The size-effect of gold nanoparticles and nanoclusters in the inhibition of amyloid-β fibrillation

Nanoparticle-assisted tubulin assembly is environment dependent

Nanomaterials acquire a biomolecular corona upon introduction to biological media, leading to biological transformations such as changes in protein function, unmasking of epitopes, and protein fibrilization. Ex vivo studies to investigate the effect of nanoparticles on protein-protein interactions are typically performed in buffer and are rarely measured quantitatively in live cells. Here, we measure the differential effect of silica nanoparticles on protein association in vitro vs. in mammalian cells. BtubA and BtubB are a pair of bacterial tubulin proteins identified in Prosthecobacter strains that self-assemble like eukaryotic tubulin, first into dimers and then into microtubules in vitro or in vivo. Förster resonance energy transfer labeling of each of the Btub monomers with a donor (mEGFP) and acceptor (mRuby3) fluorescent protein provides a quantitative tool to measure their binding interactions in the presence of unfunctionalized silica nanoparticles in buffer and in cells using fluorescence spectroscopy and microscopy. We show that silica nanoparticles enhance BtubAB dimerization in buffer due to protein corona formation. However, these nanoparticles have little effect on bacterial tubulin self-assembly in the complex mammalian cellular environment. Thus, the effect of nanomaterials on protein-protein interactions may not be readily translated from the test tube to the cell in the absence of particle surface functionalization that can enable targeted protein-nanoparticle interactions to withstand competitive binding in the nanoparticle corona from other biomolecules.

Insights into the mechanism of peptide fibril growth on gold surface

Understanding the formation of β-fibrils over the gold surface is of paramount interest in nano-bio-medicinal Chemistry. The intricate mechanism of self-assembly of neurofibrillogenic peptides and their growth over the gold surface remains elusive, as experiments are limited in unveiling the microscopic dynamic details, in particular, at the early stage of the peptide aggregation. In this work, we carried out equilibrium molecular dynamics and enhanced sampling simulations to elucidate the underlying mechanism of the growth of an amyloid-forming sequence of tau fragments over the gold surface. Our results disclose that the collective intermolecular interactions between the peptide chains and peptides with the gold surface facilitate the peptide adsorption, followed by integration, finally leading to the fibril formation.

Engineering Core/Ligands Interfacial Anchors of Nanoparticles for Efficiently Inhibiting Both Aβ and Amylin Fibrillization

Accurate construction of artificial nano-chaperones' structure is crucial for precise regulation of protein conformational transformation, facilitating effective treatment of proteopathy. However, how the ligand-anchors of nano-chaperones affect the spatial conformational changes in proteins remains unclear, limiting the development of efficient nano-chaperones. In this study, three types of gold nanoparticles (AuNPs) with different core/ligands interface anchor structures (Au─NH─R, Au─S─R, and Au─C≡C─R, R = benzoic acid) are synthesized as an ideal model to investigate the effect of interfacial anchors on Aβ and amylin fibrillization. Computational results revealed that the distinct interfacial anchors imparted diverse distributions of electrostatic potential on the nanointerface and core/ligands bond strength of AuNPs, leading to differential interactions with amyloid peptides. Experimental results demonstrated that all three types of AuNPs exhibit site-specific inhibitory effects on Aβ40 fibrillization due to preferential binding. For amylin, amino-anchored AuNPs demonstrate strong adsorption to multiple sites on amylin and effectively inhibit fibrillization. Conversely, thiol- and alkyne-anchored AuNPs adsorb at the head region of amylin, promoting folding and fibrillization. This study not only provided molecular insights into how core/ligands interfacial anchors of nanomaterials induce spatial conformational changes in amyloid peptides but also offered guidance for precisely engineering artificial-chaperones' nanointerfaces to regulate the conformational transformation of proteins.

Biosynthesis of Nanoparticles with Green Tea for Inhibition of β-Amyloid Fibrillation Coupled with Ligands Analysis

Background

Inhibition of amyloid β protein fragment (Aβ) aggregation is considered to be one of the most effective strategies for the treatment of Alzheimer's disease. (-)-Epigallocatechin-3-gallate (EGCG) has been found to be effective in this regard; however, owing to its low bioavailability, nanodelivery is recommended for practical applications. Compared to chemical reduction methods, biosynthesis avoids possible biotoxicity and cumbersome preparation processes.

Materials and Methods

The interaction between EGCG and Aβ42 was simulated by molecular docking, and green tea-conjugated gold nanoparticles (GT-Au NPs) and EGCG-Au NPs were synthesized using EGCG-enriched green tea and EGCG solutions, respectively. Surface active molecules of the particles were identified and analyzed using various liquid chromatography-tandem triple quadrupole mass spectrometry methods. ThT fluorescence assay, circular dichroism, and TEM were used to investigate the effect of synthesized particles on the inhibition of Aβ42 aggregation.

Results

EGCG as well as apigenin, quercetin, baicalin, and glutathione were identified as capping ligands stabilized on the surface of GT-Au NPs. They more or less inhibited Aβ42 aggregation or promoted fibril disaggregation, with EGCG being the most effective, which bound to Aβ42 through hydrogen bonding, hydrophobic interactions, etc. resulting in 39.86% and 88.50% inhibition of aggregation and disaggregation effects, respectively. EGCG-Au NPs were not as effective as free EGCG, whereas multiple thiols and polyphenols in green tea accelerated and optimized heavy metal detoxification. The synthesized GT-Au NPs conferred the efficacy of diverse ligands to the particles, with inhibition of aggregation and disaggregation effects of 54.69% and 88.75%, respectively, while increasing the yield, enhancing water solubility, and decreasing cost.

Conclusion

Biosynthesis of nanoparticles using green tea is a promising simple and economical drug-carrying approach to confer multiple pharmacophore molecules to Au NPs. This could be used to design new drug candidates to treat Alzheimer's disease.

Insights into the interaction and inhibitory action of palmatine on lysozyme fibrillogenesis: Spectroscopic and computational studies

Interaction under amyloidogenic condition between naturally occurring protoberberine alkaloid palmatine and hen egg white lysozyme was executed by adopting spectrofluorometric and theoretical molecular docking and dynamic simulation analysis. In spetrofluorometric method, different types of experiments were performed to explore the overall mode and mechanism of interaction. Intrinsic fluorescence quenching of lysozyme (Trp residues) by palmatine showed effective binding interaction and also yielded different binding parameters like binding constant, quenching constant and number of binding sites. Synchronous fluorescence quenching and 3D fluorescence map revealed that palmatine was able to change the microenvironment of the interacting site. Fluorescence life time measurements strongly suggested that this interaction was basically static in nature. Molecular docking result matched with fluorimetric experimental data. Efficient drug like interaction of palmatine with lysozyme at low pH and high salt concentration prompted us to analyze its antifibrillation potential. Different assays and microscopic techniques were employed for detailed analysis of lysozyme amyloidosis.Thioflavin T(ThT) assay, Congo Red (CR) assay, 8-anilino-1-naphthalenesulfonic acid (ANS) assay, Nile Red (NR) assay, anisotropy and intrinsic fluorescence measurements confirmed that palmatine successfully retarded and reduced lysozyme fibrillation. Dynamic light scattering (DLS) and atomic force microscopy (AFM) further reiterated the excellent antiamyloidogenic potency of palmatine.

Fibrillation of Human Serum Albumin Differentially Affected by Asp-, Arg-, and Tyr-Capped Gold Nanoparticles

Fibrillation of proteins is associated with a number of debilitating diseases, including various neurodegenerative disorders. Prevention of the protein fibrillation process is therefore of immense importance. We investigated the effect of amino acid-capped AuNPs on the prevention of the fibrillation process of human serum albumin (HSA), a model protein. Amino acid-capped AuNPs of varying sizes and agglomeration extents were synthesized under physiological conditions. The AuNPs were characterized by their characteristic surface plasmon resonance (SPR), and their interactions with HSA were investigated through emission spectroscopy in addition to circular dichroism (CD) spectral analyses. Fluorescence lifetime imaging (FLIM) as well as transmission electron microscopy (TEM) were used to observe the fibrillar network. Thermodynamic and kinetic analyses from CD and fluorescence emission spectra provided insights into the fibrillation pathway adopted by HSA in the presence of capped AuNPs. Kinetics of the fibrillation pathway followed by ThT fluorescence emission confirmed the sigmoidal nature of the process. The highest cooperativity was observed in the case of Asp-AuNPs with HSA. This was in accordance with the ΔG value obtained from the CD spectral analyses, where Arg-AuNPs with HSA showed the highest positive ΔG value and Asp-AuNPs with HSA showed the most negative ΔG value. The study provides information about the potential use of conjugate AuNPs to monitor the fibrillation process in proteins.

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.

Design of Magnetic Fe3O4/CeO2 "Core/Shell"-Like Nanocomposites with Pronounced Antiamyloidogenic and Antioxidant Bioactivity

"Core/shell" nanocomposites based on magnetic magnetite (Fe3O4) and redox-active cerium dioxide (CeO2) nanoparticles (NPs) are promising in the field of biomedical interests because they can combine the ability of magnetic NPs to heat up in an alternating magnetic field (AMF) with the pronounced antioxidant activity of CeO2 NPs. Thus, this report is devoted to Fe3O4/CeO2 nanocomposites (NCPs) synthesized by precipitation of the computed amount of "CeO2-shell" on the surface of prefabricated Fe3O4 NPs. The X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy data validated the formation of Fe3O4/CeO2 "core/shell"-like NCPs, in which ultrafine CeO2 NPs with an average size of approximately 3-3.5 nm neatly surround Fe3O4 NPs. The presence of a CeO2 "shell" significantly increased the stability of Fe3O4/CeO2 NCPs in aqueous suspensions: Fe3O4/CeO2 NCPs with "shell thicknesses" of 5 and 7 nm formed highly stable magnetic fluids with ζ-potential values of >+30 mV. The magnetization values of Fe3O4/CeO2 NCPs decreased with a growing CeO2 "shell" around the magnetic NPs; however, the resulting composites retained the ability to heat efficiently in an AMF. The presence of a CeO2 "shell" generates a possibility to precisely regulate tuning of the maximum heating temperature of magnetic NCPs in the 42-50 °C range and stabilize it after a certain time of exposure to an AMF by changing the thickness of the "CeO2-shell". A great improvement was observed in both antioxidant and antiamyloidogenic activities. It was found that inhibition of insulin amyloid formation, expressed in IC50 concentration, using NCPs with a "shell thickness" of 7 nm was approximately 10 times lower compared to that of pure CeO2. For these NCPs, more than 2 times higher superoxide dismutase-like activity was observed. The coupling of both Fe3O4 and CeO2 results in higher bioactivity than either of them individually, probably due to a synergistic catalytic mechanism.

Ultrasmall Coinage Metal Nanoclusters as Promising Theranostic Probes for Biomedical Applications

Ultrasmall coinage metal nanoclusters (NCs, <3 nm) have emerged as a novel class of theranostic probes due to their atomically precise size and engineered physicochemical properties. The rapid advances in the design and applications of metal NC-based theranostic probes are made possible by the atomic-level engineering of metal NCs. This Perspective article examines (i) how the functions of metal NCs are engineered for theranostic applications, (ii) how a metal NC-based theranostic probe is designed and how its physicochemical properties affect the theranostic performance, and (iii) how metal NCs are used to diagnose and treat various diseases. We first summarize the tailored properties of metal NCs for theranostic applications in terms of biocompatibility and tumor targeting. We focus our discussion on the theranostic applications of metal NCs in bioimaging-directed disease diagnosis, photoinduced disease therapy, nanomedicine, drug delivery, and optical urinalysis. Lastly, an outlook on the challenges and opportunities in the future development of metal NCs for theranostic applications is provided.

Bifunctional cysteine gold nanoclusters for β-amyloid fibril inhibition and fluorescence imaging: a distinctive approach to manage Alzheimer's disease

Alzheimer's disease (AD) is a progressive complex neurodegenerative disorder affecting millions of individuals worldwide. Currently, there is no effective treatment for AD. AD is characterized by the deposition of amyloid plaques/fibrils. One major strategy for managing this disease is by slowing the progression of AD using different drugs which could potentially limit free-radical formation, oxidative stress and lipid peroxidation and promote the survival of neurons exposed to β-amyloid. Inhibition of amyloid fibrillization and clearance of amyloid plaques/fibrils are essential for the prevention and treatment of AD. The thiophilic interaction between the side chain of an aromatic residue in a polypeptide and a sulphur atom of the compound can effectively inhibit amyloid fibril formation. In this work, we have synthesized cysteine-capped gold nanoclusters (Cy-AuNCs) which exhibit inherent red emission and can disintegrate amyloid fibrils through the aforementioned thiophilic interactions. Herein, we also used molecular docking to study the thiophilic interactions between the sulphur atom of Cy-AuNCs and the aromatic rings of the protein. Finally, the gold cluster was functionalized with a brain targeting molecule, Levodopa (AuCs-LD), to specifically target the brain and to facilitate passage through the blood brain barrier (BBB). Both Cy-AuNCs and AuCs-LD showed good biocompatibility and the inherent fluorescence properties of nanoclusters enabled real time imaging. The efficacy of the nanoclusters to disintegrate amyloid fibrils and their ability to cross the BBB were demonstrated both in vitro and in vivo in the BBB model and the AD animal model respectively. Our results imply that nanoparticle-based artificial molecular chaperones may offer a promising therapeutic approach for AD.

Effects of the aspect ratio of plasmonic gold nanorods on the inhibition of lysozyme amyloid formation

Amyloid formation due to altered protein folding and aggregation has gained significant attention due to its association with neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and systemic lysozyme amyloidosis. Amyloids are characterized by parallel and anti-parallel cross-β-strands arranged to form stacks of sheets that provide stability and rigidity to the amyloid core. The prototypic protein Hen Egg White Lysozyme (HEWL) has been extensively used to understand protein hydrolysis, fragmentation, folding, misfolding, and amyloid formation. In the present study, we have examined the efficacy of plasmonic gold nanorods (GNRs) as an anti-amyloid agent against HEWL amyloids. Our results reveal that (i) the amyloid inhibition by plasmonic GNRs is dependent on their aspect ratio, (ii) the large aspect ratio GNRs ameliorate amyloid assembly completely, and (iii) GNRs interfere at several stages along the lysozyme fibril-formation pathway and block the conversion of monomeric and oligomeric intermediates into mature fibrils. Using a multi-parametric approach, we demonstrate that GNRs drive HEWL into off-pathway and amyloid-incompetent forms. To establish GNRs as generic amyloid inhibitors, we extended our studies to another archetypal protein, Bovine Serum Albumin (BSA), and observed similar results of GNRs inhibiting BSA aggregation. We believe that our results will pave the way for the potential use of GNRs with current therapeutics to reduce the burden of amyloid-related diseases.

Insights into the remarkable attenuation of hen egg white lysozyme amyloid fibril formation mediated by biogenic gold nanoparticles stabilized by quercetin-functionalized tara gum

Aberrant protein misfolding and/or aggregation and fibrillation has been linked to the pathogenesis of several debilitating chronic diseases including Alzheimer's and Parkinson's disease. Inhibiting protein amyloidogenesis has been proposed as a viable strategy to prevent or ameliorate associated disorders. Herein, we investigated the anti-amyloidogenic properties of biogenic gold nanoparticles (QTG-GNP) prepared via a simple green chemistry route and stabilized by quercetin-functionalized tara gum (QTG). The synthesized QTG-GNP was extensively characterized for its physicochemical attributes via UV-visible spectroscopy, TEM, FESEM, EDX, DLS/Zeta potential, FTIR, RAMAN, XRD, XPS, and TGA analyses, as well as for its biological properties. The results revealed that small-sized (5.01 ± 1.17 nm), well-dispersed, highly stable and round-shaped biogenic gold nanoparticles were successfully synthesized at room temperature with QTG as the sole reductant /stabilizer. Importantly, QTG-GNP demonstrated potent anti-aggregation and fibrillation inhibitory effects against amyloidogenic hen egg white lysozyme (HEWL). Also, QTG-GNP was able to dissociate pre-formed HEWL amyloid fibrils. Furthermore, the constructed nanoparticles exhibited potent anti-radical activities against DPPH and ABTS⁺ and were cytocompatible with mouse L929 fibroblast cells. On the basis of these findings, it was established that QTG-GNP holds strong prospects for further development as an agent for countering protein aggregation and associated disease conditions.

Effect of substrate charge density on the adsorption of intrinsically disordered protein amyloid β40: a molecular dynamics study

The inhibitory effect of negatively charged gold nanoparticles (AuNPs) on amyloidogenic protein fibrillation has been established from experiments and computer simulations. Here, we investigate the effect of the charge density (σ) of gold (Au) surfaces on the adsorption of the intrinsically disordered amyloid β40 (Aβ40) monomer using molecular dynamics (MD) simulations. On the basis of the binding free energy, some key residues (ARG5, LYS16, LYS28, LEU17-ALA21, ILE31-VAL38) were found to be responsible for preventing the β-sheet formation, which is known to be a precursor for fibrillation. Until a critical charge density (σ_c) of -0.167 e nm^-2, the key residues remained adsorbed on the Au slab. A saturation in the number of condensed counterions (Na⁺) on Aβ40 was also observed at σ_c. Beyond σ_c, the condensation of Na⁺ occurs only on the Au slab, leading to competition between positively charged key residues and condensed ions. This competition was found to be responsible for the lack of adsorption of the key residues, leading to β-sheet formation for σ > -0.167 e nm^-2. This study suggests that if the key residues are not adsorbed, then β-sheet formation is observed, which can then lead to the development of proto-fibrils and subsequently fibrillation. Therefore the surface should have an optimal charge density to be an effective inhibitor of fibrillation.

Molecular Mechanisms of Neuroinflammation in Aging and Alzheimer's Disease Progression

Aging is the most prominent risk factor for late-onset Alzheimer's disease. Aging associates with a chronic inflammatory state both in the periphery and in the central nervous system, the evidence thereof and the mechanisms leading to chronic neuroinflammation being discussed. Nonetheless, neuroinflammation is significantly enhanced by the accumulation of amyloid beta and accelerates the progression of Alzheimer's disease through various pathways discussed in the present review. Decades of clinical trials targeting the 2 abnormal proteins in Alzheimer's disease, amyloid beta and tau, led to many failures. As such, targeting neuroinflammation via different strategies could prove a valuable therapeutic strategy, although much research is still needed to identify the appropriate time window. Active research focusing on identifying early biomarkers could help translating these novel strategies from bench to bedside.

Self-Therapeutic Nanomaterials: Applications in Biology and Medicine

Over past decades, nanotechnology has contributed to the biomedical field in areas including detection, diagnosis, and drug delivery via opto-electronic properties or enhancement of biological effects. Though generally considered inert delivery vehicles, a plethora of past and present evidence demonstrates that nanomaterials also exude unique intrinsic biological activity based on composition, shape, and surface functionalization. These intrinsic biological activities, termed self-therapeutic properties, take several forms, including mediation of cell-cell interactions, modulation of interactions between biomolecules, catalytic amplification of biochemical reactions, and alteration of biological signal transduction events. Moreover, study of biomolecule-nanomaterial interactions offers a promising avenue for uncovering the molecular mechanisms of biology and the evolution of disease. In this review, we observe the historical development, synthesis, and characterization of self-therapeutic nanomaterials. Next, we discuss nanomaterial interactions with biological systems, starting with administration and concluding with elimination. Finally, we apply this materials perspective to advances in intrinsic nanotherapies across the biomedical field, from cancer therapy to treatment of microbial infections and tissue regeneration. We conclude with a description of self-therapeutic nanomaterials in clinical trials and share our perspective on the direction of the field in upcoming years.

Advanced nanomaterials for modulating Alzheimer's related amyloid aggregation

Alzheimer's disease (AD) is a common neurodegenerative disease that brings about enormous economic pressure to families and society. Inhibiting abnormal aggregation of Aβ and accelerating the dissociation of aggregates is treated as an effective method to prevent and treat AD. Recently, nanomaterials have been applied in AD treatment due to their excellent physicochemical properties and drug activity. As a drug delivery platform or inhibitor, various excellent nanomaterials have exhibited potential in inhibiting Aβ fibrillation, disaggregating, and clearing mature amyloid plaques by enhancing the performance of drugs. This review comprehensively summarizes the advantages and disadvantages of nanomaterials in modulating amyloid aggregation and AD treatment. The design of various functional nanomaterials is discussed, and the strategies for improved properties toward AD treatment are analyzed. Finally, the challenges faced by nanomaterials with different dimensions in AD-related amyloid aggregate modulation are expounded, and the prospects of nanomaterials are proposed.

Nanoparticles-based anti-aging treatment of Alzheimer's disease

Age is the strongest risk factor for Alzheimer's disease (AD). In recent years, the relationship between aging and AD has been widely studied, with anti-aging therapeutics as the treatment for AD being one of the mainstream research directions. Therapeutics targeting senescent cells have shown improvement in AD symptoms and cerebral pathological changes, suggesting that anti-aging strategies may be a promising alternative for AD treatment. Nanoparticles represent an excellent approach for efficiently crossing the blood-brain barrier (BBB) to achieve better curative function and fewer side effects. Thereby, nanoparticles-based anti-aging treatment may exert potent anti-AD therapeutic efficacy. This review discusses the relationship between aging and AD and the application and prospect of anti-aging strategies and nanoparticle-based therapeutics in treating AD.

New Paradigm for Nano-Bio Interactions: Multimolecular Assembly of a Prototypical Disordered Protein with Ultrasmall Nanoparticles

Understanding the interactions between nanoparticles (NPs) and proteins is crucial for the successful application of NPs in biological contexts. Protein adsorption is dependent on particle size, and protein binding to ultrasmall (1-3 nm) NPs is considered to be generally weak. However, most studies have involved structured biomacromolecules, while the interactions of ultrasmall NPs with intrinsically disordered proteins (IDPs) have remained elusive. IDPs are abundant in eukaryotes and found to associate with NPs intracellularly. As a model system, we focused on ultrasmall gold nanoparticles (usGNPs) and tau, a cytosolic IDP associated with Alzheimer's disease. Using site-resolved NMR, steady-state fluorescence, calorimetry, and circular dichroism, we reveal that tau and usGNPs form stable multimolecular assemblies, representing a new type of nano-bio interaction. Specifically, the observed interaction hot spots explain the influence of usGNPs on tau conformational transitions, with implications for the intracellular targeting of aberrant IDP aggregation.

The Link between Oxidative Stress, Mitochondrial Dysfunction and Neuroinflammation in the Pathophysiology of Alzheimer's Disease: Therapeutic Implications and Future Perspectives

Alzheimer's disease (AD), the most common form of dementia, has increasing incidence, increasing mortality rates, and poses a huge burden on healthcare. None of the currently approved drugs for the treatment of AD influence disease progression. Many clinical trials aiming at inhibiting amyloid plaque formation, increasing amyloid beta clearance, or inhibiting neurofibrillary tangle pathology yielded inconclusive results or failed. Meanwhile, research has identified many interlinked vicious cascades implicating oxidative stress, mitochondrial dysfunction, and chronic neuroinflammation, and has pointed to novel therapeutic targets such as improving mitochondrial bioenergetics and quality control, diminishing oxidative stress, or modulating the neuroinflammatory pathways. Many novel molecules tested in vitro or in animal models have proven efficient, but their translation into clinic needs further research regarding appropriate doses, delivery routes, and possible side effects. Cell-based therapies and extracellular vesicle-mediated delivery of messenger RNAs and microRNAs seem also promising strategies allowing to target specific signaling pathways, but need further research regarding the most appropriate harvesting and culture methods as well as control of the possible tumorigenic side effects. The rapidly developing area of nanotechnology could improve drug delivery and also be used in early diagnosis.

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.

Dihydrocaffeic Acid-Decorated Iron Oxide Nanomaterials Effectively Inhibit Human Calcitonin Aggregation

To date, more than 30 human peptides or proteins have been found to form amyloid fibrils, most of which are associated with human diseases. However, currently, no cure for amyloidosis exists. Therefore, development of therapeutic strategies to inhibit amyloid formation is urgently required. Although the role of some amyloidogenic proteins has not been identified in certain diseases, their self-assembling behavior largely affects their bioactivity. Human calcitonin (hCT) is a hormone peptide containing 32 amino acids and is secreted by the parafollicular cells of the thyroid gland in the human body. It can regulate the concentration of calcium ions in the blood and block the activity of osteoclasts. Therefore, calcitonin has also been considered a therapeutic peptide. However, the aggregation of hCT hinders this process, and hCT has been replaced by salmon calcitonin in drug formulations. Recently, iron oxide nanomaterials have been developed as potential materials for various applications owing to their high biocompatibility, low toxicity, and ease of functionalization. In this study, nanoparticles (NPs) were prepared using a simple chemical coprecipitation method. We first demonstrated that dopamine-conjugated Fe₃O₄ inhibited hCT aggregation, similar to what we found when carbon dots were used as core materials in the previous study. Later, we continued to simplify the preparation process, that is, the mixing of dihydrocaffeic acid (DCA) and iron oxide NPs, to maintain their stability and inhibitory effect against hCT aggregation. Furthermore, DCA-decorated Fe₃O₄ can dissociate preformed hCT amyloid fibrils. This appears to be one of the most promising ways to stabilize hCT in solution and may be helpful for amyloidosis treatment.

Current Advancement of Immunomodulatory Drugs as Potential Pharmacotherapies for Autoimmunity Based Neurological Diseases

Dramatic advancement has been made in recent decades to understand the basis of autoimmunity-mediated neurological diseases. These diseases create a strong influence on the central nervous system (CNS) and the peripheral nervous system (PNS), leading to various clinical manifestations and numerous symptoms. Multiple sclerosis (MS) is the most prevalent autoimmune neurological disease while NMO spectrum disorder (NMOSD) is less common. Furthermore, evidence supports the presence of autoimmune mechanisms contributing to the pathogenesis of amyotrophic lateral sclerosis (ALS), which is a neurodegenerative disorder characterized by the progressive death of motor neurons. Additionally, autoimmunity is believed to be involved in the basis of Alzheimer’s and Parkinson’s diseases. In recent years, the prevalence of autoimmune-based neurological disorders has been elevated and current findings strongly suggest the role of pharmacotherapies in controlling the progression of autoimmune diseases. Therefore, this review focused on the current advancement of immunomodulatory drugs as novel approaches in the management of autoimmune neurological diseases and their future outlook.

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.

High-Throughput Colorimetric Analysis of Nanoparticle-Protein Interactions Based on the Enzyme-Mimic Properties of Nanoparticles

While an in-depth understanding of the biological behavior of engineered nanoparticles (NPs) is of great importance for their various applications, it remains challenging to quantitatively characterize NP-protein interactions in a simple and high-throughput manner. In the present work, we propose a new, colorimetric approach capable of quantitatively analyzing the adsorption of proteins onto the surface of NPs by their distinct peroxidase-mimic properties. Taking cationic AuNPs as an example, we demonstrate that this colorimetric method is capable of evaluating NP-protein interactions in a simple and high-throughput manner in multiwell plates. Important binding parameters (e.g., the binding affinity) of three different serum proteins (bovine serum albumin, transferrin, and lysozyme) as well as human serum to AuNPs with three different sizes (average diameters of 5, 10, and 15 nm) have been obtained. Based on a quantitative analysis of NP-protein interactions, we observe that the binding affinity and the inhibition efficiency of the nanozyme activity of AuNPs are strongly affected by the characteristics of proteins as well as the sizes of NPs. These results illustrate the great potential of the present colorimetric method as a simple, low-cost, and high-throughput platform for quantitatively investigating NP-protein interactions.

Dual-Functional Antioxidant and Antiamyloid Cerium Oxide Nanoparticles Fabricated by Controlled Synthesis in Water-Alcohol Solutions

Oxidative stress is known to be associated with a number of degenerative diseases. A better knowledge of the interplay between oxidative stress and amyloidogenesis is crucial for the understanding of both, aging and age-related neurodegenerative diseases. Cerium dioxide nanoparticles (CeO₂ NPs, nanoceria) due to their remarkable properties are perspective nanomaterials in the study of the processes accompanying oxidative-stress-related diseases, including amyloid-related pathologies. In the present work, we analyze the effects of CeO₂ NPs of different sizes and Ce⁴⁺/Ce³⁺ ratios on the fibrillogenesis of insulin, SOD-like enzymatic activity, oxidative stress, biocompatibility, and cell metabolic activity. CeO₂ NPs (marked as Ce1–Ce5) with controlled physical–chemical parameters, such as different sizes and various Ce⁴⁺/Ce³⁺ ratios, are synthesized by precipitation in water–alcohol solutions. All synthesized NPs are monodispersed and exhibit good stability in aqueous suspensions. ThT and ANS fluorescence assays and AFM are applied to monitor the insulin amyloid aggregation and antiamyloid aggregation activity of CeO₂ NPs. The analyzed Ce1–Ce5 nanoparticles strongly inhibit the formation of insulin amyloid aggregates in vitro. The bioactivity is analyzed using SOD and MTT assays, Western blot, fluorescence microscopy, and flow cytometry. The antioxidative effects and bioactivity of nanoparticles are size- or valence-dependent. CeO₂ NPs show great potential benefits for studying the interplay between oxidative stress and amyloid-related diseases, and can be used for verification of the role of oxidative stress in amyloid-related diseases.

High efficiency and related mechanism of Au(RC) nanoclusters on disaggregating Aβ fibrils

Revealing the disaggregating mechanism of amyloids fibrils under nanomaterials action is a key issue for their successful future use in therapy of neurodegenerative and overall amyloid-related diseases. Herein a gold nanocluster stabilized by Arg-Cys dipeptide (Au(RC)NCs) was synthesized to investigate its disaggregation activity toward Aβ fibrils by using Thioflavin-T (ThT) fluorescence assay and atomic force microscopy. It was demonstrated that Au(RC)NCs is very effective in disaggregating preformed Aβ fibrils, and characterized by the ultra-low apparent completely disaggregation concentration at the dose of 10 μg·mL^-1. A possible disaggregation mechanism based on Au(RC)NCs triggering the disassembly of Aβ fibrils into a dynamic equilibrium was proposed. The introduction of Au(RC)NCs with appropriate dose (5 μg·mL^-1) can trigger the disassemble process of mature Aβ fibrils into a critical state, at this very moment, if there is no more nano-disassembler, destruction of old Aβ fibrils and formation of new Aβ fibrils are thus in permanent dynamic equilibrium; in contrast, if there is more nano-disassembler (>10 μg·mL^-1), the dynamic equilibrium prefer to shift to the direction of Aβ further disassembly. Moreover, Au(RC)NCs with dosage over 10 μg·mL^-1 exhibited superb protection effect against Aβ-induced cytotoxicity in cell experiments. This study not only proposed a possible disassembly mechanism of amyloids fibrils under nanomaterials action, but also provide Au(RC)NCs as a promising high-effective nano-disassembler to disassemble unwanted amyloid aggregates.

Engineering Nanointerfaces of Au25 Clusters for Chaperone-Mediated Peptide Amyloidosis

Synthetic nanomaterials possessing biomolecular-chaperone functions are good candidates for modulating physicochemical interactions in many bioapplications. Despite extensive research, no general principle to engineer nanomaterial surfaces is available to precisely manipulate biomolecular conformations and behaviors, greatly limiting attempts to develop high-performance nanochaperone materials. Here, we demonstrate that, by quantifying the length (-SC_xR^±, x = 3-11) and charges (R^- = -COO^-, R⁺ = -NH₃⁺) of ligands on Au₂₅ gold nanochaperones (AuNCs), simulating binding sites and affinities of amyloid-like peptides with AuNCs, and probing peptide folding and fibrillation in the presence of AuNCs, it is possible to precisely manipulate the peptides' conformations and, thus, their amyloidosis via customizing AuNCs nanointerfaces. We show that intermediate-length liganded AuNCs with a specific charge chaperone peptides' native conformations and thus inhibit their fibrillation, while other types of AuNCs destabilize peptides and promote their fibrillation. We offer a microscopic molecular insight into peptide identity on AuNCs and provide a guideline in customizing nanochaperones via manipulating their nanointerfaces.

Gold nanoclusters eliminate obesity induced by antipsychotics

Obesity induced by antipsychotics have plagued more than 20 million people worldwide. However, no drug is available to eliminate the obesity induced by antipsychotics. Here we examined the effect and potential mechanisms of a gold nanoclusters (AuNCs) modified by N-isobutyryl-L-cysteine on the obesity induced by olanzapine, the most prescribed but obesogenic antipsychotics, in a rat model. Our results showed that AuNCs completely prevented and reversed the obesity induced by olanzapine and improved glucose metabolism profile in rats. Further mechanism investigations revealed that AuNCs exert its anti-obesity function through inhibition of olanzapine-induced dysfunction of histamine H1 receptor and proopiomelanocortin signaling therefore reducing hyperphagia, and reversing olanzapine-induced inhibition of uncoupling-protein-1 signaling which increases thermogenesis. Together with AuNCs' good biocompatibility, these findings not only provide AuNCs as a promising nanodrug candidate for treating obesity induced by antipsychotics, but also open an avenue for the potential application of AuNCs-based nanodrugs in treating general obesity.

Impact of Au144 metal clusters on the structural and inhibitory mechanism of Aβ42 peptide: A theoretical approach

One of the main causes for Alzheimer disease is the abnormal self-assembly of the amyloid-beta (Aβ) peptide, which in turn forms a toxic β-rich aggregation. A recent study suggests that gold nanoparticles (AuNPs) can inhibit the Aβ aggregation. Nevertheless, the effects of AuNPs on Aβ peptide system are still ambiguous and needs exploration that is more detailed. Molecular dynamics simulations have been carried out to investigate the aggregation mechanism of Aβ₄₂ peptide for 500 ns. During simulation, C-terminus regions of Met 35-Ala42 residues exhibits β-sheet conformations. Meanwhile, the Au₁₄₄MC coordination induces substantial α-helical character, both α-helix and 3₁₀-helix structure at 0-500ns, in the region of Asp1-Arg5 and Val36-Ile41 residues. The Au₁₄₄MC strongly coordinates with Asp1, Ala2, Glu3, Phe4, Asp7, Tyr10 and Gln15 residues that plays the significant effects to loss the β-sheet geometry in the N-terminal region and it converted into random α-helix, turn and bend conformation. On comparing the RMSF of the Aβ₄₂ peptide and Aβ₄₂-Au₁₄₄MC complex shows that the coordination of Au₁₄₄MC results in greater rigidity of the Aβ₄₂ peptide backbone regions with exemptions for the Asp1, Ala2, Glu3, Leu34, Ile41 and Ala42 residues due to the strong binding between the metal cluster and the CHC (Leu17-Ala21) region. The structural stability of the Aβ₄₂ peptide and Aβ₄₂-Au₁₄₄MC complex is enhanced by the several intermolecular and intramolecular interactions and it was visibly revealed in the H-bond. From the above results, it is very evident that the Au₁₄₄MC can be used as inhibitor agent for the oligomerization of Aβ₄₂.

Pharmacological Role of Functionalized Gold Nanoparticles in Disease Applications

Gold has always been regarded as a symbol of nobility, and its shiny golden appearance has always attracted the attention of many people. Gold has good ductility, molecular recognition properties, and good biocompatibility. At present, gold is being used in many fields. When gold particles are as small as several nanometers, their physical and chemical properties vary with their size in nanometers. The surface area of a nano-sized gold surface has a special effect. Therefore, gold nanoparticles can, directly and indirectly, give rise to different biological activities. For example, if the surface of the gold is sulfided. Various substances have a strong chemical reactivity and are easy to combine with sulfhydryl groups; hence, nanogold is often used in biomedical testing, disease diagnosis, and gene detection. Nanogold is easy to bind to proteins, such as antibodies, enzymes, or cytokines. In fact, scientists use nanogold to bind special antibodies, as a tool for targeting cancer cells. Gold nanoparticles are also directly cytotoxic to cancer cells. For diseases caused by inflammation and oxidative damage, gold nanoparticles also have antioxidant and anti-inflammatory effects. Based on these unique properties, gold nanoparticles have become the most widely studied metal nanomaterials. Many recent studies have further demonstrated that gold nanoparticles are beneficial for humans, due to their functional pharmacological properties in a variety of diseases. The content of this review will be the application of gold nanoparticles in treating or diagnosing pressing diseases, such as cancers, retinopathy, neurological diseases, skin disorders, bowel diseases, bone cartilage disorders, cardiovascular diseases, infections, and metabolic syndrome. Gold nanoparticles have shown very obvious therapeutic and application potential.

Anti-Amyloidogenic and Fibril-Disaggregating Potency of the Levodopa-Functionalized Gold Nanoroses as Exemplified in a Diphenylalanine-Based Amyloid Model

The phenomenon of proteins/peptide assembly into amyloid fibrils is associated with various neurodegenerative and age-related human disorders. Inhibition of the aggregation behavior of amyloidogenic peptides/proteins or disruption of the pre-formed aggregates is a viable therapeutic option to control the progression of various protein aggregation-related disorders such as Alzheimer's disease (AD). In the current work, we investigated both the amyloid inhibition and disaggregation proclivity of levodopa-functionalized gold nanoroses (GNRs) against various peptide-based amyloid models, including the amyloid beta peptide [Aβ (1-42) and Aβ (1-40)] and the dipeptide phenylalanine-phenylalanine (FF). Our results depicted the anti-aggregation behavior of the GNR toward FF and both forms of Aβ-derived fibrils. The peptides demonstrated a variation in their fiber-like morphology and a decline in thioflavin T fluorescence after being co-incubated with the GNR. We further demonstrated the neuroprotective effects of the GNR in neuroblastoma cells against FF and Aβ (1-42) fiber-induced toxicity, exemplified both in terms of regaining cellular viability and reducing production of reactive oxygen species. Overall, these findings support the potency of the GNR as a promising platform for combating AD.

Inhibiting protein aggregation with nanomaterials: The underlying mechanisms and impact factors

Protein aggregation is correlated with the onset and progression of protein misfolding diseases (PMDs). Inhibiting the generation of toxic aggregates of misfolded proteins has been proposed as a therapeutic approach for PMDs. Due to their unique properties, nanomaterials have been extensively investigated for their ability to inhibit protein aggregation and have shown great potential in the diagnosis and treatment of PMDs. However, the precise mechanisms by which nanomaterials interact with amyloidogenic proteins and the factors influencing these interactions remain poorly understood. Consequently, developing a rational design strategy for nanomaterials that target specific proteins in PMDs has been challenging. In this review, we elucidate the effects of nanomaterials on protein aggregation and describe the mechanisms through which nanomaterials interfere with protein aggregation. The major factors impacting protein-nanomaterial interaction such as size, charge, concentration, surface modification and morphology that can be rationally addressed to achieve the desired effects of nanomaterials on protein aggregation are summarized. The prospects and challenges to the clinical application of nanomaterials for the treatment of PMDs are also discussed.

Anti-amyloidogenic property of gold nanoparticle decorated quercetin polymer nanorods in pH and temperature induced aggregation of lysozyme

Quercetin is an abundant plant polyphenol effective against several diseases due to its antioxidant and anti-inflammatory activity. Herein, we report novel polymeric quercetin nanorods and the former decorated with gold nanoparticles for the first time. The prepared conjugates quercetin-polyvinylpyrrolidone (Q-PVP) and quercetin-polyvinylpyrrolidone-gold nanoparticles (Q-PVP-Au) were characterized by UV-visible spectroscopy, Fourier transform infrared, dynamic light scattering, and zeta potential measurements. The surface morphology of conjugates was analyzed by field emission scanning electron microscopy. These conjugates exhibit harmonized rod-like morphology with a narrow size distribution. Furthermore, the quercetin conjugates with nanorod morphology exhibited enhanced and prolonged drug release over a long period. The synthesized conjugates were investigated for lysozyme aggregation kinetics. ThT binding assay, fibril size measurement, and electron microscopy results revealed that conjugates could suppress fibrillogenesis in lysozyme. The highest amyloid aggregation inhibition activity (IC₅₀) was obtained against Q-PVP and Q-PVP-Au at 32 μg mL⁻¹ and 30 μg mL⁻¹ respectively. The amyloid aggregate disintegration activity (DC₅₀) obtained against Q-PVP and Q-PVP-Au was 27 μg mL⁻¹ and 29 μg mL⁻¹ respectively. The present quercetin conjugates exhibit enhanced bioavailability and stability. They were potent inhibitors of lysozyme aggregation that may find applications as a therapeutic agent in neurological diseases like Alzheimer's and Parkinson's.

Q-PVP, and Q-PVP-Au conjugates for inhibition of HEWL aggregation.

The curious cases of nanoparticle induced amyloidosis during protein corona formation and anti-amyloidogenic nanomaterials: Paradox or prejudice?

Protein corona (PC) formation remains a major hurdle in the successful delivery of nanomedicines to the target sites. Interacting proteins have been reported to undergo structural changes on the nanoparticle (NP) surface which invariably impacts their biological activities. Such structural changes are the result of opening of more binding sites of proteins to adsorb on the NP surface. The process of conversion of α-helix proteins to their β-sheet enriched counterpart is termed as amyloidosis and in case of PC formation, NPs apparently play the crucial role of being the nucleation centres where this process takes place. Conversely, increasing numbers of artificial nano-chaperones are being used to treat the protein misfolding disorders. Anti-amyloidogenic nanomaterials (NM) have been gaining utmost importance in inhibiting Aβ42 (hallmark peptide for Alzheimer's disease) and Hen egg white lysozyme (HEWL, model protein for systemic amyloidosis) aggregation. Interestingly, in this process, NPs inhibit protein β-sheet enrichment. These two seemingly opposite roles of NPs, propelling confirmatory change onto the smorgasbord of adsorbed native proteins and the ability of NPs in inhibiting amyloidosis creates a paradox, which has not been discussed earlier. Here, we highlight the key points from both the facets of the NP behaviour with respect to their physicochemical properties and the nature of proteins they adsorb onto them to unravel the mystery. BRIEF: Protein corona formation remains a major hurdle in achieving the desired efficacy of nanomedicine. Proteins when interact with nanoparticle (NP) surface, undergo both structural and biological changes. Again, NPs are known to exhibit anti-amyloidogenic behaviour where these play the crucial role of preventing any change in their native structure. Such seemingly different roles of NPs need sincere inquisition.

Gold Nanoparticles: Biosynthesis and Potential of Biomedical Application

Gold nanoparticles (AuNPs) are extremely promising objects for solving a wide range of biomedical problems. The gold nanoparticles production by biological method ("green synthesis") is eco-friendly and allows minimization of the amount of harmful chemical and toxic byproducts. This review is devoted to the AuNPs biosynthesis peculiarities using various living organisms (bacteria, fungi, algae, and plants). The participation of various biomolecules in the AuNPs synthesis and the influence of size, shapes, and capping agents on the functionalities are described. The proposed action mechanisms on target cells are highlighted. The biological activities of "green" AuNPs (antimicrobial, anticancer, antiviral, etc.) and the possibilities of their further biomedical application are also discussed.

Adsorption of the amyloid β40 monomer on charged gold nanoparticles and slabs: a molecular dynamics study

Negatively charged nanoparticles are known to inhibit the fibrillation of amyloidogenic protein amyloid β (Aβ40), though the overall charge on the protein is negative. In this work a molecular dynamics study is reported to investigate the interaction of Aβ40 on negatively charged gold nanoparticles (3-5 nm) and charged (positive and negative) and neutral gold slabs. The equilibrium structures of Aβ40 on gold surfaces are characterized using residue-specific contacts on the gold surface, secondary structure analysis and binding free energy calculations. The simulation results reveal that the Aβ40 protein in water interconverts into β-sheets, which are building blocks of the mature fibrils, whereas on gold nanoparticles Aβ40 unfolds and adsorbs. Both the negatively charged gold nanoparticles and gold slabs arrest the formation of β-sheets in Aβ40, whereas the positively charged gold slab does not inhibit the formation of β-sheets. The residue-specific interactions between Aβ40 and the gold surfaces are important in governing the adsorption of Aβ40 on charged surfaces.

The curvature of gold nanoparticles influences the exposure of amyloid-β and modulates its aggregation process

Gold nanoparticles (GNP) are tunable nanomaterials that can be used to develop rational therapeutic inhibitors against the formation of pathological aggregates of proteins. In the case of the pathological aggregation of the amyloid-β protein (Aβ), the shape of the GNP can slow down or accelerate its aggregation kinetics. However, there is a lack of elementary knowledge about how the curvature of GNP alters the interaction with the Aβ peptide and how this interaction modifies key molecular steps of fibril formation. In this study, we analysed the effect of flat gold nanoprisms (GNPr) and curved gold nanospheres (GNS) on in vitro Aβ42 fibril formation kinetics by using the thioflavin-based kinetic assay and global fitting analysis, with several models of aggregation. Whereas GNPr accelerate the aggregation process and maintain the molecular mechanism of aggregation, GNS slow down this process and modify the molecular mechanism to one of fragmentation/secondary nucleation, with respect to controls. These results can be explained by a differential interaction between the Aβ peptide and GNP observed by Raman spectroscopy. While flat GNPr expose key hydrophobic residues involved in the Aβ peptide aggregation, curved GNS hide these residues from the solvent. Thus, this study provides mechanistic insights to improve the rational design of GNP nanomaterials for biomedical applications in the field of amyloid-related aggregation.

Unveiling the interaction of protein fibrils with gold nanoparticles by plasmon enhanced nano-spectroscopy

The development of various degenerative diseases is suggested to be triggered by the uncontrolled organisation and aggregation of proteins into amyloid fibrils. For this reason, there are ongoing efforts to develop novel agents and approaches, including metal nanoparticle-based colloids, that dissolve amyloid structures and prevent pathogenic protein aggregation. In this contribution, the role of gold nanoparticles (AuNPs) in degrading amyloid fibrils of the model protein lysozyme is investigated. The amino acid composition of fibril surfaces before and after the incubation with AuNPs is determined at the single fibril level by exploiting the high spatial resolution and sensitivity provided by tip-enhanced and surface-enhanced Raman spectroscopies. This combined spectroscopic approach allows to reveal the molecular mechanisms driving the interaction between fibrils and AuNPs. Our results provide an important input for the understanding of amyloid fibrils and could have a potential translational impact on the development of strategies for the prevention and treatment of amyloid-related diseases.

Gallium nanoparticles as novel inhibitors of Aβ40 aggregation

Alzheimer's disease (AD) has been consistently related to the formation of senile amyloid plaques mainly composed of amyloid β (Aβ) peptides. The toxicity of Aβ aggregates has been indicated to be responsible for AD pathology. One scenario to decrease Aβ toxicity is the development of effective inhibitors against Aβ amyloid formation. In this study, we investigate the effect of gallium nitride nanoparticles (GaN NPs) as inhibitors of Aβ40 amyloid formation using a combination of biophysical approaches. Our results show that the lag phase of Aβ40 aggregation kinetics is significantly retarded by GaN NPs in a concentration dependent manner, implying the activity of GaN NPs in interfering with the formation of the crucial nucleus during Aβ aggregation. Our results also show that GaN NPs can reduce the amyloid fibril elongation rate in the course of the aggregation kinetics. It is speculated that the high polarization characteristics of GaN NPs may provoke a strong interaction between the particles and Aβ40 peptide and in this way decrease self-association of the peptide monomers to form amyloids.

Insights into Mechanism of Aβ42 Fibril Growth on Surface of Graphene Oxides: Oxidative Degree Matters

The filamentous β-amyloid deposition has been regarded as the hallmark pathology of Alzheimer's disease (AD). Nanomaterials such as graphene oxides (GOs) have achieved significant progress in the therapy of AD, but the molecular pathway of the growth propagation remains challenging to investigate, especially on the surfaces of materials. The thermodynamics and kinetics of fibril elongation on GO surfaces with different oxidative degrees have been investigated by a combination of in vitro experiments and simulations. ThT kinetics, calorimetric measurements, and TEM observations suggest that low oxidative GO-10 promotes the fibril elongation, while both high oxidative GO-20 and GO-40 inhibit the fibril elongation. Computational results reveal that the apparent regulation behaviors of GOs on filament growth depend on the balance between the promoting effect by templating the incoming of monomers and the retarding effect by capturing the monomer during docking and locking phases through hydrogen bonding. This work will promote the understanding of the interplay between biomolecules and materials, thus providing new thoughts for the rational design of novel materials for amyloidosis therapy.

Nanomaterials for Modulating the Aggregation of β-Amyloid Peptides

The aberrant aggregation of amyloid-β (Aβ) peptides in the brain has been recognized as the major hallmark of Alzheimer's disease (AD). Thus, the inhibition and dissociation of Aβ aggregation are believed to be effective therapeutic strategiesforthe prevention and treatment of AD. When integrated with traditional agents and biomolecules, nanomaterials can overcome their intrinsic shortcomings and boost their efficiency via synergistic effects. This article provides an overview of recent efforts to utilize nanomaterials with superior properties to propose effective platforms for AD treatment. The underlying mechanismsthat are involved in modulating Aβ aggregation are discussed. The summary of nanomaterials-based modulation of Aβ aggregation may help researchers to understand the critical roles in therapeutic agents and provide new insight into the exploration of more promising anti-amyloid agents and tactics in AD theranostics.

Mimosine functionalized gold nanoparticles (Mimo-AuNPs) suppress β-amyloid aggregation and neuronal toxicity

Evidence suggests that increased level/aggregation of beta-amyloid (Aβ) peptides initiate neurodegeneration and subsequent development of Alzheimer's disease (AD). At present, there is no effective treatment for AD. In this study, we reported the effects of gold nanoparticles surface-functionalized with a plant-based amino acid mimosine (Mimo-AuNPs), which is found to cross the blood-brain barrier, on the Aβ fibrillization process and toxicity. Thioflavin T kinetic assays, fluorescence imaging and electron microscopy data showed that Mimo-AuNPs were able to suppress the spontaneous and seed-induced Aβ_1-42 aggregation. Spectroscopic studies, molecular docking and biochemical analyses further revealed that Mimo-AuNPs stabilize Aβ_1-42 to remain in its monomeric state by interacting with the hydrophobic domain of Aβ_1-42 (i.e., Lys₁₆ to Ala₂₁) there by preventing a conformational shift towards the β-sheet structure. Additionally, Mimo-AuNPs were found to trigger the disassembly of matured Aβ_1-42 fibers and increased neuronal viability by reducing phosphorylation of tau protein and the production of oxyradicals. Collectively, these results reveal that the surface-functionalization of gold nanoparticles with mimosine can attenuate Aβ fibrillization and neuronal toxicity. Thus, we propose Mimo-AuNPs may be used as a potential treatment strategy towards AD-related pathologies.

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Mimosine functionalized with gold nanoparticles (Mimo-AuNPs) can cross blood-brain barrier.

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Mimo-AuNPs inhibit aggregation of Aβ peptides by interacting with its hydrophobic domain.

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Mimo-AuNPs can trigger disassembly of pre-aggregated Aβ fibers.

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Mimo-AuNPs can protect neurons against Aβ toxicity by attenuating intracellular signaling.

Potential Role of Nanoparticles in Treating the Accumulation of Amyloid-Beta Peptide in Alzheimer's Patients

The disorder of Alzheimer's is marked by progressive pathophysiological neurodegeneration. The amino acid peptides in the amyloid plaques found in the brains of people with Alzheimer's disease (AD) are known as amyloid-beta (Aβ). Current treatments are not curative, and the effects associated with AD are reduced. Improving treatment results involved the targeting of drugs at optimum therapeutic concentration. Nanotechnology is seen as an unconventional, modern technology that plays a key role in the treatment of Alzheimer's disease. Using nanoparticles, molecular detection, effective drug targeting, and their combination offer high sensitivity. The aim of this review is to shed light on the function and successful role of nanoparticles to resolve Aβ aggregation and thus to help cure Alzheimer's disease. The analysis divides these nanoparticles into three categories: polymer, lipid, and gold nanoparticles. A thorough comparison was then made between the nanoparticles, which are used according to their role, properties, and size in the procedure. The nanoparticles can prevent the accumulation of Aβ during the efficient delivery of the drug to the cells to treat Alzheimer's disease. Furthermore, this comparison demonstrated the ability of these nanoparticles to deal efficiently with Alzheimer's disease. The role of these nanoparticles varied from delivering the drug to brain cells to dealing with the disease-causing peptide.

The Application of Nanotechnology for the Diagnosis and Treatment of Brain Diseases and Disorders

Brain is by far the most complex organ in the body. It is involved in the regulation of cognitive, behavioral, and emotional activities. The organ is also a target for many diseases and disorders ranging from injuries to cancers and neurodegenerative diseases. Brain diseases are the main causes of disability and one of the leading causes of deaths. Several drugs that have shown potential in improving brain structure and functioning in animal models face many challenges including the delivery, specificity, and toxicity. For many years, researchers have been facing challenge of developing drugs that can cross the physical (blood–brain barrier), electrical, and chemical barriers of the brain and target the desired region with few adverse events. In recent years, nanotechnology emerged as an important technique for modifying and manipulating different objects at the molecular level to obtain desired features. The technique has proven to be useful in diagnosis as well as treatments of brain diseases and disorders by facilitating the delivery of drugs and improving their efficacy. As the subject is still hot, and new research findings are emerging, it is clear that nanotechnology could upgrade health care systems by providing easy and highly efficient diagnostic and treatment methods. In this review, we will focus on the application of nanotechnology in the diagnosis and treatment of brain diseases and disorders by illuminating the potential of nanoparticles.

Nanogold induces anti-inflammation against oxidative stress induced in human neural stem cells exposed to amyloid-beta peptide

Alzheimer's disease (AD) is a neurodegenerative disorder with progressive memory loss resulting in dementia. Amyloid-beta (Aβ) peptides play a critical role in the pathogenesis of the disease by promoting inflammation and oxidative stress, leading to neurodegeneration in the brains of AD patients. Numerous in vitro 3D cell culture models are useful mimics for understanding cellular changes that occur during AD under in vivo conditions. The 3D Bioprinter developed at the CELLINK INKREDIBLE was used in this study to directly investigate the influence of 3D conditions on human neural stem cells (hNSCs) exposed to Aβ. The development of anti-AD drugs is usually difficult, mainly due to a lack of therapeutic efficacy and enhanced serious side effects. Gold nanoparticles (AuNPs) demonstrate benefits in the treatment of several diseases, including AD, and may provide a novel therapeutic approach for AD patients. However, the neuroprotective mechanisms by which AuNPs exert these beneficial effects in hNSCs treated with Aβ are still not well understood. Therefore, we tested the hypothesis that AuNPs protect against Aβ-induced inflammation and oxidative stress in hNSCs under 3D conditions. Here, we showed that AuNPs improved the viability of hNSCs exposed to Aβ, which was correlated with the reduction in the expression of inflammatory cytokines, such as TNF-α and IL-1β. In addition, AuNPs rescued the levels of the transcripts of inhibitory kappa B kinase (IKK) in Aβ-treated hNSCs. The Aβ-mediated increases in mRNA, protein, and nuclear translocation levels of NF-κB (p65), a key transcription factor involved in inflammatory responses, were all significantly abrogated following co-treatment of hNSCs with AuNPs. In addition, treatment with AuNPs significantly restored iNOS and COX-2 levels in Aβ-treated hNSCs. Importantly, hNSCs co-treated with AuNPs were significantly protected from Aβ-induced oxidative stress, as detected using the DCFH-DA and DHE staining assays. Furthermore, hNSCs co-treated with AuNPs were significantly protected from the Aβ-induced reduction in the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and Nrf2 downstream antioxidant target genes (SOD-1, SOD-2, Gpx1, GSH, Catalase, and HO-1). Moreover, AuNPs reduced the aggregates and increased the proteasome activity and the expression of HSP27 and HSP70 genes in Aβ-treated hNSCs. Taken together, these findings provide the first evidence extending our understanding of the molecular mechanisms under 3D scaffold conditions by which AuNPs reverse the inflammation and oxidative stress-induced in hNSCs exposed to Aβ. These findings may facilitate the development of novel treatments for AD.