targeted nitric oxide nanoparticles deliver PD-L1 siRNA for immunotherapy against glioblastoma

While immunotherapy has emerged as a promising strategy to treat glioblastoma multiforme (GBM), the limited availability of immunotherapeutic agents in tumors due to the presence of the blood-brain barrier (BBB) and immunosuppressive tumor microenvironment dampens efficacy. Nitric oxide (NO) plays a role in modulating both the BBB and tumor vessels and could thus be delivered to disrupt the BBB and improve the delivery of immunotherapeutics into GBM tumors. Herein, we report an immunotherapeutic approach that utilizes CXCR4-targeted lipid‑calcium-phosphate nanoparticles with NO donors (LCP-NO NPs). The delivery of NO resulted in enhanced BBB permeability and thus improved gene delivery across the BBB. CXCR4-targeted LCP-NO NPs delivered siRNA against the immune checkpoint ligand PD-L1 to GBM tumors, silenced PD-L1 expression, increased cytotoxic T cell infiltration and activation in GBM tumors, and suppressed GBM progression. Thus, the codelivery of NO and PD-L1 siRNA by these CXCR4-targeted NPs may serve as a potential immunotherapy for GBM.

Harnessing Ultrasound for Targeting Drug Delivery to the Brain and Breaching the Blood–Brain Tumour Barrier

Despite significant advances in developing drugs to treat brain tumours, achieving therapeutic concentrations of the drug at the tumour site remains a major challenge due to the presence of the blood–brain barrier (BBB). Several strategies have evolved to enhance brain delivery of chemotherapeutic agents to treat tumours; however, most approaches have several limitations which hinder their clinical utility. Promising studies indicate that ultrasound can penetrate the skull to target specific brain regions and transiently open the BBB, safely and reversibly, with a high degree of spatial and temporal specificity. In this review, we initially describe the basics of therapeutic ultrasound, then detail ultrasound-based drug delivery strategies to the brain and the mechanisms by which ultrasound can improve brain tumour therapy. We review pre-clinical and clinical findings from ultrasound-mediated BBB opening and drug delivery studies and outline current therapeutic ultrasound devices and technologies designed for this purpose.

Molecular Imaging of Ultrasound-Mediated Blood-Brain Barrier Disruption in a Mouse Orthotopic Glioblastoma Model

Glioblastoma (GBM) is an aggressive and malignant primary brain tumor. The blood-brain barrier (BBB) limits the therapeutic options available to tackle this incurable tumor. Transient disruption of the BBB by focused ultrasound (FUS) is a promising and safe approach to increase the brain and tumor concentration of drugs administered systemically. Non-invasive, sensitive, and reliable imaging approaches are required to better understand the impact of FUS on the BBB and brain microenvironment. In this study, nuclear imaging (SPECT/CT and PET/CT) was used to quantify neuroinflammation 48 h post-FUS and estimate the influence of FUS on BBB opening and tumor growth in vivo. BBB disruptions were performed on healthy and GBM-bearing mice (U-87 MG xenograft orthotopic model). The BBB recovery kinetics were followed and quantified by [99mTc]Tc-DTPA SPECT/CT imaging at 0.5 h, 3 h and 24 h post-FUS. The absence of neuroinflammation was confirmed by [18F]FDG PET/CT imaging 48 h post-FUS. The presence of the tumor and its growth were evaluated by [68Ga]Ga-RGD₂ PET/CT imaging and post-mortem histological analysis, showing that tumor growth was not influenced by FUS. In conclusion, molecular imaging can be used to evaluate the time frame for systemic treatment combined with transient BBB opening and to test its efficacy over time.