Nanoparticle-chelator conjugates as inhibitors of amyloid-beta aggregation and neurotoxicity: a novel therapeutic approach for Alzheimer disease

Nanoparticles induced neurotoxicity

The early development of nanotechnology has spurred major interest on the toxicity of nanoparticles (NPs) due to their ability to penetrate the biological barriers such as the BBB. This review aims at addressing how silver (AgNPs), titanium dioxide (TiO2NPs), zinc oxide (ZnONPs), iron oxide (Fe3O4NPs), carbon NPs, Copper (Cu-NPs), silicon oxide (SiO2 NPs) nanoparticles and quantum dots cause neurotoxicity. Some of the major signaling that occur are the signaling related to oxidative stress, neuroinflammation, mitochondrial dysfunction and cell equilibrium, hence results in neuronal damage and neurodegeneration. It is critical to describe that there are multiple ways by how NPs may be toxic based on their size and surface, dosage, and the recipient's age and health condition. A review on in vitro and in vivo analysis provides information about the toxic potentials of NPs and preventive measures including modification of NP surface and antioxidant treatment. The results underline the necessity of comprehensive safety assessments to allow the further utilization of nanoparticles across the economy.

Investigation into Alzheimer's-related amyloid-β conformational transformations and stability influenced by green iron oxide nanoparticles (GIONP)

Alzheimer's disease (AD) is popularly believed to be triggered by the aggregation of amyloid beta 1-42 (Aβ - 42) peptides, eventually leading to neurodegeneration. Our study delves into the influential role played by Green Iron Oxide Nanoparticles (GIONP). GIONP are typically synthesized using a green chemistry approach, imposing curcumin as a biocompatible reducing and capping agent, leveraging its inherent antioxidant, anti-inflammatory, and neuroprotective attributes. Herein, our research particularly aims to decipher whether GIONP modulates the secondary structure of Aβ1-42 peptides with a close consideration to the surrounding physiological factors, as well as the membrane bilayer probable conformation changes. Raman spectroscopy was employed to investigate the interaction between GIONP and Aβ1-42 aggregates, demonstrating significant alterations in secondary structure dynamics of Aβ1-42 polypeptide. Fourier-transform infrared (FTIR) spectroscopy shed light on the chemical interactions between GIONP and curcumin, a capping agent. X-ray diffraction (XRD) analysis was performed to determine the crystalline structure and phase purity of the synthesized GIONP, providing insights into their stability and structural integrity. GIONP particle size distribution investigations and membrane architectures surrounding GIONP were carried out for their impact on membrane integrity and stability. The morphology of GIONP, membrane mimetic liposomal structures formation, and integrity were studied using transmission electron microscopy (TEM), accompanied with energy-dispersive X-ray spectroscopy (EDS), which displayed the elements distribution within each of the structures. The study uncovered that GIONP stabilizes the secondary structure of Aβ1-42, potentially offering modulation to the aggregation process. Furthermore, GIONP proved to have no negative impact on membrane integrity, implying that they could be safely employed as a therapeutic option for the modulation of peptide aggregation's pathological pathway of Alzheimer's disease. This study may contribute to broadening our understanding of nanoparticle-mediated therapies in modulating neurodegenerative disorders, highlighting their dual involvement in amyloid aggregation regulation and membrane structure maintenance.

Pulling back the mitochondria's iron curtain

Mitochondrial functionality and cellular iron homeostasis are closely intertwined. Mitochondria are biosynthetic hubs for essential iron cofactors such as iron-sulfur (Fe-S) clusters and heme. These cofactors, in turn, enable key mitochondrial pathways, such as energy and metabolite production. Mishandling of mitochondrial iron is associated with a spectrum of human pathologies ranging from rare genetic disorders to common conditions. Here, we review mitochondrial iron utilization and its intersection with disease.

Multifunctional Nanocarriers for Alzheimer's Disease: Befriending the Barriers

Neurodegenerative diseases (NDDs) have been increasing in incidence in recent years and are now widespread worldwide. Neuronal death is defined as the progressive loss of neuronal structure or function which is closely associated with NDDs and represents the intrinsic features of such disorders. Amyotrophic lateral sclerosis, frontotemporal dementia, Alzheimer's, Parkinson's, and Huntington's diseases (AD, PD, and HD, respectively) are considered neurodegenerative diseases that affect a large number of people worldwide. Despite the testing of various drugs, there is currently no available therapy that can remedy or effectively slow the progression of these diseases. Nanomedicine has the potential to revolutionize drug delivery for the management of NDDs. The use of nanoparticles (NPs) has recently been developed to improve drug delivery efficiency and is currently subjected to extensive studies. Nanoengineered particles, known as nanodrugs, can cross the blood-brain barrier while also being less invasive compared to the most treatment strategies in use. Polymeric, magnetic, carbonic, and inorganic NPs are examples of NPs that have been developed to improve drug delivery efficiency. Primary research studies using NPs to cure AD are promising, but thorough research is needed to introduce these approaches to clinical use. In the present review, we discussed the role of metal-based NPs, polymeric nanogels, nanocarrier systems such as liposomes, solid lipid NPs, polymeric NPs, exosomes, quantum dots, dendrimers, polymersomes, carbon nanotubes, and nanofibers and surfactant-based systems for the therapy of neurodegenerative diseases. In addition, we highlighted nanoformulations such as N-butyl cyanoacrylate, poly(butyl cyanoacrylate), D-penicillamine, citrate-coated peptide, magnetic iron oxide, chitosan (CS), lipoprotein, ceria, silica, metallic nanoparticles, cholinesterase inhibitors, an acetylcholinesterase inhibitors, metal chelators, anti-amyloid, protein, and peptide-loaded NPs for the treatment of AD.

Nanotechnology in the diagnostic and therapy for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder primarily characterized by β-amyloid plaque, intraneuronal tangles, significant neuronal loss and cognitive deficit. Treatment in the early stages of the disease is crucial for preventing or perhaps reversing the neurodegeneration in the AD cases. However, none of the current diagnostic procedures are capable of early diagnosis of AD. Further, the available treatments merely provide symptomatic alleviation in AD and do not address the underlying illness. Therefore, there is no permanent cure for AD currently. Better therapeutic outcomes need the optimum drug concentration in the central nervous system (CNS) by traversing blood-brain-barrier (BBB). Nanotechnology offers enormous promise to transform the treatment and diagnostics of neurodegenerative diseases. Nanotechnology based diagnostic tools, drug delivery systems and theragnostic are capable of highly sensitive molecular detection, effective drug targeting and their combination. Significant work has been done in this area over the last decade and prospective results have been obtained in AD therapy. This review explores the various applications of nanotechnology in addressing the varied facets of AD, ranging from early detection to therapeutic interventions. This review also looks at how nanotechnology can help with the development of disease-modifying medicines, such as the delivery of anti-amyloid, anti-tau, cholinesterase inhibitors, antioxidants and hormonal drugs. In conclusion, this paper discusses the role of nanotechnology in the early detection of AD, effective drug targeting to the CNS and theragnostic applications in the management of AD.

Designing and Formulation of Nanocarriers for "Alzheimer's and Parkinson's" Early Detection and Therapy

The potential of nanotechnology in advancing the diagnosis and treatment of neurodegenerative diseases is explored in this comprehensive literature review. The findings of these studies suggest that nanotechnology has the capacity to improve existing therapeutic approaches, create novel and safe compounds, and develop more precise imaging techniques and diagnostic methods for neurodegenerative diseases. With the emergence of the nanomedicine era, a new and innovative approach of diagnosing and treating these conditions has been introduced. Notably, the researchers' development of a nanocarrier drug delivery tool demonstrates immense potential compared to conventional therapy, as it maximizes therapeutic efficacy and minimizes undesirable as side effects.

Iron and Targeted Iron Therapy in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide. β-amyloid plaque (Aβ) deposition and hyperphosphorylated tau, as well as dysregulated energy metabolism in the brain, are key factors in the progression of AD. Many studies have observed abnormal iron accumulation in different regions of the AD brain, which is closely correlated with the clinical symptoms of AD; therefore, understanding the role of brain iron accumulation in the major pathological aspects of AD is critical for its treatment. This review discusses the main mechanisms and recent advances in the involvement of iron in the above pathological processes, including in iron-induced oxidative stress-dependent and non-dependent directions, summarizes the hypothesis that the iron-induced dysregulation of energy metabolism may be an initiating factor for AD, based on the available evidence, and further discusses the therapeutic perspectives of targeting iron.

Role of Metal Cations of Copper, Iron, and Aluminum and Multifunctional Ligands in Alzheimer's Disease: Experimental and Computational Insights

Alzheimer's disease (AD) is the most common form of dementia, affecting millions of people around the world. Even though the causes of AD are not completely understood due to its multifactorial nature, some neuropathological hallmarks of its development have been related to the high concentration of some metal cations. These roles include the participation of these metal cations in the production of reactive oxygen species, which have been involved in neuronal damage. In order to avoid the increment in the oxidative stress, multifunctional ligands used to coordinate these metal cations have been proposed as a possible treatment to AD. In this review, we present the recent advances in experimental and computational works aiming to understand the role of two redox active and essential transition-metal cations (Cu and Fe) and one nonbiological metal (Al) and the recent proposals on the development of multifunctional ligands to stop or revert the damaging effects promoted by these metal cations.

Management of Brain Cancer and Neurodegenerative Disorders with Polymer-Based Nanoparticles as a Biocompatible Platform

The blood-brain barrier (BBB) serves as a protective barrier for the central nervous system (CNS) against drugs that enter the bloodstream. The BBB is a key clinical barrier in the treatment of CNS illnesses because it restricts drug entry into the brain. To bypass this barrier and release relevant drugs into the brain matrix, nanotechnology-based delivery systems have been developed. Given the unstable nature of NPs, an appropriate amount of a biocompatible polymer coating on NPs is thought to have a key role in reducing cellular cytotoxicity while also boosting stability. Human serum albumin (HSA), poly (lactic-co-glycolic acid) (PLGA), Polylactide (PLA), poly (alkyl cyanoacrylate) (PACA), gelatin, and chitosan are only a few of the significant polymers mentioned. In this review article, we categorized polymer-coated nanoparticles from basic to complex drug delivery systems and discussed their application as novel drug carriers to the brain.

Benefits and limitations of nanomedicine treatment of brain cancers and age-dependent neurodegenerative disorders

The treatment of central nervous system (CNS) malignancies, including brain cancers, is limited by a number of obstructions, including the blood-brain barrier (BBB), the heterogeneity and high invasiveness of tumors, the inaccessibility of tissues for early diagnosis and effective surgery, and anti-cancer drug resistance. Therapies employing nanomedicine have been shown to facilitate drug penetration across the BBB and maintain biodistribution and accumulation of therapeutic agents at the desired target site. The application of lipid-, polymer-, or metal-based nanocarriers represents an advanced drug delivery system for a growing group of anti-cancer chemicals. The nanocarrier surface is designed to contain an active ligand (cancer cell marker or antibody)-binding structure which can be modified to target specific cancer cells. Glioblastoma, ependymoma, neuroblastoma, medulloblastoma, and primary CNS lymphomas were recently targeted by easily absorbed nanocarriers. The metal- (such as transferrin drug-loaded systems), polymer- (nanocapsules and nanospheres), or lipid- (such as sulfatide-containing nanoliposomes)-based nano-vehicles were loaded with apoptosis- and/or ferroptosis-stimulating agents and demonstrated promising anti-cancer effects. This review aims to discuss effective nanomedicine approaches designed to overcome the current limitations in the therapy of brain cancers and age-dependent neurodegenerative disorders. To accent current obstacles for successful CNS-based cancer therapy, we discuss nanomedicine perspectives and limitations of nanodrug use associated with the specificity of nervous tissue characteristics and the effects nanocarriers have on cognition.

Advances on Therapeutic Strategies for Alzheimer's Disease: From Medicinal Plant to Nanotechnology

Alzheimer's disease (AD) is a chronic dysfunction of neurons in the brain leading to dementia. It is characterized by gradual mental failure, abnormal cognitive functioning, personality changes, diminished verbal fluency, and speech impairment. It is caused by neuronal injury in the cerebral cortex and hippocampal area of the brain. The number of individuals with AD is growing at a quick rate. The pathology behind AD is the progress of intraneuronal fibrillary tangles, accumulation of amyloid plaque, loss of cholinergic neurons, and decrease in choline acetyltransferase. Unfortunately, AD cannot be cured, but its progression can be delayed. Various FDA-approved inhibitors of cholinesterase enzyme such as rivastigmine, galantamine, donepezil, and NDMA receptor inhibitors (memantine), are available to manage the symptoms of AD. An exhaustive literature survey was carried out using SciFinder's reports from Alzheimer's Association, PubMed, and Clinical Trials.org. The literature was explored thoroughly to obtain information on the various available strategies to prevent AD. In the context of the present scenario, several strategies are being tried including the clinical trials for the treatment of AD. We have discussed pathophysiology, various targets, FDA-approved drugs, and various drugs in clinical trials against AD. The goal of this study is to shed light on current developments and treatment options, utilizing phytopharmaceuticals, nanomedicines, nutraceuticals, and gene therapy.

Nanomedicines in the Management of Alzheimer's Disease: Current View and Future Prospects

Alzheimer's disease (AD) is a kind of dementia that creates serious challenges for sufferers' memory, thinking, and behavior. It commonly targeting the aging population and decay the brain cells, despite attempts have been performed to enhance AD diagnostic and therapeutic techniques. Hence, AD remains incurable owing to its complex and multifactorial consequences and still there is lack of appropriate diagnostics/therapeutics option for this severe brain disorder. Therefore, nanotechnology is currently bringing new tools and insights to improve the previous knowledge of AD and ultimately may provide a novel treatment option and a ray of hope to AD patients. Here in this review, we highlighted the nanotechnologies-based findings for AD, in both diagnostic and therapeutic aspects and explained how advances in the field of nanotechnology/nanomedicine could enhance patient prognosis and quality of life. It is highly expected these emerging technologies could bring a research-based revolution in the field of neurodegenerative disorders and may assist their clinical experiments and develop an efficacious drug for AD also. The main aim of review is to showcase readers the recent advances in nanotechnology-based approaches for treatment and diagnosing of AD.

Inorganic Nanomaterials versus Polymer-Based Nanoparticles for Overcoming Neurodegeneration

Neurodegenerative disorders (NDs) affect a great number of people worldwide and also have a significant socio-economic impact on the aging population. In this context, nanomedicine applied to neurological disorders provides several biotechnological strategies and nanoformulations that improve life expectancy and the quality of life of patients affected by brain disorders. However, available treatments are limited by the presence of the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (B-CSFB). In this regard, nanotechnological approaches could overcome these obstacles by updating various aspects (e.g., enhanced drug-delivery efficiency and bioavailability, BBB permeation and targeting the brain parenchyma, minimizing side effects). The aim of this review is to carefully explore the key elements of different neurological disorders and summarize the available nanomaterials applied for neurodegeneration therapy looking at several types of nanocarriers. Moreover, nutraceutical-loaded nanoparticles (NPs) and synthesized NPs using green approaches are also discussed underling the need to adopt eco-friendly procedures with a low environmental impact. The proven antioxidant properties related to several natural products provide an interesting starting point for developing efficient and green nanotools useful for neuroprotection.

Esculetin and Fucoidan Attenuate Autophagy and Apoptosis Induced by Zinc Oxide Nanoparticles through Modulating Reactive Astrocyte and Proinflammatory Cytokines in the Rat Brain

We examined the protective effects of esculetin and fucoidan against the neurotoxicity of ZnO NPs in rats. Ninety rats were divided into nine groups and pre-treated with esculetin or fucoidan 1 h before ZnO NP administration on a daily basis for 2 weeks. Serum and brain homogenates were examined by enzyme-linked immunosorbent assay (ELISA), and neurons, microglia, and astrocytes in the hippocampal region were examined with immunohistochemical analysis. The serum levels of interleukin-1-beta (IL-1β), 3-nitrotyrosine (3-NT), superoxide dismutase (SOD), and 8-hydroxy-2′-deoxyguanosine (8-OHdG) were altered in the ZnO NP treatment groups. Brain IL-1β and TNF-α levels were elevated after ZnO NP administration, and these effects were inhibited by esculetin and fucoidan. SOD, 8-OHdG, and acetylcholinesterase (AChE) levels in the brain were decreased after ZnO NP administration. The brain levels of beclin-1 and caspase-3 were elevated after ZnO NP treatment, and these effects were significantly ameliorated by esculetin and fucoidan. The number of reactive astrocytes measured by counting glial fibrillary acidic protein (GFAP)-positive cells, but not microglia, increased following ZnO NP treatment, and esculetin and fucoidan ameliorated the changes. Esculetin and fucoidan may be beneficial for preventing ZnO NP-mediated autophagy and apoptosis by the modulation of reactive astrocyte and proinflammatory cytokines in the rat brain.

Amyloid fishing: β-Amyloid adsorption using tailor-made coated titania nanoparticles

Amyloidoses are a family of diseases characterized by abnormal protein folding that leads to fibril aggregates, amyloids. Extensive research efforts are devoted to developing inhibitors to amyloid aggregates. Here we set to explore functionalized titania (TiO₂) nanoparticles (NPs) as potential amyloid inhibiting agents. TiO₂ NPs were coated by a catechol derivative, dihydroxy-phenylalanine propanoic acid (DPA), and further conjugated to the amyloids' specific dye Congo-Red (CR). TiO₂-DPA-CR NPs were found to target mature fibrils of β-amyloid (Aβ). Moreover, coated NPs incubated with Aβ proteins suppressed amyloid fibrillation. TiO₂-DPA-CR were found to target amyloids in solution and induce their sedimentation upon centrifugation. This work demonstrates the potential utilization of TiO₂-DPA NPs for labeling and facilely separating from solution mature amyloid fibrils.

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.

Naringin Chelates Excessive Iron and Prevents the Formation of Amyloid-Beta Plaques in the Hippocampus of Iron-Overloaded Mice

Metal chelating agents are antioxidant agents, which decrease the reductive potential and stabilize the oxidized metal ion form. In this study, we evaluated the naringin capacity in chelating iron and preventing amyloid-beta plaque formation in the hippocampus of iron-overloaded mice. Thirty-five NMRI male mice (8-10 weeks old) were provided. The mice were classified into five groups. Iron dextran was administered as i.p. injection (100 mg/kg/day) four times a week for four subsequent weeks. The treated groups received 30 and 60 mg/kg/day naringin for a month. After histological processing, the brain sections were stained with Perls' stain kit for iron spots, and Congo red was used to stain the brain and hippocampus for amyloid-beta plaques. 30 mg/kg/day of naringin was shown to decrease nonheme iron in an efficient manner; iron content in this group decreased to 16.83 ± 0.57 μg/g wet weight, a quantity as low as that observed in the normal saline-receiving group. The nonheme iron content in the mice receiving 60 mg/kg/day of naringin was 20.73 ± 0.65 μg/g wet weight. In addition, Aβ plaque numbers in CA1, CA3, and DG areas of the hippocampus decreased significantly following treatment with 30 or 60 mg/kg/day naringin. Naringin has a strong iron chelation capacity and is able to reduce the formation of amyloid plaques. So it can be useful for neuroprotection and prevention of Alzheimer's disease.

β-Amyloid Targeting with Two-Dimensional Covalent Organic Frameworks: Multi-Scale In-Silico Dissection of Nano-Biointerface

Cytotoxic aggregation of misfolded β-amyloid (Aβ) proteins is the main culprit suspected to be behind the development of Alzheimer's disease (AD). In this study, Aβ interactions with the novel two-dimensional (2D) covalent organic frameworks (COFs) as therapeutic options for avoiding β-amyloid aggregation have been investigated. The results from multi-scale atomistic simulations suggest that amine-functionalized COFs with a large surface area (more than 1000 m2 /gr) have the potential to prevent Aβ aggregation. Gibb's free energy analysis confirmed that COFs could prevent protofibril self-assembly in addition to inhibiting β-amyloid aggregation. Additionally, it was observed that the amine functional group and high contact area could improve the inhibitory effect of COFs on Aβ aggregation and enhance the diffusivity of COFs through the blood-brain barrier (BBB). In addition, microsecond coarse-grained (CG) simulations with three hundred amyloids reveal that the presence of COFs creates instability in the structure of amyloids and consequently prevents the fibrillation. These results suggest promising applications of engineered COFs in the treatment of AD and provide a new perspective on future experimental research.

Nanomedicine against Alzheimer's and Parkinson's Disease

Alzheimer's and Parkinson's are the two most rampant neurodegenerative disorders worldwide. Existing treatments have a limited effect on the pathophysiology but are unable to fully arrest the progression of the disease. This is due to the inability of these therapeutic molecules to efficiently cross the blood-brain barrier. We discuss how nanotechnology has enabled researchers to develop novel and efficient nano-therapeutics against these diseases. The development of nanotized drug delivery systems has permitted an efficient, site-targeted, and controlled release of drugs in the brain, thereby presenting a revolutionary therapeutic approach. Nanoparticles are also being thoroughly studied and exploited for their role in the efficient and precise diagnosis of neurodegenerative conditions. We summarize the role of different nano-carriers and RNAi-conjugated nanoparticle-based therapeutics for their efficacy in pre-clinical studies. We also discuss the challenges underlying the use of nanomedicine with a focus on their route of administration, concentration, metabolism, and any toxic effects for successful therapeutics in these diseases.

Membrane Anchored Polymers Modulate Amyloid Fibrillation

The nucleating role of cellular membrane components, such as lipid moieties on amyloid beta (Aβ_1-40 ) fibrillation, has been reported in recent years. The influence of conjugates fabricated from lipid anchors (cholesterol, diacylglycerol) and hydrophilic polymers on Aβ_1-40 fibrillation is reported here, aiming to understand the impact of polymers cloud point temperature (T_cp ) and its hydrophobic tails on the amyloid fibrillation. Novel lipid-polymer conjugates, consisting of poly(oligo(ethylene glycol)_m acrylates) and hydrophobic groups (diacylglyceryl-, cholesteryl-, octyl-, decyl-, hexadecyl-) as anchors are synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization, allowing to tune the hydrophilic-hydrophobic profile of the conjugates by varying both, the degree of polymerization (n) and number of ethylene glycol units (m) in their side chain. The impact of these conjugates on Aβ_1-40 fibrillation is investigated via in vitro kinetic studies and transmission electron microscopy (TEM). Hydrophobic lipid-anchors are significantly delaying fibrillation (both lag- and half times), observing similar fibrillar structures via TEM when compared to native Aβ_1-40 . Other hydrophobic end groups are also delaying fibrillation of Aβ_1-40 , irrespective of their "n" and "m," whereas more hydrophilic polymers (both with longer ethylene glycol-sidechains, m = 3 for octyl, decyl and m = 5 for cholesterol) are only marginally inhibited fibrillation.

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.

Alzheimer's disease and its treatment by different approaches: A review

Alzheimer's disease (AD) is a neurodegenerative disorder that impairs mental ability development and interrupts neurocognitive function. This neuropathological condition is depicted by neurodegeneration, neural loss, and development of neurofibrillary tangles and Aβ plaques. There is also a greater risk of developing AD at a later age for people with cardiovascular diseases, hypertension and diabetes. In the biomedical sciences, effective treatment for Alzheimer's disease is a severe obstacle. There is no such treatment to cure Alzheimer's disease. The drug present in the market show only symptomatic relief. The cause of Alzheimer's disease is not fully understood and the blood-brain barrier restricts drug efficacy are two main factors that hamper research. Stem cell-based therapy has been seen as an effective, secure, and creative therapeutic solution to overcoming AD because of AD's multifactorial nature and inadequate care. Current developments in nanotechnology often offer possibilities for the delivery of active drug candidates to address certain limitations. The key nanoformulations being tested against AD include polymeric nanoparticles (NP), inorganic NPs and lipid-based NPs. Nano drug delivery systems are promising vehicles for targeting several therapeutic moieties by easing drug molecules' penetration across the CNS and improving their bioavailability. In this review, we focus on the causes of the AD and their treatment by different approaches.

Alzheimer's Disease Targeted Nano-Based Drug Delivery Systems

Alzheimer's disease (AD) is the most common neurodegenerative disease, and is part of a massive and growing health care burden that is destroying the cognitive function of more than 50 million individuals worldwide. Today, therapeutic options are limited to approaches with mild symptomatic benefits. The failure in developing effective drugs is attributed to, but not limited to the highly heterogeneous nature of AD with multiple underlying hypotheses and multifactorial pathology. In addition, targeted drug delivery to the central nervous system (CNS), for the diagnosis and therapy of neurological diseases like AD, is restricted by the challenges posed by blood-brain interfaces surrounding the CNS, limiting the bioavailability of therapeutics. Research done over the last decade has focused on developing new strategies to overcome these limitations and successfully deliver drugs to the CNS. Nanoparticles, that are capable of encapsulating drugs with sustained drug release profiles and adjustable physiochemical properties, can cross the protective barriers surrounding the CNS. Thus, nanotechnology offers new hope for AD treatment as a strong alternative to conventional drug delivery mechanisms. In this review, the potential application of nanoparticle based approaches in Alzheimer's disease and their implications in therapy is discussed.

Functional nanoassemblies for the diagnosis and therapy of Alzheimer's diseases

Alzheimer's disease (AD) is a progressive neurodegenerative disease that affects populations around the world. Many therapeutics have been investigated for AD diagnosis and/or therapy, but the efficacy is largely limited by the poor bioavailability of drugs and by the presence of the blood-brain barrier. Recently, the development of nanomedicines enables efficient drug delivery to the brain, but the complex pathological mechanism of AD prevents them from successful treatment. As a type of advanced nanomedicine, multifunctional nanoassemblies self-assembled from nanoscale imaging or therapeutic agents can simultaneously target multiple pathological factors, showing great potential in the diagnosis and therapy of AD. To help readers better understand this emerging field, in this review, we first introduce the pathological mechanisms and the potential drug candidates of AD, as well as the design strategies of nanoassemblies for improving AD targeting efficiency. Moreover, the progress of dynamic nanoassemblies that can diagnose and/or treat AD in response to the endogenous or exogenous stimuli will be described. Finally, we conclude with our perspectives on the future development in this field. The objective of this review is to outline the latest progress of using nanoassemblies to overcome the complex pathological environment of AD for improved diagnosis and therapy, in hopes of accelerating the future development of intelligent AD nanomedicines. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Diagnostic Tools > in vivo Nanodiagnostics and Imaging.

Biodegradable chitosan-sodium alginate-oleic acid nanocarrier promotes bioavailability and target delivery of lutein in rat model with no toxicity

Efficient delivery of macular carotenoid lutein to target retinal tissue is possible with enhanced intestinal uptake remains a major challenge owing to the polarity, sensitivity to light, heat and solubility. In this study, to overcome such constraints, biodegradable polymers chitosan-sodium alginate-oleic acid based nano-carrier loaded with lutein (LNCs) was prepared and safety efficacy was examined in vivo. Acute-toxicity of LNCs (0.1, 1, 10 and 100 mg/kg body weight) revealed that the LD₅₀ of LNCs was higher than 100 mg/kg body weight. In subacute-toxicity of LNCs (1 and 10 mg/kg body weight) revealed no mortality with no morphological and clinical changes in rats. Histology, haematology and biochemical analysis of urine and plasma confirmed no toxicity of LNCs compared to control. Post-prandial plasma and tissue (retina) levels of lutein from LNCs were higher. Results demonstrate increased bioavailability of lutein from LNCs with no toxicity suggests applications in food and pharma.

The Antiaggregative and Antiamyloidogenic Properties of Nanoparticles: A Promising Tool for the Treatment and Diagnostics of Neurodegenerative Diseases

Due to the progressive aging of the society, the prevalence and socioeconomic burden of neurodegenerative diseases are predicted to rise. The most common neurodegenerative disorders nowadays, such as Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis, can be classified as proteinopathies. They can be either synucleinopathies, amyloidopathies, tauopathies, or TDP-43-related proteinopathies; thus, nanoparticles with a potential ability to inhibit pathological protein aggregation and/or degrade already existing aggregates can be a promising approach in the treatment of neurodegenerative diseases. As it turns out, nanoparticles can be a double-edged sword; they can either promote or inhibit protein aggregation, depending on coating, shape, size, surface charge, and concentration. In this review, we aim to emphasize the need of a breakthrough in the treatment of neurodegenerative disorders and draw attention to nanomaterials, as they can also serve as a diagnostic tool for protein aggregates or can be used in a high-throughput screening for novel antiaggregative compounds.

Neurotherapeutic applications of nanomedicine for treating Alzheimer's disease

Alzheimer's disease (AD) is a progressive, irreversible, fatal brain disease which disturbs cognitive functions. It affects 35 million people worldwide and the number of people suffering may increase to 100 million by 2050 if no effective treatments are available. The present treatment improves cognitive functions and provide temporary symptomatic relief, but do not stop or delay the disease progression. Moreover, they are mainly available as conventional oral dosage forms and these conventional oral medications lack brain specificity and also produce side effects which leads to poor patient compliance. Brain drug targeting by nanomedicines is a promising approach to improve brain targeting specificity, brain bioavailability and patient compliance. The present review discuses about the currently available pharmacotherapy for AD and the neurotherapeutic applications as well as the advancements of nanomedicine for treating AD. It also highlights the recent advancements of various nanomedicines containing phytopharmaceuticals for treating AD. It is believed that nanomedicines containing approved drugs can be transformed into the clinics hence improve the life style of AD patients.

The Application of Nanomaterials in Cell Autophagy

Autophagy is defined as separation and degradation of cytoplasmic components through autophagosomes, which plays an essential part in physiological and pathological events. Hence it is also essential for cellular homeostasis. Autophagy disorder may bring about the failure of stem cells to maintain the fundamental transformation and metabolism of cell components. However, for cancer cells, the disorder of autophagy is a feasible antitumor idea. Nanoparticles, referring to particles of the size range 1-100 nanometers, are appearing as a category of autophagy regulators. These nanoparticles may revolutionize and broaden the therapeutic strategies of many diseases, including neurodegenerative diseases, tumors, muscle disease, and so on. Researches of autophagy-induced nanomaterials mainly focus on silver particles, gold particles, silicon particles, and rare earth oxides. But in recent years, more and more materials have been found to regulate autophagy, such as nano-nucleic acid materials, nanofiber scaffolds, quantum dots, and so on. The review highlights that various kinds of nanoparticles have the power to regulate autophagy intensity in stem cells of interest and further control biological behaviors, which may become a reliable treatment choice for disease therapy.

Conjugation of RTHLVFFARK to human lysozyme creates a potent multifunctional modulator for Cu2+-mediated amyloid β-protein aggregation and cytotoxicity

Conjugation of alkaline decapeptide (RTHLVFFARK) to lysozyme creates a potent multifunctional modulator (R-hLys) for Cu²⁺-mediated amyloid β-protein aggregation and cytotoxicity.

Neurotheranostics as personalized medicines

The discipline of neurotheranostics was forged to improve diagnostic and therapeutic clinical outcomes for neurological disorders. Research was facilitated, in largest measure, by the creation of pharmacologically effective multimodal pharmaceutical formulations. Deployment of neurotheranostic agents could revolutionize staging and improve nervous system disease therapeutic outcomes. However, obstacles in formulation design, drug loading and payload delivery still remain. These will certainly be aided by multidisciplinary basic research and clinical teams with pharmacology, nanotechnology, neuroscience and pharmaceutic expertise. When successful the end results will provide "optimal" therapeutic delivery platforms. The current report reviews an extensive body of knowledge of the natural history, epidemiology, pathogenesis and therapeutics of neurologic disease with an eye on how, when and under what circumstances neurotheranostics will soon be used as personalized medicines for a broad range of neurodegenerative, neuroinflammatory and neuroinfectious diseases.

α-synuclein interaction with zero-valent iron nanoparticles accelerates structural rearrangement into amyloid-susceptible structure with increased cytotoxic tendency

Aim

It has been indicated that NPs may change the amyloidogenic steps of proteins and relevant cytotoxicity. Therefore, this report assigned to explore the impact of ZVFe NPs on the amyloidogenicity and cytotoxicity of α-synuclein as one of the many known amyloid proteins.

Methods

The characterization of α-synuclein at amyloidogenic condition either alone or with ZVFe NPs was carried out by fluorescence, CD, UV-visible spectroscopic methods, TEM study, docking, and molecular modeling. The cytotoxicity assay of α-synuclein amyloid in the absence and presence of ZVFe NPs was also done by MTT, LDH, and flow cytometry analysis.

Results

ThT fluorescence spectroscopy revealed that ZVFe NPs shorten the lag phase and accelerate the fibrillation rate of α-synuclein. Nile red and intrinsic fluorescence spectroscopy, CD, Congo red adsorption, and TEM studies indicated that ZVFe NP increased the propensity of α-synuclein into the amyloid fibrillation. Molecular docking study revealed that hydrophilic residues, such as Ser-9 and Lys-12 provide proper sites for hydrogen bonding and electrostatic interactions with adsorbed water molecules on ZVFe NPs, respectively. Molecular dynamics study determined that the interacted protein shifted from a natively discorded conformation toward a more packed structure. Cellular assay displayed that the cytotoxicity of α-synuclein amyloid against SH-SY5Y cells in the presence of ZVFe NPs is greater than the results obtained without ZVFe NPs.

Conclusion

In conclusion, the existence of ZVFe NPs promotes α-synuclein fibrillation at amyloidogenic conditions by forming a potential template for nucleation, the growth of α-synuclein fibrillation and induced cytotoxicity.

Therapeutic Macromolecular Iron Chelators

Iron is a key element for every single living process. On a fundamental level, targeting iron is a valuable approach for the treatment of disorders caused by iron overload. Utilizing iron chelators as therapeutic agents has received expanding consideration in chelation therapy. Approved low molecular weight (MW) iron chelators to treat iron overload may experience short half-lives and toxicities prompting moderately high adverse effects. In recent years, polymeric/macromolecular iron chelators have received attention as therapeutic agents. Polymeric iron chelators show unique pharmaceutical properties that are different to their conventional small molecule counterparts. These polymeric iron chelators possess longer plasma half-lives and reduced toxicities, thus exhibiting a significant supplement to currently using low MW iron chelator therapy. In this review, we have briefly discussed polymeric iron chelators and factors to be considered when designing clinically valuable iron chelators. We have also discussed applications of polymeric iron chelators in the diseases caused by iron overload associated with transfusional hemosiderosis, neurodegenerative disorders, malaria and cancer. With this, research findings for new polymeric iron chelators are also covered.

Amorphous aggregation of tau in the presence of titanium dioxide nanoparticles: biophysical, computational, and cellular studies

Background

Nanoparticles (NPs) when injected into the body can reach target tissues like nervous system and interact with tau proteins and neurons. This can trigger conformational changes of tau and may affect NP toxicity.

Methods

In this study, we used several biophysical techniques (extrinsic and intrinsic fluorescence spectroscopy, circular dichroism (CD) spectroscopy, ultraviolet (UV)-visible spectroscopy), transmission electron microscopy (TEM) investigations, molecular docking and molecular dynamics studies, and cellular assays [3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) and flow cytometry) to reveal how structural changes of tau protein can change the cytotoxicity of titanium dioxide (TiO₂) NPs against neuron-like cells (SH-SY5Y) cells.

Results

It was shown that TiO₂ NPs result in hydrophilic interactions, secondary and tertiary structural changes, and the formation of amorphous tau aggregates. Conformational changes of tau increased the induced cytotoxicity by TiO₂ NPs. These data revealed that the denatured adsorbed protein on the NP surface may enhance NP cytotoxicity.

Conclusion

Therefore, this study provides useful insights on the NP-protein interactions and discusses how the protein corona can increase cytotoxicity to determine the efficacy of targeted delivery of nanosystems.

Phyto-Therapeutic and Nanomedicinal Approaches to Cure Alzheimer's Disease: Present Status and Future Opportunities

Alzheimer's disease (AD) is characterized by cognitive inability manifested due to the accumulation of β-amyloid, formation of hyper phosphorylated neurofibrillary tangles, and a malfunctioned cholinergic system. The degeneration integrity of the neuronal network can appear long after the onset of the disease. Nanotechnology-based interventions have opened an exciting area via theranostics of AD in terms of tailored nanomedicine, which are able to target and deliver drugs across the blood-brain barrier (BBB). The exciting interface existing between medicinal plants and nanotechnology is an emerging marvel in medicine, which has delivered promising results in the treatment of AD. In order to assess the potential applications of the medicinal plants, their derived components, and various nanomedicinal approaches, a review of literature was deemed as necessary. In the present review, numerous phytochemicals and various feats in nanomedicine for the treatment of AD have been discussed mechanistically for the first time. Furthermore, recent trends in nanotechnology such as green synthesis of metal nanoparticles with reference to the treatment of AD have been elaborated. Foreseeing the recent progress, we hope that the interface of medicinal plants and nanotechnology will lead to highly effective theranostic strategies for the treatment of AD in the near future.

Recent Status of Nanomaterial Fabrication and Their Potential Applications in Neurological Disease Management

Nanomaterials (NMs) are receiving remarkable attention due to their unique properties and structure. They vary from atoms and molecules along with those of bulk materials. They can be engineered to act as drug delivery vehicles to cross blood-brain barriers (BBBs) and utilized with better efficacy and safety to deliver specific molecules into targeted cells as compared to conventional system for neurological disorders. Depending on their properties, various metal chelators, gold nanoparticles (NPs), micelles, quantum dots, polymeric NPs, liposomes, solid lipid NPs, microparticles, carbon nanotubes, and fullerenes have been utilized for various purposes including the improvement of drug delivery system, treatment response assessment, diagnosis at early stage, and management of neurological disorder by using neuro-engineering. BBB regulates micro- and macromolecule penetration/movement, thus protecting it from many kinds of illness. This phenomenon also prevents drug delivery for the neurological disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis, amyotrophic lateral sclerosis, and primary brain tumors. For some neurological disorders (AD and PD), the environmental pollution was considered as a major cause, as observed that metal and/or metal oxide from different sources are inhaled and get deposited in the lungs/brain. Old age, obesity, diabetes, and cardiovascular disease are other factors for rapid deterioration of human health and onset of AD. In addition, gene mutations have also been examined to cause the early onset familial forms of AD. AD leads to cognitive impairment and plaque deposits in the brain leading to neuronal cell death. Based on these facts and considerations, this review elucidates the importance of frequently used metal chelators, NMs and/or NPs. The present review also discusses the current status and future challenges in terms of their application in drug delivery for neurological disease management.

Application of nanodiagnostics and nanotherapy to CNS diseases

Alzheimer's disease, Parkinson's disease and stroke are the most common CNS diseases, all characterized by progressive cellular dysfunction and death in specific areas of the nervous system. Therapeutic development for these diseases has lagged behind other disease areas due to difficulties in early diagnosis, long disease courses and drug delivery challenges, not least due to the blood-brain barrier. Over recent decades, nanotechnology has been explored as a potential tool for the diagnosis, treatment and monitoring of CNS diseases. In this review, we describe the application of nanotechnology to common CNS diseases, highlighting disease pathogenesis and the underlying mechanisms and promising functional outcomes that make nanomaterials ideal candidates for early diagnosis and therapy. Moreover, we discuss the limitations of nanotechnology, and possible solutions.

Chiral modulation of amyloid beta fibrillation and cytotoxicity by enantiomeric carbon dots

Enantiomeric carbon dots (C-dots) synthesized from l-lysine or d-lysine, modulate aggregation and cytotoxicity of amyloid beta-42 (Aβ42), the primary constituent of the amyloid plaques associated with Alzheimer's disease. In particular, l-Lys-C-dots dramatically remodeled Aβ42 secondary structure and fibril morphologies, as well as inhibited Aβ42 cytotoxicity and membrane interactions.

Molecular Recognition between Aβ-Specific Single-Domain Antibody and Aβ Misfolded Aggregates

Aβ is the toxic amyloid polypeptide responsible for Alzheimer's disease (AD). Prevention and elimination of the Aβ misfolded aggregates are the promising therapeutic strategies for the AD treatments. Gammabody, the Aβ-Specific Single-domain (VH) antibody, recognizes Aβ aggregates with high affinity and specificity and reduces their toxicities. Employing the molecular dynamics simulations, we studied diverse gammabody-Aβ recognition complexes to get insights into their structural and dynamic properties and gammabody-Aβ recognitions. Among many heterogeneous binding modes, we focused on two gammabody-Aβ recognition scenarios: recognition through Aβ β-sheet backbone and on sidechain surface. We found that the gammabody primarily uses the complementarity-determining region 3 (CDR3) loop with the grafted Aβ sequence to interact with the Aβ fibril, while CDR1/CDR2 loops have very little contact. The gammabody-Aβ complexes with backbone binding mode are more stable, explaining the gammabody's specificity towards the C-terminal Aβ sequence.

Nanotechnology Based Theranostic Approaches in Alzheimer's Disease Management: Current Status and Future Perspective

BACKGROUND

Alzheimer's disease (AD), a cognitive dysfunction/dementia state amongst the elders is characterized by irreversible neurodegeneration due to varied pathophysiology. Up till now, anti-AD drugs having different pharmacology have been developed and used in clinic. Yet, these medications are not curative and only lowering the AD associated symptoms. Improvement in treatment outcome required drug targeting across the blood-brain barrier (BBB) to the central nervous system (CNS) in optimal therapeutic concentration. Nanotechnology based diagnostic tools, drug carriers and theranostics offer highly sensitive molecular detection, effective drug targeting and their combination. Over the past decade, significant works have been done in this area and we have seen very remarkable outocome in AD therapy. Various nanoparticles from organic and inorganic nanomaterial category have successfully been investigated against AD.

CONCLUSION

This paper discussed the role of nanoparticles in early detection of AD, effective drug targeting to brain and theranostic (diagnosis and therapy) approaches in AD's management.

HP-β-cyclodextrin as an inhibitor of amyloid-β aggregation and toxicity

Amyloid deposits of misfolded amyloid-β protein (Aβ) on neuronal cells are a pathological hallmark of Alzheimer's disease (AD). Prevention of the abnormal Aβ aggregation has been considered as a promising therapeutic strategy for AD treatment. To prevent reinventing the wheel, we proposed to search the existing drug database for other diseases to identify potential Aβ inhibitors. Herein, we reported the inhibitory activity of HP-β-cyclodextrin (HP-β-CD), a well-known sugar used in drug delivery, genetic vector, environmental protection and treatment of Niemann-Pick disease type C1 (NPC1), against Aβ1-42 aggregation and Aβ-induced toxicity, with the aim of adding a new function as a sugar-based Aβ inhibitor. Experimental data showed that HP-β-CD molecules were not only nontoxic to cells, but also greatly inhibited Aβ fibrillization and reduced Aβ-induced toxicity in a concentration-dependent manner. At an optimal molar ratio of Aβ : HP-β-CD = 1 : 2, HP-β-CD enabled the reduction of 60% of Aβ fibrils and increased the cell viability to 92%. Such concentration-dependent inhibitor capacity of HP-β-CD was likely attributed to several combined effects, including the enhancement of Aβ-HP-β-CD interactions, prevention of structural transition of Aβ peptides towards β-sheet structures, and reduction of self-aggregation of HP-β-CD. In parallel, molecular simulations further revealed the atomic details of HP-β-CD interacting with the Aβ oligomer, showing that HP-β-CD had a high tendency to interact with hydrophobic residues of Aβ in two β-strands and the N-terminal tail. More importantly, we identified that the inner hydrophobic cavity of HP-β-CD was a key active site for Aβ inhibition. Once the inner cavity of HP-β-CD was blocked by a small hydrophobic molecule of ferulic acid, HP-β-CD completely lost its inhibition capacity against Aβ. Given the already established pharmaceutical functions of HP-β-CD in drug delivery, our findings suggest that HP-β-CD has great potential to be designed as a sugar-based Aβ inhibitor.

Iminodiacetic acid-conjugated nanoparticles as a bifunctional modulator against Zn2+-mediated amyloid β-protein aggregation and cytotoxicity

Alzheimer's disease is characterized by the accumulation of amyloid β-protein (Aβ) fibrils in human brain, and the binding of metal ions, such as Zn²⁺, is closely associated with the aggregation and cytotoxicity of Aβ. Here, we designed and synthesized iminodiacetic acid-conjugated nanoparticles (IDA-NP) to modulate Aβ₄₂ aggregation and reduce the cytotoxicity accelerated by Zn²⁺. Results showed that IDA-NP enabled high metal-chelate capacity (752μmol/g) and potent inhibition capability against Aβ₄₂ fibrillation. Zn²⁺ ions could be completely removed by chelating to IDA-NP, which leads to the recovery of on-pathway Aβ₄₂ fibrillation. Then, the special surface character of IDA-NP inhibited Aβ₄₂ fibrillation. As a result, IDA-NP protected SH-SY5Y cells from the cytotoxicity induced by Zn²⁺-Aβ₄₂ species, as evidenced by about 80% (from 47.6% to 86.3%) increase of the cell viability. The research proved that IDA-NP was a potent bifunctional nano-modulator for preventing Zn²⁺-mediated Aβ aggregation and cytotoxicity.

Amino acid-modified chitosan nanoparticles for Cu2+ chelation to suppress CuO nanoparticle cytotoxicity

The extensive development and application of engineered nanoparticles (NPs) in various fields worldwide have been subjected to increasing concern due to their potential hazards to human health and the environment. Therefore, a simple, economical, and effective method for suppressing the toxicity of metal-based nanomaterials is needed. In this study, glutaraldehyde-crosslinked chitosan nanoparticles (CS NPs) were prepared and further modified with lysine (Ly-CS), glutamic acid (Glu-CS), or sodium borohydride reduction (R-CS), and used to suppress cytotoxicity induced by copper oxide NPs (CuO NPs) through chelation with intracellularly released copper ions. All three kinds of CS NPs had similar sizes of ∼100 nm in a dry state and ∼200 nm in cell culture medium, as determined by scanning electron microscopy, transmission electron microscopy, and dynamic light scattering. The chelating efficiency of different CS NPs followed the order Ly-CS > Glu-CS > R-CS. The CS NPs showed minimal or no toxicity to three different cell lines (HepG2, A549, and RAW264.7 cells) at 100 μg mL^-1 with similar cell internalization and exocytosis processes. Comparatively, RAW264.7 cells exhibited higher endocytosis and exocytosis rates, as revealed by flow cytometry and confocal laser scanning microscopy. CS NPs were found as agglomerates inside A549 cells and RAW264.7 cells, with the amount of agglomerates inside RAW264.7 cells decreasing significantly with prolonged incubation. All three CS NPs, especially Ly-CS and Glu-CS NPs, efficiently suppressed the cytotoxicity induced by CuO NPs, and reduced the intracellular level of reactive oxygen species.

Nanobiomaterials' applications in neurodegenerative diseases

The blood-brain barrier is the interface between the blood and brain, impeding the passage of most circulating cells and molecules, protecting the latter from foreign substances, and maintaining central nervous system homeostasis. However, its restrictive nature constitutes an obstacle, preventing therapeutic drugs from entering the brain. Usually, a large systemic dose is required to achieve pharmacological therapeutic levels in the brain, leading to adverse effects in the body. As a consequence, various strategies are being developed to enhance the amount and concentration of therapeutic compounds in the brain. One such tool is nanotechnology, in which nanostructures that are 1-100 nm are designed to deliver drugs to the brain. In this review, we examine many nanotechnology-based approaches to the treatment of neurodegenerative diseases. The review begins with a brief history of nanotechnology, followed by a discussion of its definition, the properties of most reported nanomaterials, their biocompatibility, the mechanisms of cell-material interactions, and the current status of nanotechnology in treating Alzheimer's, Parkinson's diseases, and amyotrophic lateral sclerosis. Of all strategies to deliver drug to the brain that are used in nanotechnology, drug release systems are the most frequently reported.

Biocompatible lutein-polymer-lipid nanocapsules: Acute and subacute toxicity and bioavailability in mice

Lutein-poly-(lactic-co-glycolic acid) (PLGA)-phospholipid (PL) nanocapsules were prepared (henceforth referred as lutein nanocapsules) and studied for acute, subacute oral toxicity and bioavailability of lutein in mice. Prior to examining the safety of lutein nanocapsules, particle size, zeta potential, surface morphology and interaction between lutein, PLGA and PL were studied. In acute study, mice were gavaged with a single dose of lutein nanocapsules at 0.1, 1, 10 and 100mg/kg body weight (BW) and examined for 2weeks, while in subacute study, daily mice were gavaged with a dose of 1 and 10mg/kg BW for 4weeks. Results revealed that mean size and zeta value of lutein nanocapsules were 140nm and -44mV, respectively. Acute and subacute toxicity studies did not show any mortality or treatment related adverse effect in clinical observations, ophthalmic examinations, body and organ weights. No toxicity related findings were observed in hematology, histopathology and other blood and tissue clinical chemistry parameters. In subacute study, no observed adverse effect level (NOAEL) of lutein nanocapsules was found to be at a dose of 10mg/kg BW. Feeding lutein nanocapsules resulted in a significant (p<0.01) increase in lutein level in plasma and tissue compared to the control group. Lutein nanocapsules did not cause toxicity in mice. However, human trials are warranted.