Graphene oxide inhibits hIAPP amyloid fibrillation and toxicity in insulin-producing NIT-1 cells

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

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

A review on nanotechnological perspective of "the amyloid cascade hypothesis" for neurodegenerative diseases

Neurodegenerative diseases (NDs) are characterized by progressive degeneration of neurons which deteriorates the brain functions. An early detection of the onset of NDs is utmost important, as it will provide the fast treatment strategies to prevent further progression of the disease. Conventionally, accurate diagnosis of the brain related disorders is difficult in their early phase. To solve this problem, nanotechnology based neurofunctional imaging and biomarker detection techniques have been developed which allows high specificity and sensitivity towards screening and diagnosis of NDs. Another challenge to treat the brain related disorders is to overcome the complex integrity of blood-brain-barrier (BBB) for the delivery of theranostic agents. Fortunately, utilization of nanomaterials has been pursued as promising strategy to address this challenge. Herein, we critically highlighted the recent improvements in the field of neurodiagnostic and therapeutic approaches involving innovative strategies for diagnosis, and inhibition of protein aggregates. We have provided particular emphasis on the use of nanotechnology which can push forward the blooming research growth in this field to win the battle against devastating NDs.

Exploring the Curvature-Dependence of Boron Nitride Nanoparticles on the Inhibition of hIAPP Aggregation

Nanoparticles, particularly carbon nanoparticles, have gathered significant interest in the field of anti-aggregation research. However, due to their cytotoxicity, the exploration of biocompatible nanoparticles has become a new frontier in the quest for drugs against human amyloid diseases. The application of non-cytotoxic and biocompatible boron nitride (BN) nanoparticles against amyloid aggregation has been probed to tackle this issue. BN nanoparticles displayed inhibitory activity against the aggregation of Aβ and α-syn peptides. In this work, the effect of BN nanoparticles on the dimerization of hIAPP, which is associated with the pathogenesis of type 2 diabetes, is studied. BN nanoparticles prevent the misfolding of hIAPP into β-sheet-rich aggregates. On varying the curvature, the nanoparticles display variation in the interaction preference with hIAPP. Interestingly, as the hydrophobicity of the nanoparticles increases from (5,5) BN nanotube to BN nanosheet, the interaction propensity shifts from N-terminal to the amyloid prone C-terminal of hIAPP. The hydrophobic and aromatic stacking interactions are a contributing factor toward the binding between hIAPP and BN. Due to this, the flat surface of the nanosheet shows better interaction potential toward hIAPP, compared to the nanotubes. Further, the nanoparticles can also disassemble preformed hIAPP fibrils, and the effect is more pronounced for (5,5) nanotube and the nanosheet. This study provides insight into the inhibitory mechanism of hIAPP aggregation by boron nitride nanoparticles and also an understanding of the significance of the curvature of nanoparticles in their interaction with amyloid peptides, which is valuable for the design of antiamyloid drugs.

Evaluation of pancreatic δ- cells as a potential target site of graphene oxide toxicity in Japanese medaka (Oryzias latipes) fish

In continuation to our previous investigations on graphene oxide (GO) as an endocrine disrupting chemical (EDC), in the present experiment, we have investigated endocrine pancreas of Japanese medaka adults focusing on δ-cells in the islet organs as an endpoint. Breeding pairs of adult male and female fish were exposed to 0 mg/L (control) or 20 mg/L GO by continuous immersion (IMR) for 96 h, or to 0 µg/g or 100 µg/g GO by a single intraperitoneal (IP) administration and depurated 21 days in a GO-free environment. Histological investigations indicated that the endocrine cells are concentrated in one large principal islet, and several small secondary islets scattered within the mesentery near the liver and intestine. The cells of the islet organ are in various shapes with basophilic nuclei and eosinophilic cytoplasm. Immunohistochemical evaluation using rabbit polyclonal antisomatostatin antibody indicated that immunoreactivity is localized either at the periphery or at the central region in principal islets, and throughout the secondary islets, and found to be enhanced in fish exposed to GO than controls. The soma of δ-cells exhibits neuron-like morphology and have filopodia like processes. Cell sorting as non-communicating δ-cells (NCDC), communicating cells (CC), and non- δ-cells (NDC) indicated that within an islet organ, the population of NDCC is found to be the least and NDC is the highest. Our data further indicated that GO-induced impairments in the islet organs of medaka pancreas are inconsistent and could be affected by the exposure roots as well as the sex of the fish.

Disparate Effect of Hybrid Peptidomimetics Containing Isomers of Aminobenzoic Acid on hIAPP Aggregation

The abnormal misfolding of human islet amyloid polypeptide (hIAPP) in pancreatic β-cells is implicated in the progression of type II diabetes (T2D). With the prevalence of T2D increasing worldwide, preventing the aggregation of hIAPP has been recognized as a promising therapeutic strategy to control this disease. Recently, a class of novel conformationally restricted β-sheet breaker hybrid peptidomimetics (BSBHps) was found to demonstrate efficient inhibitory ability toward amyloid formation of hIAPP. One (Ile26) or more (Gly24 and Ile26) residues in these six-membered peptide sequences, which have been extracted from the amyloidogenic core of hIAPP, N₂₂FGAIL₂₇, are substituted by three different isomers of the conformationally restricted aromatic amino acid, i.e., aminobenzoic acid (β, γ, and δ), to generate these BSBHps. The presence of the nonproteinogenic aminobenzoic acid moiety renders the BSBHps to be more stable toward proteolytic degradation. The different isomeric BSBHps exhibit contrasting influence on the self-assembly of hIAPP. The BSBHps containing β- and γ-aminobenzoic acid can sufficiently prevent hIAPP aggregation, but those with the δ-aminobenzoic group stabilize the β-sheet-rich aggregate of hIAPP. The difference in the angle between the amino and carboxyl groups in the isomers of the aminobenzoic moiety causes the BSBHps to attain discrete conformation and hence leads to variation in their binding preference with hIAPP and ultimately their inhibitory potency. This guides the pathway for the dissimilar effect of BSBHps on peptide aggregation and, therefore, provides insights into the design considerations for novel drugs against T2D.

Molecular Mechanisms of Inhibition of Protein Amyloid Fibril Formation: Evidence and Perspectives Based on Kinetic Models

Inhibition of fibril formation is considered a possible treatment strategy for amyloid-related diseases. Understanding the molecular nature of inhibitor action is crucial for the design of drug candidates. In the present review, we describe the common kinetic models of fibril formation and classify known inhibitors by the mechanism of their interactions with the aggregating protein and its oligomers. This mechanism determines the step or steps of the aggregation process that become inhibited and the observed changes in kinetics and equilibrium of fibril formation. The results of numerous studies indicate that possible approaches to antiamyloid inhibitor discovery include the search for the strong binders of protein monomers, cappers blocking the ends of the growing fibril, or the species absorbing on the surface of oligomers preventing nucleation. Strongly binding inhibitors stabilizing the native state can be promising for the structured proteins while designing the drug candidates targeting disordered proteins is challenging.

Nanoparticles and Nanocolloidal Carbon: Will They Be the Next Antidiabetic Class That Targets Fibrillation and Aggregation of Human Islet Amyloid Polypeptide in Type 2 Diabetes?

Nanotechnology is revolutionizing human medicine. Nanoparticles (NPs) are currently used for treating various cancers, for developing vaccines, and for imaging, and other promises offered by NPs might come true soon. Due to the interplay between NPs and proteins, there is more and more evidence supporting the role of NPs for treating amyloid-based diseases. NPs can induce some conformational changes of the adsorbed protein molecules via various molecular interactions, leading to inhibition of aggregation and fibrillation of several and different amyloid proteins. Though an in depth understanding of such interactions between NPs and amyloid structures is still lacking, the inhibition of protein aggregation by NPs represents a new generation of innovative and effective medicines to combat metabolic diseases such as type 2 diabetes (T2D). Here, we lay out advances made in the field of T2D notably for optimizing protein aggregation inhibition strategies. This Account covers discussions about the current understanding of β-cells, the insulin producing cells within the pancreas, under diabetic conditions, notably increased glucose and fatty acid levels, and the implication of these conditions on the formation of human islet amyloid polypeptide (hIAPP) amylin oligomers and aggregates. Owing to the great potential of carbon nanostructures to interfere with protein aggregation, an important part of this Account will be devoted to the state of the art of therapeutic options in the form of emerging nanomaterials-based amyloidosis inhibitors. Our group has recently made some substantial progress in this regard by investigating the impact of glucose and fatty acid concentrations on hIAPP aggregation and β-cell toxicity. Furthermore, the great potential of carbon nanocolloids in reversing hIAPP aggregation under diabetic conditions will be highlighted as the approach has been validated on β-cell cultures from rats. We hope that this Account will evoke new ideas and concepts in this regard. We give some lead references below on pancreatic β-cell aspects and carbon quantum dots for managing diabetics and nanomedicine related aspects, a topic of interest in our laboratory.

Ginkgo biloba in the management of the COVID-19 severity

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is linked with inflammatory disorders and the development of oxidative stress in extreme cases. Therefore, anti-inflammatory and antioxidant drugs may alleviate these complications. Ginkgo biloba L. folium extract (EGb) is a herbal medicine containing various active constituents. This review aims to provide a critical discussion on the potential role of EGb in the management of coronavirus disease 2019 (COVID-19). The antiviral effect of EGb is mediated by different mechanisms, including blocking SARS-CoV-2 3-chymotrypsin-like protease that provides trans-variant effectiveness. Moreover, EGb impedes the development of pulmonary inflammatory disorders through the diminution of neutrophil elastase activity, the release of proinflammatory cytokines, platelet aggregation, and thrombosis. Thus, EGb can attenuate the acute lung injury and acute respiratory distress syndrome in COVID-19. In conclusion, EGb offers the potential of being used as adjuvant antiviral and symptomatic therapy. Nanosystems enabling targeted delivery, personalization, and booster of effects provide the opportunity for the use of EGb in modern phytotherapy.

Recent Advances in the Discovery of Therapeutics to Curtail Islet Amyloid Polypeptide Aggregation for Type 2 Diabetes Treatment

In humans with type 2 diabetes, at least 70% of patients exhibit islet amyloid plaques formed by misfolding islet amyloid polypeptides (IAPP). The oligomeric conformation and accumulation of the IAPP plaques lead to a panoply of cytotoxic effects on the islet β-cells. Currently, no marketed therapies for the prevention or elimination of these amyloid deposits exist, and therefore significant efforts are required to address this gap. To date, most of the experimental treatments are limited to only in vitro stages of testing. In general, the proposed therapeutics use various targeting strategies, such as binding to the N-terminal region of islet amyloid polypeptide on residues 1-19 or the hydrophobic region of IAPP. Other strategies include targeting the peptide self-assembly through π-stacking. These methods are realized by using several different families of compounds, four of which are highlighted in this review: naturally occurring products, small molecules, organometallic compounds, and nanoparticles. Each of these categories holds immense potential to optimize and develop inhibitor(s) of pancreatic amyloidosis in the near future.

Targeting hIAPP fibrillation: A new paradigm to prevent β-cell death?

Loss of pancreatic β-cell mass is deleterious for type 2 diabetes patients since it reduces insulin production, critical for glucose homeostasis. The main research axis developed over the last few years was to generate new pancreatic β-cells or to transplant pancreatic islets as occurring for some specific type 1 diabetes patients. We evaluate here a new paradigm consisting in preservation of β-cells by prevention of human islet amyloid polypeptide (hIAPP) oligomers and fibrils formation leading to pancreatic β-cell death. We review the hIAPP physiology and the pathology that contributes to β-cell destruction, deciphering the various cellular steps that could be involved. Recent progress in understanding other amyloidosis such as Aβ, Tau, α-synuclein or prion, involved in neurodegenerative processes linked with inflammation, has opened new research lines of investigations to preserve neuronal cells. We evaluate and estimate their transposition to the pancreatic β-cells preservation. Among them is the control of reactive oxygen species (ROS) production occurring with inflammation and the possible implication of the mitochondrial translocator protein as a diagnostic and therapeutic target. The present review also focuses on other amyloid forming proteins from molecular to physiological and physiopathological points of view that could help to better decipher hIAPP-induced β-cell death mechanisms and to prevent hIAPP fibril formation.

Melatonin Inhibits hIAPP Oligomerization by Preventing β-Sheet and Hydrogen Bond Formation of the Amyloidogenic Region Revealed by Replica-Exchange Molecular Dynamics Simulation

The pathogenesis of type 2 diabetes (T2D) is highly related to the abnormal self-assembly of the human islet amyloid polypeptide (hIAPP) into amyloid aggregates. To inhibit hIAPP aggregation is considered a promising therapeutic strategy for T2D treatment. Melatonin (Mel) was reported to effectively impede the accumulation of hIAPP aggregates and dissolve preformed fibrils. However, the underlying mechanism at the atomic level remains elusive. Here, we performed replica-exchange molecular dynamics (REMD) simulations to investigate the inhibitory effect of Mel on hIAPP oligomerization by using hIAPP20–29 octamer as templates. The conformational ensemble shows that Mel molecules can significantly prevent the β-sheet and backbone hydrogen bond formation of hIAPP20–29 octamer and remodel hIAPP oligomers and transform them into less compact conformations with more disordered contents. The interaction analysis shows that the binding behavior of Mel is dominated by hydrogen bonding with a peptide backbone and strengthened by aromatic stacking and CH–π interactions with peptide sidechains. The strong hIAPP–Mel interaction disrupts the hIAPP20–29 association, which is supposed to inhibit amyloid aggregation and cytotoxicity. We also performed conventional MD simulations to investigate the influence and binding affinity of Mel on the preformed hIAPP1–37 fibrillar octamer. Mel was found to preferentially bind to the amyloidogenic region hIAPP20–29, whereas it has a slight influence on the structural stability of the preformed fibrils. Our findings illustrate a possible pathway by which Mel alleviates diabetes symptoms from the perspective of Mel inhibiting amyloid deposits. This work reveals the inhibitory mechanism of Mel against hIAPP20–29 oligomerization, which provides useful clues for the development of efficient anti-amyloid agents.

Antidiabetic-activity sulfated polysaccharide from Chaetomorpha linum: Characteristics of its structure and effects on oxidative stress and mitochondrial function

A water-soluble polysaccharide from the green alga Chaetomorpha linum, designated CHS2, was obtained by water extraction, preparative anion-exchange and size-exclusion chromatography. Results of chemical and spectroscopic analyses showed that CHS2 was a sulfated rhamnogalactoarabinan, and its backbone was mainly constituted by 4-linked and 3,4-linked β-l-arabinopyranose with sulfate groups at C-2/C-3 of 4-linked β-l-arabinopyranose. The branching contained 4-linked, 6-linked β-d-galactopyranose and terminal rhamnose residues. Based on the inhibition of human islet amyloid polypeptide (hIAPP) aggregation and morphology change of hIAPP aggregates in in vitro tests, it was proved that CHS2 effectively inhibited the hIAPP aggregation and possessed strong antidiabetic activity. CHS2 was nearly no toxicity in NIT-1 cells and could attenuate hIAPP-induced cytotoxicity. CHS2 may significantly reduce the generation of intracellular reactive oxygen species and hIAPP aggregation-induced oxidative stress in NIT-1 cells. CHS2 was co-localized with mitochondria, and largely protected mitochondria function from hIAPP aggregation-induced damage through stabilizing mitochondrial membrane potential and enhancing the mitochondrial complex I, II or III activity and ATP level. The data demonstrated that CHS2 could have potential prospect to become an antidiabetic drug for type 2 diabetes mellitus treatment.

Human islet amyloid polypeptide: A therapeutic target for the management of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) and other metabolic disorders are often silent and go unnoticed in patients because of the lack of suitable prognostic and diagnostic markers. The current therapeutic regimens available for managing T2DM do not reverse diabetes; instead, they delay the progression of diabetes. Their efficacy (in principle) may be significantly improved if implemented at earlier stages. The misfolding and aggregation of human islet amyloid polypeptide (hIAPP) or amylin has been associated with a gradual decrease in pancreatic β-cell function and mass in patients with T2DM. Hence, hIAPP has been recognized as a therapeutic target for managing T2DM. This review summarizes hIAPP's role in mediating dysfunction and apoptosis in pancreatic β-cells via induction of endoplasmic reticulum stress, oxidative stress, mitochondrial dysfunction, inflammatory cytokine secretion, autophagy blockade, etc. Furthermore, it explores the possibility of using intermediates of the hIAPP aggregation pathway as potential drug targets for T2DM management. Finally, the effects of common antidiabetic molecules and repurposed drugs; other hIAPP mimetics and peptides; small organic molecules and natural compounds; nanoparticles, nanobodies, and quantum dots; metals and metal complexes; and chaperones that have demonstrated potential to inhibit and/or reverse hIAPP aggregation and can, therefore, be further developed for managing T2DM have been discussed.

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Misfolded species of hIAPP form toxic oligomers in pancreatic β-cells.

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hIAPP amyloids has been detected in the pancreas of about 90% subjects with T2DM.

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Inhibitors of hIAPP aggregation can help manage T2DM.

Formation and biological effects of protein corona for food-related nanoparticles

The rapid development of nanoscience and nanoengineering provides new perspectives on the composition of food materials, and has great potential for food biology research and applications. The use of nanoparticle additives and the discovery of endogenous nanoparticles in food make it important to elucidate in vivo safety of nanomaterials. Nanoparticles will spontaneously adsorb proteins during transporting in blood and a protein corona can be formed on the nanoparticle surface inside the human body. Protein corona affects the physicochemical properties of nanoparticles and the structure and function of proteins, which in turn affects a series of biological reactions. This article reviewed basic information about protein corona of food-related nanoparticles, elucidated the influence of protein corona on nanoparticles properties and protein structure and function, and discussed the effect of protein corona on nanoparticles in vivo. The effects of protein corona on nanoparticles transport, cellular uptake, cytotoxicity, and immune response were reviewed, and the reasons for these effects were also discussed. Finally, future research perspectives for food protein corona were proposed. Protein corona gives food nanoparticles a new identity, which makes proteins bound to nanoparticles undergo structural transformations that affect their recognition by receptors in vivo. It can have positive or negative impacts on cellular uptake and toxicity of nanoparticles and even trigger immune responses. Understanding the effects of protein corona have potential in evaluating the fate of the food-related nanoparticles, providing physicochemical and biological information about the interaction between proteins and foodborne nanoparticles. The review article will help to evaluate the safety of protein coronas formed on nanoparticles in food, and may provide fundamental information for understanding and controlling nanotoxicity.

The impact of chemical engineering and technological advances on managing diabetes: present and future concepts

Monitoring blood glucose levels for diabetic patients is critical to achieve tight glycaemic control. As none of the current antidiabetic treatments restore lost functional β-cell mass in diabetic patients, insulin injections and the use of insulin pumps are most widely used in the management of glycaemia. The use of advanced and intelligent chemical engineering, together with the incorporation of micro- and nanotechnological-based processes have lately revolutionized diabetic management. The start of this concept goes back to 1974 with the description of an electrode that repeatedly measures the level of blood glucose and triggers insulin release from an infusion pump to enter the blood stream from a small reservoir upon need. Next to the insulin pumps, other drug delivery routes, including nasal, transdermal and buccal, are currently investigated. These processes necessitate competences from chemists, engineers-alike and innovative views of pharmacologists and diabetologists. Engineered micro and nanostructures hold a unique potential when it comes to drug delivery applications required for the treatment of diabetic patients. As the technical aspects of chemistry, biology and informatics on medicine are expanding fast, time has come to step back and to evaluate the impact of technology-driven chemistry on diabetics and how the bridges from research laboratories to market products are established. In this review, the large variety of therapeutic approaches proposed in the last five years for diabetic patients are discussed in an applied context. A survey of the state of the art of closed-loop insulin delivery strategies in response to blood glucose level fluctuation is provided together with insights into the emerging key technologies for diagnosis and drug development. Chemical engineering strategies centered on preserving and regenerating functional pancreatic β-cell mass are evoked in addition as they represent a permanent solution for diabetic patients.

Potential of ATP toward Prevention of hIAPP Oligomerization and Destabilization of hIAPP Protofibrils: An In Silico Perspective

The aggregation of an intrinsically disordered protein, human islet amyloid polypeptide (hIAPP), leads to one of the most prevalent endocrine disorders, type II diabetes mellitus (T2DM). Hence inhibition of hIAPP aggregation provides a possible therapeutic approach for the treatment of T2DM. In this regard, a new aspect of adenosine triphosphate (ATP), which is widely known as the energy source for biological reactions, has recently been discovered, where it can inhibit the formation of protein aggregates and simultaneously dissolve preformed aggregates at a millimolar concentration scale. In this work, we investigate the effect of ATP on the aggregation of an amyloidogenic segment of hIAPP, hIAPP_22-28, and also of the full length sequence. Using all-atom classical molecular dynamics simulations, we observe that the tendency of hIAPP to oligomerize into β-sheet conformers is inhibited by ATP, due to which the peptides remain distant, loosely packed random monomers. Moreover, it can also disassemble preformed hIAPP protofibrils. ATP preferentially interacts with the hydrophobic residues of hIAPP_22-28 fragment and the terminal and turn residues of the full length peptide. The hydrogen bonding, hydrophobic, π-π, and N-H-π stacking interactions are the driving forces for the ATP induced inhibition of hIAPP aggregation. Interestingly, the hydrophobic adenosine of ATP is found to be more in contact with the peptide residues than the hydrophilic triphosphate moiety. The insight into the inhibitory mechanism of ATP on hIAPP aggregation can prove to be beneficial for the design of novel amyloid inhibitors in the future.

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

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

In vitro and in vivo models for anti-amyloidosis nanomedicines

Amyloid diseases are global epidemics characterized by the accumulative deposits of cross-beta amyloid fibrils and plaques. Despite decades of intensive research, few solutions are available for the diagnosis, treatment, and prevention of these debilitating diseases. Since the early work on the interaction of human β₂-microglobulin and nanoparticles by Linse et al. in 2007, the field of amyloidosis inhibition has gradually evolved into a new frontier in nanomedicine offering numerous interdisciplinary research opportunities, especially for materials, chemistry and biophysics. In this review we summarise, for the first time, the in vitro and in vivo models employed thus far in the field of anti-amyloidosis nanomedicines. Based on this systematic summary, we bring forth the notion that, due to the complex and often overlapping physiopathologies of amyloid diseases, there is a crucial need for the appropriate use of in vitro and in vivo models for validating novel anti-amyloidosis nanomedicines, and there is a crucial need for the development of new animal models that reflect the behavioural, symptomatic and cross-talk hallmarks of amyloid diseases such as Alzheimer's (AD), Parkinson's (PD) diseases and type 2 diabetes (T2DM).

Liver Phosphoenolpyruvate Carboxykinase-1 Downregulation via siRNA-Functionalized Graphene Oxide Nanosheets Restores Glucose Homeostasis in a Type 2 Diabetes Mellitus In Vivo Model

Metabolic disorders have been increasing at an alarming rate, and one such example of metabolic disorder is type 2 diabetes mellitus (T2DM). Unregulated gluconeogenesis in T2DM results in increased hepatic glucose output that causes fasting and postprandial hyperglycaemia. Extensive proofs have shown that the downregulation of the key rate-limiting enzyme phosphoenolpyruvate carboxykinase-1 (PCK-1) of gluconeogenesis improved glucose homeostasis in vivo. In the present study, we have synthesized and characterized liver-specific stearic acid conjugated octaarginine (StA-R8) functionalized 4arm-2K-PEGamineylated graphene oxide nanosheets (GPR8) for the delivery of siRNA against PCK-1 in T2DM C57BL/6 mice. We found that a single intravenous administration of siRNA (3 mg/kg BW) conjugated to GPR8 (GPR8:PCK-1_{siRNA(3 mg/kg BW)} conjugate) in an optimized N/P ratio exploited as a therapeutic nanoformulation maintained glucose homeostasis for nearly 4 weeks in the T2DM mice. Efficient silencing of PCK-1 in T2DM liver tissue increased the phosphorylation of serine-256 of FOXO-1, thus showing a marked decrease in hepatic gluconeogenesis. Gluconeogenesis control and consequently glucose output from the liver furthermore partially enhanced liver and muscle insulin sensitivity results in the stimulation of the insulin/AKT-2 signaling pathway which indirectly restored glucose homeostasis in the treated T2DM group. Our therapeutic nanoformulation also improved glycogen storage in the liver and membrane translocation of GLUT4 in the muscle of the treated T2DM group. In conclusion, GPR8:PCK-1_{siRNA (3 mg/Kg BW)} restored glucose homeostasis by controlling the hepatic glucose production and improved peripheral insulin sensitivity as a consequence of reduced hyperglycemia. Thus, the current approach offered an alternative strategy for the therapeutics for T2DM.

Amyloidosis Inhibition, a New Frontier of the Protein Corona

The protein corona has served as a central dogma and a nuisance to the applications of nanomedicine and nanobiotechnology for well over a decade. Here we introduce the emerging field of amyloidosis inhibition, which aims to understand and harness the interfacial phenomena associated with a nanoparticle interacting with pathogenic amyloid proteins. Much of this interaction correlates with our understanding of the protein corona, and yet much differs, as elaborated for the first time in this Perspective. Specifically, we examine the in vitro, in silico and in vivo features of the new class of "amyloid protein corona", and discuss how the interactions with nanoparticles may halt the self-assembly of amyloid proteins. As amyloidosis is driven off pathway by the nanoparticles, the oligomeric and protofibrillar populations are suppressed to ameliorate their cytotoxicity. Furthermore, as amyloid proteins spread via the transport of bodily fluids or cross seeding, amyloidosis is inherently associated with dynamic proteins and ligands to evoke the immune system. Accordingly, we ponder the structural and medical implications of the amyloid protein corona in the presence of their stimulated cytokines. Understanding and exploiting the amyloid protein corona may facilitate the development of new theranostics against a range of debilitating amyloid diseases.

Graphene oxide sheets and quantum dots inhibit α-synuclein amyloid formation by different mechanisms

Aggregation and amyloid formation of the 140-residue presynaptic and intrinsically disordered protein α-synuclein (α-syn) is a pathological hallmark of Parkinson's disease (PD). Understanding how α-syn forms amyloid fibrils, and investigations of agents that can prevent their formation is therefore important. We demonstrate herein that two types of graphene oxide nanoparticles (sheets and quantum dots) inhibit α-syn amyloid formation by different mechanisms mediated via differential interactions with both monomers and fibrils. We have used thioflavin-T fluorescence assays and kinetic analysis, circular dichroism, dynamic light scattering, fluorescence spectroscopy and atomic force microscopy to asses the kinetic nature and efficiency of this inhibitory effect. We show that the two types of graphene oxide nanoparticles alter the morphology of α-syn fibrils, disrupting their interfilament assembly and the resulting aggregates therefore consist of single protofilaments. Our results further show that graphene oxide sheets reduce the aggregation rate of α-syn primarily by sequestering of monomers, thereby preventing primary nucleation and elongation. Graphene quantum dots, on the other hand, interact less avidly with both monomers and fibrils. Their aggregation inhibitory effect is primarily related to adsorption of aggregated species and reduction of secondary processes, and they can thus not fully prevent aggregation. This fine-tuned and differential effect of graphene nanoparticles on amyloid formation shows that rational design of these nanomaterials has great potential in engineering materials that interact with specific molecular events in the amyloid fibril formation process. The findings also provide new insight into the molecular interplay between amyloidogenic proteins and graphene-based nanomaterials in general, and opens up their potential use as agents to manipulate fibril formation.

Recent advances of two-dimensional materials in smart drug delivery nano-systems

Smart drug delivery nano-systems show significant changes in their physical or chemical properties in response to slight change in environmental physical and/or chemical signals, and further releasing drugs adjusted to the progression of the disease at the right target and rate intelligently. Two-dimensional materials possess dramatic status extend all over various scientific and technological disciplines by reason of their exceptional unique properties in application of smart drug delivery nano-systems. In this review, we summarized current progress to highlight various kinds of two-dimensional materials drug carriers which are widely explored in smart drug delivery systems as well as classification of stimuli responsive two-dimensional materials and the advantages and disadvantages of their applications. Consequently, we anticipate that this review might inspire the development of new two-dimensional materials with smart drug delivery systems, and deepen researchers' understanding of smart nano-carries based on two-dimensional materials.

Interfacial charge transfer with exfoliated graphene inhibits fibril formation in lysozyme amyloid

Amyloid fibrillation is known to contribute in a variety of diseases including neurodegenerative disorders (e.g., Alzheimer's and Parkinson's disease) and type II diabetes. The inhibition of fibrillation has been suggested as a possible therapeutic strategy to prevent neuronal and pancreatic β-cell death associated with amyloid diseases. To this end, strong hydrophobic and π-π interactions between proteins and nanomaterials at the nanobio interface could be used to mitigate the stacking of amyloid structures associated with fibrillation. In this study, the authors show that exfoliated graphene effectively inhibits the formation of amyloid fibrils using a model amyloid-forming protein, viz., hen egg white lysozyme (HEWL). While previous theoretical models posit that hydrophobic and π-π stacking interactions result in strong interactions between graphene and proteins, the authors experimentally identified the presence of additional interfacial charge transfer interactions between HEWL and graphene using micro-Raman spectroscopy and Kelvin probe force microscopy. Their photoluminescence spectroscopy and transmission electron microscopy studies evince that the interfacial charge transfer combined with hydrophobic and π-π stacking interactions, specifically between the nanomaterial and the amino acid tryptophan, increase HEWL adsorption on graphene and thereby inhibit amyloid fibrillation.

Increasing the Potential Interacting Area of Nanomedicine Enhances Its Homotypic Cancer Targeting Efficacy

The cancer cell membrane contains an arsenal of highly specific homotypic moieties that can be used to recognize its own kind. These cell membranes are often used to coat spherical nanoparticles to enhance nanomedicines' targeting specificities and uptakes. A sphere, however, has only a point contact with a surface at any given time. It is shown here that, by retaining a flatter morphology of the cracked cell membrane through stiffening with in situ synthesized gold nanomaterials, an increased area of interaction could be maintained and hence improve upon the in vitro and in vivo homotypic targeting capabilities between cancer cell types. This enhancement is especially important in vivo as any nanomedicine with targeting moieties probably has a single pass at interacting with the target cell before subsequent system clearance. Possible future clinical applications may involve the usage of a patient's autologous tumor biopsy tissues, which are very limited in supply, and therefore ensuring that we capitalize on the entire collective surface area of the cancer cell membrane available becomes an important consideration in the design and delivery our cell membrane-derived nanomedicines.

Pristine and Hydroxylated Fullerenes Prevent the Aggregation of Human Islet Amyloid Polypeptide and Display Different Inhibitory Mechanisms

Protein aggregation, involving the formation of dimers, oligomers, and fibrils, is associated with many human diseases. Type 2 diabetes is one of the common amyloidosis and linked with the aggregation of human islet amyloid polypeptide (hIAPP). A series of nanoparticles are reported to be able to interact with proteins and enhance/inhibit protein aggregation. However, the effects of C₆₀ (a model system of hydrophobic nanoparticle) and C₆₀(OH)₈ (a hydroxylated fullerene) on hIAPP aggregation remain unknown. In this study, we investigate the influences of pristine fullerene C₆₀ and hydroxylated C₆₀ on the dimerization of hIAPP using molecular dynamics (MD) simulations. Extensive replica exchange molecular dynamics (REMD) simulations show that isolated hIAPP dimers adopt β-sheet structure containing the amyloid-precursor (β-hairpin). Both C₆₀ and C₆₀(OH)₈ notably inhibit the β-sheet formation of hIAPP dimer and induce the formation of collapsed disordered coil-rich conformations. Protein—nanoparticle interaction analyses reveal that the inhibition of hIAPP aggregation by C₆₀ is mainly via hydrophobic and aromatic-stacking interactions, while the prevention of hIAPP aggregation by C₆₀(OH)₈ is mostly through collective hydrogen bonding and aromatic-stacking interactions. Conventional MD simulations indicate that both C₆₀ and C₆₀(OH)₈ weaken the interactions within hIAPP protofibril and disrupt the β-sheet structure. These results provide mechanistic insights into the possible inhibitory mechanism of C₆₀ and C₆₀(OH)₈ toward hIAPP aggregation, and they are of great reference value for the screening of potent amyloid inhibitors.

Role of surface oxygen-containing functional groups of graphene oxide quantum dots on amyloid fibrillation of two model proteins

There are many reports demonstrating that various derivatives of carbon nanoparticles are effective inhibitors of protein aggregation. As surface structural features of nanoparticles play a key role on modulating amyloid fibrillation process, in the present in vitro study, bovine insulin and hen egg white lysozyme (HEWL) were selected as two model proteins to investigate the reducing effect of graphene oxide quantum dots (GOQDs) on their assembly under amyloidogenic conditions. GOQDs were prepared through direct pyrolysis of citric acid, and the reduction step was carried out using ascorbic acid. The prepared nanoparticles were characterized by UV-Vis, X-ray photoelectron, and FT-IR spectroscopies, transmission electron and atomic force microscopies, zeta potential measurement, and Nile red fluorescence assay. They showed the tendencies to modulate the assembly of the proteins through different mechanisms. While GOQDs appeared to have the capacity to inhibit fibrillation, the presence of reduced GOQDs (rGOQDs) was found to promote protein assembly via shortening the nucleation phase, as suggested by ThT fluorescence data. Moreover, the structures produced in the presence of GOQDs or rGOQDs were totally nontoxic. We suggest that surface properties of these particles may be part of the differences in their mechanism(s) of action.

Photodegradation of porphyrin-bound hIAPP(1–37) fibrils

Amyloid deposits in pancreatic islets of type 2 diabetes mellitus (T2DM) are mainly comprised of human islet amyloid polypeptide (hIAPP), the degradation of hIAPP fibrils by photoactive porphyrin could be a preventive strategy against T2DM.

Amphiphilic surface chemistry of fullerenols is necessary for inhibiting the amyloid aggregation of alpha-synuclein NACore

Featuring small sizes, caged structures, low cytotoxicity and the capability to cross biological barriers, fullerene hydroxy derivatives named fullerenols have been explored as nanomedicinal candidates for amyloid inhibition. Understanding the surface chemistry effect of hydroxylation extents and the corresponding amyloid inhibition mechanisms is necessary for enabling applications of fullerenols and also future designs of nanomedicines in mitigating amyloid aggregation. Here, we investigated effects of C60(OH)n with n = 0-40 on the aggregation of NACore (the amyloidogenic core region of the non-amyloid-β component in α-synuclein), the amyloidogenic core of α-synuclein, by computational simulations, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thioflavin-T (ThT) fluorescence kinetics and viability assays. Computationally, NACore assembled into cross-β aggregates via intermediates including β-barrels, which are postulated as toxic oligomers of amyloid aggregation. Hydrophobic C60 preferred to self-assemble, and NACore bound to the surface of C60 nano-clusters formed β-sheet rich aggregates - i.e., having little inhibition effect. Amphiphilic C60(OH)n with n = 4-20 displayed significant inhibition effects on NACore aggregation, where hydrogen bonding between hydroxyls and peptide backbones interrupted the formation of β-sheets between peptides adsorbed onto the surfaces of fullerenols or fullerenol nano-assemblies due to hydrophobic interactions. Thus, both cross-β aggregates and β-barrel intermediates were significantly suppressed. With hydroxyls increased to 40, fullerenols became highly hydrophilic with reduced peptide binding and thus an inhibition effect on amyloid aggregation. ThT, FTIR and TEM characterization of C60(OH)n with n = 0, 24, & 40 confirmed the computational predictions. Our results and others underscore the importance of amphiphilic surface chemistry and the capability of polar groups in forming hydrogen bonds with peptide backbones to render amyloid inhibition, offering a new insight for de-novo design of anti-amyloid inhibitors.

Influence of fullerenol on hIAPP aggregation: amyloid inhibition and mechanistic aspects

C60(OH)₂₄inhibits hIAPP aggregation by suppressing the fibril-prone structure and destabilizes hIAPP protofibrils by binding to the amyloid core region.

Impact of nanoparticles on amyloid peptide and protein aggregation: a review with a focus on gold nanoparticles

Society is increasingly exposed to nanoparticles as they are ubiquitous in nature and introduced as man-made air pollutants and as functional ingredients in cosmetic products as well as in nanomedicine. Nanoparticles differ in size, shape and material properties. In addition to their intended function, the side effects on biochemical processes in organisms remain unclear. Nanoparticles can significantly influence the nucleation and aggregation process of peptides. The development of several neurodegenerative diseases, such as Alzheimer's disease, is related to the aggregation of peptides into amyloid fibrils. However, there is no comprehensive or universal mechanism to predict or explain apparent acceleration or inhibition of these aggregation processes. In this work, selected studies and possible mechanisms for amyloid peptide nucleation and aggregation, in the presence of nanoparticles, are highlighted. These studies are discussed in the context of recent data from our group on the role of gold nanoparticles in amyloid peptide aggregation using experimental methods and large-scale molecular dynamics simulations. A complex interplay of the surface properties of the nanoparticles, the properties of the peptides, as well as the resulting forces between both the nanoparticles and the peptides, appear to determine whether amyloid peptide aggregation is influenced, catalysed or inhibited by the presence of nanoparticles.

Directly probing the dissociation effects of graphene oxide nanosheets on hIAPP fibrils

The aggregation of human islet amyloid polypeptides (hIAPP) to mature fibrils is considered as the main cause of type II diabetes. Therefore destroying the pre-formed hIAPP fibrils is expected to be a promising strategy for therapeutic treatments. In this work, the dissociation effects of graphene oxide (GO) nanosheets on hIAPP mature fibrils are investigated. The results clearly demonstrate that hIAPP fibrils can be quickly adsorbed on the GO surface and efficiently broken into short fragments. Meanwhile, the β-sheet structures of hIAPP fibrils are greatly destroyed. Particularly, in situ atomic force microscopy was applied to monitor the real-time interaction between hIAPP fibrils and GO nanosheets. It provides distinct evidence that the disruption of hIAPP fibrils by GO nanosheets mainly occurs at the GO edges. Size-dependent experiments further justify the interfere of edge contribution, which suggest small-sized GO nanosheets exhibit better dissociation ability than large-sized ones. Therefore, this study not only provides valuable information that GO nanosheets (especially small-sized ones) can act as efficient nanoblades to break hIAPP fibrils, but also suggests a powerful and widely available methodology for investigating real-time interaction between nanomaterials and biomolecules.

Nucleation of β-rich oligomers and β-barrels in the early aggregation of human islet amyloid polypeptide

The self-assembly of human islet amyloid polypeptide (hIAPP) into β-sheet rich amyloid aggregates is associated with pancreatic β-cell death in type 2 diabetes (T2D). Prior experimental studies of hIAPP aggregation reported the early accumulation of α-helical intermediates before the rapid conversion into β-sheet rich amyloid fibrils, as also corroborated by our experimental characterizations with transmission electron microscopy and Fourier transform infrared spectroscopy. Although increasing evidence suggests that small oligomers populating early hIAPP aggregation play crucial roles in cytotoxicity, structures of these oligomer intermediates and their conformational conversions remain unknown, hindering our understanding of T2D disease mechanism and therapeutic design targeting these early aggregation species. We further applied large-scale discrete molecule dynamics simulations to investigate the oligomerization of full-length hIAPP, employing multiple molecular systems of increasing number of peptides. We found that the oligomerization process was dynamic, involving frequent inter-oligomeric exchanges. On average, oligomers had more α-helices than β-sheets, consistent with ensemble-based experimental measurements. However, in ~4-6% independent simulations, β-rich oligomers expected as the fibrillization intermediates were observed, especially in the pentamer and hexamer simulations. These β-rich oligomers could adopt β-barrel conformations, recently postulated to be the toxic oligomer species but only observed computationally in the aggregates of short amyloid protein fragments. Free-energy analysis revealed high energies of these β-rich oligomers, supporting the nucleated conformational changes of oligomers in amyloid aggregation. β-barrel oligomers of full-length hIAPP with well-defined three-dimensional structures may play an important pathological role in T2D etiology and may be a therapeutic target for the disease.

The Inhibitory Effect of Hydroxylated Carbon Nanotubes on the Aggregation of Human Islet Amyloid Polypeptide Revealed by a Combined Computational and Experimental Study

Fibrillar deposits formed by the aggregation of the human islet amyloid polypeptide (hIAPP) are the major pathological hallmark of type 2 diabetes mellitus (T2DM). Inhibiting the aggregation of hIAPP is considered the primary therapeutic strategy for the treatment of T2DM. Hydroxylated carbon nanoparticles have received great attention in impeding amyloid protein fibrillation owing to their reduced cytotoxicity compared to the pristine ones. In this study, we investigated the influence of hydroxylated single-walled carbon nanotubes (SWCNT-OHs) on the first step of hIAPP aggregation: dimerization by performing explicit solvent replica exchange molecular dynamics (REMD) simulations. Extensive REMD simulations demonstrate that SWCNT-OHs can dramatically inhibit interpeptide β-sheet formation and completely suppress the previously reported β-hairpin amyloidogenic precursor of hIAPP. On the basis of our simulation results, we proposed that SWCNT-OH can hinder hIAPP fibrillation. This was further confirmed by our systematic turbidity measurements, thioflavin T fluorescence, circular dichroism (CD), transmission electron microscope (TEM), and atomic force microscopy (AFM) experiments. Detailed analyses of hIAPP-SWCNT-OH interactions reveal that hydrogen bonding, van der Waals, and π-stacking interactions between hIAPP and SWCNT-OH significantly weaken the inter- and intrapeptide interactions that are crucial for β-sheet formation. Our collective computational and experimental data reveal not only the inhibitory effect but also the inhibitory mechanism of SWCNT-OH against hIAPP aggregation, thus providing new clues for the development of future drug candidates against T2DM.

Evaluation of the photo-degradation of Alzheimer's amyloid fibrils with a label-free approach

Degradation of amyloid-β (Aβ) aggregates has been considered as an attractive therapeutic and preventive strategy against Alzheimer's disease (AD). However, an in situ, real-time, and label-free technique is still lacking to understand the degradation process of Aβ aggregates. In this work, we developed a novel method to quantitatively evaluate the degradation of Aβ fibrils by photoactive meso-tetra(4-sulfonatophenyl)porphyrin under UV irradiation with quartz crystal microbalance (QCM).

Graphene quantum dots against human IAPP aggregation and toxicity in vivo

The development of biocompatible nanomaterials has become a new frontier in the detection, treatment and prevention of human amyloid diseases. Here we demonstrated the use of graphene quantum dots (GQDs) as a potent inhibitor against the in vivo aggregation and toxicity of human islet amyloid polypeptide (IAPP), a hallmark of type 2 diabetes. GQDs initiated contact with IAPP through electrostatic and hydrophobic interactions as well as hydrogen bonding, which subsequently drove the peptide fibrillization off-pathway to eliminate the toxic intermediates. Such interactions, probed in vitro by a thioflavin T kinetic assay, fluorescence quenching, circular dichroism spectroscopy, a cell viability assay and in silico by discrete molecular dynamics simulations, translated to a significant recovery of embryonic zebrafish from the damage elicited by IAPP in vivo, as indicated by improved hatching as well as alleviated reactive oxygen species production, abnormality and mortality of the organism. This study points to the potential of using zero-dimensional nanomaterials for in vivo mitigation of a range of amyloidosis.

Functional amyloid materials at surfaces/interfaces

With the development of nanotechnology, functional amyloid materials are drawing increasing attention, and numerous remarkable applications are emerging. Amyloids, defined as a class of supramolecular assemblies of misfolded proteins or peptides into β-sheet fibrils, have evolved in many new respects and offer abundant chemical/biological functions. These proteinaceous micro/nano-structures provide excellent biocompatibility, rich phase behaviours, strong mechanical properties, and stability at interfaces not only in nature but also in functional materials, displaying versatile interactions with surfaces/interfaces that have been widely adopted in bioadhesion, synthetic biology, and composites. Overall, functional amyloids at surfaces/interfaces have excellent potential applications in next-generation biotechnology and biomaterials.

Nanoscale inhibition of polymorphic and ambidextrous IAPP amyloid aggregation with small molecules

Understanding how small molecules interface amyloid fibrils on the nanoscale is of importance for developing therapeutic treatment against amyloid-based diseases. Here we show, for the first time, that human islet amyloid polypeptide (IAPP) in the fibrillar form is polymorphic and ambidextrous possessing multiple periodicities. Upon interfacing with small molecule epigallocatechin gallate (EGCG), IAPP aggregation was rendered off pathway assuming the form of soft and disordered clusters, while mature IAPP fibrils displayed kinks and branching but conserved the twisted fibril morphology. These nanoscale phenomena resulted from competitive interactions between EGCG and the IAPP amyloidogenic region, as well as end capping of the fibrils by the small molecule. This information is crucial to delineating IAPP toxicity implicated in type 2 diabetes and developing new inhibitors against amyloidogenesis.

Dual effect of PEG-PE micelle over the oligomerization and fibrillation of human islet amyloid polypeptide

The oligomerization and fibrillation of human islet amyloid polypeptide (hIAPP) play a central role in the pathogenesis of type 2 diabetes. Strategies for remodelling the formation of hIAPP oligomers and fibrils have promising application potential in type 2 diabetes therapy. Herein, we demonstrated that PEG-PE micelle could inhibit hIAPP oligomerization and fibrillation through blocking the hydrophobic interaction and the conformational change from random coil to β-sheet structures of hIAPP. In addition, we also found that PEG-PE micelle could remodel the preformed hIAPP fibrils allowing the formation of short fibrils and co-aggregates. Taken together, PEG-PE micelle could rescue hIAPP-induced cytotoxicity by decreasing the content of hIAPP oligomers and fibrils that are related to the oxidative stress and cell membrane permeability. This study could be beneficial for the design and development of antiamyloidogenic agents.

Differential effects of silver and iron oxide nanoparticles on IAPP amyloid aggregation

Recent studies have shown promise on the use of small molecules and nanoparticles (NPs) for the inhibition of protein aggregation, a hallmark of neurodegenerative diseases and type 2 diabetes (T2D). Towards this end here we show the differential effects of silver and iron oxide nanoparticles (AgNPs and IONPs) on the mesoscopic properties of human islet amyloid polypeptide (IAPP) aggregation associated with T2D. Both citrate- and branched polyethyleneimine-coated AgNPs (c-AgNPs, bPEI-AgNPs) inhibited IAPP aggregation at 500 μg mL^-1, likely through electrostatic attraction and sequestering of IAPP monomers from fibrillation. In comparison, bare, brushed polyethylene glycol- and phosphorylcholine-grafted IONPs (bPEG-IONPs, bPC-IONPs) at 500 μg mL^-1 elicited no major effect on IAPP fibril contour length, while bPC-IONPs induced significant fibril softening and looping likely mediated by dipolar interactions. While monovalent Ag⁺ up to 50 μg mL^-1 showed no effect on the contour length or stiffness of IAPP fibrils, multivalent Fe³⁺ at 5 μg mL^-1 halted IAPP fibrillation likely through ion-peptide crosslinking. Except bPEI-AgNPs, all three types of IONPs and c-AgNPs at 100 μg mL^-1 alleviated IAPP toxicity in HEK293 cells indicating no clear correlation between protein aggregation and their induced cytotoxicity. This study demonstrates the complexity of protein aggregation intervened by NPs of different physicochemical properties and - together with existing literature - facilitates nanotechnological applications for mitigating amyloid-mediated pathologies.

Star Polymers Reduce Islet Amyloid Polypeptide Toxicity via Accelerated Amyloid Aggregation

Protein aggregation into amyloid fibrils is a ubiquitous phenomenon across the spectrum of neurodegenerative disorders and type 2 diabetes. A common strategy against amyloidogenesis is to minimize the populations of toxic oligomers and protofibrils by inhibiting protein aggregation with small molecules or nanoparticles. However, melanin synthesis in nature is realized by accelerated protein fibrillation to circumvent accumulation of toxic intermediates. Accordingly, we designed and demonstrated the use of star-shaped poly(2-hydroxyethyl acrylate) (PHEA) nanostructures for promoting aggregation while ameliorating the toxicity of human islet amyloid polypeptide (IAPP), the peptide involved in glycemic control and the pathology of type 2 diabetes. The binding of PHEA elevated the β-sheet content in IAPP aggregates while rendering a new morphology of "stelliform" amyloids originating from the polymers. Atomistic molecular dynamics simulations revealed that the PHEA arms served as rodlike scaffolds for IAPP binding and subsequently accelerated IAPP aggregation by increased local peptide concentration. The tertiary structure of the star nanoparticles was found to be essential for driving the specific interactions required to impel the accelerated IAPP aggregation. This study sheds new light on the structure-toxicity relationship of IAPP and points to the potential of exploiting star polymers as a new class of therapeutic agents against amyloidogenesis.

Implications of peptide assemblies in amyloid diseases

Neurodegenerative disorders and type 2 diabetes are global epidemics compromising the quality of life of millions worldwide, with profound social and economic implications. Despite the significant differences in pathology - much of which are poorly understood - these diseases are commonly characterized by the presence of cross-β amyloid fibrils as well as the loss of neuronal or pancreatic β-cells. In this review, we document research progress on the molecular and mesoscopic self-assembly of amyloid-beta, alpha synuclein, human islet amyloid polypeptide and prions, the peptides and proteins associated with Alzheimer's, Parkinson's, type 2 diabetes and prion diseases. In addition, we discuss the toxicities of these amyloid proteins based on their self-assembly as well as their interactions with membranes, metal ions, small molecules and engineered nanoparticles. Through this presentation we show the remarkable similarities and differences in the structural transitions of the amyloid proteins through primary and secondary nucleation, the common evolution from disordered monomers to alpha-helices and then to β-sheets when the proteins encounter the cell membrane, and, the consensus (with a few exceptions) that off-pathway oligomers, rather than amyloid fibrils, are the toxic species regardless of the pathogenic protein sequence or physicochemical properties. In addition, we highlight the crucial role of molecular self-assembly in eliciting the biological and pathological consequences of the amyloid proteins within the context of their cellular environments and their spreading between cells and organs. Exploiting such structure-function-toxicity relationship may prove pivotal for the detection and mitigation of amyloid diseases.