Transient cerebral hypoperfusion assisted intraarterial cationic liposome delivery to brain tissue

Biomembrane-Derived Nanoparticles in Alzheimer's Disease Therapy: A Comprehensive Review of Synthetic Lipid Nanoparticles and Natural Cell-Derived Vesicles

Current therapies for Alzheimer's disease used in the clinic predominantly focus on reducing symptoms with limited capability to control disease progression; thus, novel drugs are urgently needed. While nanoparticles (liposomes, high-density lipoprotein-based nanoparticles) constructed with synthetic biomembranes have shown great potential in AD therapy due to their excellent biocompatibility, multifunctionality and ability to penetrate the BBB, nanoparticles derived from natural biomembranes (extracellular vesicles, cell membrane-based nanoparticles) display inherent biocompatibility, stability, homing ability and ability to penetrate the BBB, which may present a safer and more effective treatment for AD. In this paper, we reviewed the synthetic and natural biomembrane-derived nanoparticles that are used in AD therapy. The challenges associated with the clinical translation of biomembrane-derived nanoparticles and future perspectives are also discussed.

A, Gota V, Goda JS. Insight into lipid-based nanoplatform-mediated drug and gene delivery in neuro-oncology and their clinical prospects

Tumors of the Central nervous System (CNS) are a spectrum of neoplasms that range from benign lesions to highly malignant and aggressive lesions. Despite aggressive multimodal treatment approaches, the morbidity and mortality are high with dismal survival outcomes in these malignant tumors. Moreover, the non-specificity of conventional treatments substantiates the rationale for precise therapeutic strategies that selectively target infiltrating tumor cells within the brain, and minimize systemic and collateral damage. With the recent advancement of nanoplatforms for biomaterials applications, lipid-based nanoparticulate systems present an attractive and breakthrough impact on CNS tumor management. Lipid nanoparticles centered immunotherapeutic agents treating malignant CNS tumors could convene the clear need for precise treatment strategies. Immunotherapeutic agents can selectively induce specific immune responses by active or innate immune responses at the local site within the brain. In this review, we discuss the therapeutic applications of lipid-based nanoplatforms for CNS tumors with an emphasis on revolutionary approaches in brain targeting, imaging, and drug and gene delivery with immunotherapy. Lipid-based nanoparticle platforms represent one of the most promising colloidal carriers for chemotherapeutic, and immunotherapeutic drugs. Their current application in oncology especially in brain tumors has brought about a paradigm shift in cancer treatment by improving the antitumor activity of several agents that could be used to selectively target brain tumors. Subsequently, the lab-to-clinic transformation and challenges towards translational feasibility of lipid-based nanoplatforms for drug and gene/immunotherapy delivery in the context of CNS tumor management is addressed.

Alzheimer's Disease: Treatment Strategies and Their Limitations

Alzheimer's disease (AD) is the most frequent case of neurodegenerative disease and is becoming a major public health problem all over the world. Many therapeutic strategies have been explored for several decades; however, there is still no curative treatment, and the priority remains prevention. In this review, we present an update on the clinical and physiological phase of the AD spectrum, modifiable and non-modifiable risk factors for AD treatment with a focus on prevention strategies, then research models used in AD, followed by a discussion of treatment limitations. The prevention methods can significantly slow AD evolution and are currently the best strategy possible before the advanced stages of the disease. Indeed, current drug treatments have only symptomatic effects, and disease-modifying treatments are not yet available. Drug delivery to the central nervous system remains a complex process and represents a challenge for developing therapeutic and preventive strategies. Studies are underway to test new techniques to facilitate the bioavailability of molecules to the brain. After a deep study of the literature, we find the use of soft nanoparticles, in particular nanoliposomes and exosomes, as an innovative approach for preventive and therapeutic strategies in reducing the risk of AD and solving problems of brain bioavailability. Studies show the promising role of nanoliposomes and exosomes as smart drug delivery systems able to penetrate the blood-brain barrier and target brain tissues. Finally, the different drug administration techniques for neurological disorders are discussed. One of the promising therapeutic methods is the intranasal administration strategy which should be used for preclinical and clinical studies of neurodegenerative diseases.

A systematic review on intra-arterial cerebral infusions of chemotherapeutics in the treatment of glioblastoma multiforme: The state-of-the-art

Objective

To provide a comprehensive review of intra-arterial cerebral infusions of chemotherapeutics in glioblastoma multiforme treatment and discuss potential research aims. We describe technical aspects of the intra-arterial delivery, methods of blood-brain barrier disruption, the role of intraoperative imaging and clinical trials involving intra-arterial cerebral infusions of chemotherapeutics in the treatment of glioblastoma multiforme.

Method

159 articles in English were reviewed and used as the foundation for this paper. The Medline/Pubmed, Cochrane databases, Google Scholar, Scielo and PEDro databases have been used to select the most relevant and influential papers on the intra-arterial cerebral infusions of chemotherapeutics in the treatment of glioblastoma multiforme. Additionally, we have included some relevant clinical trials involving intra-arterial delivery of chemotherapeutics to other than GBM brain tumours.

Conclusion

Considering that conventional treatments for glioblastoma multiforme fall short of providing a significant therapeutic benefit, with a majority of patients relapsing, the neuro-oncological community has considered intra-arterial administration of chemotherapeutics as an alternative to oral or intravenous administration. Numerous studies have proven the safety of IA delivery of chemotherapy and its ability to ensure higher drug concentrations in targeted areas, simultaneously limiting systemic toxicity. Nonetheless, the scarcity of phase III trials prevents any declaration of a therapeutic benefit. Given that the likelihood of a single therapeutic agent which will be effective for the treatment of glioblastoma multiforme is extremely low, it is paramount to establish an adequate multimodal therapy which will have a synergistic effect on the diverse pathogenesis of GBM. Precise quantitative and spatial monitoring is necessary to guarantee the accurate delivery of the therapeutic to the tumour. New and comprehensive pharmacokinetic models, a more elaborate understanding of glioblastoma biology and effective methods of diminishing treatment-related neurotoxicity are paramount for intra-arterial cerebral infusion of chemotherapeutics to become a mainstay treatment for glioblastoma multiforme. Additional use of other imaging methods like MRI guidance during the procedure could have an edge over X-ray alone and aid in selecting proper arteries as well as infusion parameters of chemotherapeutics making the procedure safer and more effective.

Drug delivery across the blood-brain barrier for the treatment of pediatric brain tumors - An update

Even though the last decade has seen a surge in the identification of molecular targets and targeted therapies in pediatric brain tumors, the blood brain barrier (BBB) remains a significant challenge in systemic drug delivery. This continues to undermine therapeutic efficacy. Recent efforts have identified several strategies that can facilitate enhanced drug delivery into pediatric brain tumors. These include invasive methods such as intra-arterial, intrathecal, and convection enhanced delivery and non-invasive technologies that allow for transient access across the BBB, including focused ultrasound and nanotechnology. This review discusses current strategies that are being used to enhance delivery of different therapies across the BBB to the tumor site - a major unmet need in pediatric neuro-oncology.

Advances in local therapy for glioblastoma - taking the fight to the tumour

Despite advances in neurosurgery, chemotherapy and radiotherapy, glioblastoma remains one of the most treatment-resistant CNS malignancies, and the tumour inevitably recurs. The majority of recurrences appear in or near the resection cavity, usually within the area that received the highest dose of radiation. Many new therapies focus on combatting these local recurrences by implementing treatments directly in or near the tumour bed. In this Review, we discuss the latest developments in local therapy for glioblastoma, focusing on recent preclinical and clinical trials. The approaches that we discuss include novel intraoperative techniques, various treatments of the surgical cavity, stereotactic injections directly into the tumour, and new developments in convection-enhanced delivery and intra-arterial treatments.

Development and in vivo Evaluation of Hydroxy-α-Sanshool Intranasal Liposomes as a Potential Remedial Treatment for Alzheimer’s Disease

Purpose

Hydroxy-α-sanshool (HAS) improves cognitive dysfunction, but its structural instability has limited its clinical application. The present study was conducted to investigate the optimal formulation of hydroxy-α-sanshool liposomes (HAS-LPs) and its effect on ameliorating learning and memory disorders in an Alzheimer’s disease (AD) model.

Methods

In this study, HAS was prepared as HAS-LP using a thin film dispersion method. After selecting the optimal preparation conditions, HAS-LP was characterized using transmission electron microscopy (TEM) and by measuring the zeta potential, particle size, and in vitro drug release. Next, evaluated the effect of HAS-LP on the rat nasal mucosa and then applied it to AD mice. By performing behaviour experiments, pathological test and related pharmacokinetic parameters, we explored its effect on attenuating learning and memory impairment in mice.

Results

When the mass ratio of HAS:cholesterol:soybean lecithin was 1:4:16 and 15 mL of ultrapure water were added, the highest encapsulation efficiency and drug loading were obtained. HAS-LP had a particle size of 181.77 nm, a polydispersity index of 0.207 and a zeta potential of −53.8 mV, and it remained stable at 25 °C for 1 week and 4 °C for 8 weeks. Moreover, HAS-LP exhibited slow drug release and was highly consistent with the Higuchi release model. HAS-LP was not significantly toxic to the nasal mucosa and effectively alleviated D-galactose-induced learning memory deficits and protected mouse hippocampal neuronal cells. HAS-LP was highly enriched in plasma and brain tissue after administration via the nasal route and obtained some ability to target the brain.

Conclusion

HAS encapsulated in soybean lecithin and cholesterol was successfully developed, suggesting that treatment with the nanoparticles might reverse some AD symptoms. Therefore, these nanoparticles might be used as promising new candidates for the delivery of HAS to treat AD.

Understanding Drug Delivery to the Brain Using Liposome-Based Strategies: Studies that Provide Mechanistic Insights Are Essential

Brain drug delivery may be restricted by the blood-brain barrier (BBB), and enhancement by liposome-based drug delivery strategies has been investigated. As access to the human brain is limited, many studies have been performed in experimental animals. Whereas providing interesting data, such studies have room for improvement to provide mechanistic insight into the rate and extent of specifically BBB transport and intrabrain distribution processes that all together govern CNS target delivery of the free drug. This review shortly summarizes BBB transport and current liposome-based strategies to overcome BBB transport restrictions, with the emphasis on how to determine the individual mechanisms that all together determine the time course of free drug brain concentrations, following their administration as such, and in liposomes. Animal studies using microdialysis providing time course information on unbound drug in plasma and brain are highlighted, as these provide the mechanistic information needed to understand BBB drug transport of the drug, and the impact of a liposomal formulations of that drug on BBB transport. Overall, these studies show that brain distribution of a drug administered as liposomal formulation depends on both drug properties and liposomal formulation characteristics. In general, evidence suggests that active transporters at the BBB, either being influx or efflux transporters, are circumvented by liposomes. It is concluded that liposomal formulations may provide interesting changes in BBB transport. More mechanistic studies are needed to understand relevant mechanisms in liposomal drug delivery to the brain, providing an improved basis for its prediction in human using animal data.

The New Frontiers in Neurodegenerative Diseases Treatment: Liposomal-Based Strategies

In the last decade, the onset of neurodegenerative (ND) diseases is strongly widespread due to the age increase of the world population. Despite the intensive investigations boosted by the scientific community, an efficacious therapy has not been outlined yet. The drugs commonly used are only able to relieve symptom severity; following their oral or intravenous administration routes, their effectiveness is strictly limited due to their low ability to reach the Central Nervous System (CNS) overcoming the Blood Brain Barrier (BBB). Starting from these assumptions, the engineered-nanocarriers, such as lipid-nanocarriers, are suitable agents to enhance the delivery of drugs into the CNS due to their high solubility, bioavailability, and stability. Liposomal delivery systems are considered to be the ideal carriers, not only for conventional drugs but also for neuroprotective small molecules and green-extracted compounds. In the current work, the LP-based drug delivery improvements in in vivo applications against ND disorders were carefully assessed.

Strategies for Improved Intra-arterial Treatments Targeting Brain Tumors: a Systematic Review

Conventional treatments for brain tumors relying on surgery, radiation, and systemic chemotherapy are often associated with high recurrence and poor prognosis. In recent decades, intra-arterial administration of anti-cancer drugs has been considered a suitable alternative drug delivery route to intravenous and oral administration. Intra-arterial administration is believed to offer increasing drug responses by primary and metastatic brain tumors, and to be associated with better median overall survival. By directly injecting therapeutic agents into carotid or vertebral artery, intra-arterial administration rapidly increases intra-tumoral drug concentration but lowers systemic exposure. However, unexpected vascular or neural toxicity has questioned the therapeutic safety of intra-arterial drug administration and limits its widespread clinical application. Therefore, improving targeting and accuracy of intra-arterial administration has become a major research focus. This systematic review categorizes strategies for optimizing intra-arterial administration into five categories: (1) transient blood-brain barrier (BBB)/blood-tumor barrier (BTB) disruption, (2) regional cerebral hypoperfusion for peritumoral hemodynamic changes, (3) superselective endovascular intervention, (4) high-resolution imaging techniques, and (5) others such as cell and gene therapy. We summarize and discuss both preclinical and clinical research, focusing on advantages and disadvantages of different treatment strategies for a variety of cerebral tumor types.

Biophysical characterization of lutein or beta carotene-loaded cationic liposomes

The interactions between carotenoids and membrane constituents are vital for understanding the mechanism of their dynamic action. Lutein and beta-carotene were loaded separately into the bilayer of dipalmitoylphosphatidylcholine (DPPC) mixed at a molar ratio with l-α-phosphatidylethanolamine derived from sheep brain (cephalin) and stearylamine (SA) to form cationic liposomes. The molecular interaction between lutein or beta-carotene with cationic liposomes was studied using transmission electron microscopy (TEM), dynamic light scattering (DLS), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. Encapsulation efficiency (EE %) and in vitro drug release were determined. The DLS measurements confirmed the mono-dispersity of all samples. TEM results revealed that liposomal samples were oval-shaped and there was a change in their morphology and size upon encapsulation of lutein or beta-carotene. Beta-carotene was observed to adhere to the boundary surface within the liposomal assembly with external morphological alterations. EE% of lutein and beta-carotene exceeded 98.8 ± 0.3% and 87 ± 4%, respectively. Lutein doped with cationic liposomes shows better in vitro release stability (about 30%) than beta-carotene (about 45%) between the 3^rd and the 6^th hour manifested by lower leakage rate percentage of lutein which would lead to higher lutein retention. The incorporated lutein resulted in broadening and shifting of the major endothermic peak of the co-liposomes, while the incorporation of beta-carotene did not induce a noticeable shift. An FTIR study was employed to reveal structure alterations in the vesicles after the encapsulation of lutein or beta-carotene into liposomes. Encapsulation of lutein or beta-carotene into liposomes induced a change in the frequency of the symmetric and asymmetric CH₂ stretching bands in the acyl chain that may influence the order of the membrane.

The interactions between carotenoids and membrane constituents are vital for understanding the mechanism of their dynamic action.

Peptosome Coadministration Improves Nanoparticle Delivery to Tumors through NRP1-Mediated Co-Endocytosis

Improving the efficacy of nanoparticles (NPs) delivery to tumors is critical for cancer diagnosis and therapy. In our previous work, amphiphilic peptide APPA self-assembled nanocarriers were designed and constructed for cargo delivery to tumors with high efficiency. In this study, we explore the use of APPA self-assembled peptosomes as a nanoparticle adjuvant to enhance the delivery of nanoparticles and antibodies to integrin αvβ3 and neuropilin-1 (NRP1) positive tumors. The enhanced tumor delivery of coadministered NPs was confirmed by better magnetosome (Mag)-based T₂-weighted magnetic resonance imaging (MRI), liposome-based fluorescence imaging, as well as the improved anti-tumor efficacy of monoclonal antibodies (trastuzumab in this case) and doxorubicin (DOX)-containing liposomes. Interestingly, the improvement is most significant for the delivering of compounds that have active or passive tumor targeting ability, such as antibodies or NPs that have enhanced permeability and retention (EPR) effect. However, for non-targeting small molecules, the effect is not significant. In vitro and in vivo studies suggest that both peptosomes and the coadministered compounds might be internalized into cells through a NRP1 mediated co-endocytosis (CoE) pathway. The improved delivery of coadministered NPs and antibodies to tumors suggests that the coadministration with APPA self-assembled peptosomes could be a valuable approach for advancing αvβ3 and NRP1 positive tumors diagnosis and therapy.

Therapeutic strategies and nano-drug delivery applications in management of ageing Alzheimer's disease

In recent years, the incidental rate of neurodegenerative disorders has increased proportionately with the aging population. Alzheimer's disease (AD) is one of the most commonly reported neurodegenerative disorders, and it is estimated to increase by roughly 30% among the aged population. In spite of screening numerous drug candidates against various molecular targets of AD, only a few candidates - such as acetylcholinesterase inhibitors are currently utilized as an effective clinical therapy. However, targeted drug delivery of these drugs to the central nervous system (CNS) exhibits several limitations including meager solubility, low bioavailability, and reduced efficiency due to the impediments of the blood-brain barrier (BBB). Current advances in nanotechnology present opportunities to overcome such limitations in delivering active drug candidates. Nanodrug delivery systems are promising in targeting several therapeutic moieties by easing the penetration of drug molecules across the CNS and improving their bioavailability. Recently, a wide range of nano-carriers, such as polymers, emulsions, lipo-carriers, solid lipid carriers, carbon nanotubes, metal based carriers etc., have been adapted to develop successful therapeutics with sustained release and improved efficacy. Here, we discuss few recently updated nano-drug delivery applications that have been adapted in the field of AD therapeutics, and future prospects on potential molecular targets for nano-drug delivery systems.

Liposome size and charge optimization for intraarterial delivery to gliomas

Nanoparticles such as liposomes may be used as drug delivery vehicles for brain tumor therapy. Particle geometry and electrostatic properties have been hypothesized to be important determinants of effective tumor targeting after intraarterial injection. In this study, we investigate the combined roles of liposome size and surface charge on the effectiveness of delivery to gliomas after intraarterial injection. Intracarotid injection of liposomes was performed in separate cohorts of both healthy and C6 glioma-bearing Sprague Dawley rats after induction of transient cerebral hypoperfusion. Large (200 nm) and small (60-80 nm) fluorescent dye-loaded liposomes that were either cationic or neutral in surface charge were utilized. Delivery effectiveness was quantitatively measured both with real-time, in vivo and postmortem diffuse reflectance spectroscopy. Semi-quantitative multispectral fluorescence imaging was also utilized to assess the pattern and extent of liposome targeting within tumors. Large cationic liposomes demonstrated the most effective hemispheric and glioma targeting of all the liposomes tested. Selective large cationic liposome retention at the site of glioma growth was observed. The liposome deposition pattern within tumors after intraarterial injection was variable with both core penetration and peripheral deposition observed in specific tumors. This study provides evidence that liposome size and charge are important determinants of effective brain and glioma targeting after intraarterial injection. Our results support the future development of 200-nm cationic liposomal formulations of candidate intraarterial anti-glioma agents for further pre-clinical testing.

Computational pharmacokinetic rationale for intra-arterial delivery to the brain

Intra-arterial (IA) drug delivery has been proposed for the treatment of a wide range of brain diseases, including malignant brain tumors. However, pharmacokinetic optimization for IA drug delivery to the brain remains a challenge. In this report, we apply and expand the well-established Dedrick model of IA drug delivery to the brain and test the effects of modifying drug and delivery parameters. These simulations show that altering the properties of candidate drugs and physiological variables can have profound effects on regional deposition after IA injections. We show that drug and physiological optimization aimed at rapid drug extraction and sustained retention is necessary to maximize regional deposition after of IA injections.

Targeting brain tumors by intra-arterial delivery of cell-penetrating peptides: a novel approach for primary and metastatic brain malignancy

Computational modeling shows that intra-arterial delivery is most efficient when the delivered drugs rapidly and avidly bind to the target site. The cell-penetrating peptide trans-activator of transcription (TAT) is a candidate carrier molecule that could mediate such specificity for brain tumor chemotherapeutics. To test this hypothesis we first performed in vitro studies testing the uptake of TAT by one primary and three potentially metastatic brain cancer cell lines (9L, 4T-1, LLC, SKOV-3). Then we performed in vivo studies in a rat model where TAT was delivered either intra-arterially (IA) or intravenously (IV) to 9L brain tumors. We observed robust uptake of TAT by all tumor cell lines in vitro. Flow cytometry and confocal microscopy revealed a rapid uptake of fluorescein-labeled TAT within 5 min of exposure to the cancer cells. IA injections done under transient cerebral hypoperfusion (TCH) generated a four-fold greater tumor TAT concentration compared to conventional IV injections. We conclude that it is feasible to selectively target brain tumors with TAT-linked chemotherapy by the IA-TCH method.

Recent advancements in liposomes targeting strategies to cross blood-brain barrier (BBB) for the treatment of Alzheimer's disease

In this modern era, with the help of various advanced technologies, medical science has overcome most of the health-related issues successfully. Though, some diseases still remain unresolved due to various physiological barriers. One such condition is Alzheimer; a neurodegenerative disorder characterized by progressive memory impairment, behavioral abnormalities, mood swing and disturbed routine activities of the person suffering from. It is well known to all that the brain is entirely covered by a protective layer commonly known as blood brain barrier (BBB) which is responsible to maintain the homeostasis of brain by restricting the entry of toxic substances, drug molecules, various proteins and peptides, small hydrophilic molecules, large lipophilic substances and so many other peripheral components to protect the brain from any harmful stimuli. This functionally essential structure creates a major hurdle for delivery of any drug into the brain. Still, there are some provisions on BBB which facilitate the entry of useful substances in the brain via specific mechanisms like passive diffusion, receptor-mediated transcytosis, carrier-mediated transcytosis etc. Another important factor for drug transport is the selection of a suitable drug delivery systems like, liposome, which is a novel drug carrier system offering a potential approach to resolving this problem. Its unique phospholipid bilayer structure (similar to physiological membrane) had made it more compatible with the lipoidal layer of BBB and helps the drug to enter the brain. The present review work focused on various surface modifications with functional ligand (like lactoferrin, transferrin etc.) and carrier molecules (such as glutathione, glucose etc.) on the liposomal structure to enhance its brain targeting ability towards the successful treatment of Alzheimer disease.

Flow arrest intra-arterial delivery of small TAT-decorated and neutral micelles to gliomas

The cell-penetrating trans-activator of transcription (TAT) is a cationic peptide derived from human immunodeficiency virus-1. It has been used to facilitate macromolecule delivery to various cell types. This cationic peptide is capable of crossing the blood-brain barrier and therefore might be useful for enhancing the delivery of drugs that target brain tumors. Here we test the efficiency with which relatively small (20 nm) micelles can be delivered by an intra-arterial route specifically to gliomas. Utilizing the well-established method of flow-arrest intra-arterial injection we compared the degree of brain tumor deposition of cationic TAT-decorated micelles versus neutral micelles. Our in vivo and post-mortem analyses confirm glioma-specific deposition of both TAT-decorated and neutral micelles. Increased tumor deposition conferred by the positive charge on the TAT-decorated micelles was modest. Computational modeling suggested a decreased relevance of particle charge at the small sizes tested but not for larger particles. We conclude that continued optimization of micelles may represent a viable strategy for targeting brain tumors after intra-arterial injection. Particle size and charge are important to consider during the directed development of nanoparticles for intra-arterial delivery to brain tumors.

Getting into the brain: liposome-based strategies for effective drug delivery across the blood-brain barrier

This review summarizes articles that have been reported in literature on liposome-based strategies for effective drug delivery across the blood–brain barrier. Due to their unique physicochemical characteristics, liposomes have been widely investigated for their application in drug delivery and in vivo bioimaging for the treatment and/or diagnosis of neurological diseases, such as Alzheimer’s, Parkinson’s, stroke, and glioma. Several strategies have been used to deliver drug and/or imaging agents to the brain. Covalent ligation of such macromolecules as peptides, antibodies, and RNA aptamers is an effective method for receptor-targeting liposomes, which allows their blood–brain barrier penetration and/or the delivery of their therapeutic molecule specifically to the disease site. Additionally, methods have been employed for the development of liposomes that can respond to external stimuli. It can be concluded that the development of liposomes for brain delivery is still in its infancy, although these systems have the potential to revolutionize the ways in which medicine is administered.

Cationizable lipid micelles as vehicles for intraarterial glioma treatment

The relative abundance of anionic lipids on the surface of endothelia and on glioma cells suggests a workable strategy for selective drug delivery by utilizing cationic nanoparticles. Furthermore, the extracellular pH of gliomas is relatively acidic suggesting that tumor selectivity could be further enhanced if nanoparticles can be designed to cationize in such an environment. With these motivating hypotheses the objective of this study was to determine whether nanoparticulate (20 nm) micelles could be designed to improve their deposition within gliomas in an animal model. To test this, we performed intra-arterial injection of micelles labeled with an optically quantifiable dye. We observed significantly greater deposition (end-tissue concentration) of cationizable micelles as compared to non-ionizable micelles in the ipsilateral hemisphere of normal brains. More importantly, we noted enhanced deposition of cationizable as compared to non-ionizable micelles in glioma tissue as judged by semiquantitative fluorescence analysis. Micelles were generally able to penetrate to the core of the gliomas tested. Thus we conclude that cationizable micelles may be constructed as vehicles for facilitating glioma-selective delivery of compounds after intraarterial injection.

Reassessing the Role of Intra-Arterial Drug Delivery for Glioblastoma Multiforme Treatment

Effective treatment for glioblastoma (GBM) will likely require targeted delivery of several specific pharmacological agents simultaneously. Intra-arterial (IA) delivery is one technique for targeting the tumor site with multiple agents. Although IA chemotherapy for glioblastoma (GBM) has been attempted since the 1950s, the predicted benefits remain unproven in clinical practice. This review focuses on innovative approaches to IA drug delivery in treating GBM. Guided by novel in vitro and in vivo optical measurements, newer pharmacokinetic models promise to better define the complex relationship between background cerebral blood flow and drug injection parameters. Advanced optical technologies and tracers, unique nanoparticles designs, new cellular targets, and rational drug formulations are continuously modifying the therapeutic landscape for GBM. Personalized treatment approaches are emerging; however, such tailored approaches will largely depend on effective drug delivery techniques and on the ability to simultaneously deliver multidrug regimens. These new paradigms for tumor-selective drug delivery herald dramatic improvements in the effectiveness of IA chemotherapy for GBM. Therefore, within this context of so-called "precision medicine," the role of IA delivery for GBM is thoroughly reassessed.

Intra-arterial administration improves temozolomide delivery and efficacy in a model of intracerebral metastasis, but has unexpected brain toxicity

We tested the hypothesis that intra-arterial (IA) infusion of temozolomide into the internal carotid artery would safely improve drug delivery to brain and enhance chemotherapy efficacy in a chemosensitive rat brain tumor model. Quantitative autoradiography after 25 µCi (14)C-temozolomide was given by oral, intravenous, or IA route of administration, or IA with osmotic blood-brain barrier disruption (BBBD) (n = 5-7 per group) showed that both IA and IA/BBBD administration increased drug delivery in tumor by over threefold compared to normal brain (P < 0.02), and also significantly elevated delivery throughout the infused right hemisphere. Temozolomide (20 mg/kg; ~150 mg/m(2)) increased median survival when given by oral (25.5 days), intravenous (25.5 days), or IA (33 days) route of administration, compared to 17.5 days in untreated controls (n = 8 per group; overall P < 0.0001). Survival time after IA temozolomide was significantly longer than all other groups (P < 0.01 for all comparisons). BBBD temozolomide was toxic in the efficacy study, but there was no evidence of symptomatic neurotoxicity in rats given IA temozolomide. After these promising animal results, a 49 year old male with glioblastoma multiforme who failed all standard therapy received temozolomide 100 mg/m(2) IA. Upon initiation of the second course of IA infusion the patient had increased heart rate, blood pressure, and rash, and the procedure was terminated without sequelae. Follow up IA infusion of temozolomide diluent in normal rats showed damaged cerebrovasculature as determined by dye leakage. These results demonstrate that IA infusion of temozolomide was toxic, with or without BBBD. We conclude that under the current formulation temozolomide is not safe for IA infusion in patients.

Cerebral hypoperfusion-assisted intra-arterial deposition of liposomes in normal and glioma-bearing rats

BACKGROUND

Optimizing liposomal vehicles for targeted delivery to the brain has important implications for the treatment of brain tumors. The promise of efficient, brain-specific delivery of chemotherapeutic compounds via liposomal vehicles has yet to be achieved in clinical practice. Intra-arterial injection of specially designed liposomes may facilitate efficient delivery to the brain and to gliomas.

OBJECTIVE

To test the hypothesis that cationic liposomes may be effectively delivered to both normal and glioma-bearing brain tissue utilizing a strategy of intra-arterial injection during transient cerebral hypoperfusion.

METHODS

Cationic, anionic, and neutral liposomes were separately injected via the internal carotid artery of healthy rats during transient cerebral hypoperfusion. Rats bearing C6 gliomas were similarly injected with cationic liposomes. Liposomes were loaded with DilC18(5) dye whose concentrations can be measured by light absorbance and fluorescence methods.

RESULTS

After intra-arterial injection, a robust uptake of cationic in comparison with anionic and neutral liposomes into brain parenchyma was observed by diffuse reflectance spectroscopy. Postmortem multispectral fluorescence imaging revealed that liposomal cationic charge was associated with more efficient delivery to the brain. Cationic liposomes were also readily observed within glioma tissue after intra-arterial injection. However, over time, cationic liposomes were retained longer and at higher concentrations in the surrounding, peritumoral brain than in the tumor core.

CONCLUSION

This study demonstrates the feasibility of cationic liposome delivery to brain and glioma tissue after intra-arterial injection. Highly cationic liposomes directly delivered to the brain via an intracarotid route may represent an effective method for delivering antiglioma agents.

Cationic surface charge enhances early regional deposition of liposomes after intracarotid injection

Rapid first pass uptake of drugs is necessary to increase tissue deposition after intraarterial (IA) injection. Here we tested whether brain tissue deposition of a nanoparticulate liposomal carrier could be enhanced by coordinated manipulation of liposome surface charge and physiological parameters, such as IA injection during transient cerebral hypoperfusion (TCH). Different degrees of blood-brain barrier disruption were induced by focused ultrasound in three sets of Sprague-Dawley rats. Brain tissue retention was then compared for anionic, cationic, and charge-neutral liposomes after IA injection combined with TCH. The liposomes contained a non-exchangeable carbocyanine membrane optical label that could be quantified using diffuse reflectance spectroscopy (DRS) or visualized by multispectral imaging. Real-time concentration-time curves in brain were obtained after each liposomal injection. Having observed greater tissue retention of cationic liposomes compared to other liposomes in all three groups, we tested uptake of cationic liposomes in C6 tumor bearing rats. DRS and multispectral imaging of postmortem sections revealed increased liposomal uptake by the C6 brain tumor as compared to non-tumor contralateral hemisphere. We conclude that regional deposition of liposomes can be enhanced without BBB disruption using IA injection of cationic liposomal formulations in healthy and C6 tumor bearing rats.

Spatial mapping of drug delivery to brain tissue using hyperspectral spatial frequency-domain imaging

We present an application of spatial frequency-domain imaging (SFDI) to the wide-field imaging of drug delivery to brain tissue. Measurements were compared with values obtained by a previously validated variation of diffuse reflectance spectroscopy, the method of optical pharmacokinetics (OP). We demonstrate a crosscorrelation between the two methods for absorption extraction and drug concentration determination in both experimental tissue phantoms and freshly extracted rodent brain tissue. These methods were first used to assess intra-arterial (IA) delivery of cationic liposomes to brain tissue in Sprague Dawley rats under transient cerebral hypoperfusion. Results were found to be in agreement with previously published experimental data and pharmacokinetic models of IA drug delivery. We then applied the same scheme to evaluate IA mitoxantrone delivery to glioma-bearing rats. Good correlation was seen between OP and SFDI determined concentrations taken from normal and tumor averaged sites. This study shows the feasibility of mapping drug/tracer distributions and encourages the use of SFDI for spatial imaging of tissues for drug/tracer-tagged carrier deposition and pharmacokinetic studies.