T Cell-Mediated Transport of Polymer Nanoparticles across the Blood-Brain Barrier

Aducanumab delivery via focused ultrasound-induced transient blood-brain barrier opening in vivo

Focused ultrasound (FUS) with magnetic resonance imaging (MRI) guidance (MRgFUS) has emerged as a promising technique for enhancing drug delivery to the brain. Through the controlled oscillation of gas-encased microbubbles, FUS temporarily modulates the integrity of tight junctions, inducing localized blood-brain barrier disruption (BBBD) and allowing targeted drug passage. Aducanumab (ADU) has demonstrated efficacy in reducing amyloid pathology, yet its clinical application remains limited by the restrictive nature of the blood-brain barrier (BBB). This in vivo study aimed to evaluate the efficiency of ADU delivery facilitated by FUS-induced BBBD in the normal Institute of Cancer Research (ICR) mouse brain under two pressure conditions: 0.25 and 0.42 MPa. Following FUS sonication with MRI guidance, ADU concentrations in brain tissues and serum were measured via enzyme-linked immunosorbent assay (ELISA) at multiple time points. Histological analysis at 24 h post-FUS-BBBD was performed to assess ADU distribution, and tissue integrity was evaluated through hematoxylin and eosin (H&E) and Nissl staining to detect potential damage in the target regions. The results demonstrated that MRgFUS significantly increased ADU concentrations within the target areas without inducing substantial tissue damage. ADU delivery efficiency was directly correlated with the degree of BBBD, exhibiting a 7-fold increase at 0.25 MPa and a 60-fold increase at 0.42 MPa compared to sham controls, with distinct kinetic profiles observed for each condition. These findings highlight the potential of FUS-BBBD as a therapeutic strategy to enhance ADU delivery to the brain, reduce required infusion doses, and mitigate side effects associated with high-dose administration.

Recent advances in nanotherapy-based treatment of epilepsy

Epilepsy is a complex neurological disorder characterized by recurrent seizures affecting millions of people worldwide. Despite advances in drug therapy, a significant proportion of patients remain resistant to conventional antiepileptic drugs (AEDs) due to challenges such as impermeability of the blood-brain barrier (BBB), multidrug resistance, and multifaceted epileptogenesis. Nanotechnology offers promising strategies to overcome these barriers by enhancing drug delivery across the BBB, improving target specificity and minimizing systemic side effects. This review explores recent advances in different innovative strategies of nanodelivery systems for epilepsy therapy, and we will discuss the design principles, mechanisms of action and therapeutic efficacy of these nanodelivery systems. In addition, we discuss the challenges and limitations that hinder the clinical translation of nanomedicine-based therapies for epilepsy. We emphasize the need for personalized and multidisciplinary approaches as well as the importance of continued research and interdisciplinary collaboration in order to translate these innovative strategies into effective therapies. Ultimately, the use of nanotechnology has the potential to enhance seizure control, reduce the burden of epilepsy, and improve the quality of life of patients affected by this complex neurological disorder. Nanotechnology-based drug delivery systems may usher in a new era of precision medicine for epilepsy treatment.

Advancing CNS Therapeutics: Enhancing Neurological Disorders with Nanoparticle-Based Gene and Enzyme Replacement Therapies

Given the complexity of the central nervous system (CNS) and the diversity of neurological conditions, the increasing prevalence of neurological disorders poses a significant challenge to modern medicine. These disorders, ranging from neurodegenerative diseases to psychiatric conditions, not only impact individuals but also place a substantial burden on healthcare systems and society. A major obstacle in treating these conditions is the blood-brain barrier (BBB), which restricts the passage of therapeutic agents to the brain. Nanotechnology, particularly the use of nanoparticles (NPs), offers a promising solution to this challenge. NPs possess unique properties such as small size, large surface area, and modifiable surface characteristics, enabling them to cross the BBB and deliver drugs directly to the affected brain regions. This review focuses on the application of NPs in gene therapy and enzyme replacement therapy (ERT) for neurological disorders. Gene therapy involves altering or manipulating gene expression and can be enhanced by NPs designed to carry various genetic materials. Similarly, NPs can improve the efficacy of ERT for lysosomal storage disorders (LSDs) by facilitating enzyme delivery to the brain, overcoming issues like immunogenicity and instability. Taken together, this review explores the potential of NPs in revolutionizing treatment options for neurological disorders, highlighting their advantages and the future directions in this rapidly evolving field.

Nanoparticle Interactions with the Blood Brain Barrier: Insights from Drosophila and Implications for Human Astrocyte Targeted Therapies

This review explores the intricate connections between Drosophila models and the human blood-brain barrier (BBB) with nanoparticle-based approaches for neurological treatment. Drosophila serves as a powerful model organism due to its evolutionary conservation of key biological processes, particularly in the context of the BBB, which is formed by glial cells that share structural and functional similarities with mammalian endothelial cells. Recent advancements in nanoparticle technology have highlighted their potential for effective drug delivery across the BBB, utilizing mechanisms such as passive diffusion, receptor-mediated transcytosis, and carrier-mediated transport. The ability to engineer nanoparticles with specific physicochemical properties-such as size, surface charge, and functionalization-enhances their targeting capabilities, particularly towards astrocytes, which play a crucial role in maintaining BBB integrity and responding to neuroinflammation. Insights gained from Drosophila studies have informed the design of personalized nanomedicine strategies aimed at treating neurodegenerative diseases, including Alzheimer's, Parkinson's disease etc. As research progresses, the integration of findings from Drosophila models with emerging humanized BBB systems will pave the way for innovative therapeutic approaches that improve drug delivery and patient outcomes in neurological disorders.

Drug Delivery Across the Blood-Brain Barrier: A New Strategy for the Treatment of Neurological Diseases

The blood-brain barrier (BBB) serves as a highly selective barrier between the blood and the central nervous system (CNS), and its main function is to protect the brain from foreign substances. This physiological property plays a crucial role in maintaining CNS homeostasis, but at the same time greatly limits the delivery of drug molecules to the CNS, thus posing a major challenge for the treatment of neurological diseases. Given that the high incidence and low cure rate of neurological diseases have become a global public health problem, the development of effective BBB penetration technologies is important for enhancing the efficiency of CNS drug delivery, reducing systemic toxicity, and improving the therapeutic outcomes of neurological diseases. This review describes the physiological and pathological properties of the BBB, as well as the current challenges of trans-BBB drug delivery, detailing the structural basis of the BBB and its role in CNS protection. Secondly, this paper reviews the drug delivery strategies for the BBB in recent years, including physical, biological and chemical approaches, as well as nanoparticle-based delivery technologies, and provides a comprehensive assessment of the effectiveness, advantages and limitations of these delivery strategies. It is hoped that the review in this paper will provide valuable references and inspiration for future researchers in therapeutic studies of neurological diseases.

Star-polymer unimolecular micelle nanoparticles to deliver a payload across the blood-brain barrier

Nanocarrier-mediated therapeutic delivery to brain tissue is impeded by tightly controlled transportation across the blood-brain barrier (BBB). Herein, we report a well-defined core-shell star-shaped unimolecular micelle (star-UMM; a single polymer entity) as an efficient BBB-breaching nanoparticle for brain-specific administration of the fluorescent anticancer drug doxorubicin and in vivo mapping of brain tissues by the near-infrared biomarker IR780 in mice. The star-UMM was engineered by precisely programming the polymer topology having hydrophobic and hydrophilic polycaprolactone blocks and in-built with lysosomal enzyme-biodegradation stimuli to deliver the payloads at intracellular compartments. In vivo imaging in mice revealed prolonged circulation of star-UMM in blood for >72 h, and whole-organ image-quantification substantiated its efficient ability to breach the BBB. Star UMM exhibited excellent stability in blood circulation and reduced cardiotoxicity, was non-hemolytic, had substantial uptake in the cortical neurons of the mouse brain, had lysosomal enzymatic-biodegradation, and exhibited negligible immunogenicity or necrosis. This newly designed star-UMM could have long-term applications in brain-specific drug delivery.

Cell-drug conjugates

By combining living cells with therapeutics, cell-drug conjugates can potentiate the functions of both components, particularly for applications in drug delivery and therapy. The conjugates can be designed to persist in the bloodstream, undergo chemotaxis, evade surveillance by the immune system, proliferate, or maintain or transform their cellular phenotypes. In this Review, we discuss strategies for the design of cell-drug conjugates with specific functions, the techniques for their preparation, and their applications in the treatment of cancers, autoimmune diseases and other pathologies. We also discuss the translational challenges and opportunities of this class of drug-delivery systems and therapeutics.

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

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

Harnessing cells to improve transport of nanomedicines

Efficient tumour treatment is hampered by the poor selectivity of anticancer drugs, resulting in scarce tumour accumulation and undesired off-target effects. Nano-sized drug-delivery systems in the form of nanoparticles (NPs) have been proposed to improve drug distribution to solid tumours, by virtue of their ability of passive and active tumour targeting. Despite these advantages, literature studies indicated that less than 1% of the administered NPs can successfully reach the tumour mass, highlighting the necessity for more efficient drug transporters in cancer treatment. Living cells, such as blood cells, circulating immune cells, platelets, and stem cells, are often found as an infiltrating component in most solid tumours, because of their ability to naturally circumvent immune recognition, bypass biological barriers, and reach inaccessible tissues through innate tropism and active motility. Therefore, the tumour-homing ability of these cells can be harnessed to design living cell carriers able to improve the transport of drugs and NPs to tumours. Albeit promising, this approach is still in its beginnings and suffers from difficult scalability, high cost, and poor reproducibility. In this review, we present an overview of the most common cell transporters of drugs and NPs, and we discuss how different cell types interact with biological barriers to deliver cargoes of various natures to tumours. Finally, we analyse the different techniques used to load drugs or NPs in living cells and discuss their advantages and disadvantages.

To see or not to see: In vivo nanocarrier detection methods in the brain and their challenges

Nanoparticles have a great potential to significantly improve the delivery of therapeutics to the brain and may also be equipped with properties to investigate brain function. The brain, being a highly complex organ shielded by selective barriers, requires its own specialized detection system. However, a significant hurdle to achieve these goals is still the identification of individual nanoparticles within the brain with sufficient cellular, subcellular, and temporal resolution. This review aims to provide a comprehensive summary of the current knowledge on detection systems for tracking nanoparticles across the blood-brain barrier and within the brain. We discuss commonly employed in vivo and ex vivo nanoparticle identification and quantification methods, as well as various imaging modalities able to detect nanoparticles in the brain. Advantages and weaknesses of these modalities as well as the biological factors that must be considered when interpreting results obtained through nanotechnologies are summarized. Finally, we critically evaluate the prevailing limitations of existing technologies and explore potential solutions.

Functionalized liposomes: an enticing nanocarrier for management of glioma

Glioma is one of the most severe central nervous systems (CNS)-specific tumors, with rapidly growing malignant glial cells accounting for roughly half of all brain tumors and having a poor survival rate ranging from 12 to 15 months. Despite being the most often used technique for glioma therapy, conventional chemotherapy suffers from low permeability of the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) to anticancer drugs. When it comes to nanocarriers, liposomes are thought of as one of the most promising nanocarrier systems for glioma treatment. However, owing to BBB tight junctions, non-targeted liposomes, which passively accumulate in most cancer cells primarily via the increased permeability and retention effect (EPR), would not be suitable for glioma treatment. The surface modification of liposomes with various active targeting ligands has shown encouraging outcomes in the recent times by allowing various chemotherapy drugs to pass across the BBB and BBTB and enter glioma cells. This review article introduces by briefly outlining the landscape of glioma, its classification, and some of the pathogenic causes. Further, it discusses major barriers for delivering drugs to glioma such as the BBB, BBTB, and tumor microenvironment. It further discusses modified liposomes such as long-acting circulating liposomes, actively targeted liposomes, stimuli responsive liposomes. Finally, it highlighted the limitations of liposomes in the treatment of glioma and the various actively targeted liposomes undergoing clinical trials for the treatment of glioma.

Cell-Penetrating Peptides: Promising Therapeutics and Drug-Delivery Systems for Neurodegenerative Diseases

Currently, one of the most significant and rapidly growing unmet medical challenges is the treatment of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). This challenge encompasses the imperative development of efficacious therapeutic agents and overcoming the intricacies of the blood-brain barrier for successful drug delivery. Here we focus on the delivery aspect with particular emphasis on cell-penetrating peptides (CPPs), widely used in basic and translational research as they enhance drug delivery to challenging targets such as tissue and cellular compartments and thus increase therapeutic efficacy. The combination of CPPs with nanomaterials such as nanoparticles (NPs) improves the performance, accuracy, and stability of drug delivery and enables higher drug loads. Our review presents and discusses research that utilizes CPPs, either alone or in conjugation with NPs, to mitigate the pathogenic effects of neurodegenerative diseases with particular reference to AD and PD.

Dual-Responsive Nanomedicine Activates Programmed Antitumor Immunity through Targeting Lymphatic System

Effective antitumor immunotherapy depends on evoking a cascade of cancer-immune cycles with lymph nodes (LNs) as the initial sites for activating antitumor immunity, making drug administration through the lymphatic system highly attractive. Here, we describe a nanomedicine with dual responsiveness to pH and enzyme for a programmed activation of antitumor immune through the lymphatic system. The proposed nanomedicine can release the STING agonist diABZI-C2-NH2 in the LNs' acidic environment to activate dendritic cells (DCs) and T cells. Then, the remaining nanomedicine hitchhikes on the activated T cells (PD-1+ T cells) through binding to PD-1, resulting in an effective delivery into tumor tissues owing to the tumor-homing capacity of PD-1+ T cells. The enzyme matrix metalloproteinase-2 (MMP-2) being enriched in tumor tissue triggers the release of PD-1 antibody (aPD-1) which exerts immune checkpoint blockade (ICB) therapy. Eventually, the nanomedicine delivers a DNA methylation inhibitor GSK-3484862 (GSK) into tumor cells, and then the latter combines with granzyme B (GZMB) to trigger tumor cell pyroptosis. Consequently, the pyroptotic tumor cells induce robust immunogenic cell death (ICD) enhancing the DCs maturation and initiating the cascading antitumor immune response. Study on a 4T1 breast tumor mouse model demonstrates the prominent antitumor therapeutic outcome of this nanomedicine through creating a positive feedback loop of cancer-immunity cycles including immune activation in LNs, T cell-mediated drug delivery, ICB therapy, and tumor cell pyroptosis-featured ICD.

Functionalized Nanomaterials Capable of Crossing the Blood-Brain Barrier

The blood-brain barrier (BBB) is a specialized semipermeable structure that highly regulates exchanges between the central nervous system parenchyma and blood vessels. Thus, the BBB also prevents the passage of various forms of therapeutic agents, nanocarriers, and their cargos. Recently, many multidisciplinary studies focus on developing cargo-loaded nanoparticles (NPs) to overcome these challenges, which are emerging as safe and effective vehicles in neurotheranostics. In this Review, first we introduce the anatomical structure and physiological functions of the BBB. Second, we present the endogenous and exogenous transport mechanisms by which NPs cross the BBB. We report various forms of nanomaterials, carriers, and their cargos, with their detailed BBB uptake and permeability characteristics. Third, we describe the effect of regulating the size, shape, charge, and surface ligands of NPs that affect their BBB permeability, which can be exploited to enhance and promote neurotheranostics. We classify typical functionalized nanomaterials developed for BBB crossing. Fourth, we provide a comprehensive review of the recent progress in developing functional polymeric nanomaterials for applications in multimodal bioimaging, therapeutics, and drug delivery. Finally, we conclude by discussing existing challenges, directions, and future perspectives in employing functionalized nanomaterials for BBB crossing.

Neuronanomedicine for Alzheimer's and Parkinson's disease: Current progress and a guide to improve clinical translation

Neuronanomedicine is an emerging multidisciplinary field that aims to create innovative nanotechnologies to treat major neurodegenerative disorders, such as Alzheimer's (AD) and Parkinson's disease (PD). A key component of neuronanomedicine are nanoparticles, which can improve drug properties and demonstrate enhanced safety and delivery across the blood-brain barrier, a major improvement on existing therapeutic approaches. In this review, we critically analyze the latest nanoparticle-based strategies to modify underlying disease pathology to slow or halt AD/PD progression. We find that a major roadblock for neuronanomedicine translation to date is a poor understanding of how nanoparticles interact with biological systems (i.e., bio-nano interactions), which is partly due to inconsistent reporting in published works. Accordingly, this review makes a set of specific recommendations to help guide researchers to harness the unique properties of nanoparticles and thus realise breakthrough treatments for AD/PD.

A state-of-the-art liposome technology for glioblastoma treatment

Glioblastoma (GBM) is a challenging problem due to the poor BBB permeability of cancer drugs, its recurrence after the treatment, and high malignancy and is difficult to treat with the currently available therapeutic strategies. Furthermore, the prognosis and survival rate of GBM are still poor after surgical removal via conventional combination therapy. Owing to the existence of the formidable blood-brain barrier (BBB) and the aggressive, infiltrating nature of GBM growth, the diagnosis and treatment of GBM are quite challenging. Recently, liposomes and their derivatives have emerged as super cargos for the delivery of both hydrophobic and hydrophilic drugs for the treatment of glioblastoma because of their advantages, such as biocompatibility, long circulation, and ease of physical and chemical modification, which facilitate the capability of targeting specific sites, circumvention of BBB transport restrictions, and amplification of the therapeutic efficacy. Herein, we provide a timely update on the burgeoning liposome-based drug delivery systems and potential challenges in these fields for the diagnosis and treatment of brain tumors. Furthermore, we focus on the most recent liposome-based drug delivery cargos, including pH-sensitive, temperature-sensitive, and biomimetic liposomes, to enhance the multimodality in imaging and therapeutics of glioblastoma. Furthermore, we highlight the future difficulties and directions for the research and clinical translation of liposome-based drug delivery. Hopefully, this review will trigger the interest of researchers to expedite the development of liposome cargos and even their clinical translation for improving the prognosis of glioblastoma.

CNS therapeutics: Immune cells break the barriers

Peripheral immune cells can be seen as attractive vectors and drug carriers for central nervous system therapeutics because these cells have unique properties that allow them to migrate across the blood-brain barrier, enabling drug delivery to brain regions that are inaccessible to free drugs.

Tumor Abnormality-Oriented Nanomedicine Design

Anticancer nanomedicines have been proven effective in mitigating the side effects of chemotherapeutic drugs. However, challenges remain in augmenting their therapeutic efficacy. Nanomedicines responsive to the pathological abnormalities in the tumor microenvironment (TME) are expected to overcome the biological limitations of conventional nanomedicines, enhance the therapeutic efficacies, and further reduce the side effects. This Review aims to quantitate the various pathological abnormalities in the TME, which may serve as unique endogenous stimuli for the design of stimuli-responsive nanomedicines, and to provide a broad and objective perspective on the current understanding of stimuli-responsive nanomedicines for cancer treatment. We dissect the typical transport process and barriers of cancer drug delivery, highlight the key design principles of stimuli-responsive nanomedicines designed to tackle the series of barriers in the typical drug delivery process, and discuss the "all-into-one" and "one-for-all" strategies for integrating the needed properties for nanomedicines. Ultimately, we provide insight into the challenges and future perspectives toward the clinical translation of stimuli-responsive nanomedicines.

Modulation of engineered nanomaterial interactions with organ barriers for enhanced drug transport

The biomedical use of nanoparticles (NPs) has been the focus of intense research for over a decade. As most NPs are explored as carriers to alter the biodistribution, pharmacokinetics and bioavailability of associated drugs, the delivery of these NPs to the tissues of interest remains an important topic. To date, the majority of NP delivery studies have used tumor models as their tool of interest, and the limitations concerning tumor targeting of systemically administered NPs have been well studied. In recent years, the focus has also shifted to other organs, each presenting their own unique delivery challenges to overcome. In this review, we discuss the recent advances in leveraging NPs to overcome four major biological barriers including the lung mucus, the gastrointestinal mucus, the placental barrier, and the blood-brain barrier. We define the specific properties of these biological barriers, discuss the challenges related to NP transport across them, and provide an overview of recent advances in the field. We discuss the strengths and shortcomings of different strategies to facilitate NP transport across the barriers and highlight some key findings that can stimulate further advances in this field.

Engineered Living Materials for Advanced Diseases Therapy

Natural living materials serving as biotherapeutics exhibit great potential for treating various diseases owing to their immunoactivity, tissue targeting, and other biological activities. In this review, the recent developments in engineered living materials, including mammalian cells, bacteria, viruses, fungi, microalgae, plants, and their active derivatives that are used for treating various diseases are summarized. Further, the future perspectives and challenges of such engineered living material-based biotherapeutics are discussed to provide considerations for future advances in biomedical applications.

Living Cells and Cell-Derived Vesicles: A Trojan Horse Technique for Brain Delivery

Brain diseases remain a significant global healthcare burden. Conventional pharmacological therapy for brain diseases encounters huge challenges because of the blood-brain barrier (BBB) limiting the delivery of therapeutics into the brain parenchyma. To address this issue, researchers have explored various types of drug delivery systems. Cells and cell derivatives have attracted increasing interest as "Trojan horse" delivery systems for brain diseases, owing to their superior biocompatibility, low immunogenicity, and BBB penetration properties. This review provided an overview of recent advancements in cell- and cell-derivative-based delivery systems for the diagnosis and treatment of brain diseases. Additionally, it discussed the challenges and potential solutions for clinical translation.

Nonviral nanoparticle gene delivery into the CNS for neurological disorders and brain cancer applications

Nonviral nanoparticles have emerged as an attractive alternative to viral vectors for gene therapy applications, utilizing a range of lipid-based, polymeric, and inorganic materials. These materials can either encapsulate or be functionalized to bind nucleic acids and protect them from degradation. To effectively elicit changes to gene expression, the nanoparticle carrier needs to undergo a series of steps intracellularly, from interacting with the cellular membrane to facilitate cellular uptake to endosomal escape and nucleic acid release. Adjusting physiochemical properties of the nanoparticles, such as size, charge, and targeting ligands, can improve cellular uptake and ultimately gene delivery. Applications in the central nervous system (CNS; i.e., neurological diseases, brain cancers) face further extracellular barriers for a gene-carrying nanoparticle to surpass, with the most significant being the blood-brain barrier (BBB). Approaches to overcome these extracellular challenges to deliver nanoparticles into the CNS include systemic, intracerebroventricular, intrathecal, and intranasal administration. This review describes and compares different biomaterials for nonviral nanoparticle-mediated gene therapy to the CNS and explores challenges and recent preclinical and clinical developments in overcoming barriers to nanoparticle-mediated delivery to the brain. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Drug delivery to the brain – lipid nanoparticles-based approach

The complex structure of the human brain defines it as one of the most inaccessible organs in terms of drug delivery. The blood-brain barrier (BBB) represents a microvascular network involved in transporting substances between the blood and the central nervous system (CNS) – enabling the entry of nutrients and simultaneously restricting the influx of pathogens and toxins. However, its role as a protective shield for CNS also restricts drug access to the brain. Since many drugs cannot cross the BBB due to unsuitable physicochemical characteristics (i.e., high molecular weight, aqueous solubility, etc.), different technological strategies have been developed to ensure sufficient drug bioavailability. Among these, solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) are promising approaches thanks to their lipid nature, facilitating their brain uptake, small sizes, and the possibilities for subsequent functionalization to achieve targeted delivery. The review focuses on applying SLNs and NLCs as nanocarriers for brain delivery, outlining the physiological factors of BBB and the physicochemical characteristics of nanocarriers influencing this process. Recent advances in this area have also been summarized.

Advances, challenge and prospects in cell-mediated nanodrug delivery for cancer therapy: a review

Nanomedicine offers considerable opportunities to improve drugability and reduce toxicity for tumour therapy. However, the application of nanomedicine has achieved little success in clinical trials due to multiple physiological barriers to drug delivery. Circulating cells are expected to improve the physical distribution of drugs and enhance the therapeutic effect by overcoming various biological barriers in collaboration with nano-drug delivery systems owing to excellent biocompatibility, low immunogenicity and a long-circulation time and strong binding specificity. Nonetheless, we have noticed some limitations in implementing tthe strategy. In this article, we intend to introduce the latest progress in research and application of circulating cell-mediated nano-drug delivery systems, describe the main cell-related drug delivery modes, sum up the relevant points of the transport systems in the process of loading, transport and release, and lastly discuss the advantages, challenges and future development trends in cell-mediated nano-drug delivery.

Glioma diagnosis and therapy: Current challenges and nanomaterial-based solutions

Glioma is often referred to as one of the most dreadful central nervous system (CNS)-specific tumors with rapidly-proliferating cancerous glial cells, accounting for nearly half of the brain tumors at an annual incidence rate of 30-80 per a million population. Although glioma treatment remains a significant challenge for researchers and clinicians, the rapid development of nanomedicine provides tremendous opportunities for long-term glioma therapy. However, several obstacles impede the development of novel therapeutics, such as the very tight blood-brain barrier (BBB), undesirable hypoxia, and complex tumor microenvironment (TME). Several efforts have been dedicated to exploring various nanoformulations for improving BBB permeation and precise tumor ablation to address these challenges. Initially, this article briefly introduces glioma classification and various pathogenic factors. Further, currently available therapeutic approaches are illustrated in detail, including traditional chemotherapy, radiotherapy, and surgical practices. Then, different innovative treatment strategies, such as tumor-treating fields, gene therapy, immunotherapy, and phototherapy, are emphasized. In conclusion, we summarize the article with interesting perspectives, providing suggestions for future glioma diagnosis and therapy improvement.

Nanotherapeutic treatment of the invasive glioblastoma tumor microenvironment

Glioblastoma (GBM) is the most common malignant adult brain cancer with no curative treatment strategy. A significant hurdle in GBM treatment is effective therapeutic delivery to the brain-invading tumor cells that remain following surgery within functioning brain regions. Developing therapies that can either directly target these brain-invading tumor cells or act on other cell types and molecular processes supporting tumor cell invasion and recurrence are essential steps in advancing new treatments in the clinic. This review highlights some of the drug delivery strategies and nanotherapeutic technologies that are designed to target brain-invading GBM cells or non-neoplastic, invasion-supporting cells residing within the GBM tumor microenvironment.

Multivalent, Bispecific αB7-H3-αCD3 Chemically Self-Assembled Nanorings Direct Potent T Cell Responses against Medulloblastoma

Few therapeutic options have been made available for treating central nervous system tumors, especially upon recurrence. Recurrent medulloblastoma is uniformly lethal with no approved therapies. Recent preclinical studies have shown promising results for eradicating various solid tumors by targeting the overexpressed immune checkpoint molecule, B7-H3. However, due to several therapy-related toxicities and reports of tumor escape, the full potential of targeting this pan-cancer antigen has yet to be realized. Here, we designed and characterized bispecific chemically self-assembling nanorings (CSANs) that target the T cell receptor, CD3ε, and tumor associated antigen, B7-H3, derived from the humanized 8H9 single chain variable fragment. We show that the αB7-H3-αCD3 CSANs increase T cell infiltration and facilitate selective cytotoxicity of B7-H3⁺ medulloblastoma spheroids and that activity is independent of target cell MHC class I expression. Importantly, nonspecific T cell activation against the ONS 2303 medulloblastoma cell line can be reduced by tuning the valency of the αCD3 targeted monomer in the oligomerized CSAN. Intraperitoneal injections of αB7-H3-αCD3 bispecific CSANs were found to effectively cross the blood-tumor barrier into the brain and elicit significant antitumor T cell activity intracranially as well as systemically in an orthotopic medulloblastoma model. Moreover, following treatment with αB7-H3-αCD3 CSANs, intratumoral T cells were found to primarily have a central memory phenotype that displayed significant levels of characteristic activation markers. Collectively, these results demonstrate the ability of our multivalent, bispecific CSANs to direct potent antitumor T cell responses and indicate its potential utility as an alternative or complementary therapy for immune cell targeting of B7-H3⁺ brain tumors.

Recent development of contrast agents for magnetic resonance and multimodal imaging of glioblastoma

Glioblastoma (GBM) as the most common primary malignant brain tumor exhibits a high incidence and degree of malignancy as well as poor prognosis. Due to the existence of formidable blood–brain barrier (BBB) and the aggressive growth and infiltrating nature of GBM, timely diagnosis and treatment of GBM is still very challenging. Among different imaging modalities, magnetic resonance imaging (MRI) with merits including high soft tissue resolution, non-invasiveness and non-limited penetration depth has become the preferred tool for GBM diagnosis. Furthermore, multimodal imaging with combination of MRI and other imaging modalities would not only synergistically integrate the pros, but also overcome the certain limitation in each imaging modality, offering more accurate morphological and pathophysiological information of brain tumors. Since contrast agents contribute to amplify imaging signal output for unambiguous pin-pointing of tumors, tremendous efforts have been devoted to advances of contrast agents for MRI and multimodal imaging. Herein, we put special focus on summary of the most recent advances of not only MRI contrast agents including iron oxide-, manganese (Mn)-, gadolinium (Gd)-, ¹⁹F- and copper (Cu)-incorporated nanoplatforms for GBM imaging, but also dual-modal or triple-modal nanoprobes. Furthermore, potential obstacles and perspectives for future research and clinical translation of these contrast agents are discussed. We hope this review provides insights for scientists and students with interest in this area.

Biodistribution of Biomimetic Drug Carriers, Mononuclear Cells, and Extracellular Vesicles, in Nonhuman Primates

Discovery of novel drug delivery systems to the brain remains a key task for successful treatment of neurodegenerative disorders. Herein, the biodistribution of immunocyte-based carriers, peripheral blood mononuclear cells (PBMCs), and monocyte-derived EVs are investigated in adult rhesus macaques using longitudinal PET/MRI imaging. ⁶⁴ Cu-labeled drug carriers are introduced via different routes of administration: intraperitoneal (IP), intravenous (IV), or intrathecal (IT) injection. Whole body PET/MRI (or PET/CT) images are acquired at 1, 24, and 48 h post injection of ⁶⁴ Cu-labeled drug carriers, and standardized uptake values (SUV_mean and SUV_max ) in the main organs are estimated. The brain retention for both types of carriers increases based on route of administration: IP < IV < IT. Importantly, a single IT injection of PBMCs produces higher brain retention compared to IT injection of EVs. In contrast, EVs show superior brain accumulation compared to the cells when administered via IP and IV routes, respectively. Finally, a comprehensive chemistry panel of blood samples demonstrates no cytotoxic effects of either carrier. Overall, living cells and EVs have a great potential to be used for drug delivery to the brain. When identifying the ideal drug carrier, the route of administration could make big differences in CNS drug delivery.

Advances in the research of nano delivery systems in ischemic stroke

Ischemic stroke is the most common type of cerebrovascular disease with high disability rate and mortality. The blood-brain barrier (BBB) protects the homeostasis of the brain's microenvironment and impedes the penetration of 98% of drugs. Therefore, effective treatment requires the better drug transport across membranes and increased drug distribution. Nanoparticles are a good choice for drugs to cross BBB. The main pathways of nano delivery systems through BBB include passive diffusion, adsorption-mediated endocytosis, receptor-mediated transport, carrier-mediated transport, etc. At present, the materials used in brain-targeted delivery can be divided into natural polymer, synthetic polymers, inorganic materials and phospholipid. In this review, we first introduced several ways of nano delivery systems crossing the BBB, and then summarized their applications in ischemic stroke. Based on their potential and challenges in the treatment of ischemic stroke, new ideas and prospects are proposed for designing feasible and effective nano delivery systems.

Influence of nanoparticle size on blood-brain barrier penetration and the accumulation of anti-seizure medicines in the brain

Anti-seizure medicines constitute a common yet important modality to treat epilepsy. However, some of them are associated with serious side effects including hepatotoxicity and hypersensitivity. Furthermore, the blood-brain barrier (BBB) is an insurmountable obstacle for brain drug delivery. Fortunately, the introduction of the nanoparticles for drug delivery is a feasible approach to overcome these obstacles. Encapsulating drugs into nanoparticles and delivering them to specific sites shows great potential for improving the efficiency of drug delivery and reducing systemic toxicity. Several in vivo studies have investigated the effect of nanoparticle size on biodistribution in mice, but very few have investigated its effects on efficient drug delivery while crossing the BBB. Therefore, we designed a methoxy poly(lactide-co-glycolide)-b-poly(ethylene glycol) methyl ether (mPEG-PLGA) nanoparticle delivery system and explored the cell uptake efficiency of nanoparticles with different sizes and their ability to penetrate the BBB while carrying carbamazepine (CBZ). CBZ-loaded nanoparticles could significantly reduce the cytotoxicity of CBZ to L929 cells at high concentrations. Results from the endocytosis experiment involving human cerebral microvessel endothelial cell/D3 showed that the DiR-loaded mPEG_5K-PLGA_10K nanoparticles possessed the highest cell uptake efficiency. The endocytosis efficiency was 90% at 30 min, which far exceeded that of the other groups. Moreover, similar results were obtained from subsequent experiments where fluorescence images of the isolated organs of the mice were acquired. To summarize, our study demonstrated that drug delivery to the brain using nanocarriers is size dependent. Nanoparticles with the smallest particle size can be internalized more effectively, and easily penetrate the BBB, and accumulate in the brain.

A biocompatible and injectable hydrogel to boost the efficacy of stem cells in neurodegenerative diseases treatment

AIMS

Stem cell therapies emerged as treatment modalities with potential to cure neurodegenerative diseases (NDs). However, despite high expectations, their clinical use is still limited. Critical issues in treatment outcomes may be related to stem cells formulation and administration route. We develop a hydrogel as a cell carrier, consisting of compounds (phospholipids and hyaluronic acid-HA) naturally present in the central nervous system (CNS). The HA-based hydrogel physically crosslinked with liposomes is designed for direct injection into the CNS to significantly increase the bone marrow mesenchymal stem cells (BMSCs) bioavailability.

MATERIALS AND METHODS

Hydrogel compatibility is confirmed in vitro with BMSCs and in vivo through its intracerebroventricular injection in rats. To assess its efficacy, the main cause of chronic neurologic disability in young adults is selected, namely multiple sclerosis (MS). The efficacy of the developed formulation containing a lower number of cells than previously reported is demonstrated using an experimental autoimmune encephalomyelitis (EAE) rat model.

KEY FINDINGS

The distribution of the engineered hydrogel into corpus callosum can be ideal for NDs treatment, since damage of this white matter structure is responsible for important neuronal deficits. Moreover, the BMSCs-laden hydrogel significantly decreases disease severity and maximum clinical score and eliminated the relapse.

SIGNIFICANCE

The engineering of advanced therapies using this natural carrier can result in efficacious treatments for MS and related debilitating conditions.

Protease Responsive Nanogels for Transcytosis across the Blood-Brain Barrier and Intracellular Delivery of Radiopharmaceuticals to Brain Tumor Cells

Despite profound advances in treatment approaches, gliomas remain associated with very poor prognoses. The residual cells after incomplete resection often migrate and proliferate giving a seed for highly resistant gliomas. The efficacy of chemotherapeutic drugs is often strongly limited by their poor selectivity and the blood brain barrier (BBB). Therefore, the development of therapeutic carrier systems for efficient transport across the BBB and selective delivery to tumor cells remains one of the most complex problems facing molecular medicine and nano-biotechnology. To address this challenge, a stimuli sensitive nanogel is synthesized using pre-polymer approach for the effective delivery of nano-irradiation. The nanogels are cross-linked via matrix metalloproteinase (MMP-2,9) substrate and armed with Auger electron emitting drug 5-[125 I]Iodo-4"-thio-2"-deoxyuridine ([125 I]ITdU) which after release can be incorporated into the DNA of tumor cells. Functionalization with diphtheria toxin receptor ligand allows nanogel transcytosis across the BBB at tumor site. Functionalized nanogels efficiently and increasingly explore transcytosis via BBB co-cultured with glioblastoma cells. The subsequent nanogel degradation correlates with up-regulated MMP2/9. Released [125 I]ITdU follows the thymidine salvage pathway ending in its incorporation into the DNA of tumor cells. With this concept, a highly efficient strategy for intracellular delivery of radiopharmaceuticals across the challenging BBB is presented.

Combination of cell-penetrating peptides with nanomaterials for the potential therapeutics of central nervous system disorders: a review

Although nanomedicine have greatly developed and human life span has been extended, we have witnessed the soared incidence of central nervous system (CNS) diseases including neurodegenerative diseases (Alzheimer's disease, Parkinson's disease), ischemic stroke, and brain tumors, which have severely damaged the quality of life and greatly increased the economic and social burdens. Moreover, partial small molecule drugs and almost all large molecule drugs (such as recombinant protein, therapeutic antibody, and nucleic acid) cannot cross the blood-brain barrier. Therefore, it is especially important to develop a drug delivery system that can effectively deliver therapeutic drugs to the central nervous system for the treatment of central nervous system diseases. Cell penetrating peptides (CPPs) provide a potential strategy for the transport of macromolecules through the blood-brain barrier. This study analyzed and summarized the progress of CPPs in CNS diseases from three aspects: CPPs, the conjugates of CPPs and drug, and CPPs modified nanoparticles to provide scientific basis for the application of CPPs for CNS diseases.

Dynamic nanoassemblies for imaging and therapy of neurological disorders

The past decades have witnessed an increased incidence of neurological disorders (NDs) such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, ischemic stroke, and epilepsy, which significantly lower patients' life quality and increase the economic and social burden. Recently, nanomedicines composed of imaging and/or therapeutic agents have been explored to diagnose and/or treat NDs due to their enhanced bioavailability, blood-brain barrier (BBB) permeability, and targeting capacity. Intriguingly, dynamic nanoassemblies self-assembled from functional nanoparticles to simultaneously interfere with multiple pathogenic substances and pathological changes, have been regarded as one of the foremost candidates to improve the diagnostic and therapeutic efficacy of NDs. To help readers better understand this emerging field, in this review, the pathogenic mechanism of different types of NDs is briefly introduced, then the functional nanoparticles used as building blocks in the construction of dynamic nanoassemblies for NDs theranostics are summarized. Furthermore, dynamic nanoassemblies that can actively cross the BBB to target brain lesions, sensitively and efficiently diagnose or treat NDs, and effectively promote neuroregeneration are highlighted. Finally, we conclude with our perspectives on the future development in this field.

Covalent and Noncovalent Conjugation of Degradable Polymer Nanoparticles to T Lymphocytes

Cells are attractive as carriers that can help to enhance control over the biodistribution of polymer nanomedicines. One strategy to use cells as carriers is based on the cell surface immobilization of the nanoparticle cargo. While a range of strategies can be used to immobilize nanoparticles on cell surfaces, only limited effort has been made to investigate the effect of these surface modification chemistries on cell viability and functional properties. This study has explored seven different approaches for the immobilization of poly(lactic acid) (PLA) nanoparticles on the surface of two different T lymphocyte cell lines. The cell lines used were human Jurkat T cells and CD4⁺ T_EM cells. The latter cells possess blood-brain barrier (BBB) migratory properties and are attractive for the development of cell-based delivery systems to the central nervous system (CNS). PLA nanoparticles were immobilized either via covalent active ester-amine, azide-alkyne cycloaddition, and thiol-maleimide coupling, or via noncovalent approaches that use lectin-carbohydrate, electrostatic, or biotin-NeutrAvidin interactions. The cell surface immobilization of the nanoparticles was monitored with flow cytometry and confocal microscopy. By tuning the initial nanoparticle/cell ratio, T cells can be decorated with up to ∼185 nanoparticles/cell as determined by confocal microscopy. The functional properties of the nanoparticle-decorated cells were assessed by evaluating their binding to ICAM-1, a key protein involved in the adhesion of CD4⁺ T_EM cells to the BBB endothelium, as well as in a two-chamber model in vitro BBB migration assay. It was found that the migratory behavior of CD4⁺ T_EM cells carrying carboxylic acid-, biotin-, or Wheat germ agglutinin (WGA)-functionalized nanoparticles was not affected by the presence of the nanoparticle payload. In contrast, however, for cells decorated with maleimide-functionalized nanoparticles, a reduction in the number of migratory cells compared to the nonmodified control cells was observed. Investigating and understanding the impact of nanoparticle-cell surface conjugation chemistries on the viability and properties of cells is important to further improve the design of cell-based nanoparticle delivery systems. The results of this study present a first step in this direction and provide first guidelines for the surface modification of T cells, in particular in view of their possible use for drug delivery to the CNS.

Nanoparticles as a Tool in Neuro-Oncology Theranostics

The rapid growth of nanotechnology and the development of novel nanomaterials with unique physicochemical characteristics provides potential for the utility of nanomaterials in theranostics, including neuroimaging, for identifying neurodegenerative changes or central nervous system malignancy. Here we present a systematic and thorough review of the current evidence pertaining to the imaging characteristics of various nanomaterials, their associated toxicity profiles, and mechanisms for enhancing tropism in an effort to demonstrate the utility of nanoparticles as an imaging tool in neuro-oncology. Particular attention is given to carbon-based and metal oxide nanoparticles and their theranostic utility in MRI, CT, photoacoustic imaging, PET imaging, fluorescent and NIR fluorescent imaging, and SPECT imaging.

Biotin-NeutrAvidin Mediated Immobilization of Polymer Micro- and Nanoparticles on T Lymphocytes

Cells are powerful carriers that can help to improve the delivery of nanomedicines. One approach to use cells as carriers is to immobilize the nanoparticulate cargo on the cell surface. While a plethora of chemical conjugation strategies are available to bind nanoparticles to cell surfaces, only relatively little is known about the effects of particle size and cell type on the surface immobilization of nanoparticles. This study investigates the biotin-NeutrAvidin mediated immobilization of model polymer nanoparticles with sizes ranging from 40 nm to 1 μm on two different T cell lines, viz., human Jurkat cells as well as mouse SJL/PLP7 T cells, which are of potential interest for drug delivery across the blood-brain barrier. The nanoparticle cell surface immobilization and the particle surface concentration and distribution were analyzed by flow cytometry and confocal microscopy. The functional properties of nanoparticle-modified SJL/PLP7 T cells were assessed in an ICAM-1 binding assay as well as in a two-chamber setup in which the migration of the particle-modified T cells across an in vitro model of the blood-brain barrier was studied. The results of these experiments highlight the effects of particle size and cell line on the surface immobilization of nanoparticles on living cells.