Application progress of RVG peptides to facilitate the delivery of therapeutic agents into the central nervous system

Exosome-Based Macromolecular neurotherapeutic drug delivery approaches in overcoming the Blood-Brain barrier for treating brain disorders

Delivering drugs to the brain is a complex challenge in medical research, particularly for disorders like Alzheimer's and Parkinson's. The blood-brain barrier restricts the entry of many therapeutic molecules, hindering their effectiveness. Nanoparticles, a potential solution, face issues like toxicity and limited approvals. A new avenue explores the use of small extracellular vesicles (sEVs), i.e., exosomes, as natural carriers for drug delivery. sEVs, tiny structures below 150 nm, show promise due to their minimal immune response and ability to precisely deliver drugs. This review focuses on the potential of sEVs-based drug delivery systems for treating neurological disorders, brain cancers, and other brain-related issues. Notably, bioengineered sEVs-carrying therapeutic compounds exhibit promise in early studies. The unique features of sEVs, such as their small size and natural properties, position them as candidates to overcome challenges in drug delivery to the brain. Ongoing clinical trials and research into sEVs behavior within the body further highlight their potential for revolutionizing drug delivery and addressing complex brain conditions.

Advanced nanoparticle strategies for optimizing RNA therapeutic delivery in neurodegenerative disorders

Neurodegenerative diseases affect many people worldwide, and as the population ages, the incidence of these conditions increases. Alzheimer's disease (AD) and Parkinson's disease (PD) are the most prevalent neurodegenerative disorders worldwide. Different medicines are being used to control symptoms related to these conditions, but no treatment has yet been approved. Both genetic and environmental factors are involved in disease pathogenesis, and research on the pathophysiological pathways is still ongoing. The role of subcellular pathways and dysregulation in RNA pathways has been highlighted in pathophysiological studies, and treatment strategies focused on these pathways can be a promising approach. Many experiments have been conducted on delivering RNA cargo to the CNS to modulate various pathways involved. Yet another challenge to be faced is the effective transport of desired molecules to targets, which can be greatly hindered by distinct barriers limiting transport to the CNS, most noticeably the blood-brain barrier (BBB). Nanotechnology and the use of different nano-carriers for the delivery of nucleotides, peptides, proteins, and drug molecules are currently of great interest as these carriers help with better delivery and protection and, as a result, improve the effectiveness of the cargo. Nanocarriers can protect susceptible RNA molecules from possible degradation or destruction and improve their ability to reach the brain by enhancing BBB penetration. Different mechanisms for this process have been hypothesized. This review will go through the therapeutic application of RNA molecules in the treatment of AD and PD and the role of nanocarriers in overcoming delivery challenges and enhancing efficacy.

Exosomes encapsulated in hydrogels for effective central nervous system drug delivery

The targeted delivery of pharmacologically active molecules, metabolites, and growth factors to the brain parenchyma has become one of the major challenges following the onset of neurodegeneration and pathological conditions. The therapeutic effect of active biomolecules is significantly impaired after systemic administration in the central nervous system (CNS) because of the blood-brain barrier (BBB). Therefore, the development of novel therapeutic approaches capable of overcoming these limitations is under discussion. Exosomes (Exo) are nano-sized vesicles of endosomal origin that have a high distribution rate in biofluids. Recent advances have introduced Exo as naturally suitable bio-shuttles for the delivery of neurotrophic factors to the brain parenchyma. In recent years, many researchers have attempted to regulate the delivery of Exo to target sites while reducing their removal from circulation. The encapsulation of Exo in natural and synthetic hydrogels offers a valuable strategy to address the limitations of Exo, maintaining their integrity and controlling their release at a desired site. Herein, we highlight the current and novel approaches related to the application of hydrogels for the encapsulation of Exo in the field of CNS tissue engineering.

Extracellular vesicles as nanotheranostic platforms for targeted neurological disorder interventions

Central Nervous System (CNS) disorders represent a profound public health challenge that affects millions of people around the world. Diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and traumatic brain injury (TBI) exemplify the complexities and diversities that complicate their early detection and the development of effective treatments. Amid these challenges, the emergence of nanotechnology and extracellular vesicles (EVs) signals a new dawn for treating and diagnosing CNS ailments. EVs are cellularly derived lipid bilayer nanosized particles that are pivotal in intercellular communication within the CNS and have the potential to revolutionize targeted therapeutic delivery and the identification of novel biomarkers. Integrating EVs with nanotechnology amplifies their diagnostic and therapeutic capabilities, opening new avenues for managing CNS diseases. This review focuses on examining the fascinating interplay between EVs and nanotechnology in CNS theranostics. Through highlighting the remarkable advancements and unique methodologies, we aim to offer valuable perspectives on how these approaches can bring about a revolutionary change in disease management. The objective is to harness the distinctive attributes of EVs and nanotechnology to forge personalized, efficient interventions for CNS disorders, thereby providing a beacon of hope for affected individuals. In short, the confluence of EVs and nanotechnology heralds a promising frontier for targeted and impactful treatments against CNS diseases, which continue to pose significant public health challenges. By focusing on personalized and powerful diagnostic and therapeutic methods, we might improve the quality of patients.

Mesenchymal Stem Cells-based Cell-free Therapy Targeting Neuroinflammation

Emerging from several decades of extensive research, key genetic elements and biochemical mechanisms implicated in neuroinflammation have been delineated, contributing substantially to our understanding of neurodegenerative diseases (NDDs). In this minireview, we discuss data predominantly from the past three years, highlighting the pivotal roles and mechanisms of the two principal cell types implicated in neuroinflammation. The review also underscores the extended process of peripheral inflammation that predates symptomatic onset, the critical influence of neuroinflammation, and their dynamic interplay in the pathogenesis of NDDs. Confronting these complex challenges, we introduce compelling evidence supporting the use of mesenchymal stem cell-based cell-free therapy. This therapeutic strategy includes the regulation of microglia and astrocytes, modulation of peripheral nerve cell inflammation, and targeted anti-inflammatory interventions specifically designed for NDDs, while also discussing engineering and safety considerations. This innovative therapeutic approach intricately modulates the immune system across the peripheral and nervous systems, with an emphasis on achieving superior penetration and targeted delivery. The insights offered by this review have significant implications for the better understanding and management of neuroinflammation.

Biomimetic nanocarriers loaded with temozolomide by cloaking brain-targeting peptides for targeting drug delivery system to promote anticancer effects in glioblastoma cells

Glioma is the leading cancer of the central nervous system (CNS). The efficacy of glioma treatment is significantly hindered by the presence of the blood-brain barrier (BBB) and blood-brain tumour barrier (BBTB), which prevent most drugs from entering the brain and tumours. Hence, we established a novel drug delivery nanosystem of brain tumour-targeting that could self-assemble the method using an amphiphilic Zein protein isolated from corn. Zein's amphiphilicity prompted it to self-assembled into NPs, efficiently containing TMZ. This allowed us to investigate temozolomide (TMZ) for glioblastoma (GBM) treatment. To construct TMZ-encapsulated NPs (TMZ@RVG-Zein NPs), the NPs' Zein was clocked to rabies virus glycoprotein 29 (RVG29). To verify that the NPs could penetrate the BBB and precisely target and kill the GBM cancer cell line, in vitro studies were performed. The process of NPs penetrating cancer cell membranes was investigated using enzyme-linked immunosorbent assays (ELISAs) to measure the expressions of nicotinic acetylcholine receptors (nAChRs) on the U87 cell line. Therefore, effective targeted brain cancer treatment is possible by forming NP clocks, a cell-penetrating natural Zein protein with an RVG29. These NPs can penetrate the blood-brain barrier (BBB) and enter the glioblastoma (U87) cell line to release TMZ. These NPs have a distinct cocktail of biocompatibility and brain-targeting abilities, making them ideal for involving brain diseases.

Exosome-mediated delivery and regulation in neurological disease progression

Exosomes (EXOs), membranous structures originating from diverse biological sources, have recently seized the attention of researchers due to their theranostic potential for neurological diseases. Released actively by various cells, including stem cells, adipose tissue, and immune cells, EXOs wield substantial regulatory influence over the intricate landscape of neurological complications, exhibiting both positive and negative modulatory effects. In AD, EXOs play a pivotal role in disseminating and breaking down amyloid-β protein. Moreover, EXOs derived from mesenchymal stem cells showcase a remarkable capacity to mitigate pro-inflammatory phenotypes by regulating miRNAs in neurodegenerative diseases. These vesicles possess the unique ability to traverse the blood-brain barrier, governing the aggregation of mutant huntingtin protein. Understanding the exosomal functions within the CNS holds significant promise for enhancing treatment efficacy in neurological diseases. This review intricately examines the regulatory mechanisms involving EXOs in neurological disease development, highlighting therapeutic prospects and exploring their utility in exosome-based nanomedicine for various neurological complications. Additionally, the review highlights the challenges associated with drug delivery to the brain, emphasizing the complexities inherent in this critical aspect of neurotherapeutics.

Tumor-specific cytolysis by peptide-conjugated echogenic polymer micelles

Interest in multifunctional polymer nanoparticles for targeted delivery of anti-cancer drugs has grown significantly in recent years. In this study, tumor-targeting echogenic polymer micelles were prepared from poly(ethylene glycol) methyl ether-alkyl carbonate (mPEG-AC) derivatives, and their potential in cancer therapy was assessed. Various mPEG derivatives with carbonate linkages were synthesized via an alkyl halide reaction between mPEG and alkyl chloroformate. Micelle formation using polymer amphiphiles in aqueous media and the subsequent carbon dioxide (CO2) gas generation from the micelles was confirmed. Their ability to target neuroblastoma was substantially enhanced by incorporating the rabies virus glycoprotein (RVG) peptide. RVG-modified gas-generating micelles significantly inhibited tumor growth in a tumor-bearing mouse model owing to CO2 gas generation within tumor cells and resultant cytolytic effects, showing minimal side effects. The development of multifunctional polymer micelles may offer a promising therapeutic approach for various diseases, including cancer.

Exosomes in Glioma: Unraveling Their Roles in Progression, Diagnosis, and Therapy

Gliomas, the most prevalent primary malignant brain tumors, present a challenging prognosis even after undergoing surgery, radiation, and chemotherapy. Exosomes, nano-sized extracellular vesicles secreted by various cells, play a pivotal role in glioma progression and contribute to resistance against chemotherapy and radiotherapy by facilitating the transportation of biological molecules and promoting intercellular communication within the tumor microenvironment. Moreover, exosomes exhibit the remarkable ability to traverse the blood-brain barrier, positioning them as potent carriers for therapeutic delivery. These attributes hold promise for enhancing glioma diagnosis, prognosis, and treatment. Recent years have witnessed significant advancements in exosome research within the realm of tumors. In this article, we primarily focus on elucidating the role of exosomes in glioma development, highlighting the latest breakthroughs in therapeutic and diagnostic approaches, and outlining prospective directions for future research.

Smart Nanoscale Extracellular Vesicles in the Brain: Unveiling their Biology, Diagnostic Potential, and Therapeutic Applications

Information exchange is essential for the brain, where it communicates the physiological and pathological signals to the periphery and vice versa. Extracellular vesicles (EVs) are a heterogeneous group of membrane-bound cellular informants actively transferring informative calls to and from the brain via lipids, proteins, and nucleic acid cargos. In recent years, EVs have also been widely used to understand brain function, given their "cell-like" properties. On the one hand, the presence of neuron and astrocyte-derived EVs in biological fluids have been exploited as biomarkers to understand the mechanisms and progression of multiple neurological disorders; on the other, EVs have been used in designing targeted therapies due to their potential to cross the blood-brain-barrier (BBB). Despite the expanding literature on EVs in the context of central nervous system (CNS) physiology and related disorders, a comprehensive compilation of the existing knowledge still needs to be made available. In the current review, we provide a detailed insight into the multifaceted role of brain-derived extracellular vesicles (BDEVs) in the intricate regulation of brain physiology. Our focus extends to the significance of these EVs in a spectrum of disorders, including brain tumors, neurodegenerative conditions, neuropsychiatric diseases, autoimmune disorders, and others. Throughout the review, parallels are drawn for using EVs as biomarkers for various disorders, evaluating their utility in early detection and monitoring. Additionally, we discuss the promising prospects of utilizing EVs in targeted therapy while acknowledging the existing limitations and challenges associated with their applications in clinical scenarios. A foundational comprehension of the current state-of-the-art in EV research is essential for informing the design of future studies.

Knockdown of BACE1 by a multistage brain-targeting polyion complex improved memory and learning behaviors in APP/PS1 transgenic mouse model

Cleavage of Amyloid precursor protein (APP) by the β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the rate-limiting step in the production of amyloid-β (Aβ) synaptotoxins. The siRNA-mediated silencing to attenuate the expression of BACE1 to ameliorate cognitive dysfunction in mice had been investigated. To improve therapeutic gene delivery to the central nervous system, cationic copolymer poly(ethylene glycol)-b-poly[N-(N'-{N''-[N'''-(2-aminoethyl)-2-aminoethyl]-2-aminoethyl}-2-aminoethyl)aspartamide]-cholesterol was synthesized, then RVG29 and Tet1 peptides were exploited as ligands to construct a dual-targeting brain gene delivery polyion complex (Tet1/RVG29-PIC). The cell uptake of a coculture cell model showed that the Tet1/RVG29-PIC exhibited notable transport characteristics and possessed affinity towards nerve cells. In vivo transfection, Tet1/RVG29-PIC possessed the highest expression of luciferase in brain compared with that of RVG29-PIC or Tet1-PIC, which were 1.25 and 1.22 times respectively. Silence BACE1 expression using siRNA-expressing plasmid loaded Tet1/RVG29-PIC that improved behavioral deficits in the APP/PS1 mouse model, demonstrating the favorable brain delivery properties of Tet1/RVG29-PIC by synergistical engagement of GT1B and nicotinic acetylcholine receptors. Our results suggested that the nanoformulation has the potential to be exploited as a multistage-targeting gene vector for the CNS disease therapy.

Navigating the brain: the role of exosomal shuttles in precision therapeutics

Brain diseases have become one of the leading roots of mortality and disability worldwide, contributing a significant part of the disease burden on healthcare systems. The blood-brain barrier (BBB) is a primary physical and biological obstacle that allows only small molecules to pass through it. Its selective permeability is a significant challenge in delivering therapeutics into the brain for treating brain dysfunction. It is estimated that only 2% of the new central nervous system (CNS) therapeutic compounds can cross the BBB and achieve their therapeutic targets. Scientists are exploring various approaches to develop effective cargo delivery vehicles to promote better therapeutics targeting the brain with minimal off-target side effects. Despite different synthetic carriers, one of the natural brain cargo delivery systems, "exosomes," are now employed to transport drugs through the BBB. Exosomes are naturally occurring small extracellular vesicles (EVs) with unique advantages as a therapeutic delivery system for treating brain disorders. They have beneficial innate aspects of biocompatibility, higher stability, ability to cross BBB, low cytotoxicity, low immunogenicity, homing potential, targeted delivery, and reducing off-site target effects. In this review, we will discuss the limitations of synthetic carriers and the utilization of naturally occurring exosomes as brain-targeted cargo delivery vehicles and highlight the methods for modifying exosome surfaces and drug loading into exosomes. We will also enlist neurodegenerative disorders targeted with genetically modified exosomes for their treatment.

miRNA-211-5p inhibition enhances the protective effect of hucMSC-derived exosome in Aβ1-40 -induced SH-SY5Y cells by increasing NEP expression

Exosomes derived from human umbilical cord mesenchymal stem cells (hucMSCs) could alleviate Alzheimer's disease (AD) defects. Additionally, engineered exosomes are more effective in treating diseases. In this study, we established an in vitro model of AD by treating SH-SY5Y cells with Aβ1-40 . We observed that incubation with hucMSC-derived exosomes effectively protected SH-S5Y5 cells from Aβ1-40 -induced damage. Since NEP plays a central role in suppressing AD development, we screened NEP-targeting miRNAs that are differentially expressed in control and AD patients. We identified miR-211-5p as a potent repressor of NEP expression. Exosomes purified from hucMSCs overexpressing miR-211-5p inhibitor exhibited significantly greater efficiency than control exosomes in mitigating the injury caused by Aβ1-40 treatment. However, this enhanced protective effect was nullified by the knockdown of NEP. These observations demonstrate that inhibition of miR-211-5p has the potential to improve the efficacy of hucMSC-derived exosomes in AD treatment by increasing NEP expression.

Transforming native exosomes to engineered drug vehicles: A smart solution to modern cancer theranostics

Exosomes have been the hidden treasure of the cell in terms of cellular interactions, transportation and therapy. The native exosomes (NEx) secreted by the parent cells hold promising aspects in cancer diagnosis and therapy. NEx has low immunogenicity, high biocompatibility, low toxicity and high stability which enables them to be an ideal prognostic biomarker in cancer diagnosis. However, due to heterogeneity, NEx lacks specificity and accuracy to be used as therapeutic drug delivery vehicle in cancer therapy. Transforming these NEx with their innate structure and multiple receptors to engineered exosomes (EEx) can provide better opportunities in the field of cancer theranostics. The surface of the NEx exhibits numeric receptors which can be modified to pave the direction of its therapeutic drug delivery in cancer therapy. Through surface membrane, EEx can be modified with increased drug loading potentiality and higher target specificity to act as a therapeutic nanocarrier for drug delivery. This review provides insights into promising aspects of NEx as a prognostic biomarker and drug delivery tool along with its need for the transformation to EEx in cancer theranostics. We have also highlighted different methods associated with NEx transformations, their nano-bio interaction with recipient cells and major challenges of EEx for clinical application in cancer theranostics.

Schwann Cell-Derived Exosomal Vesicles: A Promising Therapy for the Injured Spinal Cord

Exosomes are nanoscale-sized membrane vesicles released by cells into their extracellular milieu. Within these nanovesicles reside a multitude of bioactive molecules, which orchestrate essential biological processes, including cell differentiation, proliferation, and survival, in the recipient cells. These bioactive properties of exosomes render them a promising choice for therapeutic use in the realm of tissue regeneration and repair. Exosomes possess notable positive attributes, including a high bioavailability, inherent safety, and stability, as well as the capacity to be functionalized so that drugs or biological agents can be encapsulated within them or to have their surface modified with ligands and receptors to imbue them with selective cell or tissue targeting. Remarkably, their small size and capacity for receptor-mediated transcytosis enable exosomes to cross the blood-brain barrier (BBB) and access the central nervous system (CNS). Unlike cell-based therapies, exosomes present fewer ethical constraints in their collection and direct use as a therapeutic approach in the human body. These advantageous qualities underscore the vast potential of exosomes as a treatment option for neurological injuries and diseases, setting them apart from other cell-based biological agents. Considering the therapeutic potential of exosomes, the current review seeks to specifically examine an area of investigation that encompasses the development of Schwann cell (SC)-derived exosomal vesicles (SCEVs) as an approach to spinal cord injury (SCI) protection and repair. SCs, the myelinating glia of the peripheral nervous system, have a long history of demonstrated benefit in repair of the injured spinal cord and peripheral nerves when transplanted, including their recent advancement to clinical investigations for feasibility and safety in humans. This review delves into the potential of utilizing SCEVs as a therapy for SCI, explores promising engineering strategies to customize SCEVs for specific actions, and examines how SCEVs may offer unique clinical advantages over SC transplantation for repair of the injured spinal cord.

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

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

Lipid nanoparticles for siRNA delivery in cancer treatment

RNA-based therapies, and siRNAs in particular, have attractive therapeutic potential for cancer treatment due to their ability to silence genes that are imperative for tumor progression. To be effective and solve issues related to their poor half-life and poor pharmacokinetic properties, siRNAs require adequate drug delivery systems that protect them from degradation and allow intracellular delivery. Among the various delivery vehicles available, lipid nanoparticles have emerged as the leading choice. These nanoparticles consist of cholesterol, phospholipids, PEG-lipids and most importantly ionizable cationic lipids. These ionizable lipids enable the binding of negatively charged siRNA, resulting in the formation of stable and neutral lipid nanoparticles with exceptionally high encapsulation efficiency. Lipid nanoparticles have demonstrated their effectiveness and versatility in delivering not only siRNAs but also multiple RNA molecules, contributing to their remarkable success. Furthermore, the advancement of efficient manufacturing techniques such as microfluidics, enables the rapid mixing of two miscible solvents without the need for shear forces. This facilitates the reproducible production of lipid nanoparticles and holds enormous potential for scalability. This is shown by the increasing number of preclinical and clinical trials evaluating the potential use of siRNA-LNPs for the treatment of solid and hematological tumors as well as in cancer immunotherapy. In this review, we provide an overview of the progress made on siRNA-LNP development for cancer treatment and outline the current preclinical and clinical landscape in this area. Finally, the translational challenges required to bring siRNA-LNPs further into the clinic are also discussed.

Non-viral approaches for gene therapy and therapeutic genome editing across the blood-brain barrier

The success of brain-targeted gene therapy and therapeutic genome editing hinges on the efficient delivery of biologics bypassing the blood-brain barrier (BBB), which presents a significant challenge in the development of treatments for central nervous system disorders. This is particularly the case for nucleic acids and genome editors that are naturally excluded by the BBB and have poor chemical stability in the bloodstream and poor cellular uptake capability, thereby requiring judiciously designed nanovectors administered systemically for intracellular delivery to brain cells such as neurons. To overcome this obstacle, various strategies for bypassing the BBB have been developed in recent years to deliver biologics to the brain via intravenous administration using non-viral vectors. This review summarizes various brain targeting strategies and recent representative reports on brain-targeted non-viral delivery systems that allow gene therapy and therapeutic genome editing via intravenous administration, and highlights ongoing challenges and future perspectives for systemic delivery of biologics to the brain via non-viral vectors.

Recent trends in MXene-based material for biomedical applications

MXene is a magical class of 2D nanomaterials and emerging in many applications in diverse fields. Due to the multiple advantageous characteristics of its fundamental components, such as structural, physicochemical, optical, and occasionally even biological characteristics. However, it is limited in the biomedical industry due to poor physiological stability, decomposition rate, and lack of controlled and sustained drug release. These limitations can be overcome when MXene forms composites with other 2D materials. The efficiency of pure MXene in biomedicine is inferior to that of MXene-based composites. The availability of functionality on the exterior part of MXene has a key role in the modification of their surface and their characteristics. This review provides an extensive discussion on the synthesizing of MXene and the role of the surface functionalities on the efficiency of MXene. In addition, a detailed discussion of the biomedical applications of MXene, including antibacterial activity, regenerative medicine, CT scan capability, drug delivery, diagnostics, MRI and biosensing capability. Furthermore, an outline of the future problems and challenges of MXene-based materials for biomedical applications was narrated. Thus, these salient features showcase the potential of MXene-based material and will be a breakthrough in biomedical applications in the near future.

Engineered EVs designed to target diseases of the CNS

Diseases of the central nervous system (CNS) are challenging to treat, mainly due to the blood-brain barrier (BBB), which restricts drugs in circulation from entering target regions in the brain. To address this issue extracellular vesicles (EVs) have gained increasing scientific interest as carriers able to cross the BBB with multiplex cargos. EVs are secreted by virtually every cell, and their escorted biomolecules are part of an intercellular information gateway between cells within the brain and with other organs. Scientists have undertaken efforts to safeguard the inherent features of EVs as therapeutic delivery vehicles, such as protecting and transferring functional cargo, as well as loading them with therapeutic small molecules, proteins, and oligonucleotides and targeting them to specific cell types for the treatment of CNS diseases. Here, we review current emerging approaches that engineer the EV surface and cargo to improve targeting and functional responses in the brain. We summarize existing applications of engineered EVs as a therapeutic delivery platform for brain diseases, some of which have been evaluated clinically.

Cyclodextrin-Based Nanoparticles for Delivery of Antisense Oligonucleotides Targeting Huntingtin

Huntington's disease (HD) is a progressive inherited neurodegenerative disease caused by a CAG repeat expansion in the huntingtin gene, which is translated into the pathologic mutant huntingtin (mHTT) protein. Despite the great potential of HTT lowering strategies and the numerous antisense oligonucleotides (ASOs) in pre- and clinical trials, sustained silencing of mHTT has not been achieved. As a strategy to improve ASO delivery, cyclodextrin-based nanoparticles (CDs) offer a promising approach. Here, three CDs with distinct chemical structures were designed and their efficacies were compared as potential platforms for the delivery of ASO targeting HTT. Results using striatal neurons and HD patient-derived fibroblasts indicate that modified γ-CDs exhibited the best uptake efficiency and successfully downregulated mHTT at protein and allele levels. The incorporation of the brain-targeting peptide RVG into the modified γ-CDs showed greater downregulation of mHTT protein and HD-causing allele SNP1 than untargeted ones in an in vitro blood-brain barrier model. Although the ASO sequence was designed as a nonallele-specific therapeutic approach, our strategy gives an additional benefit of some mHTT selectivity. Overall, this study demonstrated the CD platform's feasibility for delivering ASO-based therapeutics for HD treatment.

Engineered mesenchymal stem cell-derived extracellular vesicles: A state-of-the-art multifunctional weapon against Alzheimer's disease

With the increase of population aging, the number of Alzheimer's disease (AD) patients is also increasing. According to current estimates, approximately 11% of people over 65 suffer from AD, and that percentage rises to 42% among people over 85. However, no effective treatment capable of decelerating or stopping AD progression is available. Furthermore, AD-targeted drugs composed of synthetic molecules pose concerns regarding biodegradation, clearance, immune response, and neurotoxicity. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) are essential intercellular communication mediators holding great promise as AD therapeutics owing to their biocompatibility, versatility, effortless storage, superior safety, and the ability to transport messenger and noncoding RNAs, proteins, lipids, DNAs, and other bioactive compounds derived from cells. The functionalisation and engineering strategies of MSC-EVs are highlighted (e.g. preconditioning, drug loading, surface modification, and artificial EV fabrication), which could improve AD treatment by multiple therapeutic effects, including clearing abnormal protein accumulation and achieving neuroprotection and immunomodulatory effects. Herein, this review summarises state-of-the-art strategies to engineer MSC-EVs, discusses progress in their use as AD therapeutics, presents the perspectives and challenges associated with the related clinical applications, and concludes that engineered MSC-EVs show immense potential in AD therapy.

Polymeric Dendrimers as Nanocarrier Vectors for Neurotheranostics

Dendrimers are polymers with well-defined 3D branched structures that are vastly utilized in various neurotheranostics and biomedical applications, particularly as nanocarrier vectors. Imaging agents can be loaded into dendrimers to improve the accuracy of diagnostic imaging processes. Likewise, combining pharmaceutical agents and anticancer drugs with dendrimers can enhance their solubility, biocompatibility, and efficiency. Practically, by modifying ligands on the surface of dendrimers, effective therapeutic and diagnostic platforms can be constructed and implemented for targeted delivery. Dendrimer-based nanocarriers also show great potential in gene delivery. Since enzymes can degrade genetic materials during their blood circulation, dendrimers exhibit promising packaging and delivery alternatives, particularly for central nervous system (CNS) treatments. The DNA and RNA encapsulated in dendrimers represented by polyamidoamine that are used for targeted brain delivery, via chemical-structural adjustments and appropriate generation, significantly improve the correlation between transfection efficiency and cytotoxicity. This article reports a comprehensive review of dendrimers' structures, synthesis processes, and biological applications. Recent progress in diagnostic imaging processes and therapeutic applications for cancers and other CNS diseases are presented. Potential challenges and future directions in the development of dendrimers, which provide the theoretical basis for their broader applications in healthcare, are also discussed.

Recent advances in drug delivery and targeting to the brain

Our body keeps separating the toxic chemicals in the blood from the brain. A significant number of drugs do not enter the central nervous system (CNS) due to the blood-brain barrier (BBB). Certain diseases, such as tumor growth and stroke, are known to increase the permeability of the BBB. However, the heterogeneity of this permeation makes it difficult and unpredictable to transport drugs to the brain. In recent years, research has been directed toward increasing drug penetration inside the brain, and nanomedicine has emerged as a promising approach. Active targeting requires one or more specific ligands on the surface of nanoparticles (NPs), which brain endothelial cells (ECs) recognize, allowing controlled drug delivery compared to conventional targeting strategies. This review highlights the mechanistic insights about different cell types contributing to the development and maintenance of the BBB and summarizes the recent advancement in brain-specific NPs for different pathological conditions. Furthermore, fundamental properties of brain-targeted NPs will be discussed, and the standard lesion features classified by neurological pathology are summarized.

Therapeutic nanotechnologies for Alzheimer's disease: a critical analysis of recent trends and findings

Alzheimer's Disease (AD) is an irreversible neurodegenerative disease for which no disease modifying therapies are presently available. Besides the identification of pathological targets, AD presents numerous clinical and pharmacological challenges such as efficient active delivery to the central nervous system, cell targeting, and long-term dosing. Nanoparticles have been explored to overcome some of these challenges as drug delivery vehicles or drugs themselves. However, early promises have failed to materialize as no nanotechnology-based product has been able to reach the market and very few have moved past preclinical stages. In this review, we perform a critical analysis of the past decade's research on nanomedicine-based therapies for AD at the preclinical and clinical stages. The main obstacles to nanotechnology products and the most promising approaches were also identified, including renewed promise with gene editing, gene modulation, and vaccines.

Strategies for Targeted Delivery of Exosomes to the Brain: Advantages and Challenges

Delivering therapeutics to the central nervous system (CNS) is difficult because of the blood–brain barrier (BBB). Therapeutic delivery across the tight junctions of the BBB can be achieved through various endogenous transportation mechanisms. Receptor-mediated transcytosis (RMT) is one of the most widely investigated and used methods. Drugs can hijack RMT by expressing specific ligands that bind to receptors mediating transcytosis, such as the transferrin receptor (TfR), low-density lipoprotein receptor (LDLR), and insulin receptor (INSR). Cell-penetrating peptides and viral components originating from neurotropic viruses can also be utilized for the efficient BBB crossing of therapeutics. Exosomes, or small extracellular vesicles, have gained attention as natural nanoparticles for treating CNS diseases, owing to their potential for natural BBB crossing and broad surface engineering capability. RMT-mediated transport of exosomes expressing ligands such as LDLR-targeting apolipoprotein B has shown promising results. Although surface-modified exosomes possessing brain targetability have shown enhanced CNS delivery in preclinical studies, the successful development of clinically approved exosome therapeutics for CNS diseases requires the establishment of quantitative and qualitative methods for monitoring exosomal delivery to the brain parenchyma in vivo as well as elucidation of the mechanisms underlying the BBB crossing of surface-modified exosomes.

Modified cyclodextrin-based nanoparticles mediated delivery of siRNA for huntingtin gene silencing across an in vitro BBB model

Huntington's disease (HD) is a neurodegenerative disorder caused by a mutation in the huntingtin (HTT) gene, leading to a toxic version of the HTT protein. There are currently no disease-modifying therapies available. In this scenario, gene-based treatments for HD aimed at lowering HTT levels have become one of the most promising emerging therapeutic options. To date, however, promising results have only been achieved following direct intrathecal or intracranial injections designed to circumvent the blood-brain barrier (BBB). Consequently, efforts to develop less invasive delivery platforms are highly desirable. Here, we described a novel delivery system based on modified cyclodextrin nanoparticles (CDs) loaded with small interfering RNAs (siRNAs) targeting HTT andcomplexed with the rabies virus glycoprotein(RVG), a BBB-shuttle peptide. Results using an in vitro BBB model, indicate the formulation successfully crosses the brain endothelial cells, releases the encapsulated siRNAs into the cytoplasm of neuronal cells, and mediates downregulation of HTT. In conclusion, the CD platform is a promising option for delivery of siRNA-based therapeutics for HD with wider potential to treat other diseases with a genetically validated target in the central nervous system.

Nanovehicles in the improved treatment of infections due to brain-eating amoebae

Pathogenic free-living amoebae are known to cause fatal central nervous system infections with extremely high mortality rates. High selectivity of the blood-brain barrier hampers delivery of drugs and untargeted delivery of drugs can cause severe side effects. Nanovehicles can be used for targeted drug delivery across the blood-brain barrier. Inorganic nanoparticles have been explored as carriers for various biomedical applications and can be modified with various ligands for efficient targeting and cell selectivity while lipid-based nanoparticles have been extensively used in the development of both precision and colloidal nanovehicles. Nanomicelles and polymeric nanoparticles can also serve as nanocarriers and may be modified so that responsiveness of the nanoparticles and release of the loads are linked to specific stimuli. These nanoparticles are discussed here in the context of the treatment of central nervous system infections due to pathogenic amoebae. It is anticipated that these novel strategies can be utilized in tandem with novel drug leads currently in the pipeline and yield in the development of much needed treatments against these devastating parasites.