Carbon Nanoparticles Inhibit the Aggregation of Prion Protein as Revealed by Experiments and Atomistic Simulations

Adsorption of plasma protein human serum albumin on surface functionalized multi-walled carbon nanotubes: Insights into binding interactions and effects on protein fibrillation

Carbon nanotubes (CNTs) have potential applications in various biomedical and biotechnological fields, importance of protein-CNTs interactions in living cells, as well as their concerns about the nanotoxicity of these CNTs, have not been well investigated. This study examines by experimentally human serum albumin (HSA) interaction with different surface functionalized multi-walled carbon nanotubes (MWCNTs). The adsorption was done on HSA onto 1,2-propanediol functionalized MWCNTs (MWCNTs-OH) and cysteamine functionalized MWCNTs (MWCNTs-SH) and estimates the corresponding adsorption parameters. During the adsorption process, pristine MWCNTs (p-MWCNTs) exhibit a higher adsorption capacity compared to MWCNTs-OH and MWCNTs-SH, with the order being: p-MWCNTs > MWCNTs-SH > MWCNTs-OH. Here also Isothermal Titration Calorimetry (ITC) experiments were employed to analyze the interaction of HSA onto MWCNTs-OH and MWCNTs-SH. The possible binding parameters were indicated that HSA forms complexes with MWCNTs-OH and MWCNTs-SH at specific nearby binding sites. And anti-fibrillation activity of surface functionalized MWCNTs was assessed using Thioflavin T (ThT) and Congo Red (CR) spectroscopic techniques the secondary conformational changes were observed through circular dichroism (CD) experiments, additionally, the inhibitory role of surface functionalized MWCNTs in HSA fibril formation was confirmed through microscopic evaluations.

Recent Advancements in Nanomaterials: A Promising Way to Manage Neurodegenerative Disorders

Neurodegenerative diseases (NDs) such as dementia, Alzheimer's disease, Parkinson's disease, frontotemporal dementia, and amyotrophic lateral sclerosis are some of the most prevalent disorders currently afflicting healthcare systems. Many of these diseases share similar pathological hallmarks, including elevated oxidative stress, mitochondrial dysfunction, protein misfolding, excitotoxicity, and neuroinflammation, all of which contribute to the deterioration of the nervous system's structure and function. The development of diagnostic and therapeutic materials in the monitoring and treatment of these diseases remains challenging. One of the biggest challenges facing therapeutic and diagnostic materials is the blood-brain barrier (BBB). The BBB is a multifunctional membrane possessing a plethora of biochemical, cellular, and immunological features that ensure brain homeostasis by preventing the entry and accumulation of unwanted compounds. With regards to neurodegenerative diseases, the recent application of tailored nanomaterials (nanocarriers and nanoparticles) has led to advances in diagnostics and therapeutics. In this review, we provide an overview of commonly used nanoparticles and their applications in NDs, which may offer new therapeutic strategies for the prevention and treatment of neurodegenerative diseases.

Nanoparticle-Enhanced RT-QuIC (Nano-QuIC) Diagnostic Assay for Misfolded Proteins

Misfolded proteins associated with various neurodegenerative diseases often accumulate in tissues or circulate in biological fluids years before the clinical onset, thus representing ideal diagnostic targets. Real-time quaking-induced conversion (RT-QuIC), a protein-based seeded-amplification assay, holds great potential for early disease detection, yet challenges remain for routine diagnostic application. Chronic Wasting Disease (CWD), associated with misfolded prion proteins of cervids, serves as an ideal model for evaluating new RT-QuIC methodologies. In this study, we investigate the previously untested hypothesis that incorporating nanoparticles into RT-QuIC assays can enhance their speed and sensitivity when applied to biological samples. We show that adding 50 nm silica nanoparticles to RT-QuIC experiments (termed Nano-QuIC) for CWD diagnostics greatly improves the performance by reducing detection times 2.5-fold and increasing sensitivity 10-fold by overcoming the effect of inhibitors in complex tissue samples. Crucially, no false positives were observed with these 50 nm silica nanoparticles, demonstrating the enhanced reliability and potential for diagnostic application of Nano-QuIC in detecting misfolded proteins.

Inhibitory effects of sesquiterpene lactones on the aggregation and cytotoxicity of prion neuropeptide

The misfolding and conformational transformation of prion protein (PrP) are crucial to the progression of prion diseases. Screening for available natural inhibitors against prion proteins can contribute to the rational design and development of new anti-prion drugs and therapeutic strategies. The prion neuropeptide, PrP106-126 is commonly used as a model peptide of the abnormal PrP^Sc, and a number of potential inhibitors were explored against the amyloid fibril formation of PrP106-126. The well-known sesquiterpene lactone, artemisinin, shows diverse biological functions in anti-malarial, anti-cancer and lowering glucose. However, its inhibitory effect on PrP106-126 fibrillation is unclear. In this work, we selected two sesquiterpene lactones, artemisinin (1) and artesunate (2), to explore their roles in PrP106-126 aggregation by a series of physicochemical and biochemical methods. The results demonstrated that 1 and 2 could effectively impede the formation of amyloid fibrils and remodel the preformed fibrils. The binding of the small molecules to PrP106-126 was dominated by electrostatic, hydrophobic and hydrogen bonding interactions. In addition, both compounds exhibited neuroprotective effects by reducing peptide oligomerization. 2 showed better inhibition and regulation on peptide aggregation and cellular viability than 1 due to its specific succinate modification. Our study provides the information of sesquiterpene lactones to prevent PrP fibril formation and other related amyloidosis.

Mechanistic Insights of TiO2 Nanoparticles with Different Surface Charges on Aβ42 Peptide Early Aggregation: An In Vitro and In Silico Study

Humans may intendedly or unintendedly be exposed to nanomaterials through food, water, and air. Upon exposure, nanomaterials can pierce the bloodstream and translocate to secondary organs, including the brain, which warrants increased concern for the potential health impacts of nanomaterials. Due to their large surface area and interaction energy, nanomaterials can adsorb surrounding proteins. The misfolding and self-aggregation of amyloid-β (Aβ) have been considered significant factors in the pathogenesis of Alzheimer's disease. We thus hypothesize that brain-targeted nanomaterials may modulate Aβ aggregation and cause related neurotoxicity. Here, we showed that TiO₂ nanoparticles (NPs) and their aminated analogue (TiO₂-NH₂ NPs) adsorb the Aβ₄₂ peptide and accelerate its early oligomerization. Molecular dynamics simulation indicated that the adsorption onto TiO₂ NPs and TiO₂-NH₂ NPs surfaces can stabilize the β-sheet-rich conformations formed by the Aβ₄₂ peptide. The binding sites between TiO₂-NH₂ NPs and the Aβ₄₂ oligomer surface were mainly concentrated in the hydrophobic core region, and the β-sheet conformation spontaneously formed by Aβ₄₂ oligomers can be better stabilized through a hydrogen bond, electrostatic attraction, and hydrophobic interaction. This study will further help in the understanding of nanomaterial-related neurotoxicities and the regulation of their applications.

Self-Therapeutic Nanomaterials: Applications in Biology and Medicine

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

Advances in the understanding of protein misfolding and aggregation through molecular dynamics simulation

Aberrant protein folding known as protein misfolding is counted as one of the striking factors of neurodegenerative diseases. The extensive range of pathologies caused by protein misfolding, aggregation and subsequent accumulation are mainly classified into either gain of function diseases or loss of function diseases. In order to seek for novel strategies for treatment and diagnosis of neurodegenerative diseases, insights into the mechanism of misfolding and aggregation is essential. A comprehensive knowledge on the factors influencing misfolding and aggregation is required as well. An extensive experimental study on protein aggregation is somewhat challenging due to the insoluble and noncrystalline nature of amyloid fibrils. Thus there has been a growing use of computational approaches including Monte Carlo simulation, docking simulation, molecular dynamics simulation in the study of protein misfolding and aggregation. The review presents a discussion on molecular dynamics simulation alone as to how it has emerged as a promising tool in the understanding of protein misfolding and aggregation in general, detailing upon three different aspects considering four misfold prone proteins in particular. It is noticeable that all four proteins considered in this review i.e prion, superoxide dismutase1, huntingtin and amyloid β are linked to chronic neurodegenerative diseases with debilitating effects. Initially the review elaborates on the factors influencing the misfolding and aggregation. Next, it addresses our current understanding of the amyloid structures and the associated aggregation mechanisms, finally, summarizing the contribution of this computational tool in the search for therapeutic strategies against the respective protein-deposition diseases.

Engineered Nanoparticle-Protein Interactions Influence Protein Structural Integrity and Biological Significance

Engineered nanoparticles (ENPs) are artificially synthesized particles with unique physicochemical properties. ENPs are being extensively used in several consumer items, elevating the probability of ENP exposure to biological systems. ENPs interact with various biomolecules like lipids, proteins, nucleic acids, where proteins are most susceptible. The ENP-protein interactions are mostly studied for corona formation and its effect on the bio-reactivity of ENPs, however, an in-depth understanding of subsequent interactive effects on proteins, such as alterations in their structure, conformation, free energy, and folding is still required. The present review focuses on ENP-protein interactions and the subsequent effects on protein structure and function followed by the therapeutic potential of ENPs for protein misfolding diseases.

Interactions of the Aβ(1-42) Peptide with Boron Nitride Nanoparticles of Varying Curvature in an Aqueous Medium: Different Pathways to Inhibit β-Sheet Formation

The aggregation of amyloid β (Aβ) peptide triggered by its conformational changes leads to the commonly known neurodegenerative disease of Alzheimer's. It is believed that the formation of β sheets of the peptide plays a key role in its aggregation and subsequent fibrillization. In the current study, we have investigated the interactions of the Aβ(1-42) peptide with boron nitride nanoparticles and the effects of the latter on conformational transitions of the peptide through a series of molecular dynamics simulations. In particular, the effects of curvature of the nanoparticle surface are studied by considering boron nitride nanotubes (BNNTs) of varying diameter and also a planar boron nitride nanosheet (BNNS). Altogether, the current study involves the generation and analysis of 9.5 μs of dynamical trajectories of peptide-BNNT/BNNS pairs in an aqueous medium. It is found that BN nanoparticles of different curvatures that are studied in the present work inhibit the conformational transition of the peptide to its β-sheet form. However, such an inhibition effect follows different pathways for BN nanoparticles of different curvatures. For the BNNT with the highest surface curvature, i.e., (3,3) BNNT, the nanoparticle is found to inhibit β-sheet formation by stabilizing the helical structure of the peptide, whereas for planar BNNS, the β-sheet formation is prevented by making more favorable pathways available for transitions of the peptide to conformations of random coils and turns. The BNNTs with intermediate curvatures are found to exhibit diverse pathways of their interactions with the peptide, but in all cases, essentially no formation of the β sheet is found whereas substantial β-sheet formation is observed for Aβ(1-42) in water in the absence of any nanoparticle. The current study shows that BN nanoparticles have the potential to act as effective tools to prevent amyloid formation from Aβ peptides.

Unraveling the Histidine Tautomerism Effect on the Initial Stages of Prion Misfolding: New Insights from a Computational Perspective

The aggregation and structural conversion of normal prion peptide (PrP^C) into the pathogenic scrapie form (PrP^Sc), which can act as a seed to enhance prion amyloid fiber formation, is believed to be a crucial event in prionopathies. Previous research suggests that the prion monomer may play an important role in oligomer generation during disease pathogenesis. In the present study, extensive replica-exchange molecular dynamics (REMD) simulations were conducted to explore the conformational characteristics of the huPrP (125-160) monomer under the histidine tautomerism effect. Investigating the structural characteristics and fibrilization process is challenging because two histidine tautomers [N_ε2-H (ε) and N_δ1-H (δ)] can occur in the open neutral state. Molecular dynamics (MD) simulation outcomes have shown that the toxic εδ and δδ isomer (containing several and broader local minima) had the highest α-helix structures, with contents of 21.11% and 21.01%, respectively, and may have a strong influence on the organizational behavior of a monomeric prion. The amino acids aspartate 20 (D20)-asparagine 29 (N29) and isoleucine 15 (I15)-histidine 16 (H16), D20-arginine 27 (R27) as well as N29 formed α-helix with the highest probabilities in the δδ and εδ isomer, accordingly. On the basis of our findings, we propose the histidine tautomerization hypothesis as a new prion accumulation mechanism, which may exist to induce the formation of prion accumulates. Overall, our tautomerism hypothesis constitutes a promising perspective for enhancing understanding of prion disease pathobiology and may help in the design of a good inhibitor.

Impact of porous nanomaterials on inhibiting protein aggregation behaviour

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

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

Molecular mechanism of amyloidogenicity and neurotoxicity of a pro-aggregated tau mutant in the presence of histidine tautomerism via replica-exchange simulation

Considering ΔK280 tau mutation, δε isomer with highest sheet content may accelerate aggregation; generating small compounds to inhibit this would help tp prevent tauopathies.