Glymphatic System and Subsidiary Pathways Drive Nanoparticles Away from the Brain

Advances in Intrathecal Nanoparticle Delivery: Targeting the Blood-Cerebrospinal Fluid Barrier for Enhanced CNS Drug Delivery

The blood-cerebrospinal fluid barrier (BCSFB) tightly regulates molecular exchanges between the bloodstream and cerebrospinal fluid (CSF), creating challenges for effective central nervous system (CNS) drug delivery. This review assesses intrathecal (IT) nanoparticle (NP) delivery systems that aim to enhance drug delivery by circumventing the BCSFB, complementing approaches that target the blood-brain barrier (BBB). Active pharmaceutical ingredients (APIs) face hurdles like restricted CNS distribution and rapid clearance, which diminish the efficacy of IT therapies. NPs can be engineered to extend drug circulation times, improve CNS penetration, and facilitate sustained release. This review discusses key pharmacokinetic (PK) parameters essential for the effectiveness of these systems. NPs can quickly traverse the subarachnoid space and remain within the leptomeninges for extended periods, often exceeding three weeks. Some designs enable deeper brain parenchyma penetration. Approximately 80% of NPs in the CSF are cleared through the perivascular glymphatic pathway, with microglia-mediated transport significantly contributing to their paravascular clearance. This review synthesizes recent progress in IT-NP delivery across the BCSFB, highlighting critical findings, ongoing challenges, and the therapeutic potential of surface modifications and targeted delivery strategies.

A probe for NIR-II imaging and multimodal analysis of early Alzheimer's disease by targeting CTGF

To date, earlier diagnosis of Alzheimer's disease (AD) is still challenging. Recent studies revealed the elevated expression of connective tissue growth factor (CTGF) in AD brain is an upstream regulator of amyloid-beta (Aβ) plaque, thus CTGF could be an earlier diagnostic biomarker of AD than Aβ plaque. Herein, we develop a peptide-coated gold nanocluster that specifically targets CTGF with high affinity (KD ~ 21.9 nM). The probe can well penetrate the blood-brain-barrier (BBB) of APP/PS1 transgenic mice at early-stage (earlier than 3-month-old) in vivo, allowing non-invasive NIR-II imaging of CTGF when there is no appearance of Aβ plaque deposition. Notably, this probe can also be applied to measuring CTGF on postmortem brain sections by multimodal analysis, including fluorescence imaging, peroxidase-like chromogenic imaging, and ICP-MS quantitation, which enables distinguishment between the brains of AD patients and healthy people. This probe possesses great potential for precise diagnosis of earlier AD before Aβ plaque formation.

State-of-the-art drug delivery system to target the lymphatics

PRIMARY OBJECTIVE

The primary objective of the review is to assess the potential of lymphatic-targeted drug delivery systems, with a particular emphasis on their role in tumour therapy and vaccination efficacy.

REASON FOR LYMPHATIC TARGETING

The lymphatic system's crucial functions in maintaining bodily equilibrium, regulating metabolism, and orchestrating immune responses make it an ideal target for drug delivery. Lymph nodes, being primary sites for tumour metastasis, underscore the importance of targeting the lymphatic system for effective treatment.

OUTCOME

Nanotechnologies and innovative biomaterials have facilitated the development of lymphatic-targeted drug carriers, leveraging endogenous macromolecules to enhance drug delivery efficiency. Various systems such as liposomes, micelles, inorganic nanomaterials, hydrogels, and nano-capsules demonstrate significant potential for delivering drugs to the lymphatic system.

CONCLUSION

Understanding the physiological functions of the lymphatic system and its involvement in diseases underscores the promise of targeted drug delivery in improving treatment outcomes. The strategic targeting of the lymphatic system presents opportunities to enhance patient prognosis and advance therapeutic interventions across various medical contexts, indicating the importance of ongoing research and development in this area.

Interactions between nanoparticles and pathological changes of vascular in Alzheimer's disease

Emerging evidence suggests that vascular pathological changes play a pivotal role in the pathogenesis of Alzheimer's disease (AD). The dysfunction of the cerebral vasculature occurs in the early course of AD, characterized by alterations in vascular morphology, diminished cerebral blood flow (CBF), impairment of the neurovascular unit (NVU), vasculature inflammation, and cerebral amyloid angiopathy. Vascular dysfunction not only facilitates the influx of neurotoxic substances into the brain, triggering inflammation and immune responses but also hampers the efflux of toxic proteins such as Aβ from the brain, thereby contributing to neurodegenerative changes in AD. Furthermore, these vascular changes significantly impact drug delivery and distribution within the brain. Therefore, developing targeted delivery systems or therapeutic strategies based on vascular alterations may potentially represent a novel breakthrough in AD treatment. This review comprehensively examines various aspects of vascular alterations in AD and outlines the current interactions between nanoparticles and pathological changes of vascular.

Advances and future perspectives of intranasal drug delivery: A scientometric review

Intranasal drug delivery is as a noninvasive and efficient approach extensively utilized for treating the local, central nervous system, and systemic diseases. Despite numerous reviews delving into the application of intranasal drug delivery across biomedical fields, a comprehensive analysis of advancements and future perspectives remains elusive. This review elucidates the research progress of intranasal drug delivery through a scientometric analysis. It scrutinizes several challenges to bolster research in this domain, encompassing a thorough exploration of entry and elimination mechanisms specific to intranasal delivery, the identification of drugs compatible with the nasal cavity, the selection of dosage forms to surmount limited drug-loading capacity and poor solubility, and the identification of diseases amenable to the intranasal delivery strategy. Overall, this review furnishes a perspective aimed at galvanizing future research and development concerning intranasal drug delivery.

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.

Imaging of brain clearance pathways via MRI assessment of the glymphatic system

Glymphatic clearance dysfunction may play an important role in a variety of neurodegenerative diseases and the progression of ageing. However, in vivo imaging of the glymphatic system is challenging. In this study, we describe an MRI method based on chemical exchange saturation transfer (CEST) of the Angiopep-2 probe to visualize the clearance function of the glymphatic system. We injected rats with Angiopep-2 via the tail vein and performed in vivo MRI at 7 T to track differences in Angiopep-2 signal changes; we then applied the same principles in a bilateral deep cervical lymph node ligation rat model and in ageing rats. We demonstrated the feasibility of Angiopep-2 CEST for visualizing the clearance function of the glymphatic system. Finally, a pathological assessment was performed. Within the model group, the deep cervical lymph node ligation group and the ageing group showed higher CEST signal than the control group. We conclude that this new MRI method can visualize clearance in the glymphatic system.

mTOR-Mediated Immunometabolic Reprogramming Nanomodulators Enable Sensitive Switching of Energy Deprivation-Induced Microglial Polarization for Alzheimer's Disease Management

Metabolic reprogramming that senses brain homeostasis imbalances is necessary to drive detrimental microglial polarization, and specific targeting of this process contributes to the flexible control of pathological inflammatory responses in Alzheimer's disease (AD), displaying distinctive therapeutic benefits. Herein, glutathione-functionalized gold nanocages loaded with the immunosuppressant fingolimod hydrochloride are developed as brain-targeted and microglia-located immunometabolic reprogramming nanomodulators (GAF NPs) for AD management. By virtue of glutathione-mediated transport properties, this nanomodulator can cross the blood-brain barrier and localize to microglia in AD lesions. Through blocking Akt/mTOR/HIF-1α signaling pathways, GAF NPs not only promote the dominated metabolic shift from glycolysis to oxidative phosphorylation under immune activation but also inhibit transporter-mediated glucose overconsumption by microglia. Correlation analysis based on real-time bioenergetic assessment and 18F-labeled fluorodeoxyglucose (FDG) PET reveals that brain glucose utilization and metabolism restored by GAF NP treatment can serve as a sensitive and effective indicator for microglial M1 to M2 polarization switching, ultimately alleviating neuroinflammation and its derived neurodegeneration as well as ameliorating cognitive decline in AD mice. This work highlights a potential nanomedicine aimed at modifying mTOR-mediated immunometabolic reprogramming to halt energy deprivation-induced AD progression.

The glymphatic system: a new perspective on brain diseases

The glymphatic system is a brain-wide perivascular pathway driven by aquaporin-4 on the endfeet of astrocytes, which can deliver nutrients and active substances to the brain parenchyma through periarterial cerebrospinal fluid (CSF) influx pathway and remove metabolic wastes through perivenous clearance routes. This paper summarizes the composition, overall fluid flow, solute transport, related diseases, affecting factors, and preclinical research methods of the glymphatic system. In doing so, we aim to provide direction and reference for more relevant researchers in the future.

Stimuli-responsive heparin-drug conjugates co-assembled into stable nanomedicines for cancer therapy

The combination of chemotherapy and photodynamic therapy (PDT) has the potential to complement single-drug therapies, but chemotherapeutic agents and photosensitizers often have compromised therapeutic efficacies and strong toxic effects. In this study, we exploited nanotechnology to address this challenge by utilizing heparin as a carrier for co-delivery of chemotherapeutic drugs and photosensitizers for synergistic cancer therapy. Specifically, heparin-paclitaxel (HP-PTX) and heparin-pyropheophorbide-a (HP-Ppa) were synthesized by attaching paclitaxel (PTX), a small molecular chemotherapeutic drug, through a reactive oxygen species (ROS)-responsive linker and Ppa, a photosensitizer, to heparin, respectively. Two conjugates co-assembled into a nanomedicine, HP-PP nanoparticles (NPs), for controllable co-delivery of Ppa and PTX into tumor cells. HP-PP NPs significantly enhanced the in vitro stability of HP-Ppa and the photostability of Ppa, and the synergistic actions of chemotherapy and PDT were confirmed from both in vitro and in vivo antitumor studies. Notably, HP-PP NPs enhanced tumor accumulation of Ppa up to 11-fold and the treatment of 4T1 tumor-bearing mice with HP-PP NPs resulted in a tumor growth inhibition of 98.1% without systemic toxicity. The strategy of co-assembly of heparin conjugates may offer great potential in enhancing the efficacy of combination therapy. STATEMENT OF SIGNIFICANCE: : We proposed a nano-delivery system, HP-PP NPs, which was constructed by co-assembly of heparin-paclitaxel (HP-PTX) and heparin-pyropheophorbide-a (HP-Ppa), to co-deliver PTX and Ppa for synergistic cancer therapy. HP-PP NPs enhanced the photostability and the in vitro stability of Ppa and HP-Ppa, and induced greater cytotoxicity than HP-PTX NPs or HP-Ppa NPs. This co-delivery system displays enhanced tumor accumulation and has a remarkable synergistic antitumor effect with a tumor growth inhibition of 98.1%.

Peptide-decorated nanocarriers penetrating the blood-brain barrier for imaging and therapy of brain diseases

Blood-Brain Barrier (BBB) is one of the most important physiological barriers strictly restricting the substance exchange between blood and brain tissues. While the BBB protects the brain from infections and toxins and maintains brain homeostasis, it is also recognized as the main obstacle to the penetration of therapeutics and imaging agents into the brain. Due to high specificity and affinity, peptides are frequently exploited to decorate nanocarriers across the BBB for diagnosis and/or therapy purposes. However, there are still some challenges that restrict their clinical application, such as stability, safety and immunocompatibility. In this review, we summarize the biological and pathophysiological characteristics of the BBB, strategies across the BBB, and recent progress on peptide decorated nanocarriers for brain diseases diagnosis and therapy. The challenges and opportunities for their translation are also discussed.