Recent progress of drug nanoformulations targeting to brain

Nanoparticle-Guided Brain Drug Delivery: Expanding the Therapeutic Approach to Neurodegenerative Diseases

Neurodegenerative diseases (NDs) represent a heterogeneous group of aging-related disorders featured by progressive impairment of motor and/or cognitive functions, often accompanied by psychiatric disorders. NDs are denoted as 'protein misfolding' diseases or proteinopathies, and are classified according to their known genetic mechanisms and/or the main protein involved in disease onset and progression. Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD) are included under this nosographic umbrella, sharing histopathologically salient features, including deposition of insoluble proteins, activation of glial cells, loss of neuronal cells and synaptic connectivity. To date, there are no effective cures or disease-modifying therapies for these NDs. Several compounds have not shown efficacy in clinical trials, since they generally fail to cross the blood-brain barrier (BBB), a tightly packed layer of endothelial cells that greatly limits the brain internalization of endogenous substances. By engineering materials of a size usually within 1-100 nm, nanotechnology offers an alternative approach for promising and innovative therapeutic solutions in NDs. Nanoparticles can cross the BBB and release active molecules at target sites in the brain, minimizing side effects. This review focuses on the state-of-the-art of nanoengineered delivery systems for brain targeting in the treatment of AD, PD and HD.

Carbon Dots: An Innovative Tool for Drug Delivery in Brain Tumors

Brain tumors are particularly aggressive and represent a significant cause of morbidity and mortality in adults and children, affecting the global population and being responsible for 2.6% of all cancer deaths (as well as 30% of those in children and 20% in young adults). The blood-brain barrier (BBB) excludes almost 100% of the drugs targeting brain neoplasms, representing one of the most significant challenges to current brain cancer therapy. In the last decades, carbon dots have increasingly played the role of drug delivery systems with theranostic applications against cancer, thanks to their bright photoluminescence, solubility in bodily fluids, chemical stability, and biocompatibility. After a summary outlining brain tumors and the current drug delivery strategies devised in their therapeutic management, this review explores the most recent literature about the advances and open challenges in the employment of carbon dots as both diagnostic and therapeutic agents in the treatment of brain cancers, together with the strategies devised to allow them to cross the BBB effectively.

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

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

De novo Drug Delivery Modalities for Treating Damaged Hearts: Current Challenges and Emerging Solutions

Cardiovascular disease (CVD) is the leading cause of mortality, resulting in approximately one-third of deaths worldwide. Among CVD, acute myocardial infarctions (MI) is the leading cause of death. Current treatment modalities for treating CVD have improved over the years, but the demand for new and innovative therapies has been on the rise. The field of nanomedicine and nanotechnology has opened a new paradigm for treating damaged hearts by providing improved drug delivery methods, specifically targeting injured areas of the myocardium. With the advent of innovative biomaterials, newer therapeutics such as growth factors, stem cells, and exosomes have been successfully delivered to the injured myocardial tissue, promoting improvement in cardiac function. This review focuses on three major drug delivery modalities: nanoparticles, microspheres, and hydrogels, and their potential for treating damaged hearts following an MI.

Engineered exosomes: desirable target-tracking characteristics for cerebrovascular and neurodegenerative disease therapies

As extracellular vesicles secreted by cells, exosomes are intercellular signalosomes for cell communication and pharmacological effectors. Because of their special properties, including low toxicity and immunogenicity, biodegradability, ability to encapsulate endogenous biologically active molecules and cross the blood-brain barrier (BBB), exosomes have great therapeutic potential in cerebrovascular and neurodegenerative diseases. However, the poor targeting ability of natural exosomes greatly reduces the therapeutic effect. Using engineering technology, exosomes can obtain active targeting ability to accumulate in specific cell types and tissues by attaching targeting units to the membrane surface or loading them into cavities. In this review, we outline the improved targeting functions of bioengineered exosomes, tracing and imaging techniques, administration methods, internalization in the BBB, and therapeutic effects of exosomes in cerebrovascular and neurodegenerative diseases and further evaluate the clinical opportunities and challenges in this research field.

Recent Advances and Challenges in Nanodelivery Systems for Antimicrobial Peptides (AMPs)

Antimicrobial peptides (AMPs) can be used as alternative therapeutic agents to traditional antibiotics. These peptides have abundant natural template sources and can be isolated from animals, plants, and microorganisms. They are amphiphilic and mostly net positively charged, and they have a broad-spectrum inhibitory effect on bacteria, fungi, and viruses. AMPs possess significant rapid killing effects and do not interact with specific receptors on bacterial surfaces. As a result, drug resistance is rarely observed with treatments. AMPs, however, have some operational problems, such as a susceptibility to enzymatic (protease) degradation, toxicity in vivo, and unclear pharmacokinetics. However, nanodelivery systems loaded with AMPs provide a safe mechanism of packaging such peptides before they exert their antimicrobial actions, facilitate targeted delivery to the sites of infection, and control the release rate of peptides and reduce their toxic side effects. However, nanodelivery systems using AMPs are at an early stage of development and are still in the laboratory phase of development. There are also some challenges in incorporating AMPs into nanodelivery systems. Herein, an insight into the nanotechnology challenges in delivering AMPs, current advances, and remaining technological challenges are discussed in depth.

Evolution of blood-brain barrier in brain diseases and related systemic nanoscale brain-targeting drug delivery strategies

Blood–brain barrier (BBB) strictly controls matter exchange between blood and brain, and severely limits brain penetration of systemically administered drugs, resulting in ineffective drug therapy of brain diseases. However, during the onset and progression of brain diseases, BBB alterations evolve inevitably. In this review, we focus on nanoscale brain-targeting drug delivery strategies designed based on BBB evolutions and related applications in various brain diseases including Alzheimer's disease, Parkinson's disease, epilepsy, stroke, traumatic brain injury and brain tumor. The advances on optimization of small molecules for BBB crossing and non-systemic administration routes (e.g., intranasal treatment) for BBB bypassing are not included in this review.

In Vitro Evaluation of Nasal Aerosol Depositions: An Insight for Direct Nose to Brain Drug Delivery

The nasal cavity is an attractive route for both local and systemic drug delivery and holds great potential for access to the brain via the olfactory region, an area where the blood–brain barrier (BBB) is effectively absent. However, the olfactory region is located at the roof of the nasal cavity and only represents ~5–7% of the epithelial surface area, presenting significant challenges for the deposition of drug molecules for nose to brain drug delivery (NTBDD). Aerosolized particles have the potential to be directed to the olfactory region, but their specific deposition within this area is confounded by a complex combination of factors, which include the properties of the formulation, the delivery device and how it is used, and differences in inter-patient physiology. In this review, an in-depth examination of these different factors is provided in relation to both in vitro and in vivo studies and how advances in the fabrication of nasal cast models and analysis of aerosol deposition can be utilized to predict in vivo outcomes more accurately. The challenges faced in assessing the nasal deposition of aerosolized particles within the paediatric population are specifically considered, representing an unmet need for nasal and NTBDD to treat CNS disorders.

Systematic development of lectin conjugated microspheres for nose-to-brain delivery of rivastigmine for the treatment of Alzheimer's disease

The current study focuses on development of nasal mucoadhesive microspheres for nose-to-brain delivery of rivastigmine for Alzheimer treatment. A systematic development was employed for optimization of the formulation and process parameters influential on the quality attributes of the microspheres. The risk assessment study revealed major influence of the polymer concentration (ethylcellulose: chitosan), the concentration of surfactant solution (polyvinyl alcohol), and stirring speed as the critical factors for optimization of the microspheres. These factors were systematically optimized using Box-Behnken design and microspheres were evaluated for the particle size, entrapment efficiency, and in vitro drug release as the response variables. The optimized microspheres containing 4.4% wt/vol polymers, 1% wt/vol surfactant, and stirring speed at 1500 rpm showed particle size of 19.9 µm, entrapment efficiency of 77.8%, and drug release parameters as T_80% of 7.3 h. The surface modification of microspheres was performed with lectin by carbodiimide activation reaction and confirmed by difference in surface charge before and after chemical functionalization by zeta potential measurement which was found to be - 25.7 mV and 20.5 mV, respectively. Ex vivo study for bioadhesion strength evaluation on goat nasal mucosa indicated a significant difference (p < 0.001) between the plain (29%) and lectin functionalized microspheres (64%). In vivo behavioral and biochemical studies in the rats treated with lectin functionalized microspheres showed markedly better memory-retention vis-à-vis test and pure drug solution treated rats (p < 0.001). In a nutshell, the present studies showed successful development of nasal microspheres for enhanced brain delivery of rivastigmine for Alzheimer's treatment.

New advances in brain-targeting nano-drug delivery systems for Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide and its incidence is increasing due to the ageing population. Currently, the main limitations of AD treatment are low blood-brain barrier permeability, severe off-target of drugs, and immune abnormality. In this review, four hypotheses for Alzheimer's pathogenesis and three challenges for Alzheimer's drug delivery are discussed. In addition, this article summarises the different strategies of brain targeting nano-drug delivery systems (NDDSs) developed in the last 10 years. These strategies include receptor-mediated (transferrin receptor, low-density lipoprotein receptor-related protein, lactoferrin receptor, etc.), adsorption-mediated (cationic, alkaline polypeptide, cell-penetrating peptides, etc.), and transporter-mediated (P-gp, GLUT1, etc.). Moreover, it provides insights into novel strategies used in AD, such as exosomes, virus-like particles, and cell membrane coating particles. Hence, this review will help researchers to understand the current progress in the field of NDDSs for the central nervous system and find new directions for AD therapy.HighlightsCharacteristics and challenges based on the pathogenesis of AD were discussed.Recent advances in novel brain-targeting NDDSs for AD over the past 10 years were summarised.

An update on actively targeted liposomes in advanced drug delivery to glioma

High-grade glioma is one of the most aggressive types of cancer with a low survival rate ranging from 12 to 15 months after the first diagnosis. Though being the most common strategy for glioma therapy, conventional chemotherapy suffers providing the therapeutic dosage of common therapeutics mostly because of limited permeability of blood-brain barrier (BBB), and blood-brain tumor barrier (BBTB) to anticancer agents. Among various nanoformulations, liposomes are considered as the most popular carriers aimed for glioma therapy. However, non-targeted liposomes which passively accumulate in most of the cancer tissues mainly through the enhanced permeation and retention effect (EPR), may not be applicable for glioma therapy due to BBB tight junctions. In the recent decade, the surface modification of liposomes with different active targeting ligands has shown promising results by getting different chemotherapeutics across the BBB and BBTB and leading them into the glioma cells. The present review discusses the major barriers for drug delivery systems to glioma, elaborates the existing mechanisms for liposomes to traverse across the BBB, and explores the main strategies for incorporation of targeting ligands onto the liposomes. It subsequently investigates the most recent and relevant studies of actively targeted liposomes modified with antibodies, aptamers, monosaccharides, polysaccharides, proteins, and peptides applied for effective glioma therapy, and highlights the common challenges facing this area. Finally, the actively targeted liposomes undergoing preclinical and clinical studies for delivery of different anticancer agents to glioma cells will be reviewed.

Clofazimine functionalized polymeric nanoparticles for brain delivery in the tuberculosis treatment

Central nervous system tuberculosis (CNS-TB) is the most severe form of the disease especially due to the inability of therapeutics to cross the blood-brain barrier (BBB). Clofazimine (CFZ) stands out for presenting high in vitro activity against multi-drug resistant strains of Mycobacterium tuberculosis, however, CFZ physicochemical and pharmacokinetics properties limit drug penetration into the CNS and, consequently, its clinical use. The aim of this work was to develop polymeric nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA) and polyethylene glycol (PEG) loaded with CFZ and functionalized with a transferrin receptor (TfR)-binding peptide, aiming brain drug delivery for CNS-TB treatment by the intravenous route. The poor water solubility and high lipophilicity of CFZ was overcome through its entrapment into PLGA-PEG NPs manufactured by both conventional and microfluidic techniques using the nanoprecipitation principle. In vitro studies in brain endothelial hCMEC/D3 cells demonstrated that CFZ incorporation into the NPs was advantageous to reduce drug cytotoxicity. The TfR-binding peptide-functionalized NPs showed superior cell interaction and higher CFZ permeability across hCMEC/D3 cell monolayers compared to the non-functionalized NP control, thus indicating the efficacy of the functionalization strategy on providing CFZ transport through the BBB in vitro. The functionalized NPs demonstrate suitability for CFZ biological administration, suggested with low plasma protein binding, off-target biodistribution and precise delivery of CFZ towards the brain parenchyma.

Highlighting the usage of polymeric nanoparticles for the treatment of traumatic brain injury: A review study

There are very limited options for treating traumatic brain injury (TBI). Nanoparticles offer the potential of targeting specific cell types, and, potentially, crossing the BBB under the right conditions making them an area of active research for treating TBI. This review focuses on polymeric nanoparticles and the impact of their chemistry, size, and surface groups on their interactions with the vasculature and cells of the brain following injury. The vast majority of the work in the field focuses on acute injury, and when the work is looked at closely, it suggests that nanoparticles rely on interactions with vascular and immune cells to alter the environment of the brain. Nonetheless, there are promising results from a number of approaches that lead to behavioral improvements coupled with neuroprotection that offer promise for therapeutic outcomes. The majority of approaches have been tested immediately following injury. It is not entirely clear what impact these approaches will have in chronic TBI, but being able to modulate inflammation specifically may have a role both during and after the acute phase of injury.

Nucleolin-Targeting AS1411 Aptamer-Modified Micelle for the Co-Delivery of Doxorubicin and miR-519c to Improve the Therapeutic Efficacy in Hepatocellular Carcinoma Treatment

BACKGROUND

Multidrug resistance (MDR) has emerged to be a major hindrance in cancer therapy, which contributes to the reduced sensitivity of cancer cells toward chemotherapeutic drugs mainly owing to the over-expression of drug efflux transporters. The combination of gene therapy and chemotherapy has been considered as a potential approach to improve the anti-cancer efficacy by reversing the MDR effect.

MATERIALS AND METHODS

The AS1411 aptamer-functionalized micelles were constructed through an emulsion/solvent evaporation strategy for the simultaneous co-delivery of doxorubicin and miR-519c. The therapeutic efficacy and related mechanism of micelles were explored based on the in vitro and in vivo active targeting ability and the suppression of MDR, using hepatocellular carcinoma cell line HepG2 as a model.

RESULTS

The micelle was demonstrated to possess favorable cellular uptake and tumor penetration ability by specifically recognizing the nucleolin in an AS1411 aptamer-dependent manner. Further, the intracellular accumulation of doxorubicin was significantly improved due to the suppression of ABCG2-mediated drug efflux by miR-519c, resulting in the efficient inhibition of tumor growth.

CONCLUSION

The micelle-mediated co-delivery of doxorubicin and miR-519c provided a promising strategy to obtain ideal anti-cancer efficacy through the active targeting function and the reversion of MDR.

Native and Bioengineered Exosomes for Ischemic Stroke Therapy

Exosomes are natural cells-derived vesicles, which are at the forefront toward clinical success for various diseases, including cerebral ischemia. Exosomes mediate cell-to-cell communication in different brain cells during both physiological and pathological conditions. Exosomes are an extensively studied type of extracellular vesicle, which are considered to be the best alternative for stem cell-based therapy. They can be secreted by various cell types and have unique biological properties. Even though native exosomes have potential for ischemic stroke therapy, some undesirable features prevent their success in clinical applications, including a short half-life, poor targeting property, low concentration at the target site, rapid clearance from the lesion region, and inefficient payload. In this review, we highlight exosome trafficking and cellular uptake and survey the latest discoveries in the context of exosome research as the best fit for brain targeting owing to its natural brain-homing abilities. Furthermore, we overview the methods by which researchers have bioengineered exosomes (BioEng-Exo) for stroke therapy. Finally, we summarize studies in which exosomes were bioengineered by a third party for stroke recovery. This review provides up-to-date knowledge about the versatile nature of exosomes with a special focus on BioEng-Exo for ischemic stroke. Standard exosome bioengineering techniques are mandatory for the future and will lead exosomes toward clinical success for stroke therapy.

Review of nanotheranostics for molecular mechanisms underlying psychiatric disorders and commensurate nanotherapeutics for neuropsychiatry: The mind knockout

Bio-neuronal led psychiatric abnormalities transpired by the loss of neuronal structure and function (neurodegeneration), pro-inflammatory cytokines, microglial dysfunction, altered neurotransmission, toxicants, serotonin deficiency, kynurenine pathway, and excessively produced neurotoxic substances. These uncontrolled happenings in the etiology of psychiatric disorders initiate further changes in neurotransmitter metabolism, pathologic microglial, cell activation, and impaired neuroplasticity. Inflammatory cytokines, the outcome of dysfunctional mitochondria, dysregulation of the immune system, and under stress functions of the brain are leading biochemical factors for depression and anxiety. Nanoscale drug delivery platforms, inexpensive diagnostics using nanomaterials, nano-scale imaging technologies, and ligand-conjugated nanocrystals used for elucidating the molecular mechanisms and foremost cellular communications liable for such disorders are highly capable features to study for efficient diagnosis and therapy of the mental illness. These theranostic tools made up of multifunctional nanomaterials have the potential for effective and accurate diagnosis, imaging of psychiatric disorders, and are at the forefront of leading technologies in nanotheranostics openings field as they can collectively and efficiently target the stimulated territories of the cerebellum (cells and tissues) through molecular-scale interactions with higher bioavailability, and bio-accessibility. Specifically, the nanoplatforms based neurological changes are playing a significant role in the diagnosis of psychiatric disorders and portraying the routes of functional restoration of mental disorders by newer imaging tools at nano-level in all directions. Because of these nanotherapeutic platforms, the molecules of nanomedicine can penetrate the Blood-Brain Barrier with an increased half-life of drug molecules. The discoveries in nanotheranostics and nanotherapeutics inbuilt unique multi-functionalities are providing the best multiplicities of novel nanotherapeutic potentialities with no toxicity concerns at the level of nano range.

A review on α-mangostin as a potential multi-target-directed ligand for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by progressive memory loss, declining language skills and other cognitive disorders. AD has brought great mental and economic burden to patients, families and society. However due to the complexity of AD's pathology, drugs developed for the treatment of AD often fail in clinical or experimental trials. The main problems of current anti-AD drugs are low efficacy due to mono-target method or side effects, especially high hepatotoxicity. To tackle these two main problems, multi-target-directed ligand (MTDL) based on "one molecule, multiple targets" has been studied. MTDLs can regulate multiple biological targets at the same time, so it has shown higher efficacy, better safety. As a natural active small molecule, α-mangostin (α-M) has shown potential multi-factor anti-AD activities in a series of studies, furthermore it also has a certain hepatoprotective effect. The good availability of α-M also provides support for its application in clinical research. In this work, multiple activities of α-M related to AD therapy were reviewed, which included anti-cholinesterase, anti-amyloid-cascade, anti-inflammation, anti-oxidative stress, low toxicity, hepatoprotective effects and drug formulation. It shows that α-M is a promising candidate for the treatment of AD.

Recent progress in nanoformulations of cabazitaxel

The antitumor efficacy of various paclitaxel (PTX) and docetaxel (DTX) formulations in clinical applications is seriously affected by drug resistance. Cabazitaxel, a second-generation taxane, exhibits greater anticancer activity than paclitaxel and docetaxel and has low affinity for the P-glycoprotein (P-gp) efflux pump because of its structure. Therefore, cabazitaxel has the potential to overcome taxane resistance. However, owing to the high systemic toxicity and hydrophobicity of cabazitaxel and the instability of its commercial preparation, Jevtana®, the clinical use of cabazitaxel is restricted to patients with metastatic castration-resistant prostate cancer (mCRPC) who show progression after docetaxel-based chemotherapy. Nanomedicine is expected to overcome the limitations associated with cabazitaxel application and surmount taxane resistance. This review outlines the drug delivery systems of cabazitaxel published in recent years, summarizes the challenges faced in the development of cabazitaxel nanoformulations, and proposes strategies to overcome these challenges.

Prospects and challenges of extracellular vesicle-based drug delivery system: considering cell source

Extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, are nanosized membrane vesicles derived from most cell types. Carrying diverse biomolecules from their parent cells, EVs are important mediators of intercellular communication and thus play significant roles in physiological and pathological processes. Owing to their natural biogenesis process, EVs are generated with high biocompatibility, enhanced stability, and limited immunogenicity, which provide multiple advantages as drug delivery systems (DDSs) over traditional synthetic delivery vehicles. EVs have been reported to be used for the delivery of siRNAs, miRNAs, protein, small molecule drugs, nanoparticles, and CRISPR/Cas9 in the treatment of various diseases. As a natural drug delivery vectors, EVs can penetrate into the tissues and be bioengineered to enhance the targetability. Although EVs' characteristics make them ideal for drug delivery, EV-based drug delivery remains challenging, due to lack of standardized isolation and purification methods, limited drug loading efficiency, and insufficient clinical grade production. In this review, we summarized the current knowledge on the application of EVs as DDS from the perspective of different cell origin and weighted the advantages and bottlenecks of EV-based DDS.

A Highly Selective MNK Inhibitor Rescues Deficits Associated with Fragile X Syndrome in Mice

Fragile X syndrome (FXS) is the most common inherited source of intellectual disability in humans. FXS is caused by mutations that trigger epigenetic silencing of the Fmr1 gene. Loss of Fmr1 results in increased activity of the mitogen-activated protein kinase (MAPK) pathway. An important downstream consequence is activation of the mitogen-activated protein kinase interacting protein kinase (MNK). MNK phosphorylates the mRNA cap-binding protein, eukaryotic initiation factor 4E (eIF4E). Excessive phosphorylation of eIF4E has been directly implicated in the cognitive and behavioral deficits associated with FXS. Pharmacological reduction of eIF4E phosphorylation is one potential strategy for FXS treatment. We demonstrate that systemic dosing of a highly specific, orally available MNK inhibitor, eFT508, attenuates numerous deficits associated with loss of Fmr1 in mice. eFT508 resolves a range of phenotypic abnormalities associated with FXS including macroorchidism, aberrant spinogenesis, and alterations in synaptic plasticity. Key behavioral deficits related to anxiety, social interaction, obsessive and repetitive activities, and object recognition are ameliorated by eFT508. Collectively, this work establishes eFT508 as a potential means to reverse deficits associated with FXS.

Mechanisms for Tuning Engineered Nanomaterials to Enhance Radiation Therapy of Cancer

Engineered nanomaterials that produce reactive oxygen species on exposure to X- and gamma-rays used in radiation therapy offer promise of novel cancer treatment strategies. Similar to photodynamic therapy but suitable for large and deep tumors, this new approach where nanomaterials acting as sensitizing agents are combined with clinical radiation can be effective at well-tolerated low radiation doses. Suitably engineered nanomaterials can enhance cancer radiotherapy by increasing the tumor selectivity and decreasing side effects. Additionally, the nanomaterial platform offers therapeutically valuable functionalities, including molecular targeting, drug/gene delivery, and adaptive responses to trigger drug release. The potential of such nanomaterials to be combined with radiotherapy is widely recognized. In order for further breakthroughs to be made, and to facilitate clinical translation, the applicable principles and fundamentals should be articulated. This review focuses on mechanisms underpinning rational nanomaterial design to enhance radiation therapy, the understanding of which will enable novel ways to optimize its therapeutic efficacy. A roadmap for designing nanomaterials with optimized anticancer performance is also shown and the potential clinical significance and future translation are discussed.

Magnetic Resonance Imaging-Guided Focused Ultrasound-Based Delivery of Radiolabeled Copper Nanoclusters to Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is an invasive pediatric brainstem malignancy exclusively in children without effective treatment due to the often-intact blood-brain tumor barrier (BBTB), an impediment to the delivery of therapeutics. Herein, we used focused ultrasound (FUS) to transiently open BBTB and delivered radiolabeled nanoclusters (⁶⁴Cu-CuNCs) to tumors for positron emission tomography (PET) imaging and quantification in a mouse DIPG model. First, we optimized FUS acoustic pressure to open the blood-brain barrier (BBB) for effective delivery of ⁶⁴Cu-CuNCs to pons in wildtype mice. Then the optimized FUS pressure was used to deliver radiolabeled agents in DIPG mouse. Magnetic resonance imaging (MRI)-guided FUS-induced BBTB opening was demonstrated using a low molecular weight, short-lived ⁶⁸Ga-DOTA-ECL1i radiotracer and PET/CT before and after treatment. We then compared the delivery efficiency of ⁶⁴Cu-CuNCs to DIPG tumor with and without FUS treatment and demonstrated the FUS-enhanced delivery and time-dependent diffusion of ⁶⁴Cu-CuNCs within the tumor.

Nanoparticlized System: Promising Approach for the Management of Alzheimer's Disease through Intranasal Delivery

Alzheimer's disease (AD) is a neurodegenerative brain problem and responsible for causing dementia in aged people. AD has become most common neurological disease in the elderly population worldwide and its treatment remains still challengeable. Therefore, there is a need of an efficient drug delivery system which can deliver the drug to the target site. Nasal drug delivery has been used since prehistoric times for the treatment of neurological disorders like Alzheimer's disease (AD). For delivering drug to the brain, blood brain barrier (BBB) is a major rate limiting factor for the drugs. The desired drug concentration could not be achieved through the conventional drug delivery system. Thus, nanocarrier based drug delivery systems are promising for delivering drug to brain. Nasal route is a most convenient for targeting drug to the brain. Several factors and mechanisms need to be considered for an effective delivery of drug to the brain particularly AD. Various nanoparticlized systems such as nanoparticles, liposomes, exosomes, phytosomes, nanoemulsion, nanosphere, etc. have been recognized as an effective drug delivery system for the management of AD. These nanocarriers have been proven with improved permeability as well as bioavailability of the anti-Alzheimer's drugs. Some novel drug delivery systems of anti-Alzheimer drugs are under investigation of different phase of clinical trials. Present article highlights on the nanotechnology based intranasal drug delivery system for the treatment of Alzheimer's disease. Furthermore, consequences of AD, transportation mechanism, clinical updates and recent patents on nose to brain delivery for AD have been discussed.

Nanoparticles for drug delivery in Parkinson's disease

Although effective symptomatic treatments for Parkinson's disease (PD) have been available for some time, efficient and well-controlled drug delivery to the brain has proven to be challenging. The emergence of nanotechnology has created new opportunities not only for improving the pharmacokinetics of conventional therapies but also for developing novel treatment approaches and disease modifying therapies. Several exciting strategies including drug carrier nanoparticles targeting specific intracellular pathways and structural reconformation of tangled proteins as well as introducing reprogramming genes have already shown promise and are likely to deliver more tailored approaches to the treatment of PD in the future. This paper reviews the role of nanoparticles in PD including a discussion of both their composition and functional capacity as well as their potential to deliver better therapeutic agents.

Brain delivery of Plk1 inhibitor via chimaeric polypeptide polymersomes for safe and superb treatment of orthotopic glioblastoma

The chemotherapy toward glioblastoma (GBM) is severely challenged by blood-brain barrier and dose-limiting toxicity. Herein, we adopt brain delivery of Plk1 inhibitor volasertib (Vol), which is highly specific and presents low off-target toxicity, as a new means to treat GBM, for which angiopep-2-docked chimaeric polypeptide polymersome (ANG-CPP) was designed and prepared from poly(ethylene glycol)-b-poly(L-tyrosine)-b-poly(L-aspartic acid) for loading Vol to its watery interior via electrostatic interactions. ANG-CPP loaded with 13.9 wt% Vol (ANG-CPP-Vol) exhibited a small size of about 76 nm, superb colloidal stability (against dilution, serum and long-term storage), and enzyme-triggered drug release behavior (about 73% of Vol released within 8 h with proteinase K). In sharp contrast to free Vol, ANG-CPP-Vol induced complete G2/M cell cycle arrest in U-87 MG GBM cells giving 7.8-times better anti-tumor activity, prolonged circulation time and largely increased GBM enrichment. ANG-CPP-Vol effectively suppressed the growth of orthotopic U-87 MG GBM and significantly boosted mice survival rate. Importantly, ANG-CPP-Vol showed further reduced toxicity over free Vol. This great safety and remarkable efficacy of ANG-CPP-Vol renders it a high potential for treating GBM.

Exosomes in Gliomas: Biogenesis, Isolation, and Preliminary Applications in Nanomedicine

Exosomes are phospholipid-based particles endogenously produced by both normal and tumor cells. Initially identified as a pathway for shuttling cellular waste, for a long time they were thought to act as “garbage bags”, and only in the past few years have they emerged as a promising drug delivery system. In this review, we provide an overview of the knowledge about exosome architecture and biogenesis and the recent progress in isolation methods. Furthermore, we describe the mechanisms involved in both extra- and intracellular communication with a focus on glioma brain tumors. Glioma is considered a rare disease and is the most prominent aggressive brain malignancy. How exosomes target glial tumoral cells in vivo remains largely unknown. However, they are able to influence numerous physio-pathological aspects. Here, we discuss the role they play in this heterogeneous and complex microenvironment and their potential applications.

Heparan sulfate proteoglycan-mediated dynamin-dependent transport of neural stem cell exosomes in an in vitro blood-brain barrier model

Drug delivery to the brain is greatly hampered by the presence of the blood–brain barrier (BBB) which tightly regulates the passage of molecules from blood to brain and vice versa. Nanocarriers, in which drugs can be encapsulated, can move across the blood–brain barrier (BBB) via the process of transcytosis, thus showing promise to improve drug delivery to the brain. Here, we demonstrate the use of natural nanovesicles, that is, exosomes, derived from C17.2 neural stem cells (NSCs) to efficiently carry a protein cargo across an in vitro BBB model consisting of human brain microvascular endothelial cells. We show that the exosomes are primarily taken up in brain endothelial cells via endocytosis, while heparan sulfate proteoglycans (HSPGs) act as receptors. Taken together, our data support the view that NSC exosomes may act as biological nanocarriers for efficient passage across the BBB. Nanomedicines that target HSPGs may improve their binding to brain endothelial cells and, possibly, show subsequent transcytosis across the BBB.

Management of epileptic disorders using nanotechnology-based strategies for nose-to-brain drug delivery

INTRODUCTION

Epilepsy, a major neurological disorder affects about 1% of the Indian population. The discovery of noninvasive strategies for epilepsy presents a challenge for the scientists. Different types of nose-to-brain dosage-forms have been studied for epilepsy management. It aims to give new perspectives for developing new and existing anti-epileptic drugs. Combining nanotechnology with nose-to-brain approach can help in promoting the treatment efficacy by site-specific delivery. Also, it will minimize the side-effects and patient noncompliance observed in conventional administration routes. Peptide delivery can be an interesting approach for the management of epilepsy. Drug-loaded intranasal nanoformulations exhibit diverse prospective potentials in the management of epilepsy. Considering that, nanotherapy using nose-to-brain delivery as a prospective technique for the efficient management of epilepsy is reviewed.

AREAS COVERED

The authors have compiled all recently available data pertaining to the nose-to-brain delivery of therapeutics using nanotechnological strategies. The fundamental mechanism of nose-to-brain delivery, claims for intranasal delivery and medical devices for epilepsy are discussed.

EXPERT OPINION

Drug-loaded intranasal nanoformulations exhibit different prospective potentials in the management of epilepsy. Considering the foregoing research done in the field of nanotechnology, globally, authors propose nose-to-brain delivery of nanoformulations as a potential technique for the efficient management of epilepsy.

CB1-Antibody Modified Liposomes for Targeted Modulation of Epileptiform Activities Synchronously Detected by Microelectrode Arrays

Temporal lobe epilepsy (TLE) is a focal, recurrent, and refractory neurological disorder. Therefore, precisely targeted treatments for TLE are greatly needed. We designed anti-CB1 liposomes that can bind to CB1 receptors in the hippocampus to deliver photocaged compounds (ruthenium bipyridine triphenylphosphine γ-aminobutyric acid, RuBi-GABA) in the TLE rats. A 16-channel silicon microelectrode array (MEA) was implanted for simultaneously monitoring electrophysiological signals of neurons. The results showed that anti-CB1 liposomes were larger in size and remained in the hippocampus longer than unmodified liposomes. Following the blue light stimulation, the neural firing rates and the local field potentials of hippocampal neurons were significantly reduced. It is indicated that RuBi-GABA was enriched near hippocampal neurons due to anti-CB1 liposome delivery and photolyzed by optical stimulation, resulting dissociation of GABA to exert inhibitory actions. Furthermore, K-means cluster analysis revealed that the firing rates of interneurons were decreased to a greater extent than those of pyramidal neurons, which may have been a result of the uneven diffusion of RuBi-GABA due to liposomes binding to CB1. In this study, we developed a novel, targeted method to regulate neural electrophysiology in the hippocampus of the TLE rat using antibody-modified nanoliposomes, implantable MEA, and photocaged compounds. This method effectively suppressed hippocampal activities during seizure ictus with high spatiotemporal resolution, which is a crucial exploration of targeted therapy for epilepsy.

Bone marrow stromal cells-derived exosomes target DAB2IP to induce microglial cell autophagy, a new strategy for neural stem cell transplantation in brain injury

Bone marrow stromal cells (MSCs) are a useful source of stem cells for the treatment of various brain injury diseases due to their abundant supply and fewer ethical problems compared with transplant treatment. However, the clinical application of MSCs is limited due to allograft rejection and immunosuppression in the process of MSCs transplantation. According to previous studies, microglial cell autophagy occurs following co-culture with MSCs. In the present study, exosomes were obtained from MSCs and subsequently characterized using transmission electron microscopy, atomic force microscopy and dynamic light scattering particle size analysis. The type of microRNAs (miRs) found in the exosomes was then analyzed via gene chip. The results demonstrated that microglial cell autophagy could be induced by exosomes. This mechanism was therefore investigated further via reverse transcription-quantitative PCR, western blotting and luciferase assays. These results demonstrated that exosomes from MSCs could induce microglial cell autophagy through the miR-32-mediated regulation of disabled homolog 2-interacting protein, thus providing a theoretical basis for the clinical application of miRs in MSCs.

AmyloLipid Nanovesicles: A self-assembled lipid-modified starch hybrid system constructed for direct nose-to-brain delivery of curcumin

AmyloLipid nanovesicles (ALNs) are new lipid-modified starch complex nanoparticles developed and presented as nanocarriers of curcumin for targeting the CNS via the intranasal route. Curcumin has been indicated as a promising active agent with a variety of pharmacological activities, including a potential ability to treat brain tumors, traumatic brain injury, and CNS disorders, such as Alzheimer's disease, as it may inhibit amyloid-β-protein (Aβ) aggregation and Aβ-induced inflammation. Although curcumin has a tremendous potential as a therapeutic agent for CNS disorders, its low bioavailability and its rapid total body clearance reduce any chance for therapeutic levels to reach the brain. By using an optimized (2% crosslinked starch) curcumin-loaded ALNs, which was fabricated from a microemulsion as a precursor, an average of 141.5 ± 55.9 ng/g brain levels and 11.9 ± 12.0 ng/ml plasma concentrations were detected, one hour following intranasal administration of 160 μg/kg dose of curcumin. In comparison, 1 h after IV administration of the same dose, no CUR was detected in the brain and the mean plasma level was approximately one half of the level monitored after intranasal ALNs, i.e., 7.25 ± 0.20 ng/ml. It has been clearly demonstrated, therefore, that a well-designed ALN formulation proved itself as a promising carrier for intranasal delivery and brain targeting of curcumin.

Surface Modification of Iron Oxide-Based Magnetic Nanoparticles for Cerebral Theranostics: Application and Prospection

Combining diagnosis with therapy, magnetic iron oxide nanoparticles (INOPs) act as an important vehicle for drug delivery. However, poor biocompatibility of INOPs limits their application. To improve the shortcomings, various surface modifications have been developed, including small molecules coatings, polymers coatings, lipid coatings and lipopolymer coatings. These surface modifications facilitate iron nanoparticles to cross the blood-brain-barrier, which is essential for diagnosis and treatments of brain diseases. Here we focus on the characteristics of different coated INOPs and their application in brain disease, particularly gliomas, Alzheimer's disease (AD) and Parkinson's disease (PD). Moreover, we summarize the current progress and expect to provide help for future researches.

Endocytosis in cellular uptake of drug delivery vectors: Molecular aspects in drug development

Drug delivery vectors are widely applied to increase drug efficacy while reducing the side effects and potential toxicity of a drug. They allow for patient-tailored therapy, dose titration, and therapeutic drug monitoring. A major part of drug delivery systems makes use of large nanocarriers: liposomes or virus-like particles (VLPs). These systems allow for a relatively large amount of cargo with good stability of vectors, and they offer multiple options for targeting vectors in vivo. Here we discuss endocytic pathways that are available for drug delivery by large nanocarriers. We focus on molecular aspects of the process, including an overview of potential molecular targets for studies of drug delivery vectors and for future solutions allowing targeted drug delivery.

Solid Lipid Nanoparticles Enhanced the Neuroprotective Role of Curcumin against Epilepsy through Activation of Bcl-2 Family and P38 MAPK Pathways

Oxidative stress of neurons caused by a series of complex neuropathological processes will induce certain neurodegenerative disorders including epilepsy. Curcumin (Cur) is an effective natural antioxidant compound; however, the poor bioavailability obstructs its neural protective applications. In this study, Cur is encapsulated in solid lipid nanoparticles (SLNs) for better neuroprotective efficacy. In vitro study certified that Cur-SLNs functioned obviously better against neuronal apoptosis than Cur, by significantly decreasing the level of free radical and reversing mitochondrial function through the activation of the Bcl-2 family. In vivo experiments showed that SLNs transported Cur through the blood-brain barrier (BBB). The behavioral performance of epileptic mice was improved by Cur-SLNs, with more NeuN but less TUNEL positive cells observed in hippocampus. The in vivo mechanism was also explored. Cur-SLNs reduced neuronal apoptosis through Bcl2 family and P38 MAPK pathways. Overall, Cur-SLNs have better protective effects toward oxidative stress in neurons than free Cur both in vitro and in vivo, which suggests they may be a promising agent against neurodegenerative disorders including epilepsy.

Antioxidant nanomedicine with cytoplasmic distribution in neuronal cells shows superior neurovascular protection properties

This study investigated whether nitroxide radical (4-amino-TEMPOL)-containing nanoparticles (RNPs; antioxidant nanomedicine) can prevent neurovascular unit impairment caused by reactive oxygen species (ROS) after cerebral ischemia-reperfusion. C57BL/6J mice underwent transient middle cerebral artery occlusion (tMCAO). The mice were randomly divided and administered intra-arterial RNPs injection (9 mg/kg, 7 μM/kg), edaravone (3 mg/kg, 17 μM/kg), or phosphate-buffered saline (control group). Survival rate and neurological score were evaluated 24 h post-injection. RNPs distribution was determined using immunofluorescence staining and blood-brain barrier (BBB) disruption using Evans blue extravasation assay. Effect of RNPs and edaravone on microglia polarization into microglia M1 and M2 was evaluated. We also determined multiple ROS-scavenging activities in brain homogenates of RNPs- and edaravone-treated animals using an electron spin resonance-based spin-trapping method. Compared with edaravone, RNPs significantly improved the survival rate and neurological deficit, inhibited BBB disruption and supported polarization of microglia into M2 microglia. RNPs were localized in endothelial cells, the perivascular space, neuronal cell cytoplasm, astrocytes, and microglia. Scavenging capacities of hydroxyl, alkoxyl, and peroxyl radicals were significantly higher in the RNPs-treated group. RNPs show promising results as a future neuroprotective nanomedicine approach for cerebral ischemia-reperfusion injury.

Recent strategies and advances in the fabrication of nano lipid carriers and their application towards brain targeting

In last two decades, the lipid nanocarriers have been extensively investigated for their drug targeting efficiency towards the critical areas of the human body like CNS, cardiac region, tumor cells, etc. Owing to the flexibility and biocompatibility, the lipid-based nanocarriers, including nanoemulsion, liposomes, SLN, NLC etc. have gained much attention among various other nanocarrier systems for brain targeting of bioactives. Across different lipid nanocarriers, NLC remains to be the safest, stable, biocompatible and cost-effective drug carrier system with high encapsulation efficiency. Drug delivery to the brain always remains a challenging issue for scientists due to the complex structure and various barrier mechanisms surrounding the brain. The application of a suitable nanocarrier system and the use of any alternative route of drug administration like nose-to-brain drug delivery could overcome the hurdle and improves the therapeutic efficiency of CNS acting drugs thereof. NLC, a second-generation lipid nanocarrier, upsurges the drug permeation across the BBB due to its unique structural properties. The biocompatible lipid matrix and nano-size make it an ideal drug carrier for brain targeting. It offers many advantages over other drug carrier systems, including ease of manufacturing and scale-up to industrial level, higher drug targeting, high drug loading, control drug release, compatibility with a wide range of drug substances, non-toxic and non-irritant behavior. This review highlights recent progresses towards the development of NLC for brain targeting of bioactives with particular reference to its surface modifications, formulations aspects, pharmacokinetic behavior and efficacy towards the treatment of various neurological disorders like AD, PD, schizophrenia, epilepsy, brain cancer, CNS infection (viral and fungal), multiple sclerosis, cerebral ischemia, and cerebral malaria. This work describes in detail the role and application of NLC, along with its different fabrication techniques and associated limitations. Specific emphasis is given to compile a summary and graphical data on the area explored by scientists and researchers worldwide towards the treatment of neurological disorders with or without NLC. The article also highlights a brief insight into two prime approaches for brain targeting, including drug delivery across BBB and direct nose-to-brain drug delivery along with the current global status of specific neurological disorders.

Combined-therapeutic strategies synergistically potentiate glioblastoma multiforme treatment via nanotechnology

Glioblastoma multiforme (GBM) is a highly aggressive and devastating brain tumor characterized by poor prognosis and high rates of recurrence. Numerous therapeutic strategies and delivery systems are developed to prolong the survival time. They exhibit enhanced therapeutic effects in animal models, whereas few of them is applied in clinical trials. Taking into account the drug-resistance and high recurrence of GBM, combined-therapeutic strategies are exploited to maximize therapeutic efficacy. The combined therapies demonstrate superior results than those of single therapies against GBM. The co-therapeutic agents, the timing of therapeutic strategies and the delivery systems greatly affect the overall outcomes. Herein, the current advances in combined therapies for glioblastoma via systemic administration are exhibited in this review. And we will discuss the pros and cons of these combined-therapeutic strategies via nanotechnology, and provide the guidance for developing rational delivery systems to optimize treatments against GBM and other malignancies in central nervous system.

Rabies virus glycoprotein-amplified hierarchical targeted hybrids capable of magneto-electric penetration delivery to orthotopic brain tumor

Compact nanohybrids can potentially unite various therapeutic features and reduce side effects for precise cancer therapy. However, the poor accumulation and limited tumor penetration of drugs at the tumor impede the manifestation of nanomedicine. We developed a rabies virus glycoprotein (RVG)-amplified hierarchical targeted hybrid that acts as a stealthy and magnetolytic carrier that transports dual tumor-penetrating agents incorporating two drugs (boron-doped graphene quantum dots (B-GQDs)/doxorubicin and pH-responsive dendrimers (pH-Den)/palbociclib). The developed RVG-decorated hybrids (RVG-hybrids) enhance the accumulation of drugs at tumor by partially bypassing the BBB via spinal cord transportation and pH-induced aggregation of hierarchical targeting. The penetrated delivery of dual pH-Den and B-GQD drugs to deep tumors is actuated by magnetoelectric effect, which are able to generate electrons to achieve electrostatic repulsion and disassemble the hybrids into components of a few nanometers in size. The synergy of magnetoelectric drug penetration and chemotherapy was achieved by delivery of the B-GQDs and pH-Den to orthotopic tumors, which prolonged the host survival time. This RVG-amplified dual hierarchical delivery integrated with controlled and penetrated release from this hybrid improve the distribution of the therapeutic agents at the brain tumor for synergistic therapy, exhibiting potential for clinic use.

Chitosan mediated solid lipid nanoparticles for enhanced liver delivery of zedoary turmeric oil in vivo

Zedoary turmeric oil (ZTO) has a strong antitumor activity. However, its volatility, insolubility, low bioavailability, and difficulty of medication owing to oily liquid limit its clinical applications. Solid lipid nanoparticles can provide hydrophobic environment to dissolve hydrophobic drug and solidify the oily active composition to decrease the volatility and facilitate the medication. Chitosan has been widely used in pharmaceutics in recent years and coating with chitosan further enhances the internalization of particles by cells due to charge attract. Here, Chitosan (CS)-coated solid lipid nanoparticles (SLN) loaded with ZTO was prepared and characterized using dynamic laser scanner (DLS) and transmission electron microscope (TEM). The uptake and distribution of drug were evaluated in vitro and in vivo. The average sizes of ZTO-SLN and CS-ZTO-SLN were 134.3 ± 3.42 nm and 210.7 ± 4.59 nm, respectively. CS coating inverted the surface charge of particles from -8.93 ± 1.92 mV to +9.12 ± 2.03 mV. The liver accumulation of CS-ZTO-SLN was higher than ZTO-SLN (chitosan-uncoated particles) by analysis of tissue homogenate using HPLC, and the bioavailability of ZTO was also obviously improved. The results suggested that SLN coated with CS improved the features of ZTO formulation and efficiently deliver drug to the liver.

PEGylated nanocarriers: A promising tool for targeted delivery to the brain

Targeted drug delivery across the blood-brain barrier is an extremely challenging quest in the fight with fatal brain ailments, with the major hurdles being short circulation time, reticuloendothelial system (RES) uptake, and excretion of nanocarriers. PEGylation has emerged as a boon for targeted drug delivery to the brain. It is well established that PEGylation can increase the circulation time of nanocarriers by avoiding RES uptake, which is indispensable for increasing the brain's uptake of nanocarriers. PEGylation also acts as a linker for ligand molecules to achieve active targeting to the brain. Using PEGylation, novel approaches are being investigated to facilitate ligand-receptor interactions at the brain endothelium to ease the entry of therapeutic drugs into the brain. In addition, PEGylation made it simpler to assess the brain tissue for delivering diagnostic molecules and theranostic nanocarriers. The potential of PEGylated nanocarriers is being investigated vastly to boost the therapeutic effect several fold in the treatment of brain diseases. This review sheds light on the contribution of PEGylated nanocarriers, especially liposomes, polymeric nanoparticles, and dendrimers for brain-specific delivery of bioactives.

Dual-responsive nanogels based on oligo(ethylene glycol) methacrylates and acidic co-monomers

Ethylene glycol-based nanogels (NGs) have demonstrated their potential for the development of next-generation formulations for biomedical applications due to their interesting properties. In this work, monodispersed NGs based on oligo(ethylene glycol) methacrylates (OEG) were synthesized through free radical precipitation/dispersion polymerization assisted by ultrasonication. Di(ethylene glycol)methyl ether methacrylate (DEGMA) and oligo(ethylene glycol) methacrylate (OEGMA; Mn 475 g mol-1) were used as the main monomers, acrylic acid (AA) or itaconic acid (IA) as co-monomers (OEG-co-AA and OEG-co-IA, respectively) and tetraethylene glycol dimethacrylate (TEGDMA) as crosslinker. The physicochemical properties of OEG-co-AA and OEG-co-IA NGs were studied including hydrodynamic diameter, poly-dispersity index, zeta potential and pH/temperature responsiveness. Samples with 4 mol% of both AA and IA showed nanometric sizes. Regarding their thermo-responsiveness, unexpected differences between NGs with AA or with IA were observed. Besides, NGs did not impair the cell viability of a breast tumour cell line even when high concentrations were added to the culture medium. The properties of the synthetized NGs showed that either NGs with 4% AA or with 4% IA are outstanding candidates for biomedical applications.

Dual and multi-targeted nanoparticles for site-specific brain drug delivery

In recent years, nanomedicines have emerged as a promising method for central nervous system drug delivery, enabling the drugs to overcome the blood-brain barrier and accumulate preferentially in the brain. Despite the current success of brain-targeted nanomedicines, limitations still exist in terms of the targeting specificity. Based on the molecular mechanism, the exact cell populations and subcellular organelles where the injury occurs and the drugs take effect have been increasingly accepted as a more specific target for the next generation of nanomedicines. Dual and multi-targeted nanoparticles integrate different targeting functionalities and have provided a paradigm for precisely delivering the drug to the pathological site inside the brain. The targeting process often involves the sequential or synchronized navigation of the targeting moieties, which allows highly controlled drug delivery compared to conventional targeting strategies. Herein, we focus on the up-to-date design of pathological site-specific nanoparticles for brain drug delivery, highlighting the dual and multi-targeting strategies that were employed and their impact on improving targeting specificity and therapeutic effects. Furthermore, the background discussion of the basic properties of a brain-targeted nanoparticle and the common lesion features classified by neurological pathology are systematically summarized.