Engineered Polymer Nanoparticles Containing Hydrophobic Dipeptide for Inhibition of Amyloid-β Fibrillation

Inhibitors of amyloid fibril formation

Many diseases are caused by misfolded and denatured proteins, leading to neurodegenerative diseases. In recent decades researchers have developed a variety of compounds, including polymeric inhibitors and natural compounds, antibodies, and chaperones, to inhibit protein aggregation, decrease the toxic effects of amyloid fibrils, and facilitate refolding proteins. The causes and mechanisms of amyloid formation are still unclear, and there are no effective treatments for Amyloid diseases. This section describes research and achievements in the field of inhibiting amyloid accumulation and also discusses the importance of various strategies in facilitating the removal of aggregates species (refolding) in the treatment of neurological diseases such as chemical methods like as, small molecules, metal chelators, polymeric inhibitors, and nanomaterials, as well as the use of biomolecules (peptide and, protein, nucleic acid, and saccharide) as amyloid inhibitors, are also highlighted.

Tailoring Hierarchical Structure and Rare Earth Affinity of Compositionally Identical Polymers via Sequence Control

Macromolecule sequence, structure, and function are inherently intertwined. While well-established relationships exist in proteins, they are more challenging to define for synthetic polymer nanoparticles due to their molecular weight, sequence, and conformational dispersities. To explore the impact of sequence on nanoparticle structure, we synthesized a set of 16 compositionally identical, sequence-controlled polymers with distinct monomer patterning of dimethyl acrylamide and a bioinspired, structure-driving di(phenylalanine) acrylamide (FF). Sequence control was achieved through multiblock polymerizations, yielding unique ensembles of polymer sequences which were simulated by kinetic Monte Carlo simulations. Systematic analysis of the global (tertiary- and quaternary-like) structure in this amphiphilic copolymer series revealed the effect of multiple sequence descriptors: the number of domains, the hydropathy of terminal domains, and the patchiness (density) of FF within a domain, each of which impacted both chain collapse and the distribution of single- and multichain assemblies. Furthermore, both the conformational freedom of chain segments and local-scale, β-sheet-like interactions were sensitive to the patchiness of FF. To connect sequence, structure, and target function, we evaluated an additional series of nine sequence-controlled copolymers as sequestrants for rare earth elements (REEs) by incorporating a functional acrylic acid monomer into select polymer scaffolds. We identified key sequence variables that influence the binding affinity, capacity, and selectivity of the polymers for REEs. Collectively, these results highlight the potential of and boundaries of sequence control via multiblock polymerizations to drive primary sequence ensembles hierarchical structures, and ultimately the functionality of compositionally identical polymeric materials.

Biopolymers as promising vehicles for drug delivery to the brain

The brain is a privileged organ, tightly guarded by a network of endothelial cells, pericytes, and glial cells called the blood brain barrier. This barrier facilitates tight regulation of the transport of molecules, ions, and cells from the blood to the brain. While this feature ensures protection to the brain, it also presents a challenge for drug delivery for brain diseases. It is, therefore, crucial to identify molecules and/or vehicles that carry drugs, cross the blood brain barrier, and reach targets within the central nervous system. Biopolymers are large polymeric molecules obtained from biological sources. In comparison with synthetic polymers, biopolymers are structurally more complex and their 3D architecture makes them biologically active. Researchers are therefore investigating biopolymers as safe and efficient carriers of brain-targeted therapeutic agents. In this article, we bring together various approaches toward achieving this objective with a note on the prospects for biopolymer-based neurotherapeutic/neurorestorative/neuroprotective interventions. Finally, as a representative paradigm, we discuss the potential use of nanocarrier biopolymers in targeting protein aggregation diseases.

RAFT-synthesis and self-assembly-induced emission of pendant diphenylalanine-tetraphenylethylene copolymers

Manipulation of the properties of aggregation-induced emission luminogens (AIEgens) by combining self-assembling motifs has attracted significant interest as a promising approach to developing various advanced materials. In this study, pendant diphenylalanine-tetraphenylethylene (TPE) copolymers exhibiting the ability for self-assembly and AIE properties were synthesized via reversible addition-fragmentation chain-transfer (RAFT) copolymerization. The resulting anionic and non-ionic amphiphilic copolymers with a carbon-carbon main chain bearing diphenylalanine-TPE through-space interactions self-assembled into nanorods and nanofibers, showing blue emissions originating from the aggregation of TPE side chains in the assembled structures. Suitable tuning of the comonomer composition, monomer structure, and environmental conditions (e.g., solvent polarity) enables manipulation of the self-assembled structures, AIE properties, and aggregation-induced circular dichroism by achiral TPE units via through-space interactions with diphenylalanine moieties.

Design of Self-Assembled Nanoparticles as a Potent Inhibitor and Fluorescent Probe for β-Amyloid Fibrillization

Alzheimer's disease (AD) remains incurable due to its complex pathogenesis. The deposition of β-amyloid (Aβ) in the brain appears much earlier than any clinical symptoms and plays an essential role in the occurrence and development of AD neuropathology, which implies the importance of early theranostics. Herein, we designed a self-assembled bifunctional nanoparticle (LC8-pCG-fLC8) for Aβ fluorescent diagnosis and inhibition. The nanoparticle was synthesized by click chemistry from Aβ-targeting peptide Ac-LVFFARKC-NH2 (LC8) and an Aβ fluorescent probe f with the zwitterionic copolymer poly(carboxybetaine methacrylate-glycidyl methacrylate) (p(CBMA-GMA), pCG). Owing to the high reactivity of epoxy groups, the peptide concentration of LC8-pCG-fLC8 nanoparticles reached about 4 times higher than that of the existing inhibitor LVFFARK@poly(carboxybetaine) (LK7@pCB). LC8-pCG-fLC8 exhibited remarkable inhibitory capability (suppression efficiency of 83.0% at 20 μM), altered the aggregation pathway of Aβ, and increased the survival rate of amyloid-induced cultured cells from 76.5% to 98.0% at 20 μM. Notably, LC8-pCG-fLC8 possessed excellent binding affinity, good biostability, and high fluorescence responsivity to β-sheet-rich Aβ oligomers and fibrils, which could be used for the early diagnosis of Aβ aggregation. More importantly, in vivo tests using transgenic C. elegans CL2006 stain showed that LC8-pCG-fLC8 could specifically image Aβ plaques, prolong the lifespan (from 13 to 17 days), and attenuate the AD-like symptoms (reducing paralysis and Aβ deposition). Therefore, self-assembled nanoparticles hold great potential in AD theranostics.

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.

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.

Synthesis and self-assembly of a diphenylalanine–tetraphenylethylene hybrid monomer and RAFT polymers with aggregation-induced emission

A hybrid monomer consisting of diphenylalanine with the self-assembling ability and tetraphenylethylene with aggregation-induced emission properties was synthesized and employed for reversible addition–fragmentation chain transfer polymerization.

Artificial Chiral Interfaces against Amyloid-β Peptide Aggregation: Research Progress and Challenges

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by an imbalance between the production and clearance of amyloid-β (Aβ) species. AD not only influences the life quality of the patients but also heavily burdens the families and society. Therefore, it is an urgent mission to research and develop some new anti-amyloid aggregation drugs. In recent years, there were research and development of engineered nanostructures as Aβ amyloid inhibitors have attracted extensive attention and become a new frontier in nanomedicine. The effects of nanostructural surface properties (e.g., morphology, charge, hydrophobicity) on inhibition of Aβ aggregation are modulated by adsorbed Aβ peptides. Nevertheless, chirality has been seldom considered in recognition of Aβ species and modulation of Aβ aggregations. Moreover, a more relevant question for chiral inhibitors is little known about the molecular mechanism of how to interface chiral effects Aβ targeting recognition and effective mitigation of amyloidosis at the molecular level. Herein, we review recent experimental and theoretical results acquired in the specific areas of artificial chiral nanostructure inhibitors. This article will be essential to provide a microlevel insight into the effects of chiral nanointerfaces on amyloidosis processes as well as the development of chiral inhibitor drugs against Aβ fibrillation.

Engineered polymer nanoparticles incorporating l-amino acid groups as affinity reagents for fibrinogen

Synthetic polymer hydrogel nanoparticles (NPs) were developed to function as abiotic affinity reagents for fibrinogen. These NPs were made using both temperature-sensitive N-isopropyl acrylamide (NIPAm) and l-amino acid monomers. Five kinds of l-amino acids were acryloylated to obtain functional monomers: l-phenylalanine (Phe) and l-leucine (Leu) with hydrophobic side chains, l-glutamic acid (Glu) with negative charges, and l-lysine (Lys) and l-arginine (Arg) with positive charges. After incubating the NPs with fibrinogen, γ-globulin, and human serum albumin (HSA) respectively, the NPs that incorporated N-acryloyl-Arg monomers (AArg@NPs) showed the strongest and most specific binding affinity to fibrinogen, when compared with γ-globulin and HSA. Additionally, the fibrinogen-AArg binding model had the best docking scores, and this may be due to the interaction of positively charged AArg@NPs and the negatively charged fibrinogen D domain and the hydrophobic interaction between them. The specific adsorption of AArg@NPs to fibrinogen was also confirmed by the immunoprecipitation assay, as the AArg@NPs selectively trapped the fibrinogen from a human plasma protein mixture. AArg@NPs had a strong selectivity for, and specificity to, fibrinogen and may be developed as a potential human fibrinogen-specific affinity reagent.

Modulating Insulin Aggregation with Charge Variable Cholic Acid-Derived Polymers

To understand the effect of cholic acid (CA)-based charge variable polymeric architectures on modulating the insulin aggregation process, herein, we have designed side-chain cholate-containing charge variable polymers. Three different types of copolymers from 2-(methacryloyloxy)ethyl cholate with anionic or cationic or neutral units have been synthesized by reversible addition-fragmentation chain transfer polymerization. The effects of these copolymers on the insulin fibrillation process was studied by multiple biophysical approaches including different types of spectroscopic and microscopic analyses. Interestingly, the CA-based cationic polymer (CP-10) was observed to inhibit the insulin fibrillation process in a dose-dependent manner and to act as an effective anti-amyloidogenic agent. Corresponding anionic (AP-10) and neutral (NP-10) copolymers with cholate pendants remained insignificant in controlling the aggregation process. Tyrosine fluorescence assays and Nile red fluorescence measurements demonstrate the role of hydrophobic interaction to explain the inhibitory potencies of CP-10. Furthermore, circular dichroism spectroscopic measurements were carried out to explore the secondary structural changes of insulin fibrils in the presence of cationic polymers with and without cholate moieties. Isothermal titration calorimetry measurements revealed the involvement of electrostatic polar interaction between the CA-based cationic polymer and insulin at different stages of fibrillation. Overall, this work demonstrates the efficacy of the CA-based cationic polymer in controlling the insulin aggregation process and provides a novel dimension to the studies on protein aggregation.

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.

Breaker peptides against amyloid-β aggregation: a potential therapeutic strategy for Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, for which blocking the early steps of extracellular misfolded amyloid-β (Aβ) aggregation is a promising therapeutic approach. However, the pathological features of AD progression include the accumulation of intracellular tau protein, membrane-catalyzed cell death and the abnormal deposition of Aβ. Here, we focus on anti-amyloid breaker peptides derived from the Aβ sequence and non-Aβ-based peptides containing both natural and modified amino acids. Critical aspects of the breaker peptides include N-methylation, conformational restriction through cyclization, incorporation of unnatural amino acid, fluorinated molecules, polymeric nanoparticles and PEGylation. This review confers a general idea of such breaker peptides with in vitro and in vivo studies, which may advance our understanding of AD pathology and develop an effective treatment strategy against AD.

Dependence of the Nanoscale Composite Morphology of Fe3O4 Nanoparticle-Infused Lysozyme Amyloid Fibrils on Timing of Infusion: A Combined SAXS and AFM Study

Understanding the formation process and the spatial distribution of nanoparticle (NP) clusters on amyloid fibrils is an essential step for the development of NP-based methods to inhibit aggregation of amyloidal proteins or reverse the assembling trend of the proto-fibrillary complexes that prompts pathogenesis of neuro degeneration. For this, a detailed structural determination of the diverse hybrid assemblies that are forming is needed, which can be achieved by advanced X-ray scattering techniques. Using a combined solution small angle X-ray scattering (SAXS) and atomic force microscopy (AFM) approach, this study investigates the intrinsic trends of the interaction between lysozyme amyloid fibrils (LAFs) and Fe3O4 NPs before and after fibrillization at nanometer resolution. AFM images reveal that the number of NP clusters interacting with the lysozyme fibers does not increase significantly with NP volume concentration, suggesting a saturation in NP aggregation on the fibrillary surface. The data indicate that the number of non-adsorbed Fe3O4 NPs is highly dependent on the timing of NP infusion within the synthesis process. SAXS data yield access to the spatial distribution, aggregation manner and density of NP clusters on the fibrillary surfaces. Employing modern data analysis approaches, the shape and internal structural morphology of the so formed nanocomposites are revealed. The combined experimental approach suggests that while Fe3O4 NPs infusion does not prevent the fibril-formation, the variation of NP concentration and size at different stages of the fibrillization process can impose a pronounced impact on the superficial and internal structural morphologies of these nanocomposites. These findings may be applicable in devising advanced therapeutic treatments for neurodegenerative diseases and designing novel bio-inorganic magnetic devices. Our results further demonstrate that modern X-ray methods give access to the structure of-and insight into the formation process of-biological-inorganic hybrid structures in solution.

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.

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.

Chiral gold nanoparticles enantioselectively rescue memory deficits in a mouse model of Alzheimer's disease

Preventing aggregation of amyloid beta (Aβ) peptides is a promising strategy for the treatment of Alzheimer’s disease (AD), and gold nanoparticles have previously been explored as a potential anti-Aβ therapeutics. Here we design and prepare 3.3 nm L- and D-glutathione stabilized gold nanoparticles (denoted as L3.3 and D3.3, respectively). Both chiral nanoparticles are able to inhibit aggregation of Aβ42 and cross the blood-brain barrier (BBB) following intravenous administration without noticeable toxicity. D3.3 possesses a larger binding affinity to Aβ42 and higher brain biodistribution compared with its enantiomer L3.3, giving rise to stronger inhibition of Aβ42 fibrillation and better rescue of behavioral impairments in AD model mice. This conjugation of a small nanoparticle with chiral recognition moiety provides a potential therapeutic approach for AD.

Nanoparticles are being explored as a potential method to target Aβ aggregation in Alzheimer’s disease. Here, the authors develop gold nanoparticles that were capped with chiral L or D-glutathione which has been shown to improve BBB permeability and demonstrate their ability to improve cognitive function in a mouse model of AD.

Nanomaterial synthesis, an enabler of amyloidosis inhibition against human diseases

Amyloid diseases are global epidemics with no cure currently available. In the past decade, the use of engineered nanomaterials as inhibitors or probes against the pathogenic aggregation of amyloid peptides and proteins has emerged as a new frontier in nanomedicine. In this Minireview, we summarize for the first time the pivotal role of chemical synthesis in enabling the development of this multidisciplinary field.

Hyperthermia Induced by Near-Infrared Laser-Irradiated CsWO3 Nanoparticles Disintegrates Preformed Lysozyme Amyloid Fibrils

This research study attempts to prove the concept of the applicability of hyperthermia to treating the lysozyme amyloid fibrils (LAF)'s self-assembled fibrillary aggregates by a feedback-modulated temperature controller ranging from 26 °C to 80 °C, and separately, by near-infrared (NIR) laser-irradiated cesium tungstate (CsWO₃) nanoparticle (NPs). The dependence of the final morphology of the amyloidal assembly on external heating and the photothermal effect of the NPs on treating the fibrillary assembly were investigated and analyzed. Experimentally, atomic force microscopy (AFM), optical stereoscopy, and scanning electron microscopy (SEM) were used primarily to ensure mutual interaction between LAF and NPs, optically elucidate the surface contour and final fibrillary assembly upon the influence of thermal treatment, and further reveal fine-details of the optical samples. Finally, conclusive remarks are drawn that the fibrillary structures doped with the NPs exhibit an increasing degree of unique orthogonality. As the temperature rises, utter deformation of the dendritic structures of fibrillary assemblies at 70 °C was found, and NIR laser-irradiated CsWO₃ NPs have been demonstrated to be useful in topically destructing pre-assembled LAFs, which may be conducive to the future development of neurodegenerative therapeutic techniques.

Bleomycin modulates amyloid aggregation in β-amyloid and hIAPP

Aberrant misfolding and amyloid aggregation, which result in amyloid fibrils, are frequent and critical pathological incidents in various neurodegenerative disorders. Multiple drugs or inhibitors have been investigated to avert amyloid aggregation in individual peptides, exhibiting sequence-dependent inhibition mechanisms. Establishing or inventing inhibitors capable of preventing amyloid aggregation in a wide variety of amyloid peptides is quite a daunting task. Bleomycin (BLM), a complex glycopeptide, has been widely used as an antibiotic and antitumor drug due to its ability to inhibit DNA metabolism, and as an antineoplastic, especially for solid tumors. In this study, we investigated the dual inhibitory effects of BLM on Aβ aggregation, associated with Alzheimer's disease and hIAPP, which is linked to type 2 diabetes, using both computational and experimental techniques. Combined results from drug repurposing and replica exchange molecular dynamics simulations demonstrate that BLM binds to the β-sheet region considered a hotspot for amyloid fibrils of Aβ and hIAPP. BLM was also found to be involved in β-sheet destabilization and, ultimately, in its reduction. Further, experimental validation through in vitro amyloid aggregation assays was obtained wherein the fibrillar load was decreased for the BLM-treated Aβ and hIAPP peptides in comparison to controls. For the first time, this study shows that BLM is a dual inhibitor of Aβ and hIAPP amyloid aggregation. In the future, the conformational optimization and processing of BLM may help develop various efficient sequence-dependent inhibitors against amyloid aggregation in various amyloid peptides.

Bleomycin acts as a dual inhibitor against both amyloid β and human islet amyloid polypeptide by binding to the β-sheet grooves considered as the amyloids hotspot.

Insulin fibrillation: toward strategies for attenuating the process

The environmental factors affecting the rate of insulin fibrillation. The factors are representative.

Inhibition of Amyloid Fibrillation by Small Molecules and Nanomaterials: Strategic Development of Pharmaceuticals Against Amyloidosis

Amyloid fibrils are a special class of self-assembled protein molecules, which exhibit various toxic effects in cells. Different physiological disorders such as Alzheimer's, Parkinson's, Huntington's diseases, etc. happen due to amyloid formation and lack of proper cellular mechanism for the removal of fibrils. Therefore, inhibition of amyloid fibrillation will find immense applications to combat the diseases associated with amyloidosis. The development of therapeutics against amyloidosis is definitely challenging and numerous strategies have been followed to find out anti-amyloidogenic molecules. Inhibition of amyloid aggregation of proteins can be achieved either by stabilizing the native conformation or by decreasing the chances of assembly formation by the unfolded/misfolded structures. Various small molecules such as naturally occurring polyphenols, flavonoids, small organic molecules, surfactants, dyes, chaperones, etc. have demonstrated their capability to interrupt the amyloid fibrillation of proteins. In addition to that, in last few years, different nanomaterials were evolved as effective therapeutic inhibitors against amyloidosis. Aromatic and hydrophobic interactions between the partially unfolded protein molecules and the inhibitors had been pointed as a general mechanism for inhibition. In this review article, we are presenting an overview on the inhibition of amyloidosis by using different small molecules (both natural and synthetic origin) as well as nanomaterials for development of pharmaceutical strategies against amyloid diseases.

Vinblastine-Loaded Nanoparticles with Enhanced Tumor-Targeting Efficiency and Decreasing Toxicity: Developed by One-Step Molecular Imprinting Process

Molecularly imprinted polymers have exhibited good performance as carriers on drug loading and sustained release. In this paper, vinblastine (VBL)-loaded polymeric nanoparticles (VBL-NPs) were prepared by a one-step molecular imprinting process, avoiding the waste and incomplete removal of the template, and evaluated as targeting carriers for VBL delivery after modification. Using acryloyl amino acid comonomers and disulfide cross-linkers, VBL-NPs were synthesized and then conjugated with poly(ethylene glycol)-folate. The dynamic size of the obtained VBL-NPs-PEG-FA was 258.3 nm (PDI = 0.250), and the encapsulation efficiency was 45.82 ± 1.45%. The nanoparticles of VBL-NPs-PEG-FA were able to completely release VBL during 48 h under a mimic tumor intracellular condition (pH 4.5, 10 mM glutathione (GSH)), displaying significant redox responsiveness, whereas the release rates were much slower in the mimic body liquid (pH 7.4, 2 μM GSH) and tumor extracellular environment (pH 6.5, 2 μM GSH). Furthermore, the carriers NPs-PEG-FA, prepared without VBL, showed satisfactory intrinsic hemocompatibility, cellular compatibility, and tumor-targeting properties: they could rapidly and efficiently accumulate to folate receptor positive Hela cells and then internalized via receptor-mediated endocytosis, and the retention in tumor tissues could last for over 48 h. Interestingly, VBL-NPs-PEG-FA could evidently increase the accumulation of VBL in tumor tissues while decreasing the distribution of VBL in organs, exert similar anticancer efficacy against Hela tumors in the xenograft model of nude mice to VBL injection, and significantly improve the abnormality of liver and spleen observed in VBL injection. VBL-NPs-PEG-FA has the potential to be the delivery carrier for VBL by enhancing the tumor-targeting efficacy of VBL and decreasing toxicity to normal tissues.

Influence of crowding and surfaces on protein amyloidogenesis: A thermo-kinetic perspective

The last few decades have irreversibly implicated protein self-assembly and aggregation leading to amyloid fibril formation in proteopathies that include several neurodegenerative diseases. Emerging studies recognize the importance of eliciting the pathways leading to protein aggregation in the context of the crowded intracellular environment rather than in conventional in vitro conditions. It is found that crowded environments can have acceleratory as well as inhibitory effects on protein aggregation, depending on the interplay of underlying factors on the crucial rate limiting steps. The aggregation mechanism and transient species formed along the pathway are further altered when they interface with natural and artificial surfaces in the cellular milieu. An increasing number of studies probe the autocatalytic nature of amyloid surfaces as well as membrane bilayer effects on amyloidogenesis. Moreover, exposure to modern nanosurfaces via nanomedicines and other sources potentially invokes beneficial or deleterious biological response that needs rigorous investigation. Mounting evidences indicate that nanoparticles can either promote or impede amyloid aggregation, spurring efforts to tune their interactions for developing effective anti-amyloid strategies. Mechanistic insights into nanoparticle mediated aggregation pathways are therefore crucial for engineering anti-amyloid nanoparticle strategies that are biocompatible and sustainable. This review is a compilation of studies that contribute to the current understanding of the altering effects of molecular crowding as well as natural and artificial surfaces on protein amyloidogenesis.

Obstacles to translating the promise of nanoparticles into viable amyloid disease therapeutics

Nanoparticles (NPs) constitute a powerful therapeutic platform with exciting prospects as potential inhibitors of amyloid-[Formula: see text] (Aβ) aggregation, a process associated with Alzheimer's disease (AD). Researchers have synthesized and tested a large collection of NPs with disparate sizes, shapes, electrostatic properties and surface ligands that evoke a variety of responses on Aβ aggregation. In spite of a decade of research on the NP-Aβ system and many promising experimental results, NPs have failed to progress to any level of clinical trials for AD. A theoretical framework with which to approach this physical system is presented featuring two simple metrics, (1) the extent to which NPs adsorb Aβ, and (2) the degree to which interaction with a NP alters Aβ conformation relative to aggregation propensity. Most of our current understanding of these two interactions has been gained through experimentation, and many of these studies are reviewed herein. We also provide a potential roadmap for studies that we believe could produce viable NPs as an effective AD therapeutic platform.

Modulation of amyloid β peptide aggregation by hydrophilic polymers

Careful balance of hydrophilicity of precisely engineered polymers alters aggregation of the amyloidogenic protein Aβ_1–40.

Dual Size-Dependent Effect of Fe₃O₄ Magnetic Nanoparticles Upon Interaction with Lysozyme Amyloid Fibrils: Disintegration and Adsorption

Nanomedicine compounds containing nanoparticles, such as iron oxides and gold, have been demonstrated to be effective in promoting different magnitudes of interaction with amyloid β fibrils, of which disintegrating or inhibiting effects are of great importance to treating fibrillary aggregation-induced neurological disorders such as Alzheimer’s disease. This research herein studies the interaction between lysozyme amyloid fibrils, a type of fibers derived from hen egg white lysozyme, and Fe₃O₄ magnetic nanoparticles (MNPs) of an assorted diameter sizes of 5 nm, 10 nm and 20 nm, using atomic force microscopy (AFM). Specifically, the effects of the sizes of negatively charged MNPs on the resultant amyloid fibrillary mixture was investigated. Our results of AFM images indicated that the interaction between MNPs and the fibrils commences immediately after adding MNPs to the fibril solution, and the actions of such MNPs-doped fibrillary interplay, either integration or segmentation, is strongly dependent on the size and volume concentration of MNPs. In the cases of 5 nm and 20 nm particles of equivalent volume concentration, the adsorption and agglomeration of MNPs onto the fibrillary surfaces was observed, whereas, interestingly, MNPs with diameter size of 10 nm enables segmentation of the slender fibrils into debris when a proper implemented volume concentration was found, which signifies utter destruction of the amyloid fibrillary structure.

Basified Human Lysozyme: A Potent Inhibitor against Amyloid β-Protein Fibrillogenesis

The aggregation of amyloid β-proteins (Aβ) has been recognized as a key process in the pathogenesis of Alzheimer's disease (AD), so inhibiting Aβ aggregation is an important strategy to prevent the onset and treatment of AD. Our recent work indicated that decreasing the positive charges (or introducing negative charges) on human lysozyme (hLys) was unfavorable in keeping the inhibiting capability of hLys on Aβ aggregation. Therefore, we have herein proposed to basify hLys by conversion of the carboxyl groups into amino groups by modification with ethylene diamine. Basified hLys (Lys-B) preparations of three modification degrees (MDs), denoted as hLys-B1 (MD, 1.5), hLys-B2 (MD, 3.3), and hLys-B3 (MD, 4.4), were synthesized for modulating Aβ fibrillogenesis. The hLys-B preparations kept the stability and biocompatibility as native hLys did, whereas the inhibitory potency of hLys-B on Aβ fibrillogenesis increased with increasing MD. Cytotoxicity analysis showed that cell viability with 2.5 μM hLys-B3 increased from 62.5% (with 25 μM Aβ only) to 76.1%, similar to the case with 12.5 μM hLys (75.5%); cell viability with 6.25 μM hLys-B3 increased to 82.0%, similar to the case with 25 μM hLys (80.9%). The results indicate about four- to fivefold increase in the inhibition efficiency of hLys by the amino modification. Mechanistic analysis suggests that such a superior inhibitory capability of hLys-B was attributed to its more widely distributed positive charges, which promoted broad electrostatic interactions between Aβ and hLys-B. Thus, hLys-B suppressed the conformational transition of Aβ to β-sheet structures at low concentrations (e.g., 2.5 μM hLys-B3), leading to changes in the aggregation pathway and the formation of Aβ species with less cytotoxicity. The findings provided new insights into the development of more potent protein-based inhibitors against Aβ fibrillogenesis.

Defragmentation of lysozyme derived Amyloid β fibril using Biocompatible Magnetic fluid

We present here a modulating effect on lysozyme derived Amyloid β fibrils by aqueous magnetic fluid. This non-conventional approach of treatment of lysozyme derived Amyloid β fibrils showed lysing of Amyloid fibrils to its secondary structures which can be seen using optical microscope and scanning electron microscopic image. The size of lysozyme derived amyloid fibrils before and after treatment was measured using dynamic light scattering technique. The mechanism of defragmentation of lysozyme derived Amyloid β fibrils by magnetic fluid is explained. This is a first report to identify the secondary structure of protein using Fourier Transform Infrared (FTIR) and Circular Dichroism (CD) spectra after lysing. The cyto-toxicity study of this magnetic fluid on neuronal (SH-SY5Y) and non-neuronal (NRK) cell lines shows non-toxicity up to a concentration of 250 μg/mL. The study indicates a novel and unique complementary approach to treat the amyloidogenic brain diseases.

Genistein: A Dual Inhibitor of Both Amyloid β and Human Islet Amylin Peptides

Abnormal misfolding and aggregation of amyloid peptides into amyloid fibrils are common and critical pathological events in many neurodegenerative diseases. Most inhibitors or drugs have been developed to prevent amyloid aggregation of a specific peptide, showing sequence-dependent inhibition mechanisms. It is more challenging to develop or discover inhibitors capable of preventing the aggregation of two or more different amyloid peptides. Genistein, a major phytoestrogen in soybean, has been widely used as an anti-inflammation and cerebrovascular drug due to its antioxidation and antiacetylcholinesterase effects. Herein, we examine the inhibitory effects of genistein on the aggregation of amyloid-β (Aβ, associated with Alzheimer's disease) and human islet amylin (hIAPP, associated with type 2 diabetes) and Aβ- and hIAPP-induced neurotoxicity using a combination of experimental and computational approaches. Collective experimental results from thioflavin T (ThT), atomic force microscopy (AFM), and circular dichroism (CD) demonstrate that genistein shows strong inhibition ability to prevent the conformational transition of both Aβ and hIAPP monomers to β-sheet structures, thus reducing final amyloid fibrillization from Aβ and hIAPP monomer aggregation by 40-63%. Further 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH), and large unilamellar vesicle (LUV) assays show that genistein helps to increase cell viability, decrease cell apoptosis, and reduce cell membrane leakage, where the cell protection effect of genistein is likely correlated with its reduced membrane leakage. Comparative molecular dynamics (MD) simulations reveal that genistein prefers to bind the β-sheet groove, a common structural motif of amyloid fibrils, of both Aβ and hIAPP oligomers to interfere with their self-aggregation. This work for the first time demonstrates genistein as a dual inhibitor of Aβ and hIAPP aggregation. Further structural optimization and refinement of genistein may generate a series of effective sequence-independent inhibitors against the aggregation and toxicity of different amyloid peptides.

Bifunctionality of Iminodiacetic Acid-Modified Lysozyme on Inhibiting Zn2+-Mediated Amyloid β-Protein Aggregation

Aggregation of amyloid β-proteins (Aβ) mediated by metal ions such as Zn²⁺ has been suggested to be implicated in the progression of Alzheimer's disease (AD). Hence, development of bifunctional agents capable of inhibiting Aβ aggregation and modulating metal-Aβ species is an effective strategy for the treatment of AD. In this work, we modified iminodiacetic acid (IDA) onto human lysozyme (hLys) surface to create an inhibitor of Zn²⁺-mediated Aβ aggregation and cytotoxicity. The IDA-modified hLys (IDA-hLys) retained the stability and biocompatibility of native hLys. Extensive biophysical and biological analyses indicated that IDA-hLys significantly attenuated Zn²⁺-mediated Aβ aggregation and cytotoxicity due to its strong binding affinity for Zn²⁺, whereas native hLys showed little effect. Stopped-flow fluorescence spectroscopy showed that IDA-hLys could protect Aβ from Zn²⁺-induced aggregation and rapidly depolymerize Zn²⁺-Aβ aggregates. The research indicates that IDA-hLys is a bifunctional agent capable of inhibiting Aβ fibrillization and modulating Zn²⁺-mediated Aβ aggregation and cytotoxicity as a strong Zn²⁺ chelator.

Graphene oxide-iron oxide nanocomposite as an inhibitor of Aβ 42 amyloid peptide aggregation

Inhibiting amyloid β (Aβ) aggregation has drawn much attention because it is one of the main reasons for the cause of Alzheimer's disease (AD). Here we have synthesized a nanocomposite of graphene oxide-iron oxide (GOIO) and demonstrated its ability of modulating Aβ aggregation. The inhibition effects of the GOIO nanocomposite on Aβ aggregates was studied by Thioflavin T fluorescence assay, circular dichroism and transmission electron microscopy, respectively. Furthermore, the cell viability study revealed that the GOIO nanocomposite can reduce the toxicity of Aβ fibrils to neuroblastoma cells. Our results demonstrated that the combination of GO and IO as a nanocomposite material has a potential use for the design new therapeutic agents for the treatment of Alzheimer's disease.

Design of a Molecular Hybrid of Dual Peptide Inhibitors Coupled on AuNPs for Enhanced Inhibition of Amyloid β-Protein Aggregation and Cytotoxicity

Aggregation of amyloid-β protein (Aβ) is a pathological hallmark of Alzheimer's disease (AD), so the inhibition of Aβ aggregation is an important strategy for the prevention and treatment of AD. Herein, we proposed to design molecular hybrids of peptide inhibitors by combining two peptide inhibitors, VVIA and LPFFD, into single sequences and examined their effects on Aβ₄₂ aggregation and cytotoxicity. The hybrid peptides exhibit increased but moderate inhibitory activity as compared to their two precursors. By conjugating the peptides onto gold nanoparticles (AuNPs), however, the inhibition activity of the corresponding peptide@AuNPs against Aβ₄₂ aggregation and cytotoxicity is greatly improved. Among them, VVIACLPFFD (VCD10)@AuNP is the most effective, which increases cell viability from 48% to 82% at a dosage as low as 0.1 nmol L^-1 (NPs) or 40 nmol L^-1 (peptide). The superior capacity of VCD10@AuNPs is considered due to its branched dual-inhibitor sequence, and its special surface orientation and conformation. These structural features promote its synergetic interactions with Aβ on AuNP surface, leading to strong inhibitions of Aβ oligomerization and fibrillation and the cytotoxicity caused by the aggregation species. The findings suggest that potent inhibitors can be derived by hybridization of multiple peptide inhibitors with the hybrid products coupled onto nanoparticles.

Assessing safety and protein interactions of surface-modified iron oxide nanoparticles for potential use in biomedical areas

We have investigated the electrostatic interaction between bare iron oxide nanoparticles (IONPs) or low molecular weight chitosan coated iron oxide nanoparticles (LMWC-IONPs) and hen egg white lysozyme (HEWL) at different pH values using protein-nanoparticle reverse charge parity model. Physicochemical characterization of both IONPs and LMWC-IONPs were carried out using DLS, TEM, FE-SEM, XRD, TGA, XPS and VSM analysis. DLS, TEM and FE-SEM results indicated that both IONPs were monodispersed, with size ranging from 8 to 20nm. The coating of LMWC on IONPs was confirmed using zeta potential, TGA, XRD and XPS measurements. The cytotoxicity of both IONPs and LMWC-IONPs was studied in vitro in A549 human lung alveolar epithelial cells to assess their use in biomedical applications. Furthermore, the interactions between protein-nanoparticles were investigated by UV-visible, fluorescence and circular dichroism spectroscopic techniques. The present study suggests that water soluble LMWC surface modified IONPs are the promising nanomaterials. The safety and biocompatibility of these nanoparticles render them suitable for biomedical applications.

Hydrophobic Nanoparticles Reduce the β-Sheet Content of SEVI Amyloid Fibrils and Inhibit SEVI-Enhanced HIV Infectivity

Semen-derived enhancer of virus infection (SEVI) fibrils are naturally abundant amyloid aggregates found in semen that facilitate viral attachment and internalization of human immunodeficiency virus (HIV) in cells, thereby increasing the probability of infection. Mature SEVI fibrils are composed of aggregated peptides exhibiting high β-sheet secondary structural characteristics. Herein, we show that polymers containing hydrophobic side chains can interact with SEVI and reduce its β-sheet content by ∼45% compared with the β-sheet content of SEVI in the presence of polymers with hydrophilic side chains, as estimated by polarization modulation-infrared reflectance absorption spectroscopy measurements. A nanoparticle (NP) formulation of this hydrophobic polymer reduced SEVI-mediated HIV infection in TMZ-bl cells by 60% compared with the control treatment. Although these NPs lacked specific amyloid-targeting groups, thus requiring high concentrations to observe biological activity, the use of hydrophobic interactions to alter the secondary structure of amyloids represents a useful approach to neutralizing the SEVI function. These results could, therefore, have general implications in the design of novel materials that can modify the activity of amyloids associated with a variety of other neurological and systemic diseases.