Drug delivery across the blood-brain barrier: recent advances in the use of nanocarriers

Applications of Phyto-Nanotechnology for the Treatment of Neurodegenerative Disorders

The strategies involved in the development of therapeutics for neurodegenerative disorders are very complex and challenging due to the existence of the blood-brain barrier (BBB), a closely spaced network of blood vessels and endothelial cells that functions to prevent the entry of unwanted substances in the brain. The emergence and advancement of nanotechnology shows favourable prospects to overcome this phenomenon. Engineered nanoparticles conjugated with drug moieties and imaging agents that have dimensions between 1 and 100 nm could potentially be used to ensure enhanced efficacy, cellular uptake, specific transport, and delivery of specific molecules to the brain, owing to their modified physico-chemical features. The conjugates of nanoparticles and medicinal plants, or their components known as nano phytomedicine, have been gaining significance lately in the development of novel neuro-therapeutics owing to their natural abundance, promising targeted delivery to the brain, and lesser potential to show adverse effects. In the present review, the promising application, and recent trends of combined nanotechnology and phytomedicine for the treatment of neurological disorders (ND) as compared to conventional therapies, have been addressed. Nanotechnology-based efforts performed in bioinformatics for early diagnosis as well as futuristic precision medicine in ND have also been discussed in the context of computational approach.

Nanomedicine in Clinical Photodynamic Therapy for the Treatment of Brain Tumors

The current treatment for malignant brain tumors includes surgical resection, radiotherapy, and chemotherapy. Nevertheless, the survival rate for patients with glioblastoma multiforme (GBM) with a high grade of malignancy is less than one year. From a clinical point of view, effective treatment of GBM is limited by several challenges. First, the anatomical complexity of the brain influences the extent of resection because a fine balance must be struck between maximal removal of malignant tissue and minimal surgical risk. Second, the central nervous system has a distinct microenvironment that is protected by the blood–brain barrier, restricting systemically delivered drugs from accessing the brain. Additionally, GBM is characterized by high intra-tumor and inter-tumor heterogeneity at cellular and histological levels. This peculiarity of GBM-constituent tissues induces different responses to therapeutic agents, leading to failure of targeted therapies. Unlike surgical resection and radiotherapy, photodynamic therapy (PDT) can treat micro-invasive areas while protecting sensitive brain regions. PDT involves photoactivation of photosensitizers (PSs) that are selectively incorporated into tumor cells. Photo-irradiation activates the PS by transfer of energy, resulting in production of reactive oxygen species to induce cell death. Clinical outcomes of PDT-treated GBM can be advanced in terms of nanomedicine. This review discusses clinical PDT applications of nanomedicine for the treatment of GBM.

Enhancing the Therapeutic Potential of Extracellular Vesicles Using Peptide Technology

Extracellular vesicles are lipid-bilayer-enclosed nanoparticles present in the majority of biological fluids that mediate intercellular communication. EVs are able to transfer their contents (including nucleic acids, proteins, lipids, and small molecules) to recipient cells, and thus hold great promise as drug delivery vehicles. However, their therapeutic application is limited by lack of efficient cargo loading strategies, a need to improve EV tissue-targeting capabilities and a requirement to improve escape from the endolysosomal system. These challenges can be effectively addressed by modifying EVs with peptides which confer specific advantageous properties, thus enhancing their therapeutic potential. Here we provide an overview of the applications of peptide technology with respect to EV therapeutics. We focus on the utility of EV-modifying peptides for the purposes of promoting cargo loading, tissue-targeting and endosomal escape, leading to enhanced delivery of the EV cargo to desired cells/tissues and subcellular target locations. Both endogenous and exogenous methods for modifying EVs with peptides are considered.

Nanocarriers Call the Last Shot in the Treatment of Brain Cancers

Our brain is protected by physio-biological barriers. The blood–brain barrier (BBB) main mechanism of protection relates to the abundance of tight junctions (TJs) and efflux pumps. Although BBB is crucial for healthy brain protection against toxins, it also leads to failure in a devastating disease like brain cancer. Recently, nanocarriers have been shown to pass through the BBB and improve patients’ survival rates, thus becoming promising treatment strategies. Among nanocarriers, inorganic nanocarriers, solid lipid nanoparticles, liposomes, polymers, micelles, and dendrimers have reached clinical trials after delivering promising results in preclinical investigations. The size of these nanocarriers is between 10 and 1000 nm and is modified by surface attachment of proteins, peptides, antibodies, or surfactants. Multiple research groups have reported transcellular entrance as the main mechanism allowing for these nanocarriers to cross BBB. Transport proteins and transcellular lipophilic pathways exist in BBB for small and lipophilic molecules. Nanocarriers cannot enter via the paracellular route, which is limited to water-soluble agents due to the TJs and their small pore size. There are currently several nanocarriers in clinical trials for the treatment of brain cancer. This article reviews challenges as well as fitting attributes of nanocarriers for brain tumor treatment in preclinical and clinical studies.

Recent Advances in Functional Polymer Materials for Energy, Water, and Biomedical Applications: A Review

Academic research regarding polymeric materials has been of great interest. Likewise, polymer industries are considered as the most familiar petrochemical industries. Despite the valuable and continuous advancements in various polymeric material technologies over the last century, many varieties and advances related to the field of polymer science and engineering still promise a great potential for exciting new applications. Research, development, and industrial support have been the key factors behind the great progress in the field of polymer applications. This work provides insight into the recent energy applications of polymers, including energy storage and production. The study of polymeric materials in the field of enhanced oil recovery and water treatment technologies will be presented and evaluated. In addition, in this review, we wish to emphasize the great importance of various functional polymers as effective adsorbents of organic pollutants from industrial wastewater. Furthermore, recent advances in biomedical applications are reviewed and discussed.

Multifunctional exosome-mimetics for targeted anti-glioblastoma therapy by manipulating protein corona

Targeted drug delivery to the glioblastoma (GBM) overcoming blood–brain barrier (BBB) has been challenging. Exosomes are promising vehicles for brain tumor drug delivery, but the production and purification hinder its application for nanomedicine. Besides, the formation of protein corona (PC) may affect the behaviour of nanocarriers. Here, multifunctional exosomes-mimetics (EM) are developed and decorated with angiopep-2 (Ang) for enhancing GBM drug delivery by manipulating PC. Docetaxel (DTX)-loaded EM with Ang modification (DTX@Ang-EM) show less absorption of serum proteins and phagocytosis by macrophages. Ang-EM show enhanced BBB penetration ability and targeting ability to the GBM. Ang-EM-mediated delivery increase the concentration of DTX in the tumor area. The multifunctional DTX@Ang-EM exhibits significant inhibition effects on orthotopic GBM growth with reduced side effects of the chemotherapeutic. Findings from this study indicate that the developed DTX@Ang-EM provide a new strategy for targeted brain drug delivery and GBM therapy.

Preparation, characterization, and in vivo biodistribution study of intranasal 131I-clonazepam-loaded phospholipid magnesome as a promising brain delivery system: Biodistribution and pharmacokinetic behavior of intranasal 131I-Clonazepam loaded phospholipid magnesome as a potential brain targeting system

OBJECTIVE

Clonazepam (CP) is a potent long-acting nitrobenzodiazepine derivative that could be used for targeting peripheral benzodiazepine receptors. Phospholipid magnesome is a new vesicular nanosystem recently developed for brain targeting. Improving the uptake of ¹³¹I-CP to the brain might be effective for the diagnosis and/or radiotherapy of certain brain diseases and/or tumors.

METHODS

CP was radiolabeled with ¹³¹I using direct electrophilic substitution reaction. Quality control of ¹³¹I-CP was performed using different techniques. Different formulas of ¹³¹I-CP were prepared and characterized according to particle size and polydispersity index. The structural features of the optimized formula were then interpreted using transmission electron microscopy and scanning electron microscopy, whereas pharmacokinetic and in vivo behaviors were estimated using the intravenous and intranasal delivery routes.

RESULTS

The heart and blood demonstrated lower uptake of ¹³¹I-CP, which inevitably decreased the nontarget effects of radioiodine. Intranasally administered ¹³¹I-CP-loaded magnesomes (INMg) had noticeably higher brain uptake (7.1 ± 0.09%ID/g) with rapid onset of action within 5 min and effective pharmacokinetic behavior. INMg had a drug targeting efficiency and nose-to-brain direct transport percentage of 121.1% and 94.6%, respectively as well as a relative bioavailability of 441.04 ± 75.5%.

CONCLUSION

The present study showed that ¹³¹I-CP-loaded magnesomes can be a beneficial brain-targeting approach for improving the diagnosis and/or radiotherapy of certain brain diseases.

The Multifaceted Role of Curcumin in Advanced Nanocurcumin Form in the Treatment and Management of Chronic Disorders

Curcumin is the primary polyphenol in turmeric's curcuminoid class. It has a wide range of therapeutic applications, such as anti-inflammatory, antioxidant, antidiabetic, hepatoprotective, antibacterial, and anticancer effects against various cancers, but has poor solubility and low bioavailability. Objective: To improve curcumin's bioavailability, plasma concentration, and cellular permeability processes. The nanocurcumin approach over curcumin has been proven appropriate for encapsulating or loading curcumin (nanocurcumin) to increase its therapeutic potential. Conclusion: Though incorporating curcumin into nanocurcumin form may be a viable method for overcoming its intrinsic limitations, and there are reasonable concerns regarding its toxicological safety once it enters biological pathways. This review article mainly highlights the therapeutic benefits of nanocurcumin over curcumin.

Tween® Preserves Enzyme Activity and Stability in PLGA Nanoparticles

Enzymes, as natural and potentially long-term treatment options, have become one of the most sought-after pharmaceutical molecules to be delivered with nanoparticles (NPs); however, their instability during formulation often leads to underwhelming results. Various molecules, including the Tween^® polysorbate series, have demonstrated enzyme activity protection but are often used uncontrolled without optimization. Here, poly(lactic-co-glycolic) acid (PLGA) NPs loaded with β-glucosidase (β-Glu) solutions containing Tween^® 20, 60, or 80 were compared. Mixing the enzyme with Tween^® pre-formulation had no effect on particle size or physical characteristics, but increased the amount of enzyme loaded. More importantly, NPs made with Tween^® 20:enzyme solutions maintained significantly higher enzyme activity. Therefore, Tween^® 20:enzyme solutions ranging from 60:1 to 2419:1 mol:mol were further analyzed. Isothermal titration calorimetry analysis demonstrated low affinity and unquantifiable binding between Tween^® 20 and β-Glu. Incorporating these solutions in NPs showed no effect on size, zeta potential, or morphology. The amount of enzyme and Tween^® 20 in the NPs was constant for all samples, but a trend towards higher activity with higher molar rapports of Tween^® 20:β-Glu was observed. Finally, a burst release from NPs in the first hour with Tween^®:β-Glu solutions was the same as free enzyme, but the enzyme remained active longer in solution. These results highlight the importance of stabilizers during NP formulation and how optimizing their use to stabilize an enzyme can help researchers design more efficient and effective enzyme loaded NPs.

Anti-glioblastoma effects of nanomicelle-curcumin plus erlotinib

Glioblastoma (GBM), one of the most significant brain neoplasms, is characterized by high metastasis and recurrence. Crossing the blood-brain barrier is one of the main therapeutic obstacles, seriously hampering therapeutic agents entering the brain. This research investigated the co-delivery of erlotinib and curcumin via nanomicelles for enhancing anti-GBM treatment in vitro. For this purpose, curcumin and nanomicelle-curcumin (50 μM) were investigated alone and also with erlotinib (50 μM) in U87 glioblastoma cells. The cell viability of U87 cells after exposure to curcumin/nanomicelle curcumin/erlotinib and their combinations was measured by CCK-8 assay. The expression of the Wnt signaling-related genes was measured by qRT-PCR assay. The altered expression of NF-kB and proteins associated with angiogenesis, apoptosis, and autophagy were investigated by western blot assay. Compared with the control, all treatments reduced the viability of U87 glioblastoma cells. Furthermore, the level of proteins related to angiogenesis and Wnt pathway-associated genes in the nanomicelle-curcumin + erlotinib group were significantly decreased compared to the curcumin, erlotinib, and control groups. Each treatment regulated autophagy and apoptosis-associated proteins. Total phospho-NF-κB (p65) and total NF-κB (p65) declined in each treatment at the protein levels. Overall, nanomicelle-curcumin alone or combined with erlotinib showed anti-GBM activity in the U87 cell line by regulating the signaling pathways in GBM pathogenesis and thus may be a promising nanodrug candidate for application in the field of GBM therapy.

Nanobiotechnology-assisted therapies to manage brain cancer in personalized manner

There are numerous investigated factors that limit brain cancer treatment efficacy such as ability of prescribed therapy to cross the blood-brain barrier (BBB), tumor specific delivery of a therapeutics, transport within brain interstitium, and resistance of tumor cells against therapies. Recent breakthroughs in the field of nano-biotechnology associated with developing multifunctional nano-theranostic emerged as an effective way to manage brain cancer in terms of higher efficacy and least possible adverse effects. Keeping challenges and state-of-art accomplishments into consideration, this review proposes a comprehensive, careful, and critical discussion focused on efficient nano-enabled platforms including nanocarriers for drug delivery across the BBB and nano-assisted therapies (e.g., nano-immunotherapy, nano-stem cell therapy, and nano-gene therapy) investigated for brain cancer treatment. Besides therapeutic efficacy point-of-view, efforts are being made to explore ways projected to tune such developed nano-therapeutic for treating patients in personalized manner via controlling size, drug loading, delivery, and retention. Personalized brain tumor management based on advanced nano-therapies can potentially lead to excellent therapeutic benefits based on unique genetic signatures in patients and their individual disease profile. Moreover, applicability of nano-systems as stimulants to manage the brain cancer growth factors has also been discussed in photodynamic therapy and radiotherapy. Overall, this review offers a comprehensive information on emerging opportunities in nanotechnology for advancing the brain cancer treatment.

Transferrin-Pep63-liposomes accelerate the clearance of Aβ and rescue impaired synaptic plasticity in early Alzheimer's disease models

Alzheimer’s disease (AD) is characterized by aberrant accumulation of extracellular β-amyloid (Aβ) peptides in the brain. Soluble Aβ oligomers are thought to be the most neurotoxic species and are correlated with cognitive dysfunction in early AD. However, there is still no effective treatment so far. We determined that Pep63, a small peptide, had a neuroprotective effect on synaptic plasticity and memory in our previous study. Here, we developed novel and multifunctional liposomes targeting both Aβ oligomers and fibrils based on a liposome delivery system. Transferrin-Pep63-liposomes (Tf-Pep63-Lip), possessing the ability for blood-brain barrier targeting, were also incorporated with phosphatidic acid (PA) and loaded with neuroprotective Pep63. We discovered that administration of Tf-Pep63-Lip could significantly reduce the Aβ burden in the hippocampus, and improve cognitive deficits in 6-month-old APP/PS1 mice in the Morris-Water maze task and fear-conditioning test with the combined effects of PA and Pep63. Tf-Pep63-Lip could capture Aβ oligomers or fibrils and then facilitated microglial chemotaxis nearby for clearance. Simultaneously, Tf-Pep63-Lip hindered Aβ1-42 aggregation and disaggregated Aβ1-42 assembly due to multivalent PA-Aβ. Pep63 effectively inhibited the binding between EphB2 and Aβ oligomers after release from liposomes and rescued NMDA receptors trafficking, the basis of synaptic plasticity. No side effects were observed in either APP/PS1 or wild-type mice, indicating that Tf-Pep63-Lip might be safe under the dosing regimen used in our experiment. Taken together, our results suggested that Tf-Pep63-Lip may serve as a safe and efficient agent for AD combination therapy.

The effect of serum starvation on tight junctional proteins and barrier formation in Caco-2 cells

Assessing the ability of pharmaceutics to cross biological barriers and reach the site-of-action requires faithful representation of these barriers in vitro. Difficulties have arisen in replicating in vivo resistance in vitro. This paper investigated serum starvation as a method to increase Caco-2 barrier stability and resistance. The effect of serum starvation on tight junction production was examined using transwell models; specifically, transendothelial electrical resistance (TEER), and the expression and localization of tight junction proteins, occludin and zonula occludens-1 (ZO-1), were studied using western blotting and immunofluorescence. Changing cells to serum-free media 2 days post-seeding resulted in TEER readings of nearly 5000 Ω cm² but the TEER rapidly declined subsequently. Meanwhile, exchanging cells to serum-free media 4–6 days post-seeding produced barriers with resistance readings between 3000 and 4000 Ω cm², which could be maintained for 18 days. This corresponded to an increase in occludin levels. Serum starvation as a means of barrier formation is simple, reproducible, and cost-effective. It could feasibly be implemented in a variety of pre-clinical pharmaceutical assessments of drug permeability across various biological barriers with the view to improving the clinical translation of novel therapeutics.

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Serum starvation increases the intracellular resistance of Caco-2 cells.

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Max TEER values of 4783 ± 610 Ω cm² were achieved in serum free conditions.

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A barrier of 3000–4000 Ω cm² could be maintained for up to 18 days.

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Serum starvation leads to a significant increase in occludin expression.

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Occludin levels correlate significantly with corresponding TEER values.

Dynamic nanoassemblies for imaging and therapy of neurological disorders

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

The combination of nanotechnology and traditional Chinese medicine (TCM) inspires the modernization of TCM: review on nanotechnology in TCM-based drug delivery systems

Fast development of combination of nanotechnology with traditional Chinese medicine (TCM) broadens the field of application of TCM. Besides, it increases the research ideas and contributes to TCM modernization. As expected, TCM will be developed into the nanodrug delivery system by nanotechnology with careful design, which will enhance the medicinal value of TCM to cure and prevent disease based on benefits brought by nanometer scale. Here, formulations, relevant preparations methods, and characteristics of nano-TCM were introduced. In addition, the main excellent performances of nano-TCM were clearly elaborated. What is more, the review was intended to address the studies committed to application of nanotechnology in TCM over the years, including development of Chinese medicine active ingredients, complete TCM, and Chinese herbal compounds based on nanotechnology. Finally, this review discussed the safety of nano-TCM and presented future development trends in the way to realize the modernization of TCM. Overall, using the emerging nanotechnology in TCM is promising to promote progress of TCM in international platform. Recent researches on modernization of traditional Chinese medicine (TCM) urged by nanotechnology are introduced, and formulations, advantages, and applications of nano-TCM are reviewed to provide strong proofs.

PLGA-Based Nanoparticles for Neuroprotective Drug Delivery in Neurodegenerative Diseases

Treatment of neurodegenerative diseases has become one of the most challenging topics of the last decades due to their prevalence and increasing societal cost. The crucial point of the non-invasive therapeutic strategy for neurological disorder treatment relies on the drugs' passage through the blood-brain barrier (BBB). Indeed, this biological barrier is involved in cerebral vascular homeostasis by its tight junctions, for example. One way to overcome this limit and deliver neuroprotective substances in the brain relies on nanotechnology-based approaches. Poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs) are biocompatible, non-toxic, and provide many benefits, including improved drug solubility, protection against enzymatic digestion, increased targeting efficiency, and enhanced cellular internalization. This review will present an overview of the latest findings and advances in the PLGA NP-based approach for neuroprotective drug delivery in the case of neurodegenerative disease treatment (i.e., Alzheimer's, Parkinson's, Huntington's diseases, Amyotrophic Lateral, and Multiple Sclerosis).

Exosomes and biomimetic nanovesicles-mediated anti-glioblastoma therapy: A head-to-head comparison

Exosomes (Exos) are promising vehicles for brain drug delivery due to nanosize and the ability to breach the blood-brain barrier (BBB). But the low yield of natural exosomes limits its application for nanomedicine. The generation of bioinspired nanovesicles (BNVs) that mimicking Exos is attractive, but there is a lack of comparative evaluation of Exos and BNVs. Here, we perform the first head-to-head comparison study of Exos and BNVs for brain tumor drug delivery. We show that BNVs derived from brain-derived endothelial cells are competent alternative nanocarrier to natural exosomes. The drug-loading capacity of Exos and BNVs are similar, but the yield of BNVs is substantially higher (500-fold) than Exos. Doxorubicin (DOX)-loaded BNVs (BNV/DOX) and DOX-loaded Exos (Exo/DOX) showed similar pharmacokinetic profiles and prolonged circulation od DOX. Despite inconsistent mechanisms, BNV/DOX can across the BBB, and exhibit suppression effects similar to Exo/DOX on the progress of glioblastoma (GBM) in zebrafish and in vivo subcutaneous and orthotopic xenografts mice models, with minimal systemic toxicity. Findings from this head-to-head comparison study indicate that autologous BNVs is a effective alternative of Exos for brain tumor nanomedicine.

Human Glioblastoma Visualization: Triple Receptor-Targeting Fluorescent Complex of Dye, SIWV Tetra-Peptide, and Serum Albumin Protein

Fluorescence guided surgery (FGS) has been highlighted in the clinical site for guiding surgical procedures and providing the surgeon with a real-time visualization of the operating field. FGS is a powerful technique for precise surgery, particularly tumor resection; however, clinically approved fluorescent dyes have often shown several limitations during FGS, such as non-tumor-targeting, low in vivo stability, insufficient emission intensity, and low blood-brain barrier penetration. In this study, we disclose a fluorescent dye complex, peptide, and protein for the targeted visualization of human glioblastoma (GBM) cells and tissues. Our noble triple receptor-targeting fluorescent complex (named BSA-OXN-SIWV) consists of (i) dipolar oxazepine dye (OXN), which has high stability, low cytotoxicity, bright fluorescence, and two-photon excitable, (ii) tetra-peptide (SIWV) for the targeting of the caveolin-1 receptor, and (iii) bovine serum-albumin (BSA) protein for the targeting of albondin (gp60) and secreted protein acidic and rich in cysteine receptor. The photophysical properties and binding mode of BSA-OXN-SIWV were analyzed, and the imaging of GBM cell lines and human clinical GBM tissues were successfully demonstrated in this study. Our findings hold great promise for the application of BSA-OXN-SIWV to GBM identification and the surgery at clinical sites, as a new FGS agent.

Multitarget therapeutic approaches for Alzheimer's and Parkinson's diseases: an opportunity or an illusion?

Alzheimer's and Parkinson's disease are the most prevalent neurodegenerative diseases and the leading causes of dementia worldwide. The etiology of these multifactorial pathologies is not completely known. The available therapeutic approaches can cause temporary relief of symptoms but cannot slow down their progression or cure them. Life-changing therapeutic solutions are urgently needed, as the number of people suffering from these pathologies has been increasing quickly over the last few decades. Several targets are being studied, and innovative approaches are being pursued to find new therapeutic options. This overview is focused on the most recent information regarding the paradigm of using multitarget compounds to treat both Alzheimer's and Parkinson's disease.

Self-Assembled Micelles of Amphiphilic PEGylated Drugs for Cancer Treatment

Generally, poor solubility and imprecise delivery of chemotherapeutic drugs can compromise their efficacies for clinical cancer treatment. In order to address such concerns, poor water-soluble drugs are conjugated with poly(ethylene glycol) (PEG) to obtain PEGylated drugs, which have improved water solubility and can also self-assemble in an aqueous solution to form micelles (PEGylated drug micelles). The surface PEG layer enhances the micelles' colloidal stability and reduces the interaction with physiological surroundings. Meanwhile, PEGylated drug micelles are tumor- targeting via the enhanced permeation and retention (EPR) effect to improve antitumor efficacy in comparison with free drugs. PEGylated drug micelles employ drugs as parts of the carrier medium, which increases the micelles' drug loading capacity relatively. The development of stimuli- responsive PEGylated drug micelles facilitates the drug release to be smart and controllable. Moreover, the PEGylated drug micelles show great potentials in overcoming the challenges of cancer therapy, such as multidrug resistance (MDR), angiogenesis, immunosuppression, and so on. In this review, we highlight the research progresses of PEGylated drug micelles, including the structures and properties, smart stimuli-responsive PEGylated drug micelles, and the challenges that have been overcome by PEGylated drug micelles.

Nanomedicine-based technologies and novel biomarkers for the diagnosis and treatment of Alzheimer's disease: from current to future challenges

Increasing life expectancy has led to an aging population, which has consequently increased the prevalence of dementia. Alzheimer's disease (AD), the most common form of dementia worldwide, is estimated to make up 50-80% of all cases. AD cases are expected to reach 131 million by 2050, and this increasing prevalence will critically burden economies and health systems in the next decades. There is currently no treatment that can stop or reverse disease progression. In addition, the late diagnosis of AD constitutes a major obstacle to effective disease management. Therefore, improved diagnostic tools and new treatments for AD are urgently needed. In this review, we investigate and describe both well-established and recently discovered AD biomarkers that could potentially be used to detect AD at early stages and allow the monitoring of disease progression. Proteins such as NfL, MMPs, p-tau217, YKL-40, SNAP-25, VCAM-1, and Ng / BACE are some of the most promising biomarkers because of their successful use as diagnostic tools. In addition, we explore the most recent molecular strategies for an AD therapeutic approach and nanomedicine-based technologies, used to both target drugs to the brain and serve as devices for tracking disease progression diagnostic biomarkers. State-of-the-art nanoparticles, such as polymeric, lipid, and metal-based, are being widely investigated for their potential to improve the effectiveness of both conventional drugs and novel compounds for treating AD. The most recent studies on these nanodevices are deeply explained and discussed in this review.

Nanomedicine: A Promising Way to Manage Alzheimer's Disease

Alzheimer's disease (AD) is a devastating disease of the aging population characterized by the progressive and slow brain decay due to the formation of extracellular plaques in the hippocampus. AD cells encompass tangles of twisted strands of aggregated microtubule binding proteins surrounded by plaques. Delivering corresponding drugs in the brain to deal with these clinical pathologies, we face a naturally built strong, protective barrier between circulating blood and brain cells called the blood-brain barrier (BBB). Nanomedicines provide state-of-the-art alternative approaches to overcome the challenges in drug transport across the BBB. The current review presents the advances in the roles of nanomedicines in both the diagnosis and treatment of AD. We intend to provide an overview of how nanotechnology has revolutionized the approaches used to manage AD and highlight the current key bottlenecks and future perspective in this field. Furthermore, the emerging nanomedicines for managing brain diseases like AD could promote the booming growth of research and their clinical availability.

Recent advances in the design of inorganic and nano-clay particles for the treatment of brain disorders

Inorganic materials, in particular nanoclays and silica nanoparticles, have attracted enormous attention due to their versatile and tuneable properties, making them ideal candidates for a wide range of biomedical applications, such as drug delivery. This review aims at overviewing recent developments of inorganic nanoparticles (like porous or mesoporous silica particles) and different nano-clay materials (like montmorillonite, laponites or halloysite nanotubes) employed for overcoming the blood brain barrier (BBB) in the treatment and therapy of major brain diseases such as Alzheimer's, Parkinson's, glioma or amyotrophic lateral sclerosis. Recent strategies of crossing the BBB through invasive and not invasive administration routes by using different types of nanoparticles compared to nano-clays and inorganic particles are overviewed.

Drug delivery and targeting to brain tumors: considerations for crossing the blood-brain barrier

Introduction: The blood-brain barrier (BBB) selectively impedes the transportation of drug molecules into the brain, which makes the drug delivery and targeting of brain tumors very challenging.Areas covered: Having surveyed the recent literature, comprehensive insights are given into the impacts of the BBB on the advanced drug delivery and targeting modalities for brain tumors.Expert opinion: Brain capillary endothelial cells form the BBB in association with astrocytes, pericytes, neurons, and extracellular matrix. Coop of these forms the complex setting of neurovascular unite. The BBB maintains the brain homeostasis by restrictive controlling of the blood circulating nutrients/substances trafficking. Despite substantial progress on therapy of brain tumors, there is no impeccable strategy to safely deliver chemotherapeutics into the brain. Various strategies have been applied to deliver chemotherapeutics into the brain (e.g. BBB opening, direct delivery by infusion, injection, microdialysis, and implants, and smart nanosystems), which hold different pros and cons. Of note, smart nanoscale multifunctional nanomedicines can serve as targeting, imaging, and treatment modality for brain tumors. Given that aggressive brain tumors (e.g. gliomas) are often unresponsive to any treatments, an in-depth understanding of the molecular/cellular complexity of brain tumors might help the development of smart and effective treatment modalities.

Think Big, Start Small: How Nanomedicine Could Alleviate the Burden of Rare CNS Diseases

The complexity and organization of the central nervous system (CNS) is widely modulated by the presence of the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB), which both act as biochemical, dynamic obstacles impeding any type of undesirable exogenous exchanges. The disruption of these barriers is usually associated with the development of neuropathologies which can be the consequence of genetic disorders, local antigenic invasions, or autoimmune diseases. These disorders can take the shape of rare CNS-related diseases (other than Alzheimer's and Parkinson's) which a exhibit relatively low or moderate prevalence and could be part of a potential line of treatments from current nanotargeted therapies. Indeed, one of the most promising therapeutical alternatives in that field comes from the development of nanotechnologies which can be divided between drug delivery systems and diagnostic tools. Unfortunately, the number of studies dedicated to treating these rare diseases using nanotherapeutics is limited, which is mostly due to a lack of interest from industrial pharmaceutical companies. In the present review, we will provide an overview of some of these rare CNS diseases, discuss the physiopathology of these disorders, shed light on how nanotherapies could be of interest as a credible line of treatment, and finally address the major issues which can hinder the development of efficient therapies in that area.

Unlocking the Power of Exosomes for Crossing Biological Barriers in Drug Delivery

Since the 2013 Nobel Prize was awarded for the discovery of vesicle trafficking, a subgroup of nanovesicles called exosomes has been driving the research field to a new regime for understanding cellular communication. This exosome-dominated traffic control system has increased understanding of many diseases, including cancer metastasis, diabetes, and HIV. In addition to the important diagnostic role, exosomes are particularly attractive for drug delivery, due to their distinctive properties in cellular information transfer and uptake. Compared to viral and non-viral synthetic systems, the natural, cell-derived exosomes exhibit intrinsic payload and bioavailability. Most importantly, exosomes easily cross biological barriers, obstacles that continue to challenge other drug delivery nanoparticle systems. Recent emerging studies have shown numerous critical roles of exosomes in many biological barriers, including the blood–brain barrier (BBB), blood–cerebrospinal fluid barrier (BCSFB), blood–lymph barrier (BlyB), blood–air barrier (BAB), stromal barrier (SB), blood–labyrinth barrier (BLaB), blood–retinal barrier (BRB), and placental barrier (PB), which opens exciting new possibilities for using exosomes as the delivery platform. However, the systematic reviews summarizing such discoveries are still limited. This review covers state-of-the-art exosome research on crossing several important biological barriers with a focus on the current, accepted models used to explain the mechanisms of barrier crossing, including tight junctions. The potential to design and engineer exosomes to enhance delivery efficacy, leading to future applications in precision medicine and immunotherapy, is discussed.

The membrane axis of Alzheimer's nanomedicine

Alzheimer's disease (AD) is a major neurological disorder impairing its carrier's cognitive function, memory and lifespan. While the development of AD nanomedicine is still nascent, the field is evolving into a new scientific frontier driven by the diverse physicochemical properties and theranostic potential of nanomaterials and nanocomposites. Characteristic to the AD pathology is the deposition of amyloid plaques and tangles of amyloid beta (Aβ) and tau, whose aggregation kinetics may be curbed by nanoparticle inhibitors via sequence-specific targeting or nonspecific interactions with the amyloidogenic proteins. As literature implicates cell membrane as a culprit in AD pathogenesis, here we summarize the membrane axis of AD nanomedicine and present a new rationale that the field development may greatly benefit from harnessing our existing knowledge of Aβ-membrane interaction, nanoparticle-membrane interaction and Aβ-nanoparticle interaction.

Brain delivery of quercetin-loaded exosomes improved cognitive function in AD mice by inhibiting phosphorylated tau-mediated neurofibrillary tangles

It is reported that quercetin (Que) can prevent tau pathology and induce neuroprotection by improving cognitive and functional symptoms in the treatment of Alzheimer's disease (AD). However, its clinical application has been limited due to its poor brain targeting and bioavailability. Exosomes are considered as cargo carriers for intercellular communication and especially serve as a natural and important drug brain delivery platform for achieving better treatment of central neurological diseases. Here, we developed plasma exosomes (Exo) loaded with Que (Exo-Que) to improve the drug bioavailability, enhance the brain targeting of Que and potently ameliorate cognitive dysfunction in okadaic acid (OA)-induced AD mice. Our results showed that Exo-Que improved brain targeting of Que as well as significantly enhanced bioavailability of Que. Furthermore, compared with free Que, Exo-Que better relieved the symptoms of AD by inhibiting cyclin-dependent kinase 5 (CDK5)-mediated phosphorylation of Tau and reducing formation of insoluble neurofibrillary tangles (NFTs), suggesting its therapeutic potential for better treatment of AD.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

The Role of Natural Compounds and their Nanocarriers in the Treatment of CNS Inflammation

Neuroinflammation, which is involved in various inflammatory cascades in nervous tissues, can result in persistent and chronic apoptotic neuronal cell death and programmed cell death, triggering various degenerative disorders of the central nervous system (CNS). The neuroprotective effects of natural compounds against neuroinflammation are mainly mediated by their antioxidant, anti-inflammatory, and antiapoptotic properties that specifically promote or inhibit various molecular signal transduction pathways. However, natural compounds have several limitations, such as their pharmacokinetic properties and stability, which hinder their clinical development and use as medicines. This review discusses the molecular mechanisms of neuroinflammation and degenerative diseases of CNS. In addition, it emphasizes potential natural compounds and their promising nanocarriers for overcoming their limitations in the treatment of neuroinflammation. Moreover, recent promising CNS inflammation-targeted nanocarrier systems implementing lesion site-specific active targeting strategies for CNS inflammation are also discussed.

A Reevaluation of Chitosan-Decorated Nanoparticles to Cross the Blood-Brain Barrier

The blood-brain barrier (BBB) is a sophisticated and very selective dynamic interface composed of endothelial cells expressing enzymes, transport systems, and receptors that regulate the passage of nutrients, ions, oxygen, and other essential molecules to the brain, regulating its homeostasis. Moreover, the BBB performs a vital function in protecting the brain from pathogens and other dangerous agents in the blood circulation. Despite its crucial role, this barrier represents a difficult obstacle for the treatment of brain diseases because many therapeutic agents cannot cross it. Thus, different strategies based on nanoparticles have been explored in recent years. Concerning this, chitosan-decorated nanoparticles have demonstrated enormous potential for drug delivery across the BBB and treatment of Alzheimer's disease, Parkinson's disease, gliomas, cerebral ischemia, and schizophrenia. Our main objective was to highlight the high potential of chitosan adsorption to improve the penetrability through the BBB of nanoformulations for diseases of CNS. Therefore, we describe the BBB structure and function, as well as the routes of chitosan for crossing it. Moreover, we define the methods of decoration of nanoparticles with chitosan and provide numerous examples of their potential utilization in a variety of brain diseases. Lastly, we discuss future directions, mentioning the need for extensive characterization of proposed nanoformulations and clinical trials for evaluation of their efficacy.

Exosomes Derived from Brain Metastatic Breast Cancer Cells Destroy the Blood-Brain Barrier by Carrying lncRNA GS1-600G8.5

Brain metastasis is a major cause of death in breast cancer patients. The greatest event for brain metastasis is the breaching of the blood-brain barrier (BBB) by cancer cells. The role of exosomes in cancer metastasis is clear, whereas the role of exosomes in the integrity of the BBB is unknown. Here, we established a highly brain metastatic breast cancer cell line by three cycles of in vivo selection. The effect of exosomes on the BBB was evaluated in vitro by tracking, transepithelial/transendothelial electrical resistance (TEER), and permeability assays. BBB-associated exosomal long noncoding RNA (lncRNA) was selected from the GEO dataset and verified by real-time PCR, TEER, permeability, and Transwell assays. The cells obtained by the in vivo selection showed higher brain metastatic capacity in vivo and higher migration and invasion in vitro compared to the parental cells. Exosomes from the highly brain metastatic cells were internalized by brain microvascular endothelial cells (BMECs), which reduced TEER and increased permeability of BBB. The exosomes derived from the highly metastatic cells promoted invasion of the breast cancer cells in the BBB model. lncRNA GS1-600G8.5 was highly expressed in the highly brain metastatic cells and their exosomes, as compared to the samples with reduced metastatic behavior. Silencing of GS1-600G8.5 significantly abrogated the BBB destructive effect of exosomes. GS1-600G8.5-deficient exosomes failed to promote the infiltration of cancer cells through the BBB. Furthermore, BMECs treated with GS1-600G8.5-deprived exosomes expressed higher tight junction proteins than those treated with the control exosomes. These data suggest the exosomes derived from highly brain metastatic breast cancer cells might destroy the BBB system and promote the passage of cancer cells across the BBB, by transferring lncRNA GS1-600G8.5.