Drug targeting to the brain

Targeting specific brain districts for advanced nanotherapies: A review from the perspective of precision nanomedicine

Numerous studies are focused on nanoparticle penetration into the brain functionalizing them with ligands useful to cross the blood-brain barrier. However, cell targeting is also crucial, given that cerebral pathologies frequently affect specific brain cells or areas. Functionalize nanoparticles with the most appropriate targeting elements, tailor their physical parameters, and consider the brain's complex anatomy are essential aspects for precise therapy and diagnosis. In this review, we addressed the state of the art on targeted nanoparticles for drug delivery in diseased brain regions, outlining progress, limitations, and ongoing challenges. We also provide a summary and overview of general design principles that can be applied to nanotherapies, considering the areas and cell types affected by the most common brain disorders. We then emphasize lingering uncertainties that hinder the translational possibilities of nanotherapies for clinical use. Finally, we offer suggestions for continuing preclinical investigations to enhance the overall effectiveness of precision nanomedicine in addressing neurological conditions. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Poliovirus capsid protein VP3 can penetrate vascular endothelial cells

The poliovirus (PV) enters the central nervous system (CNS) via the bloodstream, suggesting the existence of a mechanism to cross the blood-brain barrier. Here, we report that PV capsid proteins (VP1 and VP3) can penetrate cells, with VP3 being more invasive. Two independent parts of VP3 are responsible for this function. Both peptides can penetrate human umbilical cord vascular endothelial cells, and one peptide of VP3 could also penetrate peripheral blood mononuclear cells. In an in vitro blood-brain barrier model using rat-derived astrocytes, pericytes, and endothelial cells, both peptides were observed to traverse from the blood side to the brain side at 6 h after administration. These results provide insights into the molecular mechanisms underlying PV invasion into the CNS.

Engineered Antibodies to Improve Efficacy against Neurodegenerative Disorders

Antibodies that can selectively remove rogue proteins in the brain are an obvious choice to treat neurodegenerative disorders (NDs), but after decades of efforts, only two antibodies to treat Alzheimer's disease are approved, dozens are in the testing phase, and one was withdrawn, and the other halted, likely due to efficacy issues. However, these outcomes should have been evident since these antibodies cannot enter the brain sufficiently due to the blood-brain barrier (BBB) protectant. However, all products can be rejuvenated by binding them with transferrin, preferably as smaller fragments. This model can be tested quickly and at a low cost and should be applied to bapineuzumab, solanezumab, crenezumab, gantenerumab, aducanumab, lecanemab, donanemab, cinpanemab, and gantenerumab, and their fragments. This paper demonstrates that conjugating with transferrin does not alter the binding to brain proteins such as amyloid-β (Aβ) and α-synuclein. We also present a selection of conjugate designs that will allow cleavage upon entering the brain to prevent their exocytosis while keeping the fragments connected to enable optimal binding to proteins. The identified products can be readily tested and returned to patients with the lowest regulatory cost and delays. These engineered antibodies can be manufactured by recombinant engineering, preferably by mRNA technology, as a more affordable solution to meet the dire need to treat neurodegenerative disorders effectively.

Systemic Treatment with siRNA Targeting Gamma-Secretase Activating Protein Inhibits Amyloid-β Accumulation in Alzheimer's Disease

Amyloid-β (Aβ) peptide aggregation in the brain is a key factor in Alzheimer's disease. However, direct inhibition of β-secretase or γ-secretase proves ineffective in reducing Aβ accumulation and improving cognition in Alzheimer's. Recent findings suggest that inhibiting gamma-secretase activating protein (GSAP) can decrease Aβ generation without affecting crucial γ-secretase substrates. Dimerization of Lep9R3LC (diLep9R3LC) was confirmed by Ellman's test. The peptide-small interfering RNA (siRNA) complex ratio, particle size, and surface charge were analyzed using electrophoretic mobility shift assay, and dynamic light scattering, respectively. In a 3xTg mice model of Alzheimer's disease, diLep9R3LC:siRNA complexes were intravenously administered twice a week for 8 weeks. Assessments included gene silencing, protein expression, and behavioral improvement using reverse transcription polymerase chain reaction, quantitative polymerase chain reaction, western blotting, Y-maze, and object recognition tests. The efficacy of Lep9R3LC dimerization was ~80% after a 3-d reaction by Ellman's test. In N2a cells, diLep9R3LC:siGSAP complexes achieved ~70% silencing at 48 h posttransfection. In 7-month-old male 3xTg mice, GSAP knockdown was ~30% in the cortex and ~50% in the hippocampus. The behavior improved in mice treated with diLep9R3LC:siGSAP complexes, showing a 60% increase in entries and an 80% increase object recognition. A novel dipeptide, diLep9R3LC, complexed with siRNA targeting GSAP (siGSAP), efficiently delivers siRNA to the mouse brain, targeting the hippocampus. The treatment inhibits Aβ accumulation, reduces GSK-3β-associated with tau hyperphosphorylation, and improves Alzheimer's behavior. Our findings highlight diLep9R3LC:siGSAP's potential for Alzheimer's and as a siRNA carrier for central nervous system-related diseases.

Innovative Therapeutic Strategies in Alzheimer's Disease: A Synergistic Approach to Neurodegenerative Disorders

Alzheimer's disease (AD) remains a significant challenge in the field of neurodegenerative disorders, even nearly a century after its discovery, due to the elusive nature of its causes. The development of drugs that target multiple aspects of the disease has emerged as a promising strategy to address the complexities of AD and related conditions. The immune system's role, particularly in AD, has gained considerable interest, with nanobodies representing a new frontier in biomedical research. Advances in targeting antibodies against amyloid-β (Aβ) and using messenger RNA for genetic translation have revolutionized the production of antibodies and drug development, opening new possibilities for treatment. Despite these advancements, conventional therapies for AD, such as Cognex, Exelon, Razadyne, and Aricept, often have limited long-term effectiveness, underscoring the need for innovative solutions. This necessity has led to the incorporation advanced technologies like artificial intelligence and machine learning into the drug discovery process for neurodegenerative diseases. These technologies help identify therapeutic targets and optimize lead compounds, offering a more effective approach to addressing the challenges of AD and similar conditions.

Treating Alzheimer's disease using nanoparticle-mediated drug delivery strategies/systems

The administration of promising medications for the treatment of neurodegenerative disorders (NDDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) is significantly hampered by the blood-brain barrier (BBB). Nanotechnology has recently come to light as a viable strategy for overcoming this obstacle and improving drug delivery to the brain. With a focus on current developments and prospects, this review article examines the use of nanoparticles to overcome the BBB constraints to improve drug therapy for AD The potential for several nanoparticle-based approaches, such as those utilizing lipid-based, polymeric, and inorganic nanoparticles, to enhance drug transport across the BBB are highlighted. To shed insight on their involvement in aiding effective drug transport to the brain, methods of nanoparticle-mediated drug delivery, such as surface modifications, functionalization, and particular targeting ligands, are also investigated. The article also discusses the most recent findings on innovative medication formulations encapsulated within nanoparticles and the therapeutic effects they have shown in both preclinical and clinical testing. This sector has difficulties and restrictions, such as the need for increased safety, scalability, and translation to clinical applications. However, the major emphasis of this review aims to provide insight and contribute to the knowledge of how nanotechnology can potentially revolutionize the worldwide treatment of NDDs, particularly AD, to enhance clinical outcomes.

Brain Targeting Nanomedicines: Pitfalls and Promise

Brain diseases are the most devastating problem among the world's increasingly aging population, and the number of patients with neurological diseases is expected to increase in the future. Although methods for delivering drugs to the brain have advanced significantly, none of these approaches provide satisfactory results for the treatment of brain diseases. This remains a challenge due to the unique anatomy and physiology of the brain, including tight regulation and limited access of substances across the blood-brain barrier. Nanoparticles are considered an ideal drug delivery system to hard-to-reach organs such as the brain. The development of new drugs and new nanomaterial-based brain treatments has opened various opportunities for scientists to develop brain-specific delivery systems that could improve treatment outcomes for patients with brain disorders such as Alzheimer's disease, Parkinson's disease, stroke and brain tumors. In this review, we discuss noteworthy literature that examines recent developments in brain-targeted nanomedicines used in the treatment of neurological diseases.

Transcytosis-Driven Treatment of Neurodegenerative Disorders by mRNA-Expressed Antibody-Transferrin Conjugates

The recent setbacks in the withdrawal and approval delays of antibody treatments of neurodegenerative disorders (NDs), attributed to their poor entry across the blood-brain barrier (BBB), emphasize the need to bring novel approaches to enhance the entry across the BBB. One such approach is conjugating the antibodies that bind brain proteins responsible for NDs with the transferrin molecule. This glycoprotein transports iron into cells, connecting with the transferrin receptors (TfRs), piggybacking an antibody-transferrin complex that can subsequently release the antibody in the brain or stay connected while letting the antibody bind. This process increases the concentration of antibodies in the brain, enhancing therapeutic efficacy with targeted delivery and minimum systemic side effects. Currently, this approach is experimented with using drug-transferring conjugates assembled in vitro. Still, a more efficient and safer alternative is to express the conjugate using mRNA technology, as detailed in this paper. This approach will expedite safer discoveries that can be made available at a much lower cost than the recombinant process with in vitro conjugation. Most importantly, the recommendations made in this paper may save the antibodies against the NDs that seem to be failing despite their regulatory approvals.

Lipid-mediated protein corona regulation with increased apolipoprotein A-I recruitment for glioma targeting

Protein corona has long been a source of concern, as it might impair the targeting efficacy of targeted drug delivery systems. However, engineered up-regulating the adsorption of certain functional serum proteins could provide nanoparticles with specific targeting drug delivery capacity. Herein, apolipoprotein A-I absorption increased nanoparticles (SPC-PLGA NPs), composed with the Food and Drug Administration approved intravenously injectable soybean phosphatidylcholine (SPC) and poly (DL-lactide-co-glycolide) (PLGA), were fabricated for enhanced glioma targeting. Due to the high affinity of SPC and apolipoprotein A-I, the percentage of apolipoprotein A-I in the protein corona of SPC-PLGA NPs was 2.19-fold higher than that of nanoparticles without SPC, which made SPC-PLGA NPs have superior glioma targeting ability through binding to scavenger receptor class BI on blood-brain barrier and glioma cells both in vitro and in vivo. SPC-PLGA NPs loaded with paclitaxel could effectively reduce glioma invasion and prolong the survival time of glioma-bearing mice. In conclusion, we provided a good example of the direction of achieving targeting drug delivery based on protein corona regulation.

Expanding assay range to accommodate a monoclonal antibody therapeutic quantification in blood and cerebrospinal fluid

Antibody therapeutic levels in neurodegenerative diseases are often measured in both serum and cerebrospinal fluid (CSF). Due to 0.1% drug partition from serum to CSF and the higher sensitivity needs, usually two different assays are required. The different Gyrolab Bioaffy compact discs can extend the dynamic range of assays. Here, an assay was developed and adapted on two different Gyrolab Bioaffy compact discs (200 and 4000 nl) to achieve the required sensitivity and assay dynamic range needed for the measurement of drug in both serum and CSF. This was accomplished by using the same critical reagents with minimal assay development to transition from a serum to a CSF assay.

Calming the Nerves via the Immune Instructive Physiochemical Properties of Self-Assembling Peptide Hydrogels

Current therapies for the devastating damage caused by traumatic brain injuries (TBI) are limited. This is in part due to poor drug efficacy to modulate neuroinflammation, angiogenesis and/or promoting neuroprotection and is the combined result of challenges in getting drugs across the blood brain barrier, in a targeted approach. The negative impact of the injured extracellular matrix (ECM) has been identified as a factor in restricting post-injury plasticity of residual neurons and is shown to reduce the functional integration of grafted cells. Therefore, new strategies are needed to manipulate the extracellular environment at the subacute phase to enhance brain regeneration. In this review, potential strategies are to be discussed for the treatment of TBI by using self-assembling peptide (SAP) hydrogels, fabricated via the rational design of supramolecular peptide scaffolds, as an artificial ECM which under the appropriate conditions yields a supramolecular hydrogel. Sequence selection of the peptides allows the tuning of these hydrogels' physical and biochemical properties such as charge, hydrophobicity, cell adhesiveness, stiffness, factor presentation, degradation profile and responsiveness to (external) stimuli. This review aims to facilitate the development of more intelligent biomaterials in the future to satisfy the parameters, requirements, and opportunities for the effective treatment of TBI.

Breaking Barriers in Neuro-Oncology: A Scoping Literature Review on Invasive and Non-Invasive Techniques for Blood-Brain Barrier Disruption

The blood-brain barrier (BBB) poses a significant challenge to drug delivery for brain tumors, with most chemotherapeutics having limited permeability into non-malignant brain tissue and only restricted access to primary and metastatic brain cancers. Consequently, due to the drug's inability to effectively penetrate the BBB, outcomes following brain chemotherapy continue to be suboptimal. Several methods to open the BBB and obtain higher drug concentrations in tumors have been proposed, with the selection of the optimal method depending on the size of the targeted tumor volume, the chosen therapeutic agent, and individual patient characteristics. Herein, we aim to comprehensively describe osmotic disruption with intra-arterial drug administration, intrathecal/intraventricular administration, laser interstitial thermal therapy, convection-enhanced delivery, and ultrasound methods, including high-intensity focused and low-intensity ultrasound as well as tumor-treating fields. We explain the scientific concept behind each method, preclinical/clinical research, advantages and disadvantages, indications, and potential avenues for improvement. Given that each method has its limitations, it is unlikely that the future of BBB disruption will rely on a single method but rather on a synergistic effect of a combined approach. Disruption of the BBB with osmotic infusion or high-intensity focused ultrasound, followed by the intra-arterial delivery of drugs, is a promising approach. Real-time monitoring of drug delivery will be necessary for optimal results.

Exit pathways of therapeutic antibodies from the brain and retention strategies

Treating brain diseases requires therapeutics to pass the blood-brain barrier (BBB) which is nearly impermeable for large biologics such as antibodies. Several methods now facilitate crossing or circumventing the BBB for antibody therapeutics. Some of these exploit receptor-mediated transcytosis, others use direct delivery bypassing the BBB. However, successful delivery into the brain does not preclude exit back to the systemic circulation. Various mechanisms are implicated in the active and passive export of antibodies from the central nervous system. Here we review findings on active export via transcytosis of therapeutic antibodies - in particular, the role of the neonatal Fc receptor (FcRn) - and discuss a possible contribution of passive efflux pathways such as lymphatic and perivascular drainage. We point out open questions and how to address these experimentally. In addition, we suggest how emerging findings could aid the design of the next generation of therapeutic antibodies for neurologic diseases.

Neostigmine and atropine as a treatment for postdural puncture headache after spinal anesthesia in cesarean section: A case report

Key Clinical message

Neostigmine and atropine offer a promising treatment option for postdural puncture headache (PDPH) following spinal anesthesia in cesarean section, providing effective relief with a favorable risk-benefit profile.

Abstract

Postdural puncture headache (PDPH) is a common consequence of cesarean section surgeries after spinal anesthesia. This case study describes the successful treatment of PDPH with intravenous neostigmine and atropine. A 31 years female who underwent elective cesarean section with spinal anesthesia developed a severe headache on the 6th postoperative day and was diagnosed to have PDPH. PDPH failed to respond to conventional treatment modalities like hydration, a Non-steroidal anti-inflammatory drug, and sphenopalatine ganglion block. Epidural blood patch could not be performed due to lack of consent. A trial dose of intravenous neostigmine (20 mcg/kg) along with atropine (10 mcg/kg) successfully provided symptomatic and clinical relief. The combination of neostigmine and atropine demonstrates a rapid onset of action, providing patients with effective analgesia while avoiding the need for invasive procedures such as epidural blood patches and offers quicker pain relief. This promising result warrants additional research.

Characterization of Binding Properties of Cr(Phen)3 3+ and Ru(Phen)3 2+ Complexes with Human Lactoferrin

This work presents research about [Cr(phen)3 ]3+ and [Ru(phen)3 ]2+ interaction with human lactoferrin (HLf), a key carrier protein of ferric cations. The photochemical and photophysical properties of [Cr(phen)3 ]3+ and [Ru(phen)3 ]2+ have been widely studied in the last decades due to their potential use as photosensitizers in photodynamic therapy (PDT). The behavior between the complexes and the protein was studied employing UV-visible absorption, fluorescence emission and circular dichroism spectroscopic techniques. It was found that both complexes bind to HLf with a large binding constant (Kb ): 9.46 × 104 for the chromium complex and 4.16 × 104 for the ruthenium one at 299 K. Thermodynamic parameters were obtained from the Van't Hoff equation. Analyses of entropy (ΔS), enthalpy (ΔH) and free energy changes (ΔG) indicate that these complexes bind to HLf because of entropy-driven processes and electrostatic interactions. According to circular dichroism experiments, no conformational changes have been observed in the secondary and tertiary structure of the protein in the presence of any of the studied complexes. These experimental results suggest that [Cr(phen)3 ]3+ and [Ru(phen)3 ]2+ bind to HLf, indicating that this protein could act as a carrier of these complexes in further applications.

Noninvasive disruption of the blood-brain barrier in the marmoset monkey

The common marmoset monkey (Callithrix jacchus) is a species of rising prominence in the neurosciences due to its small size, ease of handling, fast breeding, and its shared functional and structural brain characteristics with Old World primates. With increasing attention on modeling human brain diseases in marmosets, understanding how to deliver therapeutic or neurotropic agents to the marmoset brain noninvasively is of great preclinical importance. In other species, including humans, transcranial focused ultrasound (tFUS) aided by intravenously injected microbubbles has proven to be a transient, reliable, and safe method for disrupting the blood-brain barrier (BBB), allowing the focal passage of therapeutic agents that do not otherwise readily traverse the tight endothelial junctions of the BBB. The critical gap that we address here is to document parameters to disrupt the BBB reliably and safely in marmosets using tFUS. By integrating our marmoset brain atlases and the use of a marmoset-specific stereotactic targeting system, we conduct a series of systematic transcranial sonication experiments in nine marmosets. We demonstrate the effects of center frequency, acoustic pressure, burst period, and duration, establish a minimum microbubble dose, estimate microbubble clearance time, and estimate the duration that the BBB remains open to passage. Successful BBB disruption is reported in vivo with MRI-based contrast agents, as well as Evans blue staining assessed ex vivo. Histology (Hematoxylin and Eosin staining) and immunohistochemistry indicate that the BBB can be safely and reliably opened with the parameters derived from these experiments. The series of experiments presented here establish methods for safely, reproducibly, and focally perturbing the BBB using tFUS in the common marmoset monkey that can serve as a basis for noninvasive delivery of therapeutic or neurotropic agents.

A prediction model for magnetic particle imaging-based magnetic hyperthermia applied to a brain tumor model

BACKGROUND AND OBJECTIVE

Brain tumor is a global health concern at the moment. Thus far, the only treatments available are radiotherapy and chemotherapy, which have several drawbacks such as low survival rates and low treatment efficacy due to obstruction of the blood-brain barrier. Magnetic hyperthermia (MH) using magnetic nanoparticles (MNPs) is a promising non-invasive approach that has the potential for tumor treatment in deep tissues. Due to the limitations of the current drug-targeting systems, only a small proportion of the injected MNPs can be delivered to the desired area and the rest are distributed throughout the body. Thus, the application of conventional MH can lead to damage to healthy tissues.

METHODS

Magnetic particle imaging (MPI)-guided treatment platform for MH is an emerging approach that can be used for spatial localization of MH to arbitrarily selected regions by using the MPI magnetic field gradient. Although the feasibility of this method has been demonstrated experimentally, a multidimensional prediction model, which is of crucial importance for treatment planning, has not yet been developed. Hence, in this study, the time dependent magnetization equation derived by Martsenyuk, Raikher, and Shliomis (which is a macroscopic equation of motion derived from the Fokker-Planck equation for particles with Brownian relaxation mechanism) and the bio-heat equations have been used to develop and investigate a three-dimensional model that predicts specific loss power (SLP), its spatio-thermal resolution (temperature distribution), and the fraction of damage in brain tumors.

RESULTS

Based on the simulation results, the spatio-thermal resolution in focused heating depends, in a complex manner, on several parameters ranging from MNPs properties to magnetic fields characteristics, and coils configuration. However, to achieve a high performance in focused heating, the direction and the relative amplitude of the AC magnetic heating field with respect to the magnetic field gradient are among the most important parameters that need to be optimized. The temperature distribution and fraction of the damage in a simple brain model bearing a tumor were also obtained.

CONCLUSIONS

The complexity in the relationship between the MNPs properties and fields parameter imposes a trade-off between the heating efficiency of MNPs and the accuracy (resolution) of the focused heating. Therefore, the system configuration and field parameters should be chosen carefully for each specific treatment scenario. In future, the results of the model are expected to lead to the development of an MPI-guided MH treatment platform for brain tumor therapy. However, for more accurate quantitative results in such a platform, a magnetization dynamics model that takes into account coupled Néel-Brownian relaxation mechanism in the MNPs should be developed.

Angiopep-2-conjugated FeTi@Au core-shell nanoparticles for tumor targeted dual-mode magnetic resonance imaging and hyperthermic glioma therapy

Herein, we fabricated gold surface-coated iron titanium core-shell (FeTi@Au) nanoparticles (NPs) with conjugation of angiopep-2 (ANG) (FeTi@Au-ANG) NPs for targeted delivery and improved NPs penetration by receptor-mediated endocytosis to achieve hyperthermic treatment of gliomas. The synthesized "core-shell" FeTi@Au-ANG NPs exhibited spherical in shape with around 16 nm particle size and increased temperature upon alternating magnetic field (AMF) stimulation, rendering them effective for localized hyperthermic therapy of cancer cells. Effective targeted delivery of FeTi@Au-ANG NPs was demonstrated in vitro by improved transport and cellular uptake, and increased apoptosis in glioma cells (C6) compared with normal fibroblast cells (L929). FeTi@Au-ANG NPs exhibited higher deposition in brain tissues and a superior therapeutic effect in an orthotopic intracranial xenograft mouse model. Taken together, our data indicate that FeTi@Au-ANG NPs hold significant promise as a targeted delivery strategy for glioma treatment using hyperthermia.

Transferrin receptor 1 targeted nanomedicine for brain tumor therapy

Achieving effective drug delivery to traverse the blood-brain barrier (BBB) and target tumor cells remains the greatest challenge for brain tumor therapy. Importantly, the overexpressed membrane receptors on the brain endothelial cells, especially transferrin receptor 1 (TfR1), which mediate their ligands/antibodies to overcome the BBB by transcytosis, have been emerging as promising targets for brain tumor therapy. By employing ligands (e.g., transferrin, H-ferritin), antibodies or targeting peptides of TfR1 or aptamers, various functional nano-formulations have been developed in the last decade. These agents showed great potential for the treatment of brain diseases due to their ideal size, high loading capacity, controlled drug release and suitable pharmacokinetics. Herein, we summarize the latest advances on TfR1-targeted nanomedicine for brain tumor therapy. Moreover, we also discuss the strategies of improving stability, targeting ability and accumulation of nano-formulations in brain tumors for better outcomes. In this review, we hope to provide inspiration for the rational design of TfR1-targeted nanomedicine against brain tumors.

Targeted nano-delivery of chemotherapy via intranasal route suppresses in vivo glioblastoma growth and prolongs survival in the intracranial mouse model

Nanotechnology-based drug delivery platforms have shown great potential in overcoming the limitations of conventional therapy for glioblastoma (GBM). However, permeation across the blood-brain barrier (BBB), physiological complexity of the brain, and glioma targeting strategies cannot entirely meet the challenging requirements of distinctive therapeutic delivery stages. The objective of this research is to fabricate lipid nanoparticles (LNPs) for the co-delivery of paclitaxel (PTX) and miltefosine (HePc) a proapoptotic agent decorated with transferrin (Tf-PTX-LNPs) and investigate its anti-glioma activity both in vitro and in vivo orthotopic NOD/SCID GBM mouse model. The present study demonstrates the anti-glioma effect of the dual drug combination of PTX and proapoptotic HePc lipid-based transferrin receptor (TfR) targeted alternative delivery (direct nose to brain transportation) of the nanoparticulate system (Tf-PTX-LNPs, 364 ± 5 nm, -43 ± 9 mV) to overcome the O⁶-methylguanine-DNA methyltransferase induce drug-resistant for improving the effectiveness of GBM therapy. The resulting nasally targeted LNPs present good biocompatibility, stability, high BBB transcytosis through selective TfR-mediated uptake by tumor cells, and effective tumor penetration in the brain of GBM induced mice. We observed markedly enhanced anti-proliferative efficacy of the targeted LNPs in U87MG cells compared to free drug. Nasal targeted LNPs had shown significantly improved brain concentration (C_max fivefold and AUC_0-24 4.9 fold) with early t_max (0.5 h) than the free drug. In vivo intracranial GBM-bearing targeted LNPs treated mice exhibited significantly prolonged survival with improved anti-tumor efficacy accompanied by reduced toxicity compared to systemic Taxol^® and nasal free drug. These findings indicate that the nasal delivery of targeted synergistic nanocarrier holds great promise as a non-invasive adjuvant chemotherapy therapy of GBM.

Stem Cell-derived Extracellular Vesicles: A Promising Nano Delivery Platform to the Brain?

A very important cause of the frustration with drug therapy for central nervous system (CNS) diseases is the failure of drug delivery. The blood-brain barrier (BBB) prevents most therapeutic molecules from entering the brain while maintaining CNS homeostasis. Scientists are keen to develop new brain drug delivery systems to solve this dilemma. Extracellular vesicles (EVs), as a class of naturally derived nanoscale vesicles, have been extensively studied in drug delivery due to their superior properties. This review will briefly present current brain drug delivery strategies, including invasive and non-invasive techniques that target the brain, and the application of nanocarriers developed for brain drug delivery in recent years, especially EVs. The cellular origin of EVs affects the surface protein, size, yield, luminal composition, and other properties of EVs, which are also crucial in determining whether EVs are useful as drug carriers. Stem cell-derived EVs, which inherit the properties of parental cells and avoid the drawbacks of cell therapy, have always been favored by researchers. Thus, in this review, we will focus on the application of stem cell-derived EVs for drug delivery in the CNS. Various nucleic acids, proteins, and small-molecule drugs are loaded into EVs with or without modification and undergo targeted delivery to the brain to achieve their therapeutic effects. In addition, the challenges facing the clinical application of EVs as drug carriers will also be discussed. The directions of future efforts may be to improve drug loading efficiency and precise targeting.

Lactoferrin for Mental Health: Neuro-Redox Regulation and Neuroprotective Effects across the Blood-Brain Barrier with Special Reference to Neuro-COVID-19

Overall mental health depends in part on the blood-brain barrier, which regulates nutrient transfer in-and-out of the brain and its central nervous system. Lactoferrin, an innate metal-transport protein, synthesized in the substantia nigra, particularly in dopaminergic neurons and activated microglia is vital for brain physiology. Lactoferrin rapidly crosses the blood-brain barrier via receptor-mediated transcytosis and accumulates in the brain capillary endothelial cells. Lactoferrin receptors are additionally present on glioma cells, brain micro-vessels, and neurons. As a regulator of neuro-redox, microglial lactoferrin is critical for protection/repair of neurons and healthy brain function. Iron imbalance and oxidative stress are common among patients with neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease, dementia, depression, and multiple sclerosis. As an endogenous iron-chelator, lactoferrin prevents iron accumulation and dopamine depletion in Parkinson's disease patients. Oral lactoferrin supplementation could modulate the p-Akt/PTEN pathway, reduce Aβ deposition, and ameliorate cognitive decline in Alzheimer's disease. Novel lactoferrin-based nano-therapeutics have emerged as effective drug-delivery systems for clinical management of neurodegenerative disorders. Recent emergence of the Coronavirus disease-2019 (COVID-19) pandemic, initially considered a respiratory illness, demonstrated a broader virulence spectrum with the ability to cross the blood-brain barrier and inflict a plethora of neuropathological manifestations in the brain - the Neuro-COVID-19. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are widely reported in Parkinson's disease, Alzheimer's disease, dementia, and multiple sclerosis patients with aggravated clinical outcomes. Lactoferrin, credited with several neuroprotective benefits in the brain could serve as a potential adjuvant in the clinical management of Neuro-COVID-19.

Targeting interleukin-13 receptor α2 (IL-13Rα2) for glioblastoma therapy with surface functionalized nanocarriers

Despite surgical and therapeutic advances, glioblastoma multiforme (GBM) is among the most fatal primary brain tumor that is aggressive in nature. Patients with GBM have a median lifespan of just 15 months when treated with the current standard of therapy, which includes surgical resection and concomitant chemo-radiotherapy. In recent years, nanotechnology has shown considerable promise in treating a variety of illnesses, and certain nanomaterials have been proven to pass the blood-brain barrier (BBB) and stay in glioblastoma tissues. Recent preclinical research suggests that the diagnosis and treatment of brain tumor is significantly explored through the intervention of nanomaterials that has showed enhanced effect. In order to elicit an antitumor response, it is necessary to retain the therapeutic candidates within glioblastoma tissues and this job is effectively carried out by nanocarrier particularly functionalized nanocarriers. In the arena of neoplastic diseases including GBM have achieved great attention in recent decades. Furthermore, interleukin-13 receptor α chain variant 2 (IL13Rα2) is a highly expressed and studied target in GBM that is lacked by the surrounding environment. The absence of IL13Rα2 in surrounding normal tissues has made it a suitable target in glioblastoma therapy. In this review article, we highlighted the role of IL13Rα2 as a potential target in GBM along with design and fabrication of efficient targeting strategies for IL13Rα2 through surface functionalized nanocarriers.

Increased brain uptake of pterostilbene loaded folate modified micellar delivery system

Effective chemotherapy for clinical treatment of brain diseases is still lacking due to the poor penetration of the blood-brain barrier (BBB). The aim of this study was to construct a folate modified pterostilbene (Pt) loaded polymeric micellar delivery system (F-Pt/M) with mPEG-PCL as carrier material to aim at penetrating the BBB for brain tissue targeting via receptor-mediated endocytosis. In this study, F-Pt/M was prepared using thin-film hydration method and then optimized by response surface methodology (RSM) with the entrapment efficiency (EE), drug loading (DL) and hydrodynamic diameter (HD) as indexes. The average hydrodynamic diameter and zeta potential of optimal F-Pt/M were 133.2 nm and 24.6 mV, respectively. DL (18.3%) and EE (98.6%) made the solubility of Pt in water about 25 times higher than that of crude Pt. Results of DSC evaluation revealed that drugs were successfully encapsulated inside the polymeric micelles. TEM images showed that homogeneous spherical micellar structures with a narrow size distribution were developed. The release result in vitro showed that F-Pt/M presented sustained release behavior compared to control free Pt solution. Compared to non-targeted Pt/M, F-Pt/M had a significantly higher cytotoxicity against FR-overexpressing A172 cells. In vitro cellular uptake tests illustrated that the micellar delivery system could significantly improve the accumulation of drugs in target cells via receptor-mediated endocytosis. BBB penetration value (P) of F-Pt/M was about 4 folds higher than that of free Pt group. In addition, drug targeting index (DTI) was calculated to determine targeting of F-Pt/M to the brain which was found to be 4.89, implying improved brain targeting was achieved. Hence, the developed F-Pt/M exhibited great potential for delivering more drug molecules across the BBB for the treatment of brain diseases.

Multifunctional nanomedicine strategies to manage brain diseases

Brain diseases represent a substantial social and economic burden, currently affecting one in six individuals worldwide. Brain research has been focus of great attention in order to unravel the pathogenesis and complexity of brain diseases at the cellular, molecular, and microenvironmental levels. Due to the intrinsic nature of the brain, the presence of the highly restrictive blood-brain barrier (BBB), and the pathophysiology of most diseases, therapies can hardly be considered successful purely by the administration of one drug to a patient. Apart from improving pharmacokinetic parameters, tailoring biodistribution, and reducing the number of side effects, nanomedicines are able to actively co-target the therapeutics to the brain parenchyma and brain lesions, as well as to achieve the delivery of multiple cargos with therapeutic, diagnostic, and theranostic properties. Among other multivalent effects that can be personalized according to the disease needs, this represents a promising class of novel nanosystems, termed multifunctional nanomedicines. Herein, we review the principal mechanisms of therapeutic resistance of the most prevalent brain diseases, how to overcome this therapeutic resistance through the use of multifunctional nanomedicines that tackle multiple fronts of the disease microenvironment, and the promising therapeutic responses achieved by some of the most cutting-edge multifunctional nanomedicines reported in literature.

Ultrasound-assisted brain delivery of nanomedicines for brain tumor therapy: advance and prospect

Nowadays, brain tumors are challenging problems, and the key of therapy is ensuring therapeutic drugs cross the blood-brain barrier (BBB) effectively. Although the efficiency of drug transport across the BBB can be increased by innovating and modifying nanomedicines, they exert insufficient therapeutic effects on brain tumors due to the complex environment of the brain. It is worth noting that ultrasound combined with the cavitation effect of microbubbles can assist BBB opening and enhance brain delivery of nanomedicines. This ultrasound-assisted brain delivery (UABD) technology with related nanomedicines (UABD nanomedicines) can safely open the BBB, facilitate the entry of drugs into the brain, and enhance the therapeutic effect on brain tumors. UABD nanomedicines, as the main component of UABD technology, have great potential in clinical application and have been an important area of interest in the field of brain tumor therapy. However, research on UABD nanomedicines is still in its early stages despite the fact that they have been associated with many disciplines, including material science, brain science, ultrasound, biology, and medicine. Some aspects of UABD theory and technology remain unclear, especially the mechanisms of BBB opening, relationship between materials of nanomedicines and UABD technology, cavitation and UABD nanomedicines design theories. This review introduces the research status of UABD nanomedicines, investigates their properties and applications of brain tumor therapy, discusses the advantages and drawbacks of UABD nanomedicines for the treatment of brain tumors, and offers their prospects. We hope to encourage researchers from various fields to participate in this area and collaborate on developing UABD nanomedicines into powerful tools for brain tumor therapy.

Combinatorial therapeutic strategies for enhanced delivery of therapeutics to brain cancer cells through nanocarriers: current trends and future perspectives

Brain cancer is the most aggressive one among various cancers. It has a drastic impact on people's lives because of the failure in treatment efficacy of the currently employed strategies. Various strategies used to relieve pain in brain cancer patients and to prolong survival time include radiotherapy, chemotherapy, and surgery. Nevertheless, several inevitable limitations are accompanied by such treatments due to unsatisfactory curative effects. Generally, the treatment of cancers is very challenging due to many reasons including drugs’ intrinsic factors and physiological barriers. Blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCSFB) are the two additional hurdles in the way of therapeutic agents to brain tumors delivery. Combinatorial and targeted therapies specifically in cancer show a very promising role where nanocarriers’ based formulations are designed primarily to achieve tumor-specific drug release. A dual-targeting strategy is a versatile way of chemotherapeutics delivery to brain tumors that gets the aid of combined ligands and mediators that cross the BBB and reaches the target site efficiently. In contrast to single targeting where one receptor or mediator is targeted, the dual-targeting strategy is expected to produce a multiple-fold increase in therapeutic efficacy for cancer therapy, especially in brain tumors. In a nutshell, a dual-targeting strategy for brain tumors enhances the delivery efficiency of chemotherapeutic agents via penetration across the blood-brain barrier and enhances the targeting of tumor cells. This review article highlights the ongoing status of the brain tumor therapy enhanced by nanoparticle based delivery with the aid of dual-targeting strategies. The future perspectives in this regard have also been highlighted.

Lipid-Based Nanocarriers for Neurological Disorders: A Review of the State-of-the-Art and Therapeutic Success to Date

Neurodegenerative disorders including Alzheimer's, Parkinson's, and dementia are chronic and advanced diseases that are associated with loss of neurons and other related pathologies. Furthermore, these disorders involve structural and functional defections of the blood-brain barrier (BBB). Consequently, advances in medicines and therapeutics have led to a better appreciation of various pathways associated with the development of neurodegenerative disorders, thus focusing on drug discovery and research for targeted drug therapy to the central nervous system (CNS). Although the BBB functions as a shield to prevent toxins in the blood from reaching the brain, drug delivery to the CNS is hindered by its presence. Owing to this, various formulation approaches, including the use of lipid-based nanocarriers, have been proposed to address shortcomings related to BBB permeation in CNS-targeted therapy, thus showing the potential of these carriers for translation into clinical use. Nevertheless, to date, none of these nanocarriers has been granted market authorization following the successful completion of all stages of clinical trials. While the aforementioned benefits of using lipid-based carriers underscores the need to fast-track their translational development into clinical practice, technological advances need to be initiated to achieve appropriate capacity for scale-up and the production of affordable dosage forms.

Bioconcentration of neuroactive pharmaceuticals in fish: Relation to lipophilicity, experimental design and toxicity in the aquatic environment

Uptake of contaminants is linked to their toxicity and is usually estimated through their lipophilicity (logK_ow). Here, we review current literature regarding bioconcentration, i.e. uptake of contaminants from the external environment only, and the effects of exposure to neuroactive pharmaceuticals in fish. We aim to determine if lipophilicity is a suitable predictor of bioconcentration of these compounds in fish, to identify major drivers of bioconcentration and explore the link between bioconcentration potential and toxicity, focusing on survival, growth, condition, behaviour and reproduction endpoints. Additionally, we compare concentrations known to elicit significant effects in fish with current environmental concentrations, identifying exposure risk in ecosystems. The majority of studies have focused on antidepressants, mainly fluoxetine, and encompasses mostly freshwater species. Few studies determined pharmaceuticals bioconcentration, and even a smaller portion combined bioconcentration with other toxicity endpoints. Results show that lipophilicity isn't a good predictor of neuroactive pharmaceuticals' bioconcentration in fish, which in turn is highly influenced by experimental parameters, including abiotic conditions, species and life-stage. The need for increased standardization of experimental settings is key towards improving accuracy of environmental risk assessments and application in future regulatory schemes. Still, increased fish lethality was linked to increased bioconcentration, yet no other correlations were observed when considering effects on growth, condition, behaviour or reproduction, likely as a result of insufficient and variable data. In the context of current environmental concentrations, several neuroactive pharmaceuticals were found to be potentially threatening, while data on occurrence is lacking for some compounds, particularly in brackish/marine systems. Specifically, nine compounds (fluoxetine, citalopram, sertraline, amitriptyline, venlafaxine, clozapine, carbamazepine, metamfetamine and oxazepam) were found at concentrations either above or critically close to minimum response concentrations, thus likely to affect fish in freshwater and brackish or marine environments, which supports further exploration in risk management strategies and monitoring programs in aquatic environments.

Synthesis and Characterization of Fatty Acid Grafted Chitosan Polymeric Micelles for Improved Gene Delivery of VGF to the Brain through Intranasal Route

Multifunctional fatty acid grafted polymeric micelles are an effective and promising approach for drug and gene delivery to the brain. An alternative approach to bypass the blood-brain barrier is administration through intranasal route. Multifunctional fatty acid grafted polymeric micelles were prepared and characterized for pVGF delivery to the brain. In vitro pVGF expression was analyzed in bEnd.3 cells, primary astrocytes, and neurons. Comparative in-vivo pVGF expression was analyzed to evaluate the effective route of administration between intranasal and intravenous. Biocompatible, multifunctional polymeric micelles were prepared, having an average size of 200 nm, and cationic zeta potential. Modified polymers were found to be hemo- and cyto-compatible. When transfected with the different modified chitosan formulations, significantly (p < 0.05) higher VGF expression was observed in primary astrocytes and neurons using the mannose, Tat peptide, and oleic acid grafted chitosan polymer. Compared to intravenous administration, intranasal administration of pVGF in polyplex formulation led to significantly (p < 0.05) higher pVGF expression. Developed multifunctional polymeric micelles were an effective pVGF delivery platform to the brain. Mannose and Tat ligand tagging improved the pVGF delivery to the brain.

Rational Design and Identification of Harmine-Inspired, N-Heterocyclic DYRK1A Inhibitors Employing a Functional Genomic In Vivo Drosophila Model System

Deregulation of dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) plays a significant role in developmental brain defects, early-onset neurodegeneration, neuronal cell loss, dementia, and several types of cancer. Herein, we report the discovery of three new classes of N-heterocyclic DYRK1A inhibitors based on the potent, yet toxic kinase inhibitors, harmine and harmol. An initial in vitro evaluation of the small molecule library assembled revealed that the core heterocyclic motifs benzofuranones, oxindoles, and pyrrolones, showed statistically significant DYRK1A inhibition. Further, the utilization of a low cost, high-throughput functional genomic in vivo model system to identify small molecule inhibitors that normalize DYRK1A overexpression phenotypes is described. This in vivo assay substantiated the in vitro results, and the resulting correspondence validates generated classes as architectural motifs that serve as potential DYRK1A inhibitors. Further expansion and analysis of these core compound structures will allow discovery of safe, more effective chemical inhibitors of DYRK1A to ameliorate phenotypes caused by DYRK1A overexpression.

Diagnosis of Glioblastoma by Immuno-Positron Emission Tomography

Simple Summary

Neuroimaging has transformed the way brain tumors are diagnosed and treated. Although different non-invasive modalities provide very helpful information, in some situations, they present a limited value. By merging the specificity of antibodies with the resolution, sensitivity, and quantitative capabilities of positron emission tomography (PET), “Immuno-PET” allows us to conduct the non-invasive diagnosis and monitoring of patients over time using antibody-based probes as an in vivo, integrated, quantifiable, 3D, full-body “immunohistochemistry”, like a “virtual biopsy”. This review provides and focuses on immuno-PET applications and future perspectives of this promising imaging approach for glioblastoma.

Abstract

Neuroimaging has transformed neuro-oncology and the way that glioblastoma is diagnosed and treated. Magnetic Resonance Imaging (MRI) is the most widely used non-invasive technique in the primary diagnosis of glioblastoma. Although MRI provides very powerful anatomical information, it has proven to be of limited value for diagnosing glioblastomas in some situations. The final diagnosis requires a brain biopsy that may not depict the high intratumoral heterogeneity present in this tumor type. The revolution in “cancer-omics” is transforming the molecular classification of gliomas. However, many of the clinically relevant alterations revealed by these studies have not yet been integrated into the clinical management of patients, in part due to the lack of non-invasive biomarker-based imaging tools. An innovative option for biomarker identification in vivo is termed “immunotargeted imaging”. By merging the high target specificity of antibodies with the high spatial resolution, sensitivity, and quantitative capabilities of positron emission tomography (PET), “Immuno-PET” allows us to conduct the non-invasive diagnosis and monitoring of patients over time using antibody-based probes as an in vivo, integrated, quantifiable, 3D, full-body “immunohistochemistry” in patients. This review provides the state of the art of immuno-PET applications and future perspectives on this imaging approach for glioblastoma.

Simultaneous Localized Brain Mild Hyperthermia and Blood-Brain Barrier Opening via Feedback-Controlled Transcranial MR-guided Focused Ultrasound and Microbubbles

OBJECTIVE

Non-invasive methods to enhance drug delivery and efficacy in the brain have been pursued for decades. Focused ultrasound hyperthermia (HT) combined with thermosensitive therapeutics have been demonstrated promising in enhancing local drug delivery to solid tumors. We hypothesized that the presence of microbubbles (MBs) combined with transcranial MR-guided focused ultrasound (MRgFUS) could be used to reduce the ultrasound power required for HT while simultaneously increasing drug delivery by locally opening the blood-brain barrier (BBB).

METHODS

Transcranial HT (42 C, 10 min) was performed in wild-type mice using a small animal MRgFUS system incorporated into a 9.4T Bruker MR scanner, with infusions of saline or Definity MBs with doses of 20 or 100 l/kg/min (denoted as MB-20 and MB-100). MR thermometry data was continuously acquired as feedback for the ultrasound controller during the procedure.

RESULTS

Spatiotemporally precise transcranial HT was achieved in both saline and MB groups. A significant ultrasound power reduction (-45.7%, p = 0.006) was observed in the MB-20 group compared to saline. Localized BBB opening was achieved in MB groups confirmed by CE-T1w MR images. There were no structural abnormalities, edema, hemorrhage, or acute microglial activation in all groups, confirmed by T2w MR imaging and histology.

CONCLUSION

Our investigations showed that it is feasible and safe to achieve spatiotemporally precise brain HT at significantly reduced power and simultaneous localized BBB opening via transcranial MRgFUS and MBs.

SIGNIFICANCE

This study provides a new synergistic brain drug delivery method with clinical translation potential.

Complexing amphotericin B with gold nanoparticles improves fungal clearance from the brains of mice infected with Cryptococcal neoformans

Amphotericin B (AmB) is used to treat cryptococcal meningoencephalitis. However, the mortality rate remains high. Higher doses of AmB in deoxycholate buffer (AmBd) are toxic to human red blood cells (hRBC) and have no effect on brain organism load in mice. Here we show that while AmBd lysed 96% of hRBC, AmB complexed with gold nanoparticles (AuNP-SA-AmB) lysed only 27% of hRBC. In vitro growth of C. neoformans was inhibited by 0.25 μg/ml AmBd and 0.04 μg/ml of AuNP-SA-AmB. In mice infected with C. neoformans, five daily treatments with AuNP-SA-AmB containing 0.25 mg/kg AmB significantly lowered the fungal burden in the brain tissue compared to either untreated or treatment with 0.25 mg/kg of AmBd. When a single dose of AmBd was injected intravenously into BALB/c mice, 81.61% of AmB cleared in the α-phase and 18.39% cleared in the β-phase at a rate of 0.34% per hour. In contrast, when AuNP-SA-AmB was injected, 49.19% of AmB cleared in the α-phase and 50.81% of AmB cleared in the β-phase at a rate of 0.27% per hour. These results suggest that AmB complexed with gold nanoparticles is less toxic to hRBC, is more effective against C. neoformans and persists longer in blood when injected into mice resulting in more effective clearing of C. neoformans from the brain tissue.

LAY SUMMARY

Amphotericin B (AmB) was complexed with gold nanoparticles (AuNP-SA-AmB) to improve brain delivery. AuNP-SA-AmB was more effective than AmB alone in clearing of Cryptococcus neoformans from the brain tissue of infected mice. This may be due to longer plasma half-life of AmB as AuNP-SA-AmB.

Exosomes in Alzheimer's Disease: From Being Pathological Players to Potential Diagnostics and Therapeutics

Exosomes (EXOs) were given attention as an extracellular vesicle (EV) with a pivotal pathophysiological role in the development of certain neurodegenerative disorders (NDD), such as Parkinson's and Alzheimer's disease (AD). EXOs have shown the potential to carry pathological and therapeutic cargo; thus, researchers have harnessed EXOs in drug delivery applications. EXOs have shown low immunogenicity as natural drug delivery vehicles, thus ensuring efficient drug delivery without causing significant adverse reactions. Recently, EXOs provided potential drug delivery opportunities in AD and promising future clinical applications with the diagnosis of NDD and were studied for their usefulness in disease detection and prediction prior to the emergence of symptoms. In the future, the microfluidics technique will play an essential role in isolating and detecting EXOs to diagnose AD before the development of advanced symptoms. This review is not reiterative literature but will discuss why EXOs have strong potential in treating AD and how they can be used as a tool to predict and diagnose this disorder.

Efficient Anti-Glioma Therapy Through the Brain-Targeted RVG15-Modified Liposomes Loading Paclitaxel-Cholesterol Complex

Background

Glioma is the most common primary malignant brain tumor with a dreadful overall survival and high mortality. One of the most difficult challenges in clinical treatment is that most drugs hardly pass through the blood–brain barrier (BBB) and achieve efficient accumulation at tumor sites. Thus, to circumvent this hurdle, developing an effectively traversing BBB drug delivery nanovehicle is of significant clinical importance. Rabies virus glycoprotein (RVG) is a derivative peptide that can specifically bind to nicotinic acetylcholine receptor (nAChR) widely overexpressed on BBB and glioma cells for the invasion of rabies virus into the brain. Inspired by this, RVG has been demonstrated to potentiate drugs across the BBB, promote the permeability, and further enhance drug tumor-specific selectivity and penetration.

Methods

Here, we used the RVG15, rescreened from the well-known RVG29, to develop a brain-targeted liposome (RVG15-Lipo) for enhanced BBB permeability and tumor-specific delivery of paclitaxel (PTX). The paclitaxel-cholesterol complex (PTX-CHO) was prepared and then actively loaded into liposomes to acquire high entrapment efficiency (EE) and fine stability. Meanwhile, physicochemical properties, in vitro and in vivo delivery efficiency and therapeutic effect were investigated thoroughly.

Results

The particle size and zeta potential of PTX-CHO-RVG15-Lipo were 128.15 ± 1.63 nm and −15.55 ± 0.78 mV, respectively. Compared with free PTX, PTX-CHO-RVG15-Lipo exhibited excellent targeting efficiency and safety in HBMEC and C6 cells, and better transport efficiency across the BBB in vitro model. Furthermore, PTX-CHO-RVG15-Lipo could noticeably improve the accumulation of PTX in the brain, and then promote the chemotherapeutic drugs penetration in C6^luc orthotopic glioma based on in vivo imaging assays. The in vivo antitumor results indicated that PTX-CHO-RVG15-Lipo significantly inhibited glioma growth and metabasis, therefore improved survival rate of tumor-bearing mice with little adverse effect.

Conclusion

Our study demonstrated that the RVG15 was a promising brain-targeted specific ligands owing to the superior BBB penetration and tumor targeting ability. Based on the outstanding therapeutic effect both in vitro and in vivo, PTX-CHO-RVG15-Lipo was proved to be a potential delivery system for PTX to treat glioma in clinic.

Transportation of Single-Domain Antibodies through the Blood-Brain Barrier

Single-domain antibodies derive from the heavy-chain-only antibodies of Camelidae (camel, dromedary, llama, alpaca, vicuñas, and guananos; i.e., nanobodies) and cartilaginous fishes (i.e., VNARs). Their small size, antigen specificity, plasticity, and potential to recognize unique conformational epitopes represent a diagnostic and therapeutic opportunity for many central nervous system (CNS) pathologies. However, the blood–brain barrier (BBB) poses a challenge for their delivery into the brain parenchyma. Nevertheless, numerous neurological diseases and brain pathologies, including cancer, result in BBB leakiness favoring single-domain antibodies uptake into the CNS. Some single-domain antibodies have been reported to naturally cross the BBB. In addition, different strategies and methods to deliver both nanobodies and VNARs into the brain parenchyma can be exploited when the BBB is intact. These include device-based and physicochemical disruption of the BBB, receptor and adsorptive-mediated transcytosis, somatic gene transfer, and the use of carriers/shuttles such as cell-penetrating peptides, liposomes, extracellular vesicles, and nanoparticles. Approaches based on single-domain antibodies are reaching the clinic for other diseases. Several tailoring methods can be followed to favor the transport of nanobodies and VNARs to the CNS, avoiding the limitations imposed by the BBB to fulfill their therapeutic, diagnostic, and theragnostic promises for the benefit of patients suffering from CNS pathologies.

Targeting Systems to the Brain Obtained by Merging Prodrugs, Nanoparticles, and Nasal Administration

About 40 years ago the lipidization of hydrophilic drugs was proposed to induce their brain targeting by transforming them into lipophilic prodrugs. Unfortunately, lipidization often transforms a hydrophilic neuroactive agent into an active efflux transporter (AET) substrate, with consequent rejection from the brain after permeation across the blood brain barrier (BBB). Currently, the prodrug approach has greatly evolved in comparison to lipidization. This review describes the evolution of the prodrug approach for brain targeting considering the design of prodrugs as active influx substrates or molecules able to inhibit or elude AETs. Moreover, the prodrug approach appears strategic in optimization of the encapsulation of neuroactive drugs in nanoparticulate systems that can be designed to induce their receptor-mediated transport (RMT) across the BBB by appropriate decorations on their surface. Nasal administration is described as a valuable alternative to obtain the brain targeting of drugs, evidencing that the prodrug approach can allow the optimization of micro or nanoparticulate nasal formulations of neuroactive agents in order to obtain this goal. Furthermore, nasal administration is also proposed for prodrugs characterized by peripheral instability but potentially able to induce their targeting inside cells of the brain.

Design, optimization and pharmacokinetic evaluation of Piribedil loaded solid lipid nanoparticles dispersed in nasal in situ gelling system for effective management of Parkinson's disease

Piribedil (PBD) is an anti-Parkinson's drug that gained interest recently due to its unique pharmacological profile. But its clinical use is severely limited by drug delivery issues like high dosing frequency (up to 5 tablets/day), low oral bioavailability (<10%), severe GI side-effects, etc. In this work, we have developed solid lipid nanoparticles (PBD-SLNs) to access the nose to brain pathways for direct uptake of PBD. PBD-SLNs were optimized using design of experiments approach to a mean particle size of 358 nm, and drug loading of 15%. The optimized PBD-SLNs were found to be nearly spherical in shape and showed good stability. Further, the SLNs were loaded in thermoresponsive Methyl Cellulose in situ gel (PBD-SLN-ISG) to delay mucociliary clearance upon intranasal administration in rats. Intranasal administration at the olfactory region was achieved with a cannula-microtip setup. In vivo pharmacokinetic studies showed that PBD-SLN-ISG increased the PBD (AUC)_brain by about 4-folds and reduced the (C_max)_plasma by 2.3-folds when compared to plain intranasal suspension of PBD (PBD-Susp). Further, PBD-Susp showed limited direct nose to brain uptake with direct transport percentage (DTP) values less than 0, while the optimized PBD-SLN-ISG showed DTP value of 27% indicating efficient direct nose to brain uptake.

Role of Polymeric Local Drug Delivery in Multimodal Treatment of Malignant Glioma: A Review

Malignant gliomas (MGs) are the most common and devastating primary brain tumor. At present, surgical interventions, radiotherapy, and chemotherapy are only marginally effective in prolonging the life expectancy of patients with MGs. Inherent heterogeneity, aggressive invasion and infiltration, intact physical barriers, and the numerous mechanisms underlying chemotherapy and radiotherapy resistance contribute to the poor prognosis for patients with MGs. Various studies have investigated methods to overcome these obstacles in MG treatment. In this review, we address difficulties in MG treatment and focus on promising polymeric local drug delivery systems. In contrast to most local delivery systems, which are directly implanted into the residual cavity after intratumoral injection or the surgical removal of a tumor, some rapidly developing and promising nanotechnological methods—including surface-decorated nanoparticles, magnetic nanoparticles, and focused ultrasound assist transport—are administered through (systemic) intravascular injection. We also discuss further synergistic and multimodal strategies for heightening therapeutic efficacy. Finally, we outline the challenges and therapeutic potential of these polymeric drug delivery systems.

Glucose and Triphenylphosphonium Co-Modified Redox-Sensitive Liposomes to Synergistically Treat Glioma with Doxorubicin and Lonidamine

Glioma is one of the most lethal and complex tumors, and thus, an effective drug delivery system must selectively target the tumor sites and release its cargos in a controlled manner. For the first time, we combined chemotherapeutic agent doxorubicin (DOX) and chemosensitizer lonidamine (LND) to synergistically treat glioma. We also designed and prepared multitargeted redox-sensitive liposomes (Lip-SPG) co-modified with glucose and triphenylphosphonium (TPP) to effectively deliver DOX and LND for anti-glioma therapy. The anti-glioma evaluation shows that DOX and LND have a synergistic effect and Lip-SPG could further enhance their cooperation. In vitro, Lip-SPG could increase the cellular uptake and mitochondrial uptake on bEnd.3 cells and C6 cells with multitargeting ability on the brain, tumor, and mitochondria mediated by glucose and TPP. Lip-SPG can also escape from lysosomes before entering the mitochondria. The anti-glioma efficacy in vitro shows that Lip-SPG can inhibit tumor cell proliferation and induce apoptosis. In addition, Lip-SPG have a remarkable interference to mitochondria, such as reducing intracellular ATP production, inducing ROS generation, and promoting mitochondrial membrane potential depolarization. Furthermore, in vivo, the introduction of PEGylation via glutathione-sensitive disulfide bonds endows Lip-SPG with favorable pharmacokinetic properties, brain targeting ability, low toxicity to normal tissues, and great anti-glioma efficacy with the survival time extended from 19 to 39 days. In conclusion, Lip-SPG are an effective delivery system for synergistically treating glioma with DOX and LND.

Rediscovering Tocophersolan: A Renaissance for Nano-Based Drug Delivery and Nanotheranostic Applications

A unique and pleiotropic polymer, d-alpha-tocopheryl polyethylene glycol succinate (Tocophersolan), is a polymeric, synthetic version of vitamin E. Tocophersolan has attracted enormous attention as a versatile excipient in different biomedical applications including drug delivery systems and nutraceuticals. The multiple inherent properties of Tocophersolan allow it to play flexible roles in drug delivery system design, including excipients with outstanding biocompatibility, solubilizer with the ability to promote drug dissolution, drug permeation enhancer, P-glycoprotein inhibitor, and anticancer compound. For these reasons, Tocophersolan has been widely used for improving the bioavailability of numerous pharmaceutical active ingredients. Tocophersolan has been approved by stringent regulatory authorities (such as the US FDA, EMA, and PMDA) as a safe pharmaceutical excipient. In this review, the current advances in nano-based delivery systems consisting of Tocophersolan, with possibilities for futuristic applications in drug delivery, gene therapy, and nanotheranostics, were systematically curated.

Rethinking CRITID Procedure of Brain Targeting Drug Delivery: Circulation, Blood Brain Barrier Recognition, Intracellular Transport, Diseased Cell Targeting, Internalization, and Drug Release

The past decades have witnessed great progress in nanoparticle (NP)-based brain-targeting drug delivery systems, while their therapeutic potentials are yet to be fully exploited given that the majority of them are lost during the delivery process. Rational design of brain-targeting drug delivery systems requires a deep understanding of the entire delivery process along with the issues that they may encounter. Herein, this review first analyzes the typical delivery process of a systemically administrated NPs-based brain-targeting drug delivery system and proposes a six-step CRITID delivery cascade: circulation in systemic blood, recognizing receptor on blood-brain barrier (BBB), intracellular transport, diseased cell targeting after entering into parenchyma, internalization by diseased cells, and finally intracellular drug release. By dissecting the entire delivery process into six steps, this review seeks to provide a deep understanding of the issues that may restrict the delivery efficiency of brain-targeting drug delivery systems as well as the specific requirements that may guarantee minimal loss at each step. Currently developed strategies used for troubleshooting these issues are reviewed and some state-of-the-art design features meeting these requirements are highlighted. The CRITID delivery cascade can serve as a guideline for designing more efficient and specific brain-targeting drug delivery systems.

Aerosolized In Vivo 3D Localization of Nose-to-Brain Nanocarrier Delivery Using Multimodality Neuroimaging in a Rat Model-Protocol Development

The fate of intranasal aerosolized radiolabeled polymeric micellar nanoparticles (LPNPs) was tracked with positron emission tomography/computer tomography (PET/CT) imaging in a rat model to measure nose-to-brain delivery. A quantitative temporal and spatial testing protocol for new radio-nanotheranostic agents was sought in vivo. LPNPs labeled with a zirconium 89 (⁸⁹Zr) PET tracer were administered via intranasal or intravenous delivery, followed by serial PET/CT imaging. After 2 h of continuous imaging, the animals were sacrificed, and the brain substructures (olfactory bulb, forebrain, and brainstem) were isolated. The activity in each brain region was measured for comparison with the corresponding PET/CT region of interest via activity measurements. Serial imaging of the LPNPs (100 nm PLA–PEG–DSPE+⁸⁹Zr) delivered intranasally via nasal tubing demonstrated increased activity in the brain after 1 and 2 h following intranasal drug delivery (INDD) compared to intravenous administration, which correlated with ex vivo gamma counting and autoradiography. Although assessment of delivery from nose to brain is a promising approach, the technology has several limitations that require further development. An experimental protocol for aerosolized intranasal delivery is presented herein, which may provide a platform for better targeting the olfactory epithelium.

Angiopep-2-modified calcium arsenite-loaded liposomes for targeted and pH-responsive delivery for anti-glioma therapy

The blood-brain barrier (BBB) is the most critical obstacle in the treatment of central nervous system disorders, such as glioma, the most typical type of brain tumor. To overcome the BBB and enhance drug-penetration abilities, we used angiopep-2-modified liposomes to deliver arsenic trioxide (ATO) across the BBB, targeting the glioma. Angiopep-2-modified calcium arsenite-loaded liposomes (A2-PEG-LP@CaAs), with uniformly distributed hydrodynamic diameter (96.75 ± 0.57 nm), were prepared using the acetate gradient method with high drug-loading capacity (7.13 ± 0.72%) and entrapment efficiency (54.30 ± 9.81%). In the acid tumor microenvironment, arsenic was responsively released, thereby exerting an anti-glioma effect. The anti-glioma effect of A2-PEG-LP@CaAs was investigated both in vitro and in vivo. As a result, A2-PEG-LP@CaAs exhibited a potent, targeted anti-glioma effect mediated by the lipoprotein receptor-related (LRP) receptor, which is overexpressed in both the BBB and glioma. Therefore, A2-PEG-LP@CaAs could dramatically promote the anti-glioma effect of ATO, as a promising strategy for glioma therapy.

Targeting receptor-ligand chemistry for drug delivery across blood-brain barrier in brain diseases

The blood-brain barrier (BBB) is composed of a layer of endothelial cells that is interspersed with a series of tight junctions and characterized by the absence of fenestrations. The permeability of this barrier is controlled by junctions such as tight junctions and adherent junctions as well as several cells such as astrocytes, pericytes, vascular endothelial cells, neurons, microglia, and efflux transporters with relatively enhanced expression. It plays a major role in maintaining homeostasis in the brain and exerts a protective regulatory control on the influx and efflux of molecules. However, it proves to be a challenge for drug delivery strategies that target brain diseases like Dementia, Parkinson's Disease, Alzheimer's Disease, Brain Cancer or Stroke, Huntington's Disease, Lou Gehrig's Disease, etc. Conventional modes of drug delivery are invasive and have been known to contribute to a "leaky BBB", recent studies have highlighted the efficiency and relative safety of receptor-mediated drug delivery. Several receptors are exhibited on the BBB, and actively participate in nutrient uptake, and recognize specific ligands that modulate the process of endocytosis. The strategy employed in receptor-mediated drug delivery exploits this process of "tricking" the receptors into internalizing ligands that are conjugated to carrier systems like liposomes, nanoparticles, monoclonal antibodies, enzymes etc. These in turn are modified with drug molecules, therefore leading to delivery to desired target cells in brain tissue. This review comprehensively explores each of those receptors that can be modified to serve such purposes as well as the currently employed strategies that have led to increased cellular uptake and transport efficiency.