Nanomaterials for reducing amyloid cytotoxicity

Inhibiting the Aggregation of Aβ by Natural Product Molecules

The abnormal aggregation of Aβ has been considered one of the primary causative factors for Alzheimer's disease. Diverse molecular entities have been developed to mitigate the formation of toxic Aβ aggregates within the brain by inhibiting Aβ aggregation. Recognizing that many FDA-approved drugs are derived from natural products, we present a summary of recent discoveries involving natural product molecules with inhibitory effects on Aβ aggregation. By consolidating these findings, our review offers researchers a concise overview of the latest advancements in natural product-based interventions for Alzheimer's disease.

Efficient inhibition of amyloid fibrillation and cytotoxicity of α-synuclein and human insulin using biosynthesized silver nanoparticles decorated by green tea polyphenols

Green tea polyphenols (GTPs), particularly epigallocatechin-3-gallate, stand out among natural small molecules screened for their ability to target protein aggregates due to their potent anti-amyloidogenic and neuroprotective activities against various disease-related peptides and proteins. However, the clinical applications of GTPs in amyloid-related diseases have been greatly limited by drawbacks such as poor chemical stability and low bioavailability. To address these limitations, this study utilized an Iranian green tea polyphenolic extract as a reducing agent to neutralize silver ions and facilitate the formation of silver nanoparticle capped by GTPs (GTPs-capped AgNPs). The results obtained from this study demonstrate that GTPs-capped AgNPs are more effective than free GTPs at inhibiting amyloid fibrillation and reducing cytotoxicity induced by amyloid fibrils of human insulin and α-synuclein (α-syn). This improved efficacy is attributed to the increased surface/volume ratio of GTPs-capped AgNPs, which can enhance their binding affinity to amyloidogenic species and boosts their antioxidant activity. The mechanism by which GTPs-capped AgNPs inhibit amyloid fibrillation appears to vary depending on the target protein. For structured protein human insulin, GTPs-capped AgNPs hinder fibrillation by constraining the protein in its native-like state. In contrast, GTPs-capped AgNPs modulate fibrillation of intrinsically disordered proteins like α-syn by redirecting the aggregation pathway towards the formation of non-toxic off-pathway oligomers or amorphous aggregates. These findings highlight polyphenol-functionalized nanoparticles as a promising strategy for targeting protein aggregates associated with neurodegenerative diseases.

Uncovering supramolecular chirality codes for the design of tunable biomaterials

In neurodegenerative diseases, polymorphism and supramolecular assembly of β-sheet amyloids are implicated in many different etiologies and may adopt either a left- or right-handed supramolecular chirality. Yet, the underlying principles of how sequence regulates supramolecular chirality remains unknown. Here, we characterize the sequence specificity of the central core of amyloid-β 42 and design derivatives which enable chirality inversion at biologically relevant temperatures. We further find that C-terminal modifications can tune the energy barrier of a left-to-right chiral inversion. Leveraging this design principle, we demonstrate how temperature-triggered chiral inversion of peptides hosting therapeutic payloads modulates the dosed release of an anticancer drug. These results suggest a generalizable approach for fine-tuning supramolecular chirality that can be applied in developing treatments to regulate amyloid morphology in neurodegeneration as well as in other disease states.

2D nanostructures: Potential in diagnosis and treatment of Alzheimer's disease

Two-dimensional (2D) nanomaterials have garnered enormous attention seemingly due to their unusual architecture and properties. Graphene and graphene oxide based 2D nanomaterials remained the most sought after for several years but the quest to design superior 2D nanomaterials which can find wider application gave rise to development of non-graphene 2D materials as well. Consequently, in addition to graphene based 2D nanomaterials, 2D nanostructures designed using macromolecules (such as DNAs, proteins, peptides and peptoids), transition metal dichalcogenides, transition-metal carbides and/or nitrides (MXene), black phosphorous, chitosan, hexagonal boron nitrides, and graphitic carbon nitride, and covalent organic frameworks have been developed. Interestingly, these 2D nanomaterials have found applications in diagnosis and treatment of various diseases including Alzheimer's disease (AD). Although AD is one of the most debilitating neurodegenerative conditions across the globe; unfortunately, there remains a paucity of effective diagnostic and/or therapeutic intervention for it till date. In this scenario, nanomaterial-based biosensors, or therapeutics especially 2D nanostructures are emerging to be promising in this regard. This review summarizes the diagnostic and therapeutic platforms developed for AD using 2D nanostructures. Collectively, it is worth mentioning that these 2D nanomaterials would seemingly provide an alternative and intriguing platform for biomedical interventions.

Interfacial effect on the ability of peptide-modified gold nanoclusters to inhibit hIAPP fibrillation and cytotoxicity

Deposit of amyloid peptides in the cells is related to various amyloidosis diseases. A variety of nanomaterials have been developed to resist amyloid deposit. Most of the research on the inhibition of nanomaterials against amyloid aggregation are undertaken in solution, while the membranes that may mediate fibrillar aggregation and affect interaction of inhibitors with amyloid peptides in biotic environment are little taken into account. In this study, we synthesized three kinds of gold nanoclusters modified with cysteine (C@AuNCs), glutathione (GSH@AuNCs) and a peptide derived from the core region of hIAPP fibrillation (C-HL-8P@AuNCs), and investigated their inhibitory activities against hIAPP fibrillation in the absence and presence of lipid vesicles (POPC/POPG 4:1 LUVs) by the experiments of ThT fluorescence kinetics, AFM and CD. We also explored the inhibitions of hIAPP-induced membrane damage and cytotoxicity by peptide@AuNCs using fluorescent dye leakage and cell viability assays. Our study revealed that the inhibitory efficiency of these peptide@AuNCs against hIAPP fibrillation follows C-HL-8P@AuNCs≅GSH@AuNCs>C@AuNCs in lipid-free solution and C-HL-8P@AuNCs≫GSH@AuNCs>C@AuNCs in lipid membrane environment. Compared with the results obtained in lipid-free solution, the inhibitions of hIAPP fibrillation observed in lipid membrane environment were more associated with the inhibitions of hIAPP-induced damages of lipid vesicles and INS-1 cells (C-HL-8P@AuNCs≫GSH@AuNCs>C@AuNCs). An additional hydrophobic interaction with the homologous core region of hIAPP, which is only provided by C-HL-8P@AuNCs and largely suppressed in lipid-free solution, enhanced in the membrane environment and therefore made C-HL-8P@AuNCs much more powerful than GSH@AuNCs and C@AuNCs in the inhibitions of hIAPP fibrillation and cytotoxicity.

Deeper insight into ferroptosis: association with Alzheimer's, Parkinson's disease, and brain tumors and their possible treatment by nanomaterials induced ferroptosis

Ferroptosis is an emerging and novel type of iron-dependent programmed cell death which is mainly caused by the excessive deposition of free intracellular iron in the brain cells. This deposited free iron exerts a ferroptosis pathway, resulting in lipid peroxidation (LiPr). There are mainly three ferroptosis pathways viz. iron metabolism-mediated cysteine/glutamate, and LiPr-mediated. Iron is required by the brain as a redox metal for several physiological activities. Due to the iron homeostasis balance disruption, the brain gets adversely affected which further causes neurodegenerative diseases (NDDs) like Parkinson's and Alzheimer's disease, strokes, and brain tumors like glioblastoma (GBS), and glioma. Nanotechnology has played an important role in the prevention and treatment of these NDDs. A synergistic effect of nanomaterials and ferroptosis could prove to be an effective and efficient approach in the field of nanomedicine. In the current review, the authors have highlighted all the latest research in the field of ferroptosis, specifically emphasizing on the role of major molecular key players and various mechanisms involved in the ferroptosis pathway. Moreover, here the authors have also addressed the correlation of ferroptosis with the pathophysiology of NDDs and theragnostic effect of ferroptosis and nanomaterials for the prevention and treatment of NDDs.

Understanding the Molecular Mechanisms of Polyphenol Inhibition of Amyloid β Aggregation

Alzheimer's disease (AD) is highly associated with self-aggregation of amyloid β (Aβ) proteins into fibrils. Inhibition of Aβ aggregation by polyphenols is one of the major therapeutic strategies for AD. Among them, four polyphenols (brazilin, resveratrol, hematoxylin, and rosmarinic acid) have been reported to be effective at inhibiting Aβ aggregation, but the inhibition mechanisms are still unclear. In this work, these four polyphenols were selected to explore their interactions with the Aβ17-42 pentamer by molecular dynamics simulation. All four polyphenols can bind to the pentamer tightly but prefer different binding sites. Conversion of the β-sheet to the random coil, fewer interchain hydrogen bonds, and weaker salt bridges were observed after binding. Interestingly, different Aβ17-42 pentamer destabilizing mechanisms for resveratrol and hematoxylin were found. Resveratrol inserts into the hydrophobic core of the pentamer by forming hydrogen bonds with Asp23 and Lys28, while hematoxylin prefers to bind beside chain A of the pentamer, which leads to β-sheet offset and dissociation of the β1 sheet of chain E. This work reveals the interactions between the Aβ17-42 pentamer and four polyphenols and discusses the relationship between inhibitor structures and their inhibition mechanisms, which also provides useful guidance for screening effective Aβ aggregation inhibitors and drug design against AD.

Nanotube breakthroughs: unveiling the potential of carbon nanotubes as a dual therapeutic arsenal for Alzheimer's disease and brain tumors

Alzheimer's disease (AD) and brain tumors are debilitating neurological conditions that pose significant challenges in current medical practices. Existing treatment options for AD primarily focus on symptom management, and brain tumors often require aggressive therapeutic approaches. Novel disease-modifying strategies and therapeutic agents are urgently needed to address the underlying causes of AD pathogenesis and improve brain tumor management. In recent years, nanoparticles (NPs) have shown promise as valuable tools in diagnosing and managing various brain disorders, including AD. Among these, carbon nanotubes (CNTs) have garnered attention for their unique properties and biomedical potential. Their ability to cross the blood-brain barrier (BBB) with ease opens up new possibilities for targeted drug delivery and neuroprotection. This literature review aims to explore the versatile nature of CNTs, which can be functionalized with various biomolecules or substances due to their sp2 hybridization. This adaptability enables them to specifically target cells and deliver medications under specific environmental conditions. Moreover, CNTs possess an exceptional capacity to penetrate cell membranes, making them valuable tools in the treatment of AD and brain tumors. By delving into the role of CNTs in biomedicine, this review sheds light on their potential in managing AD, offering a glimpse of hope for effective disease-modifying options. Understanding the mechanisms of CNTs' action and their capabilities in targeting and delivering medication to affected cells will pave the way for innovative therapeutic strategies that can improve the lives of those afflicted with these devastating neurological conditions. The exploration of CNTs as a dual therapeutic arsenal for both brain tumors and Alzheimer's disease holds great promise and may usher in a new era of effective treatment strategies for these challenging conditions.

Methylene Blue-Doped Carbonized Polymer Dots: A Potent Photooxygenation Scavenger Targeting Alzheimer's β-Amyloid

The abnormal aggregation of β-amyloid protein (Aβ) is one of the main pathological hallmarks of Alzheimer's disease (AD), and thus development of potent scavengers targeting Aβ is considered an effective strategy for AD treatment. Herein, photosensitizer-doped carbonized polymer dots (PS-CPDs) were synthesized by a one-step hydrothermal method using photosensitizer (PS) and o-phenylenediamine (oPD) as precursors, and furtherly applied to inhibit Aβ aggregation via photooxygenation. The inhibition efficiency of such PS-CPDs can be adjusted by varying the type of photosensitizer, and among them, methylene blue-doped carbonized polymer dots (MB-CPDs) showed the strongest photooxygenation inhibition capability. The results demonstrated that under 650 nm NIR light irradiation, MB-CPDs (2 μg/mL) produced reactive oxygen species (ROS) to efficiently inhibit Aβ fibrillization and disaggregate mature Aβ fibrils and increased the cultured cell viability from 50% to 83%. In vivo studies confirmed that MB-CPDs extended the lifespan of AD nematodes by 4 days. Notably, the inhibitory capability of MB-CPDs is much stronger than that of MB and previously reported carbonized polymer dots. This work indicated that potent photooxygenation carbon dots can be obtained by using a photosensitizer as one of the precursors, and the results have provided new insights into the design of potent photooxygenation carbon nanomaterials targeting Aβ in AD treatment.

Epigallocatechin gallate-derived carbonized polymer dots: A multifunctional scavenger targeting Alzheimer's β-amyloid plaques

The design of high-efficiency scavengers targeting β-amyloid protein (Aβ) plaques in the progress of Alzheimer's disease (AD) has been recognized as an effective way to prevent and treat AD. Herein, epigallocatechin gallate (EGCG)-derived carbonized polymer dots (E-CPDs) were synthesized for the first time via a hydrothermal method using EGCG, an Aβ inhibitor, as one of the raw materials. The inhibitory efficiency and fluorescent property of E-CPDs were elegantly modulated by adjusting the molar ratio of EGCG to nitrogen-containing dopant, o-phenylenediamine (oPD), and 75E-CPDs fabricated with 75 mM EGCG and 50 mM oPD showed the highest inhibitory capability. The multifunctionality of 75E-CPDs on inhibition of Aβ fibrillization, Aβ fibrils disaggregation, amyloid fluorescent detection, and intracellular reactive oxygen species scavenging was demonstrated. 75E-CPDs inhibited the formation of β-sheet-rich Aβ aggregates, alleviated Aβ-induced cytotoxicity of cultured cells from 47% to 15%, and prolonged the lifespan of AD nematodes by scavenging in vivo amyloid plaques, demonstrating much higher performance than either EGCG or EGCG-free carbon dots. Notably, 75E-CPDs could rapidly disaggregate Aβ fibrils on "second" scale, faster than any other disaggregating agents. The aromatic structure as well as hydroxyl and carboxyl groups existing on 75E-CPDs surface, which would interact with Aβ species via hydrogen bonding, electrostatic interactions, and hydrophobic interactions, played critical roles in their inhibition and disaggregation capabilities. This work reveals that potent CDs can be fabricated by using an Aβ inhibitor as the precursor, providing a new perspective for the design of multifunctional scavengers targeting amyloid plaques. STATEMENT OF SIGNIFICANCE: Alzheimer's disease (AD) is one of the top ten causes of death worldwide and seriously threatens human health. Recently, carbon nanomaterials have attracted much attention because of their good biocompatibility and capability in modulating Aβ aggregation via multiple interactions. This work has for the first time fabricated epigallocatechin gallate-derived carbonized polymer dots (E-CPDs) and revealed the multifunctional potency of E-CPDs on alleviating the multifaced symptoms associated with β-amyloid protein (Aβ) fibrillization in the progression of AD. Notably, E-CPDs exhibited enhanced fluorescence emission upon binding to Aβ fibrils, possessing potential as Aβ fluorescent probes. It is believed that this work would open a new horizon in the design of multifunctional carbon nanomaterials as a potent amyloid scavenger for AD theranostics.

Mechanistic insights into the size-dependent effects of nanoparticles on inhibiting and accelerating amyloid fibril formation

The aggregation of peptides into amyloid fibrils has been linked to ageing-related diseases, such as Alzheimer's and type 2 diabetes. Interfaces, particularly those with large nanostructured surfaces, can affect the kinetics of peptide aggregation, which ranges from complete inhibition to strong acceleration. While a number of physiochemical parameters determine interfacial effects, we focus here on the role of nanoparticle (NP) size and curvature. We used thioflavin T (ThT) fluorescence assays to demonstrate the size-dependent effects of NPs on amyloid fibril formation for the peptides Aβ₄₀, NNFGAIL, GNNQQNY and VQIYVK. While 5 nm gold NPs (AuNP-5) retarded or inhibited the aggregation of all peptides except NNFGAIL, larger 20 nm gold NPs (AuNP-20) tended to accelerate or not influence peptide aggregation. Differences in the NP effects for the peptides resulted from the different peptide properties (size, tendency to aggregate) and associated surface binding affinities. Additional dynamic light scattering (DLS), electron microscopy, and atomic force microscopy (AFM) experiments with the Aβ₄₀ peptide confirmed size-dependent NP effects on peptide aggregation, and also suggested a structural influence on the formed fibrils. NPs can serve as a surface for the adsorption of peptide monomers and enable nucleation to oligomers and fibril formation. However, molecular dynamics (MD) simulations showed that peptide oligomers were less stable at smaller NPs. High surface curvatures destabilized prefibrillar structures, which provides a possible explanation for inhibitory effects on fibril growth, provided that peptide-NP surface binding was relevant for fibril formation. These mechanistic insights can support the design of future nanostructured materials.

The Effect of Trehalose Coating for Magnetite Nanoparticles on Stability of Egg White Lysozyme

In this study, the protein stability of hen egg-white lysozymes (HEWL) by Fe₃O₄ and Fe₃O₄-coated trehalose (Fe₃O₄@Tre) magnetic nanoparticles (NPs) is investigated. For this purpose, the co-precipitation method was used to synthesize magnetic NPs. The synthesized NPs were characterized by XRD, FT-IR spectroscopy, FE-SEM, and VSM analysis. In addition, the stability of HEWLs exposed to different NP concentrations in the range of 0.001–0.1 mg mL⁻¹ was investigated by circular dichroism (CD) spectroscopy, fluorescence, and UV-Vis analysis. Based on the results, in the NP concentration range of 0.001–0.04 mg mL⁻¹ the protein structure is more stable, and this range was identified as the range of kosmotropic concentration. The helicity was measured at two concentration points of 0.02 and 0.1 mg mL⁻¹. According to the results, the α-helix at 0.02 mg mL⁻¹ of Fe₃O₄ and Fe₃O₄@Tre was increased from 35.5% for native protein to 37.7% and 38.7%, respectively. The helicity decreased to 36.1% and 37.4%, respectively, with increasing the concentration of Fe₃O₄ and Fe₃O₄@Tre to 0.1 mg mL⁻¹. The formation of hydrated water shells around protein molecules occurred by using Fe₃O₄@Tre NPs. Hence, it can be concluded that the trehalose as a functional group along with magnetic NPs can improve the stability of proteins in biological environments.

Nontoxic silicene photothermal agents with high near-infrared absorption for disassembly of Alzheimer's amyloid‑β fibrils

The disassembly and eliminating the amyloid-β (Aβ) aggregates has become an effective way to treat Alzheimer's disease (AD). Herein, for the first time, the near-infrared (NIR) activated silicene nanosheets (SNSs) have been identified as an effective nontoxic photothermal conversion agent for irreversibly disassembly of the Aβ_33-42 aggregates. The SNSs synthesized by a combination of mild oxidation method and liquid exfoliation method possess good biocompatibility and biodegradability, and high near-infrared photothermal conversion capabilities. Under NIR light, the SNSs could disassemble the large and dense Aβ_33-42 mature fibrils into short fibrils and even form thin films, leading to the degradation rate of 96.47%. The circular dichroism spectrum, fluorescent spectra, and nanostructure were analyzed to monitor the photothermal degradation of mature Aβ_33-42 fibrils for elaborating the mechanism beneath. This study might provide a clue for developing potential therapeutic strategy for AD and related neurodegenerative diseases.

Synthesis of carbon quantum dots for application of alleviating amyloid-β mediated neurotoxicity

Alzheimer's disease (AD) has been an intractable neurodegenerative disease among the elderly in the worldwide. One of the important pathogenic factors in AD is the aggregation of amyloid-β 1-42 (Aβ42) in AD patients' brain. Inhibition of Aβ peptide aggregation is considered as one of the effective approaches against AD. Herein, a pulsed laser ablation (PLA) method is used to fabricate ultra-small carbon quantum dots (C-QDs) with uniform size. The reduced Aβ42 aggregation by the C-QDs was confirmed by transmission electron microscopy (TEM), thioflavin T assay and circular dichroism (CD) spectroscopy. The results of cell viability experiments showed that the presence of the C-QDs could significantly reduce the cytotoxicity of Aβ42. Furthermore, in vivo studies demonstrate that C-QDs can decrease Aβ42 deposits and promote the biological activity of an AD model of Caenorhabditis elegans CL2006. This work demonstrates the viability of using ultrasmall C-QDs to inhibit amyloid-β aggregation and alleviate amyloid-β mediated neurotoxicity.

Physical and chemical properties of carbon nanotubes in view of mechanistic neuroscience investigations. Some outlook from condensed matter, materials science and physical chemistry

The open border between non-living and living matter, suggested by increasingly emerging fields of nanoscience interfaced to biological systems, requires a detailed knowledge of nanomaterials properties. An account of the wide spectrum of phenomena, belonging to physical chemistry of interfaces, materials science, solid state physics at the nanoscale and bioelectrochemistry, thus is acquainted for a comprehensive application of carbon nanotubes interphased with neuron cells. This review points out a number of conceptual tools to further address the ongoing advances in coupling neuronal networks with (carbon) nanotube meshworks, and to deepen the basic issues that govern a biological cell or tissue interacting with a nanomaterial. Emphasis is given here to the properties and roles of carbon nanotube systems at relevant spatiotemporal scales of individual molecules, junctions and molecular layers, as well as to the point of view of a condensed matter or materials scientist. Carbon nanotube interactions with blood-brain barrier, drug delivery, biocompatibility and functionalization issues are also regarded.

Zinc oxide nanoparticle interface moderation with tyrosine and tryptophan reverses the pro-amyloidogenic property of the particle

Zinc oxide nanoparticle with negative surface potential (ZnONP) enhances bovine insulin fibrillation. Here, we are exploring ZnONP with positive surface potential (ZnONP_Unc) and surface functionalized with tyrosine and tryptophan amino acids to observe the effects of surface potential and surface functional groups on the fibrillation. ZnONP_Unc, despite of inversed surface potential, enhances the insulin fibrillation with increase in the interface concentration at physiological pH. Whereas, the interface moderation with the amino acids mitigates the surface-mediated insulin fibrillation propensity. Additionally, the study indicates that the change in interfacial functional groups at ZnONP_Unc significantly reverses the interface-mediated destabilization of insulin conformation. The functional groups from the amino acids, like CO, N-H and aromatic functional groups, are anticipated to further stabilize the insulin conformation by forming hydrogen bond and van der Waals interactions with the key amyloidogenic sequences of insulin, A13-A20 from A-chain and B9-B20 from B-chain. Hence, the altered interaction profile, with change in interfacial functional groups, mitigates the interface-mediated insulin fibrillation and the ZnONP_Unc-/fibril-mediated cytotoxicity.

Molecular mechanisms of resveratrol and EGCG in the inhibition of Aβ42 aggregation and disruption of Aβ42 protofibril: similarities and differences

The aggregation of amyloid-β protein (Aβ) into fibrillary deposits is implicated in Alzheimer's disease (AD), and inhibiting Aβ aggregation and clearing Aβ fibrils are considered as promising strategies to treat AD. It has been reported that resveratrol (RSV) and epigallocatechin-3-gallate (EGCG), two of the most extensively studied natural polyphenols, are able to inhibit Aβ fibrillization and remodel the preformed fibrillary aggregates into amorphous, non-toxic species. However, the mechanisms by which RSV inhibits Aβ₄₂ aggregation and disrupts Aβ₄₂ protofibril, as well as the inhibitory/disruptive mechanistic similarities and differences between RSV and EGCG, remain mostly elusive. Herein, we performed extensive all-atom molecular dynamics (MD) simulations on Aβ₄₂ dimers (the early aggregation state of Aβ₄₂) and protofibrils (the intermediate of Aβ₄₂ fibril formation and elongation) in the absence/presence of RSV or EGCG molecules. Our simulations show that both RSV and EGCG can bind with Aβ₄₂ monomers and inhibit the dimerization of Aβ₄₂. The binding of RSV with Aβ₄₂ peptide is mostly viaπ-π stacking interactions, while the binding of EGCG with Aβ₄₂ is mainly through hydrophobic, π-π stacking, and hydrogen-bonding interactions. Moreover, both RSV and EGCG disrupt the β-sheet structure and K28-A42 salt bridges, leading to a disruption of Aβ₄₂ protofibril structure. RSV mainly binds with residues whose side-chains point inwards from the surface of the protofibril, while EGCG mostly binds with residues whose side-chains point outwards from the surface of the protofibril. Furthermore, RSV interacts with Aβ₄₂ protofibrils mostly viaπ-π stacking interactions, while EGCG interacts with Aβ₄₂ protofibrils mainly via hydrogen-bonding and hydrophobic interactions. For comparison, we also explore the effects of RSV/EGCG molecules on the aggregation inhibition and protofibril disruption of the Iowa mutant (D23N) Aβ. Our findings may pave the way for the design of more effective drug candidates as well as the utilization of cocktail therapy using RSV and EGCG for the treatment of AD.

Inhibition of Amyloid Aggregation and Toxicity with Janus Iron Oxide Nanoparticles

Amyloid aggregation is a ubiquitous form of protein misfolding underlying the pathologies of Alzheimer's disease (AD), Parkinson's disease (PD) and type 2 diabetes (T2D), three primary forms of human amyloid diseases. While much has been learned about the origin, diagnosis and management of these neurological and metabolic disorders, no cure is currently available due in part to the dynamic and heterogeneous nature of the toxic oligomers induced by amyloid aggregation. Here we synthesized beta casein-coated iron oxide nanoparticles (βCas IONPs) via a BPA-P(OEGA-b-DBM) block copolymer linker. Using a thioflavin T kinetic assay, transmission electron microscopy, Fourier transform infrared spectroscopy, discrete molecular dynamics simulations and cell viability assays, we examined the Janus characteristics and the inhibition potential of βCas IONPs against the aggregation of amyloid beta (Aβ), alpha synuclein (αS) and human islet amyloid polypeptide (IAPP) which are implicated in the pathologies of AD, PD and T2D. Incubation of zebrafish embryos with the amyloid proteins largely inhibited hatching and elicited reactive oxygen species, which were effectively rescued by the inhibitor. Furthermore, Aβ-induced damage to mouse brain was mitigated in vivo with the inhibitor. This study revealed the potential of Janus nanoparticles as a new nanomedicine against a diverse range of amyloid diseases.

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.

Antimicrobial α-defensins as multi-target inhibitors against amyloid formation and microbial infection

Amyloid aggregation and microbial infection are considered as pathological risk factors for developing amyloid diseases, including Alzheimer's disease (AD), type II diabetes (T2D), Parkinson's disease (PD), and medullary thyroid carcinoma (MTC). Due to the multifactorial nature of amyloid diseases, single-target drugs and treatments have mostly failed to inhibit amyloid aggregation and microbial infection simultaneously, thus leading to marginal benefits for amyloid inhibition and medical treatments. Herein, we proposed and demonstrated a new "anti-amyloid and antimicrobial hypothesis" to discover two host-defense antimicrobial peptides of α-defensins containing β-rich structures (human neutrophil peptide of HNP-1 and rabbit neutrophil peptide of NP-3A), which have demonstrated multi-target, sequence-independent functions to (i) prevent the aggregation and misfolding of different amyloid proteins of amyloid-β (Aβ, associated with AD), human islet amyloid polypeptide (hIAPP, associated with T2D), and human calcitonin (hCT, associated with MTC) at sub-stoichiometric concentrations, (ii) reduce amyloid-induced cell toxicity, and (iii) retain their original antimicrobial activity upon the formation of complexes with amyloid peptides. Further structural analysis showed that the sequence-independent amyloid inhibition function of α-defensins mainly stems from their cross-interactions with amyloid proteins via β-structure interactions. The discovery of antimicrobial peptides containing β-structures to inhibit both microbial infection and amyloid aggregation greatly expands the new therapeutic potential of antimicrobial peptides as multi-target amyloid inhibitors for better understanding pathological causes and treatments of amyloid diseases.

Polyoxometalates as Effective Nano-inhibitors of Amyloid Aggregation of Pro-inflammatory S100A9 Protein Involved in Neurodegenerative Diseases

Pro-inflammatory and amyloidogenic S100A9 protein is central to the amyloid-neuroinflammatory cascade in neurodegenerative diseases. Polyoxometalates (POMs) constitute a diverse group of nanomaterials, which showed potency in amyloid inhibition. Here, we have demonstrated that two selected nanosized niobium POMs, Nb₁₀ and TiNb₉, can act as potent inhibitors of S100A9 amyloid assembly. Kinetics analysis based on ThT fluorescence experiments showed that addition of either Nb₁₀ or TiNb₉ reduces the S100A9 amyloid formation rate and amyloid quantity. Atomic force microscopy imaging demonstrated the complete absence of long S100A9 amyloid fibrils at increasing concentrations of either POM and the presence of only round-shaped and slightly elongated aggregates. Molecular dynamics simulation revealed that both Nb₁₀ and TiNb₉ bind to native S100A9 homo-dimer by forming ionic interactions with the positively charged Lys residue-rich patches on the protein surface. The acrylamide quenching of intrinsic fluorescence showed that POM binding does not perturb the Trp 88 environment. The far and near UV circular dichroism revealed no large-scale perturbation of S100A9 secondary and tertiary structures upon POM binding. These indicate that POM binding involves only local conformational changes in the binding sites. By using intrinsic and 8-anilino-1-naphthalene sulfonate fluorescence titration experiments, we found that POMs bind to S100A9 with a K_d of ca. 2.5 μM. We suggest that the region, including Lys 50 to Lys 54 and characterized by high amyloid propensity, could be the key sequences involved in S1009 amyloid self-assembly. The inhibition and complete hindering of S100A9 amyloid pathways may be used in the therapeutic applications targeting the amyloid-neuroinflammatory cascade in neurodegenerative diseases.

Application of carbon nano onions in the biomedical field: recent advances and challenges

Carbon nano onions (CNOs) are carbonaceous nanostructures composed of multiple concentric shells of fullerenes. These cage-within-cage structures remain as one of the most exciting and fascinating carbon forms, along with graphene and its derivatives, due to their unique chemical and physical properties. Their exceptional biocompatibility and biosafety make them an attractive choice in a wide range of areas, including biological systems. This nanomaterial displays low toxicity, high dispersity in aqueous solutions (upon surface functionalization), and high pharmaceutical efficiency. Even though CNOs were discovered almost simultaneously along with carbon nanotubes (CNTs), their potential in biomedical applications still appears unrealized. The existence of CNOs is equally important, just like any other carbon nanostructures such as CNTs and fullerenes, because they display the ability of carbon to form another unique nanostructure with wonderful properties. Therefore, this mini-review summarizes recent studies geared towards developing CNOs for various biomedical applications, including sensing, drug delivery, imaging, tissue engineering, and as a therapeutic drug. It concludes by discussing other potential applications of this unique nanomaterial.

Current Strategies for Modulating Aβ Aggregation with Multifunctional Agents

Alzheimer's disease (AD), as the primary cause of dementia, has seriously affected millions of people worldwide and brought a very heavy financial and social burden. With the growth of population and aging, the situation will worsen unless efficacious drugs are found to reverse, stop, or even slow down disease progression. More and more evidence has demonstrated that amyloid-β (Aβ) aggregation is an upstream causative factor in AD pathogenesis and then triggers a slew of pathological events. Furthermore, the concentrated redox metal ions in the AD brain, especially Cu(II), can significantly exacerbate Aβ aggregation and contribute to the formation of neurotoxic reactive oxygen species (ROS). Therefore, the inhibition of Aβ aggregation and relief of amyloidosis-initiated neurotoxicity play a critical role in AD treatment. Until now, several methods have been proposed to modulate Aβ aggregation, such as developing aggregation inhibitors to interfere with Aβ assembly via noncovalent interactions, copper chelators to cut off metal-accelerated Aβ aggregation and concomitant cytotoxicity, photooxidation to reduce the hydrophobicity and aggregation tendency of Aβ, thermal dissociation to disrupt amyloid aggregates susceptible to temperature, degradation with artificial protease to fracture the Aβ peptide into small fragments, and the clearance of peripheral Aβ to bypass the obstruction of the BBB and reduce the Aβ burden.In this Account, we focus on our contributions to the development of Aβ-targeted multifunctional molecules and nanoparticles, emphasizing the diversified strategies and synergistic therapeutic effects. These therapeutic agents possess the following multifunctionalities: (1) compared with frequently used aggregation inhibitors restricted by intrinsically feeble and sensitive noncovalent interactions, multifunctional agents can efficiently block Aβ aggregation by exploiting two or more Aβ-specific inhibition strategies simultaneously; (2) apart from regulating Aβ aggregation, multipronged agents can also target and modulate other pathological factors in AD pathogenesis, such as increased oxidative stress, abnormal copper accumulation, and irreversible neuron loss; (3) multifunctional platforms with both diagnostic and therapeutic modalities through integrating in situ imaging, real-time diagnostics, a multitarget direction, stimuli-responsive drug release, and the blood-brain barrier (BBB) translocation features are instrumental in improving drug levels at trouble sites, diminishing off-target adverse reactions, evaluating therapeutic effects, and averting overtreatment.Given the fact that amyloid aggregation, local inflammation, and metal dyshomeostasis are universal biomarkers shared by various neurodegenerative disorders, this Account provides a perspective for the evolution of customized therapeutic agents with multiple reactivities for other neurodegenerative diseases. In addition, recent studies have indicated that Aβ aggregates can enter the nucleus and induce DNA damage and anomalous conformational transition. We also explore the influences of DNA on the biological effects of Aβ aggregates.

Photoresponsive materials for intensified modulation of Alzheimer's amyloid-β protein aggregation: A review

The abnormal self-assembly of amyloid-β protein (Aβ) into toxic aggregates is a major pathological hallmark of Alzheimer's disease (AD). Modulation of Aβ fibrillization with pharmacological modalities has become an active field of research, which aims to mitigate Aβ-induced neurotoxicity and ameliorate impaired recognition. Among the various strategies for AD treatment, phototherapy, including photothermal therapy (PTT), photodynamic therapy (PDT), and photoresponsive release systems have attracted increased attention because of the spatiotemporal controllability. Under the irradiation of light, the heat or reactive oxygen species generated by photothermal or photodynamic processes significantly enhances the efficacy of the inhibitor or modulator, and the "caged" drug can be accurately released at the intended site, thus avoiding adverse effects. This review, from a viewpoint of materials, focuses on the recent advances in modulating Aβ aggregation by light that irradiates on the materials that function on modulating Aβ aggregation. Representative examples of PTT, PDT, and photoresponsive drug release systems are discussed in terms of inhibitory mechanism, the unique properties of materials, and the design of modulators. The major challenges of phototherapy against AD are addressed and the promising prospects are proposed. It is concluded that the noninvasive light-assisted approaches will become a promising strategy for intensifying the modulation of Aβ aggregation and thus facilitating AD treatment. STATEMENT OF SIGNIFICANCE: Alzheimer's disease (AD) with the hallmark of amyloid-β protein (Aβ) deposition is affecting more than 50 million people globally. It is urgent to explore intelligent materials to modulate Aβ aggregation. This review summarizes the intensified modulation of Aβ aggregation by a variety of photoresponsive materials including photothermal, photosensitizing and photoresponsive release materials, focusing on their characteristics and functionalities. We believe this review would arouse more interest in the research field of stimuli-responsive materials and promote their clinical applications in AD therapy.

Amyloid Oligomers: A Joint Experimental/Computational Perspective on Alzheimer's Disease, Parkinson's Disease, Type II Diabetes, and Amyotrophic Lateral Sclerosis

Protein misfolding and aggregation is observed in many amyloidogenic diseases affecting either the central nervous system or a variety of peripheral tissues. Structural and dynamic characterization of all species along the pathways from monomers to fibrils is challenging by experimental and computational means because they involve intrinsically disordered proteins in most diseases. Yet understanding how amyloid species become toxic is the challenge in developing a treatment for these diseases. Here we review what computer, in vitro, in vivo, and pharmacological experiments tell us about the accumulation and deposition of the oligomers of the (Aβ, tau), α-synuclein, IAPP, and superoxide dismutase 1 proteins, which have been the mainstream concept underlying Alzheimer's disease (AD), Parkinson's disease (PD), type II diabetes (T2D), and amyotrophic lateral sclerosis (ALS) research, respectively, for many years.

The application of multifunctional nanomaterials in Alzheimer's disease: A potential theranostics strategy

By virtue of their small size, nanomaterials can cross the blood-brain barrier and, when modified to target specific cells or regions, can achieve high bioavailability at the intended site of action. Modified nanomaterials are therefore promising agents for the diagnosis and treatment of neurodegenerative diseases such as Alzheimer's disease (AD). Here we review the roles and mechanisms of action of nanomaterials in AD. First, we discuss the general characteristics of nanomaterials and their application to nanomedicine. Then, we summarize recent studies on the diagnosis and treatment of AD using modified nanomaterials. These studies indicate that using nanomaterials is a potential strategy for AD treatment by slowing the progression of AD through enhanced therapeutic effects.

Isomeric Effect of Nano-Inhibitors on Aβ40 Fibrillation at The Nano-Bio Interface

Chemical and physical properties of nanobio interface substantially affect the conformational transitions of adjacent biomolecules. Previous studies have reported the chiral effect and charge effect of nanobio interface on the misfolding, aggregation, and fibrillation of amyloid protein. However, the isomeric effect of nanobio interface on protein/peptides amyloidosis is still unclear. Here, three isomeric nanobio interfaces were designed and fabricated based on the same sized gold nanoclusters (AuNCs) modified with 4-mercaptobenzoic acid (p-MBA), 3-mercaptobenzoic acid (m-MBA), and 2-mercaptobenzoic acid (o-MBA). Then three isomeric AuNCs were employed as models to explore the isomeric effect on the misfolding, aggregation, and fibrillation of Aβ₄₀ at nanobio interfaces. Site-specific replacement experiments on the basis of theoretical analysis revealed the possible mechanism of Aβ₄₀ interacting with isomeric ligands of AuNCs at the nanobio interfaces. The distance and orientation of -COOH group from the surface of AuNCs can affect the electrostatic interaction between isomeric ligands and the positively charged residues (R5, K16, and K28) of Aβ₄₀, which may affect the inhibition efficiency of isomeric AuNCs on protein amyloidosis. Actually, the amyloid fibrillation kinetics results together with atomic force microscope (AFM) images, dynamic light scattering (DLS) results and circular dichroism (CD) spectra indeed proved that all the three isomeric AuNCs could inhibit the misfolding, aggregation and fibrillation of Aβ₄₀ in a dose-dependent manner, and the inhibition efficiency was definitely different from each other. The inhibition efficiency of o-MBA-AuNCs was higher than that of m-MBA-AuNCs and p-MBA-AuNCs at the same dosage. These results provide an insight for isomeric effect at nanobio interfaces, and open an avenue for structure-based nanodrug design target Alzheimer's disease (AD) and even other protein conformational diseases.

Impact of porous nanomaterials on inhibiting protein aggregation behaviour

Aggregation of intrinsically disordered as well as the ordered proteins under certain premises or physiological conditions leads to pathological disorder. Here we have presented a detailed investigation on the effect of a porous metallic (Au) and a non-metallic (Si) nanomaterial on the formation of ordered (fiber-like/amyloid) and disordered (amorphous) aggregates of proteins. Porous nanogold (PNG) was found to reduce the amyloid aggregation of insulin but does not have much impact on the lag phase in the aggregation kinetics, whereas porous nano-silica (PNS) was found both to decrease the amount of aggregation as well as prolong the lag phase of amyloid fiber formation from insulin. On the other hand, both the porous nanoparticles are found to decrease the extent of amorphous aggregation (with slight improvement for PNS) of pathogenic huntingtin (Htt) protein in Huntington's disease cell model. This is a noted direct observation in controlling and understanding protein aggregation diseases which may help us to formulate nanotherapeutic drugs for future clinical applications.

Aggregation of intrinsically disordered as well as the ordered proteins under certain premises or physiological conditions leads to pathological disorder.

Biophysical, Biochemical, and Behavioral Implications of ApoE3 Conjugated Donepezil Nanomedicine in a Aβ1-42 Induced Alzheimer's Disease Rat Model

Alzheimer's disease (AD) is a progressive neurological disorder and is the most common type of dementia. Amyloid β (Aβ) plaques play an important role in the pathophysiology of AD. However, the existing therapeutic strategies are not effective for the management of both Aβ-induced neurotoxicity and Aβ fibrils clearance in biological conditions. Herein, we have developed lipoprotein conjugated polymeric nanoparticles that can boost the clearance rate of Aβ fibrils and mitigate Aβ-induced neurotoxicity in AD rat. These nanoparticles were designed by loading donepezil in an amphiphilic polymer with a lipoprotein (ApoE3) integrated over the surface. Polymeric nanoparticles were prepared by a nanoprecipitation method, and ApoE3 was conjugated to the polymer layer by polysorbate 80. In the present study, we intended to examine the protective effect of ApoE3 nanoparticles against Aβ-induced neurotoxicity both in vitro and in vivo to evaluate if these can reduce the Aβ fibril formation and cognitive and behavioral deficits observed in AD induced rats. In the in vitro study, neurotoxicity induced by Aβ_1-42 in human neuroblastoma (SH-SY5Y) cells was found to be significantly reduced upon treatment with ApoE3 donepezil nanoparticles. The presence of the ApoE3 significantly modified the morphology of Aβ fibrils and also inhibited the formation Aβ oligomers. Moreover, in the in vivo study, following treatment, AD induced rats were tested on Morris water maze (MWM) and passive avoidance task for their cognitive ability and sacrificed for biochemical estimations. From our observations, ApoE3 donepezil nanoparticles exhibited neuroprotection in the Aβ_1-42 induced model by mitigating the pathological features and cognitive impairments. Thus, we anticipate that the nanosized lipoprotein carriers will possibly offer a rational therapeutic strategy in the formulation development of AD.

Graphene oxide improves postoperative cognitive dysfunction by maximally alleviating amyloid beta burden in mice

Rationale: Graphene oxide (GO) based nanomaterials have shown potential for the diagnosis and treatment of amyloid-β (Aβ)-related diseases, mainly on Alzheimer's disease (AD). However, these nanomaterials have limitations. How GO is beneficial to eliminate Aβ burden, and its physiological function in Aβ-related diseases, still needs to be investigated. Moreover, postoperative cognitive dysfunction (POCD) is an Aβ-related common central nervous system complication, however, nanomedicine treatment is lacking.

Methods: To evaluate the effects of GO on Aβ levels, HEK293T-APP-GFP and SHSY5Y-APP-GFP cells are established. Intramedullary fixation surgery for tibial fractures under inhalation anesthesia is used to induce dysfunction of fear memory in mice. The fear memory of mice is assessed by fear conditioning test.

Results: GO treatment maximally alleviated Aβ levels by simultaneously reducing Aβ generation and enhancing its degradation through inhibiting β-cleavage of amyloid precursor protein (APP) and improving endosomal Aβ delivery to lysosomes, respectively. In postoperative mice, the hippocampal Aβ levels were significantly increased and hippocampal-dependent fear memory was impaired. However, GO administration significantly reduced hippocampal Aβ levels and improved the cognitive function of the postoperative mice.

Conclusion: GO improves fear memory of postoperative mice by maximally alleviating Aβ accumulation, providing new evidence for the application of GO-based nanomedicines in Aβ-related diseases.

Blood-Brain Barrier Permeable Chitosan Oligosaccharides Interfere with β-Amyloid Aggregation and Alleviate β-Amyloid Protein Mediated Neurotoxicity and Neuroinflammation in a Dose- and Degree of Polymerization-Dependent Manner

It is proven that β-amyloid (Aβ) aggregates containing cross-β-sheet structures led to oxidative stress, neuroinflammation, and neuronal loss via multiple pathways. Therefore, reduction of Aβ neurotoxicity via inhibiting aggregation of Aβ or dissociating toxic Aβ aggregates into nontoxic forms might be effective therapeutic methods for Alzheimer's disease (AD) treatment. This study was designed to explore interference of chitosan oligosaccharides (COS) on β-(1-42)-amyloid protein (Aβ42) aggregation and Aβ42-induced cytotoxicity. Here it was demonstrated that COS showed good blood-brain barrier (BBB) penetration ability in vitro and in vivo. The experimental results showed that COS efficiently interfered with Aβ42 aggregation in dose- and degree of polymerization (DP)-dependent manners, and COS monomer with DP6 showed the best effect on preventing conformational transition into β-sheet-rich structures. Based on the binding affinity analysis by microscale thermophoresis (MST), it was confirmed that COS could directly bind with Aβ42 in a DP-dependent manner. Our findings demonstrated that different performance of COS monomers with different DPs against Aβ42 assembly was, to some extent, attributable to their different binding capacities with Aβ42. As a result, COS significantly ameliorated Aβ42-induced cytotoxicity. Taken together, our studies would point towards a potential role of COS in treatment of AD.

Investigating the effect of sugar-terminated nanoparticles on amyloid fibrillogenesis of β-lactoglobulin

In vivo tissue deposition of fibrillar protein aggregates is the cause of several degenerative diseases. Evidence suggests that interfering with the pathology-associated amyloid fibrillogenesis by inhibitory molecules is envisaged as the primary therapeutic strategy. Amyloid fibril formation of proteins has been demonstrated to be influenced by nanoparticles/nanomaterials. As compared with their molecular form counterpart, this work examined the effect of sucrose-terminated nanoparticles on the in vitro amyloid fibrillogenesis and structural properties of β-lactoglobulin at pH 2.0 and 80 °C. ThT binding and electron microscopy results demonstrated that sucrose-terminated nanoparticles were able to suppress β-lactoglobulin fibrillogenesis in a concentration-dependent fashion. Importantly, sucrose-terminated nanoparticles showed better β-lactoglobulin fibril-inhibiting ability than sucrose molecules. ANS fluorescence and right-angle light scattering results showed reduced solvent exposure and decreased aggregation, respectively, in the β-lactoglobulin samples upon treatment with sucrose-terminated nanoparticles. Moreover, fluorescence quenching analyses revealed that the static quenching mechanism and formation of a non-fluorescent fluorophore-nanoparticle complex are involved in the nanoparticle-β-lactoglobulin interaction. We believe that the results from this study may suggest that the nanoparticle form of biocompatible sugar-related osmolytes may serve as effective inhibiting/suppressing agents toward protein fibrillogenesis.

Graphene Quantum Dots as Flourishing Nanomaterials for Bio-Imaging, Therapy Development, and Micro-Supercapacitors

Graphene quantum dots (GQDs) are considerably a new member of the carbon family and shine amongst other members, thanks to their superior electrochemical, optical, and structural properties as well as biocompatibility features that enable us to engage them in various bioengineering purposes. Especially, the quantum confinement and edge effects are giving GQDs their tremendous character, while their heteroatom doping attributes enable us to specifically and meritoriously tune their prospective characteristics for innumerable operations. Considering the substantial role offered by GQDs in the area of biomedicine and nanoscience, through this review paper, we primarily focus on their applications in bio-imaging, micro-supercapacitors, as well as in therapy development. The size-dependent aspects, functionalization, and particular utilization of the GQDs are discussed in detail with respect to their distinct nano-bio-technological applications.

A Biocompatible Second Near-Infrared Nanozyme for Spatiotemporal and Non-Invasive Attenuation of Amyloid Deposition through Scalp and Skull

Phototherapy, such as photodynamic therapy and photothermal therapy, holds great potential for modulation of Alzheimer's β-amyloid (Aβ) self-assembly. Unfortunately, current works for phototherapy of Alzheimer's disease (AD) are just employing either visible or first near-infrared (NIR-I) light with limited tissue penetration, which can not avoid damaging nearby normal tissues of AD patients through the dense skull and scalp. To overcome the shortcomings of AD phototherapy, herein we report an amyloid targeting, N-doped three-dimensional mesoporous carbon nanosphere (KD8@N-MCNs) as a second near-infrared (NIR-II) PTT agent. This makes it possible for photothermal dissociation of Aβ aggregates through the scalp and skull in a NIR-II window without hurting nearby normal tissues. Besides, KD8@N-MCNs have both superoxide dismutase and catalase activities, which can scavenge intracellular superfluous reactive oxygen species and alleviate neuroinflammation in vivo. Furthermore, KD8@N-MCNs efficiently cross the blood-brain barrier owing to the covalently grafted target peptides of KLVFFAED on the nanosphere surface. In vivo studies demonstrate that KD8@N-MCNs decrease Aβ deposits, ameliorate memory deficits, and alleviate neuroinflammation in the 3xTg-AD mouse model. Our work provides a biocompatible and non-invasive way to attenuate AD-associated pathology.

Fullerenes as an Effective Amyloid Fibrils Disaggregating Nanomaterial

Nowadays, determining the disassembly mechanism of amyloids under nanomaterials action is a crucial issue for their successful future use in therapy of neurodegenerative and overall amyloid-related diseases. In this study, the antiamyloid disassembly activity of fullerenes C₆₀ and C₇₀ dispersed in 1-methyl-2-pyrrolidinone (NMP) toward amyloid fibrils preformed from lysozyme and insulin was investigated using a combination of different experimental techniques. Thioflavin T fluorescence assay and atomic force microscopy were applied for monitoring of disaggregation activity of fullerenes. It was demonstrated that both types of fullerene-based complexes are very effective in disassembling preformed fibrils, and characterized by the low apparent half-maximal disaggregation concentration (DC₅₀) in the range of ∼22-30 μg mL^-1. Small-angle neutron scattering was employed to monitor the different stages of the disassembly process with respect to the size and morphology of the aggregates. Based on the obtained results, a possible disassembly mechanism for amyloid fibrils interacting with fullerene/NMP complexes was proposed. The study is a principal step in understanding of the fullerenes destruction mechanism of the protein amyloids, as well as providing valuable information on how macromolecules can be engineered to disassemble unwanted amyloid aggregates by different mechanisms.

Nanosilver Mitigates Biofilm Formation via FapC Amyloidosis Inhibition

Multidrug resistance of bacteria is a major challenge due to the wide-spread use of antibiotics. While a range of strategies have been developed in recent years, suppression of bacterial activity and virulence via their network of extracellular amyloid has rarely been explored, especially with nanomaterials. Here, silver nanoparticles and nanoclusters (AgNPs and AgNCs) capped with cationic branched polyethylenimine polymer are synthesized, and their antimicrobial potentials are determined at concentrations safe to mammalian cells. Compared with the ultrasmall AgNCs, AgNPs entail stronger binding to suppress the fibrillization of FapC, a major protein constituent of the extracellular amyloid matrix of Pseudomonas aeruginosa. Both types of nanoparticles exhibit concentration-dependent antibiofilm and antimicrobial properties against P. aeruginosa. At concentrations of 1 × 10-6 m or below, both the bactericidal activity of AgNCs and the antibiofilm capacity of AgNPs are associated with their structure-mediated bio-nano interactions but not ion release. For AgNPs, specifically, their antibiofilm potency correlates with their capacity of FapC fibrillization inhibition, but not with their bactericidal activity. This study demonstrates the antimicrobial potential of safe nanotechnology through the novel route of amyloidosis inhibition.

Ferrocene-modified peptides as inhibitors against insulin amyloid aggregation based on molecular simulation

Peptide-based inhibitors have gradually been implicated as drugs for treating protein folding diseases because of their favorable biocompatibility and low toxicity. To develop potential therapeutic strategies for amyloid-related disorders, short peptides modified by Fc, ferrocene-l-Phe-l-Phe (Fc-FF) and ferrocene-l-Phe-l-Tyr (Fc-FY), were used as inhibitors for the investigation of the aggregation behavior of insulin. Firstly, molecular docking predicted the interaction between both Fc-peptides and insulin. Then, the experimental data from ThT, DLS, CD and TEM confirmed that Fc-FF and Fc-FY effectively inhibited insulin fibrillation and disaggregated mature insulin fibrils. Based on a dose-dependent manner, both Fc-peptides can strongly inhibit insulin fibrillation, extend lag phase time, reduce final fibril formation (beyond 99% by Fc-peptides of 400 µM), decrease the formation of high-content β-sheet structures and reduce the size of insulin fibrils. Additionally, we found that compared with Fc-FY, the better inhibitory effect of Fc-FF at concentration below 400 µM was mainly resulted from the difference in π-π interaction and hydrogen bonds between Fc-peptides and insulin, according to molecular dynamics analysis. Our results demonstrated Fc-peptides, Fc-FF and Fc-FY, may play effective roles in the development of new therapeutic drugs or strategies for amyloid-related disorders, and the molecular dynamics simulation may be helpful for designing appropriate inhibitors of anti-amyloidosis diseases.

Geometry-induced protein reorientation on the spikes of plasmonic gold nanostars

Functionalized gold nanostars (AuStrs) are remarkable candidates for drug delivery, photothermal therapy and imaging due to their large surface area to volume ratio and plasmonic properties. In this study, we address the challenge of achieving therapeutically controlled dosing using these high aspect ratio nanoparticle vectors by tailoring the nanostar loading area and protein conformation. We synthesized a library of different Au nanostars with varied geometries for potential biomedical applications. The Au nanostars were subsequently coated with different amounts of transferrin (Tf) and a novel depletion method was devised to measure the amount of Tf bound to the surface of the nanostructures. This methodology allowed us to show that coating thickness could be controllably varied and moulded onto the nanoparticle's high index features, whilst simultaneously preserving the key properties of the particle. The orientation of the Tf was measured on nanostars and spheres using transmission electron microscopy by negatively staining the Tf. The Tf was conformal on the nanostars, and protein packing efficiency increased on the AuStrs by 14-fold due to a geometry-induced protein reorientation at the nanoparticle surface. Interestingly, the reorientation of the transferrin observed at the AuStrs spikes did not occur at the AuStrs tips thus highlighting surface energy effects associated with surface curvature.

Core/Shell PEGS/HA Hybrid Nanoparticle Via Micelle-Coordinated Mineralization for Tumor-Specific Therapy

Nanomicelles, by virtue of their prominent biocompatibility, degradability, and ability to solubilize hydrophobic drugs, have been widely used as the most effective delivery platform for anticancer drugs. However, undesirable drug-loading capacity, unfeasible modification, poor in vivo stability, and intratumoral penetration remain to be addressed. Herein, we introduce a novel core/shell PEGylated poly(glycerol sebacate) (PEGS)/hydroxyapatite (HA) hybrid nanomicelle based on a unique triblock PEGS substrate with functional carboxyls in terminals and free hydroxyls as pendant groups. The hydrophobic doxorubicin (DOX) can be controllably encapsulated in the core of nanomicelles via hydrogen bonding, and ensuing in situ mineralization of HA occurs as a shell layer with the electrostatic effect between the carboxylate radical (COO^-) and calcium ion (Ca²⁺). Through optimizing the coordination of PEGS nanomicelles and HA mineralization, 20-30 nm spherical nanoparticles can be formed with considerable drug loading (0.38 mg DOX/1 mg nanoparticles) and a sensitive pH-responsive release (about 50% release amount at pH 5.6 while <5% release amount at pH 7.4 in 24 h). In further in vitro studies, this PEGS/HA hybrid nanoparticle system exhibits excellent selective tumor inhibitory efficacy, while in in vivo studies, high efficacy of tumor suppression and low incidence of toxicity can be evidenced in a DOX-loaded PEGS/HA group (71.7% decrease in average tumor volume compared to a control group after 15 day hypodermic treatment). The core/shell PEGS/HA nanoparticle coordinated with PEGS nanomicelles and in situ HA mineralization represents high drug-loading capacity, multifunctional possibility, and tumor-selective and responsive release profiles and could offer a highly promising platform for tumor therapy in clinical application.

LVFFARK-PEG-Stabilized Black Phosphorus Nanosheets Potently Inhibit Amyloid-β Fibrillogenesis

Deposition of amyloid-β (Aβ) aggregates in the brain is a main pathological hallmark of Alzheimer's disease (AD), so inhibition of Aβ aggregation has been considered as a promising strategy for AD prevention and treatment. Black phosphorus (BP) is a 2D nanomaterial with high biocompatibility and unique biodegradability, but its potential application in biomedicine suffers from the rapid degradability and unfunctionability. To overcome the drawbacks and broaden its application, we have herein designed an Aβ inhibitor (LK7)-coupled and polyethylene glycol (PEG)-stabilized BP-based nanosystem. The PEGylated-LK7-BP nanosheets (PEG-LK7@BP) not only exhibited a good stability but also demonstrated a significantly enhanced inhibitory potency on Aβ₄₂ fibrillogenesis in comparison with its counterparts. This elaborately designed PEG-LK7@BP stopped the conformational transition and suppressed the fibrillization of Aβ₄₂, so it could completely rescue cultured cells from the toxicity of Aβ₄₂ (by increasing the cell viability from 72 to 100%) at 100 μg/mL. It is considered that PEG-LK7@BP could bind Aβ species by enhanced electrostatic and hydrophobic interactions and thus efficiently alleviated Aβ-Aβ interactions. Meanwhile, the coupled LK7 on the BP surface formed a high local concentration that enhanced the affinity between the nanosystem and Aβ species. Finally, PEG could improve the stability and dispersibility of the nanoplatform to make it show an increased inhibitory effect on the amyloid formation. Hence, this work proved that PEG-LK7@BP is a promising nanosystem for the development of amyloid inhibitors fighting against AD.

Effect of CTerm of human albumin on the aggregation propensity of Aβ1-42 peptide: a potential of mean force study

Alzheimer's disease (AD) is the most common progressive neurodegenerative brain disorder. It is characterized by the presence of extracellular aggregated fibrillary form of amyloid beta (Aβ) peptide and intraneuronal neurofibrillary tangles caused by the hyperphosphorylation of tau protein. Monomeric form of Aβ peptide in α-conformation is not toxic but it can undergo self-aggregation to form β-conformation which is neurotoxic. The most promising approach to combat AD is to prevent the self-aggregation of Aβ peptide. Recently, it has been reported that C-terminal (CTerm) of human albumin (HA) binds to the Aβ_1-42 peptide and impairs the Aβ_1-42 aggregation and promotes disassembly of Aβ_1-42 aggregates. In this work, using potential of mean force (PMF) and binding free energy (BFE) calculations, we have demonstrated the effect of CTerm of HA on the dimerization of Aβ_1-42 peptide. From the PMF profile, we noticed Aβ_1-42-CTerm Heterodimer (10.99 kcal mol - 1) complex to have higher disassociation energy than Aβ_1-42-Aβ_1-42 homodimer (2.23 kcal mol - 1) complex. And also from the BFE calculations, we found that the binding affinity between Aβ_1-42 peptide and CTerm (ΔG_bind = -32.27 kcal mol - 1 from MM-GBSA and ΔG_bind = -2.83 kcal mol - 1 from MM-PBSA (molecular mechanics-Poisson - Boltzmann surface area)) to be stronger than the Aβ_1-42 peptide and another Aβ_1-42 peptide (ΔG_bind = -16.20 kcal mol - 1 from MM-GBSA and ΔG_bind = -1.95 kcal mol - 1 from MM-PBSA). In this study, our findings from PMF and BFE analysis of the two complexes provide salient structural, binding and unbinding features and thermodynamics that support the ability of CTerm of HA in affecting the dimerization of Aβ_1-42. Communicated by Ramaswamy H. Sarma.

Au23(CR)14 nanocluster restores fibril Aβ's unfolded state with abolished cytotoxicity and dissolves endogenous Aβ plaques

The misfolding of amyloid-β (Aβ) peptides from the natural unfolded state to β-sheet structure is a critical step, leading to abnormal fibrillation and formation of endogenous Aβ plaques in Alzheimer's disease (AD). Previous studies have reported inhibition of Aβ fibrillation or disassembly of exogenous Aβ fibrils in vitro. However, soluble Aβ oligomers have been reported with increased cytotoxicity; this might partly explain why current clinical trials targeting disassembly of Aβ fibrils by anti-Aβ antibodies have failed so far. Here we show that Au₂₃(CR)₁₄ (a new Au nanocluster modified by Cys-Arg (CR) dipeptide) is able to completely dissolve exogenous mature Aβ fibrils into monomers and restore the natural unfolded state of Aβ peptides from misfolded β-sheets. Furthermore, the cytotoxicity of Aβ₄₀ fibrils when dissolved by Au₂₃(CR)₁₄ is fully abolished. More importantly, Au₂₃(CR)₁₄ is able to completely dissolve endogenous Aβ plaques in brain slices from transgenic AD model mice. In addition, Au₂₃(CR)₁₄ has good biocompatibility and infiltration ability across the blood-brain barrier. Taken together, this work presents a promising therapeutics candidate for AD treatment, and manifests the potential of nanotechnological approaches in the development of nanomedicines.

Adsorption of Amyloidogenic Peptides to Functionalized Surfaces Is Biased by Charge and Hydrophilicity

Surfaces are abundant in living systems, such as in the form of cellular membranes, and govern many biological processes. In this study, the adsorption of the amyloidogenic model peptides GNNQQNY, NNFGAIL, and VQIVYK as well as the amyloid-forming antimicrobial peptide uperin 3.5 (U3.5) were studied at low concentrations (100 μM) to different surfaces. The technique of a quartz crystal microbalance with dissipation monitoring (QCM-D) was applied as it enables the monitoring of mass binding to sensors at nanogram sensitivity. Gold-coated quartz sensors were used as unmodified gold surfaces or functionalized with self-assembled monolayers (SAMs) of alkanethiols (terminated as methyl, amino, carboxyl, and hydroxyl) resulting in different adsorption affinities of the peptides. Our objective was to evaluate the underlying role of the nature and feature of interfaces in biological systems which could concentrate peptides and impact or trigger peptide aggregation processes. In overall, the largely hydrophobic peptides adsorbed with preference to hydrophobic or countercharged surfaces. Further, the glycoprotein lubricin (LUB) was tested as an antiadhesive coating. Despite its hydrophilicity, the adsorption of peptides to LUB coated sensors was similar to the adsorption to unmodified gold surfaces, which indicates that some peptides diffused through the LUB layer to reach the underlying gold sensor surface. The LUB protein-antiadhesive is thus more effective as a biomaterial coating against larger biomolecules than small peptides under the conditions used here. This study provides directions toward a better understanding of amyloid peptide adsorption to biologically relevant interfaces, such as cellular membranes.