Salvaging brain ischemia by increasing neuroprotectant uptake via nanoagonist mediated blood brain barrier permeability enhancement

Deciphering the mechanistic impact of acupuncture on the neurovascular unit in acute ischemic stroke: Insights from basic research in a narrative review

Ischemic stroke(IS), a severe acute cerebrovascular disease, not only imposes a heavy economic burden on society but also presents numerous challenges in treatment. During the acute phase, while thrombolysis and thrombectomy serve as primary treatments, these approaches are restricted by a narrow therapeutic window. During rehabilitation, commonly used neuroprotective agents struggle with their low drug delivery efficiency and inadequate preclinical testing, and the long-term pharmacological and toxicity effects of nanomedicines remain undefined. Meanwhile, acupuncture as a therapeutic approach is widely acknowledged for its effectiveness in treating IS and has been recommended by the World Health Organization (WHO) as an alternative and complementary therapy, even though its exact mechanisms remain unclear. This review aims to summarize the known mechanisms of acupuncture and electroacupuncture (EA) in the treatment of IS. Research shows that acupuncture treatment mainly protects the neurovascular unit through five mechanisms: 1) reducing neuronal apoptosis and promoting neuronal repair and proliferation; 2) maintaining the integrity of the blood-brain barrier (BBB); 3) inhibiting the overactivation and polarization imbalance of microglia; 4) regulating the movement of vascular smooth muscle (VSM) cells; 5) promoting the proliferation of oligodendrocyte precursors. Through an in-depth analysis, this review reveals the multi-level, multi-dimensional impact of acupuncture treatment on the neurovascular unit (NVU) following IS, providing stronger evidence and a theoretical basis for its clinical application.

Potential application of aptamers combined with DNA nanoflowers in neurodegenerative diseases

The efficacy of neurotherapeutic drugs hinges on their ability to traverse the blood-brain barrier and access the brain, which is crucial for treating or alleviating neurodegenerative diseases (NDs). Given the absence of definitive cures for NDs, early diagnosis and intervention become paramount in impeding disease progression. However, conventional therapeutic drugs and existing diagnostic approaches must meet clinical demands. Consequently, there is a pressing need to advance drug delivery systems and early diagnostic methods tailored for NDs. Certain aptamers endowed with specific functionalities find widespread utility in the targeted therapy and diagnosis of NDs. DNA nanoflowers (DNFs), distinctive flower-shaped DNA nanomaterials, are intricately self-assembled through rolling ring amplification (RCA) of circular DNA templates. Notably, imbuing DNFs with diverse functionalities becomes seamlessly achievable by integrating aptamer sequences with specific functions into RCA templates, resulting in a novel nanomaterial, aptamer-bound DNFs (ADNFs) that amalgamates the advantageous features of both components. This article delves into the characteristics and applications of aptamers and DNFs, exploring the potential or application of ADNFs in drug-targeted delivery, direct treatment, early diagnosis, etc. The objective is to offer prospective ideas for the clinical treatment or diagnosis of NDs, thereby contributing to the ongoing efforts in this critical field.

Brain Delivery of Protein Therapeutics by Cell Matrix-Inspired Biomimetic Nanocarrier

Protein therapeutics are anticipated to offer significant treatment options for central nervous system (CNS) diseases. However, the majority of proteins are unable to traverse the blood-brain barrier (BBB) and reach their CNS target sites. Inspired by the natural environment of active proteins, the cell matrix components hyaluronic acid (HA) and protamine (PRTM) are used to self-assemble with proteins to form a protein-loaded biomimetic core and then incorporated into ApoE3-reconstituted high-density lipoprotein (rHDL) to form a protein-loaded biomimetic nanocarrier (Protein-HA-PRTM-rHDL). This cell matrix-inspired biomimetic nanocarrier facilitates the penetration of protein therapeutics across the BBB and enables their access to intracellular target sites. Specifically, CAT-HA-PRTM-rHDL facilitates rapid intracellular delivery and release of catalase (CAT) via macropinocytosis-activated membrane fusion, resulting in improved spatial learning and memory in traumatic brain injury (TBI) model mice (significantly reduces the latency of TBI mice and doubles the number of crossing platforms), and enhances motor function and prolongs survival in amyotrophic lateral sclerosis (ALS) model mice (extended the median survival of ALS mice by more than 10 days). Collectively, this cell matrix-inspired nanoplatform enables the efficient CNS delivery of protein therapeutics and provides a novel approach for the treatment of CNS diseases.

The blood-brain barrier, a key bridge to treat neurodegenerative diseases

As a highly selective and semi-permeable barrier that separates the circulating blood from the brain and central nervous system (CNS), the blood-brain barrier (BBB) plays a critical role in the onset and treatment of neurodegenerative diseases (NDs). To delay or reverse the NDs progression, the dysfunction of BBB should be improved to protect the brain from harmful substances. Simultaneously, a highly efficient drug delivery across the BBB is indispensable. Here, we summarized several methods to improve BBB dysfunction in NDs, including knocking out risk geneAPOE4, regulating circadian rhythms, restoring the gut microenvironment, and activating the Wnt/β-catenin signaling pathway. Then we discussed the advances in BBB penetration techniques, such as transient BBB opening, carrier-mediated drug delivery, and nasal administration, which facilitates drug delivery across the BBB. Furthermore, various in vivo and in vitro BBB models and research methods related to NDs are reviewed. Based on the current research progress, the treatment of NDs in the long term should prioritize the integrity of the BBB. However, a treatment approach that combines precise control of transient BBB permeability and non-invasive targeted BBB drug delivery holds profound significance in improving treatment effectiveness, safety, and clinical feasibility during drug therapy. This review involves the cross application of biology, materials science, imaging, engineering and other disciplines in the field of BBB, aiming to provide multi-dimensional research directions and clinical ideas for the treating NDs.

Harnessing nanobiotechnology for cerebral ischemic stroke management

Cerebral ischemic stroke remains one of the most serious neurological disorders that pose threats to human health, causing a large amount of long-term disability or even death throughout the world. Based on its physiologic and pathological features, there are limited available therapeutic options for effective ischemic stroke management. Encouragingly, a rapid advancement of nanobiotechnology is bringing new insights into exploring more alternative strategies against cerebral ischemic stroke, which can cleverly overcome the limitations related to conventional treatment methods. Therefore, this review focuses on the recent achievements of nanobiotechnology for ischemic stroke management, which emphasizes diverse targeted delivery strategies using various nanoplatforms including liposomes, micelles, polymeric nanoparticles, nanogels, inorganic nanomaterials, and cell-derived nano-vectors based on the pathophysiological features of ischemic stroke. Moreover, different therapeutic approaches against ischemic stroke such as neuroprotection, anti-inflammation, thrombolysis, increased blood-brain barrier penetration and reactive oxygen species scavenging are highlighted. Meanwhile, this review discusses how these versatile nanoplatforms were designed to assist in the treatment of ischemic stroke. Based on this, challenges, opportunities, and future perspectives using nanobiotechnology through rational design for effective ischemic stroke management are revealed.

Advances of nano drug delivery system for the theranostics of ischemic stroke

From the global perspective, stroke refers to a highly common cause of disability and death. Ischemic stroke (IS), attributed to blood vessel blockage, preventing the flow of blood to brain, acts as the most common form of stroke. Thus far, thrombolytic therapy is the only clinical treatment for IS with the approval from the FDA. Moreover, the physiology barrier complicates therapeutically and diagnostically related intervention development of IS. Accordingly, developing efficient and powerful curative approaches for IS diagnosis and treatment is urgently required. The advent of nanotechnology has brought dawn and hope to better curative and imaging forms for the management of IS. This work reviews the recent advances and challenges correlated with the nano drug delivery system for IS therapy and diagnosis. The overview of the current knowledge of the important molecular pathological mechanisms in cerebral ischemia and how the drugs cross the blood brain barrier will also be briefly summarized.

Application and Utility of Liposomal Neuroprotective Agents and Biomimetic Nanoparticles for the Treatment of Ischemic Stroke

Ischemic stroke is still one of the leading causes of high mortality and severe disability worldwide. Therapeutic options for ischemic stroke and subsequent cerebral ischemia/reperfusion injury remain limited due to challenges associated with drug permeability through the blood-brain barrier (BBB). Neuroprotectant delivery with nanoparticles, including liposomes, offers a promising solution to address this problem, as BBB disruption following ischemic stroke allows nanoparticles to pass through the intercellular gaps between endothelial cells. To ameliorate ischemic brain damage, a number of nanotherapeutics encapsulating neuroprotective agents, as well as surface-modified nanoparticles with specific ligands targeting the injured brain regions, have been developed. Combination therapy with nanoparticles encapsulating neuroprotectants and tissue plasminogen activator (t-PA), a globally approved thrombolytic agent, has been demonstrated to extend the narrow therapeutic time window of t-PA. In addition, the design of biomimetic drug delivery systems (DDS) employing circulating cells (e.g., leukocytes, platelets) with unique properties has recently been investigated to overcome the injured BBB, utilizing these cells’ inherent capability to penetrate the ischemic brain. Herein, we review recent findings on the application and utility of nanoparticle DDS, particularly liposomes, and various approaches to developing biomimetic DDS functionalized with cellular membranes/membrane proteins for the treatment of ischemic stroke.

Nanomedicines, an emerging therapeutic regimen for treatment of ischemic cerebral stroke: A review

Owing to its intricate pathophysiology, cerebral stroke is a serious medical condition caused by interruption or obstruction of blood supply (blockage of vasculature) to the brain tissues which results in diminished supply of essential nutrients and oxygen (hypoxia) and ultimate necrosis of neuronal tissues. A prompt risks assessment and immediate rational therapeutic plan with proficient neuroprotection play critically important role in the effective management of this neuronal emergency. Various conventional medications are being used for treatment of acute ischemic cerebral stroke but fibrinolytic agents, alone or in combination with other agents are considered the mainstay. These clot-busting agents effectively restore blood supply (reperfusion) to ischemic regions of the brain; however, their clinical significance is hampered due to various factors such as short plasma half-life, limited distribution to brain tissues due to the presence of highly efficient physiological barrier, blood brain barrier (BBB), and lacking of target-specific delivery to the ischemic brain regions. To alleviate these issues, various types of nanomedicines such as polymeric nanoparticles (NPs), liposomes, nanoemulsion, micelles and dendrimers have been designed and evaluated. The implication of these newer therapies (nanomedicines) have revolutionized the therapeutic outcomes by improving the plasma half-life, permeation across BBB, efficient distribution to ischemic cerebral tissues and neuroprotection. Furthermore, the adaptation of some diverse techniques including PEGylation, tethering of targeting ligands on the surfaces of nanomedicines, and pH responsive features have also been pondered. The implication of these emerging adaptations have shown remarkable potential in maximizing the targeting efficiency of drugs to ischemic brain tissues, simultaneous delivery of drugs and imaging agents (for early prognosis as well as monitoring of therapy), and therapeutic outcomes such as long-term neuroprotection.

Automatic Brain Extraction for Rodent MRI Images

Rodent models are increasingly important in translational neuroimaging research. In rodent neuroimaging, particularly magnetic resonance imaging (MRI) studies, brain extraction is a critical data preprocessing component. Current brain extraction methods for rodent MRI usually require manual adjustment of input parameters due to widely different image qualities and/or contrasts. Here we propose a novel method, termed SHape descriptor selected Extremal Regions after Morphologically filtering (SHERM), which only requires a brain template mask as the input and is capable of automatically and reliably extracting the brain tissue in both rat and mouse MRI images. The method identifies a set of brain mask candidates, extracted from MRI images morphologically opened and closed sequentially with multiple kernel sizes, that match the shape of the brain template. These brain mask candidates are then merged to generate the brain mask. This method, along with four other state-of-the-art rodent brain extraction methods, were benchmarked on four separate datasets including both rat and mouse MRI images. Without involving any parameter tuning, our method performed comparably to the other four methods on all datasets, and its performance was robust with stably high true positive rates and low false positive rates. Taken together, this study provides a reliable automatic brain extraction method that can contribute to the establishment of automatic pipelines for rodent neuroimaging data analysis.

Blood-Brain Barrier Modulation to Improve Glioma Drug Delivery

The blood-brain barrier (BBB) is formed by brain microvascular endothelial cells that are sealed by tight junctions, making it a significant obstacle for most brain therapeutics. The poor BBB penetration of newly developed therapeutics has therefore played a major role in limiting their clinical success. A particularly challenging therapeutic target is glioma, which is the most frequently occurring malignant brain tumor. Thus, to enhance therapeutic uptake in tumors, researchers have been developing strategies to modulate BBB permeability. However, most conventional BBB opening strategies are difficult to apply in the clinical setting due to their broad, non-specific modulation of the BBB, which can result in damage to normal brain tissue. In this review, we have summarized strategies that could potentially be used to selectively and efficiently modulate the tumor BBB for more effective glioma treatment.

Inducing a Transient Increase in Blood-Brain Barrier Permeability for Improved Liposomal Drug Therapy of Glioblastoma Multiforme

The blood-brain barrier (BBB) selectively controls the passage of endogenous and exogenous molecules between systemic circulation and the brain parenchyma. Nanocarrier-based drugs such as liposomes and nanoparticles are an attractive prospect for cancer therapy since they can carry a drug payload and be modified to improve targeting and retention at the desired site. However, the BBB prevents most therapeutic drugs from entering the brain, including physically restricting the passage of liposomes and nanoparticles. In this paper, we show that a low dose of systemically injected recombinant human vascular endothelial growth factor induces a short period of increased BBB permeability. We have shown increased delivery of a range of nanomedicines to the brain including contrast agents for imaging, varying sizes of nanoparticles, small molecule chemotherapeutics, tracer dyes, and liposomal chemotherapeutics. However, this effect was not uniform across all brain regions, and permeability varied depending on the drug or molecule measured. We have found that this window of BBB permeability effect is transient, with normal BBB integrity restored within 4 h. This strategy, combined with liposomal doxorubicin, was able to significantly extend survival in a mouse model of human glioblastoma. We have found no evidence of systemic toxicity, and the technique was replicated in pigs, demonstrating that this technique could be scaled up and potentially be translated to the clinic, thus allowing the use of nanocarrier-based therapies for brain disorders.

Efficient discovery and capture of new neuronal nitric oxide synthase-postsynaptic density protein-95 uncouplers from herbal medicines using magnetic molecularly imprinted polymers as artificial antibodies

In the scope of stroke treatment, new neuronal nitric oxide synthase-postsynaptic density protein-95 uncouplers from herbal medicines were discovered and captured. To do so, highly selective magnetic molecularly imprinted polymers with a core-shell structure were prepared as artificial antibodies. According to the results of computational simulations, we designed and synthesized various polymers with varying amounts and types of template, functional monomer, cross-linker, and solvent. Characterization and performance tests revealed that the most appropriate artificial antibodies showed uniform spherical morphologies, large adsorption capacities, fast-binding kinetics, high selectivity, and quick separation. These artificial antibodies were then used as sorbents for dispersive magnetic solid-phase extraction coupled with high-performance liquid chromatography and mass spectrometry to capture and identify structural analogs to ZL006 from extracts of Scutellariae radix, Psoraleae fructus, and Trifolium pratense. Furthermore, according to the neuroprotective effect and coimmunoprecipitation test, Baicalein, Neobavaisoflavone, Corylifol A, and Biochanin A can be the potential uncouplers of neuronal nitric oxide synthase-postsynaptic density protein-95. Therefore, this present study contributes valuable information for the discovery of neuronal nitric oxide synthase-postsynaptic density protein-95 uncouplers from herbal medicines.

The application of nanoparticles for neuroprotection in acute ischemic stroke

Stroke still represents one of the most common causes of death and disability worldwide. Acute ischemic stroke (AIS), caused by brain arterial occlusion resulting from a thrombus or embolus, is the most common form of stroke. However, current therapies in AIS are inadequate, and the only US FDA approved treatment is the thrombolytic drug Alteplase. Therefore, establishing effective therapeutic strategies for AIS is urgently needed. Using nanoparticle-based technologies to deliver neuroprotective agents to the ischemic area has attracted increasing attention of late. In this review, the important molecular pathological mechanisms in cerebral ischemia are briefly summarized, the potential of nanoparticulate drug-delivery systems for AIS intervention and recovery are introduced and problems in the medical application of nanoparticles will also be discussed.

Image-guided chemotherapy with specifically tuned blood brain barrier permeability in glioma margins

Blood-brain barrier (BBB) disruption is frequently observed in the glioma region. However, the tumor uptake of drugs is still too low to meet the threshold of therapeutic purpose.

Method: A tumor vasculature-targeted nanoagonist was developed. Glioma targeting specificity of the nanoagonist was evaluated by in vivo optical imaging. BBB permeability at the glioma margin was quantitatively measured by dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Single-photon emission computed tomography imaging/computed tomography (SPECT/CT) quantitatively determined the glioma uptake of the radiolabeled model drug. T2-weighted MRI monitored the tumor volume.

Results: Immunostaining studies demonstrated that the BBB remained partially intact in the invasive margin of patients' gliomas regardless of their malignancies. DCE-MRI showed that vascular permeability in the glioma margin reached its maximum at 45 min post nanoagonist administration. In vivo optical imaging indicated the high glioma targeting specificity of the nanoagonist. SPECT/CT showed the significantly enhanced glioma uptake of the model drug after pre-treatment with the nanoagonist. Image-guided paclitaxel injection after nanoagonist-mediated BBB modulation more efficiently attenuated tumor growth and extended survival than in animal models treated with paclitaxel or temozolomide alone.

Conclusion: Thus, image-guided drug delivery following BBB permeability modulation holds promise to enhance the efficacy of chemotherapeutics to glioma.

Combination Therapy with LXW7 and Ceria Nanoparticles Protects against Acute Cerebral Ischemia/Reperfusion Injury in Rats

Ischemia/reperfusion is known to greatly increase oxidative stress in the penumbra, which results in brain damage. Integrin αvβ3 is selectively up-regulated with ischemic injury to the brain and remains elevated throughout reperfusion. We determined whether or not a new compound biotinylated-LXW7-ceria nanoparticle (CeNP) (bLXW7-CeNP) plays a role in brain protection in the rat model of middle cerebral artery occlusion/reperfusion and shows better effects than CeNPs alone in improving the outcomes of focal oxidative stress and apoptosis more effectively. Male Sprague-Dawley rats were subjected to focal cerebral ischemia for 2 h followed by a 24-h reperfusion. Drug treatment was intravenously administered via the caudal vein 1 h after occlusion. Rats were randomly divided into the following 4 groups: bLXW7-CeNP treatment group (0.5 mg/kg); CeNP treatment group (0.5 mg/kg); control saline group; and sham group. Brains were harvested 24 h after reperfusion, and the neurologic deficit scores, infarction volume, blood-brain barrier (BBB) disruption, and the level of oxidative stress and apoptosis were determined. Results showed that the bLXW7-CeNP and CeNP treatments could improve neurologic deficit scores, infarction volume, BBB disruption, and the level of oxidative stress and apoptosis. Compound bLXW7-CeNP treatment exhibited better effects than CeNp treatment and showed remarkable statistical differences in the infarction volume, the degree of BBB breakdown, the apoptosis and oxidative stress, apart from neurologic deficit scores. Thus, we concluded that bLXW7-CeNP protects against acute cerebral ischemia/reperfusion injury. BLXW7, as a ligand of integrin αvβ3, may be able to effectively localize the anti-oxidant CeNPs to the ischemic penumbra region, which may provide more adequate opportunities for CeNPs to exert anti-oxidative stress effects and subsequently reduce apoptosis in acute cerebral ischemia/reperfusion.

Borneol Attenuates Ultrasound-Targeted Microbubble Destruction-Induced Blood-Brain Barrier Opening in Focal Cerebral Ischemia

Ultrasound-targeted microbubble destruction (UTMD) and the herb medicine borneol can both facilitate the delivery of therapeutic agents to diseased brain regions and serve as promising adjuvant neuroprotective therapies. Our preliminary experiments showed that UTMD could exacerbate ischemic blood–brain barrier (BBB) opening, while borneol can protect the BBB. In this study, we tested the hypothesis that the combination of UTMD and borneol could attenuate UTMD-induced injury to the BBB under ischemic stroke conditions. Male albino mice were subjected to 60-min middle cerebral artery occlusion (MCAO) with reperfusion. Borneol and UTMD was given to mice 3 days before and 24 h after MCAO induction. BBB permeability, brain water contents, ultrastructural changes of the BBB and histopathological alterations were evaluated. Our data demonstrated that UTMD aggravated the leakage of Evans blue dye, ultrastructural alterations of cerebral microvasculature, brain edema, and even induced cerebral hemorrhage in ischemic stroke mice. Pretreatment with borneol significantly attenuated the above detrimental effects of UTMD on the BBB. This study indicates that under ischemic stroke conditions, the BBB becomes vulnerable to UTMD intervention, and the combination of borneol can help to maintain the integrity of the BBB.

Nanoagonist-mediated endothelial tight junction opening: A strategy for safely increasing brain drug delivery in mice

Even though opening endothelial tight junctions is an efficient way to up-regulate brain drug delivery, the extravasation of blood-borne components from the compromised tight junctions can result in adverse consequences such as edema and neuronal injuries. In this work, we developed a nanoagonist that temporarily opened tight junctions by signaling adenosine 2A receptor, a type of G protein-coupled receptor expressed on brain capillary endothelial cells. Magnetic resonance imaging demonstrated remarkable blood-brain barrier permeability enhancements and significantly increased brain uptakes of both small molecular and macromolecular paramagnetic agents after nanoagonist administration. Gamma ray imaging and transmission electron microscope observed tight junction opening followed by spontaneous recovery after nanoagonist treatment. Immunofluorescence staining showed the unspoiled basal membrane, pericytes and astrocyte endfeet that enwrapped the vascular endothelium. Importantly, edema, apoptosis and neuronal injuries observed after hypertonic agent mediated tight junction-opening were not observed after nanoagonist intervention. The uncompromised neurovascular units may prevent the leakage of blood-borne constituents into brain parenchyma and accelerate tight junction recovery. Considering blood-brain barrier impermeability is a major obstacle in the treatment of central nervous system diseases, nanoagonist-mediated tight junction opening provides a promising strategy to enhance brain drug delivery with minimized adverse effects.

Edaravone-Encapsulated Agonistic Micelles Rescue Ischemic Brain Tissue by Tuning Blood-Brain Barrier Permeability

Thrombolysis has been a standard treatment for ischemic stroke. However, only 2-7% patients benefit from it because the thrombolytic agent has to be injected within 4.5 h after the onset of symptoms to avoid the increasing risk of intracerebral hemorrhage. As the only clinically approved neuroprotective drug, edaravone (EDV) rescues ischemic brain tissues by eradicating over-produced reactive oxygen species (ROS) without the limitation of therapeutic time-window. However, EDV's short circulation half-life and inadequate cerebral uptake attenuate its therapeutic efficacy. Here we developed an EDV-encapsulated agonistic micelle (EDV-AM) to specifically deliver EDV into brain ischemia by actively tuning blood-brain barrier (BBB) permeability. The EDV-AM actively up-regulated endothelial monolayer permeability in vitro. HPLC studies showed that EDV-AM delivered more EDV into brain ischemia than free EDV after intravenous injection. Magnetic resonance imaging also demonstrated that EDV-AM more rapidly salvaged ischemic tissue than free EDV. Diffusion tensor imaging indicated the highest efficiency of EDV-AM in accelerating axonal remodeling in the ipsilesional white matter and improving functional behaviors of ischemic stroke models. The agonistic micelle holds promise to improve the therapeutic efficiency of ischemic stroke patients who miss the thrombolytic treatment.

Crossing the Blood-Brain Barrier: Recent Advances in Drug Delivery to the Brain

CNS disorders are on the rise despite advancements in our understanding of their pathophysiological mechanisms. A major hurdle to the treatment of these disorders is the blood-brain barrier (BBB), which serves as an arduous janitor to protect the brain. Many drugs are being discovered for CNS disorders, which, however fail to enter the market because of their inability to cross the BBB. This is a pronounced challenge for the pharmaceutical fraternity. Hence, in addition to the discovery of novel entities and drug candidates, scientists are also developing new formulations of existing drugs for brain targeting. Several approaches have been investigated to allow therapeutics to cross the BBB. As the molecular structure of the BBB is better elucidated, several key approaches for brain targeting include physiological transport mechanisms such as adsorptive-mediated transcytosis, inhibition of active efflux pumps, receptor-mediated transport, cell-mediated endocytosis, and the use of peptide vectors. Drug-delivery approaches comprise delivery from microspheres, biodegradable wafers, and colloidal drug-carrier systems (e.g., liposomes, nanoparticles, nanogels, dendrimers, micelles, nanoemulsions, polymersomes, exosomes, and quantum dots). The current review discusses the latest advancements in these approaches, with a major focus on articles published in 2015 and 2016. In addition, we also cover the alternative delivery routes, such as intranasal and convection-enhanced diffusion methods, and disruption of the BBB for brain targeting.

Automated Ischemic Lesion Segmentation in MRI Mouse Brain Data after Transient Middle Cerebral Artery Occlusion

Magnetic resonance imaging (MRI) has become increasingly important in ischemic stroke experiments in mice, especially because it enables longitudinal studies. Still, quantitative analysis of MRI data remains challenging mainly because segmentation of mouse brain lesions in MRI data heavily relies on time-consuming manual tracing and thresholding techniques. Therefore, in the present study, a fully automated approach was developed to analyze longitudinal MRI data for quantification of ischemic lesion volume progression in the mouse brain. We present a level-set-based lesion segmentation algorithm that is built using a minimal set of assumptions and requires only one MRI sequence (T2) as input. To validate our algorithm we used a heterogeneous data set consisting of 121 mouse brain scans of various age groups and time points after infarct induction and obtained using different MRI hardware and acquisition parameters. We evaluated the volumetric accuracy and regional overlap of ischemic lesions segmented by our automated method against the ground truth obtained in a semi-automated fashion that includes a highly time-consuming manual correction step. Our method shows good agreement with human observations and is accurate on heterogeneous data, whilst requiring much shorter average execution time. The algorithm developed here was compiled into a toolbox and made publically available, as well as all the data sets.

Increased Nanoparticle Delivery to Brain Tumors by Autocatalytic Priming for Improved Treatment and Imaging

The blood-brain barrier (BBB) is partially disrupted in brain tumors. Despite the gaps in the BBB, there is an inadequate amount of pharmacological agents delivered into the brain. Thus, the low delivery efficiency renders many of these agents ineffective in treating brain cancer. In this report, we proposed an "autocatalytic" approach for increasing the transport of nanoparticles into the brain. In this strategy, a small number of nanoparticles enter into the brain via transcytosis or through the BBB gaps. After penetrating the BBB, the nanoparticles release BBB modulators, which enables more nanoparticles to be transported, creating a positive feedback loop for increased delivery. Specifically, we demonstrated that these autocatalytic brain tumor-targeting poly(amine-co-ester) terpolymer nanoparticles (ABTT NPs) can readily cross the BBB and preferentially accumulate in brain tumors at a concentration of 4.3- and 94.0-fold greater than that in the liver and in brain regions without tumors, respectively. We further demonstrated that ABTT NPs were capable of mediating brain cancer gene therapy and chemotherapy. Our results suggest ABTT NPs can prime the brain to increase the systemic delivery of therapeutics for treating brain malignancies.

Tuning Endothelial Permeability with Functionalized Nanodiamonds

Cancer nanomedicine vehicles are required to cross the vascular barrier to reach the tumor site in order to ensure the successful delivery of their therapeutic load. Here, nanodiamond (ND) variants were shown to induce surface dependent vascular barrier leakiness. The ND-induced leakiness was found to be mediated by the increase in intracellular reactive oxygen species (ROS) and Ca(2+). These then in turn triggered the loss in endothelial cell-endothelial cell connections of the vascular barrier and also triggered their quasi-stable cytoskeletal remodelling. This ND driven increase in leakiness allowed more doxorubicin drug to penetrate through the vascular barrier to reach the cancer cells. This increase in the doxorubicin penetration subsequently led to an increase in the cancer killing effect. Overall, tuning the vascular barrier leakiness through ND surface group functionalization could provide an alternative strategy for the cancer nanomedicine to traverse across the vascular barrier.