Nucleation of protein fibrillation by nanoparticles

Unveiling the theranostic potential of SPIONs in Alzheimer's disease management

Alzheimer's disease (AD) is a devastating kind of dementia that is becoming more common worldwide. Toxic amyloid-beta (Aβ) aggregates are the primary cause of AD onset and development. Superparamagnetic iron oxide nanoparticles (SPIONs) have received a lot of interest in AD therapy over the last decade because of their ability to redirect the Aβ fibrillation process and improve associated brain dysfunction. The potential diagnostic application of SPIONs in AD has dramatically increased this interest. Furthermore, surface-modified engineered SPIONs function as drug carriers to improve the efficacy of current therapies. Various preclinical and clinical studies on the role of SPIONs in AD pathology have produced encouraging results. However, due to their physicochemical properties (e.g., size, surface charge, and particle concentration) in the biological milieu, SPIONs may play the role of a preventive or accelerative agent in AD. Even though SPIONs are potential therapeutic and diagnostic options in AD, significant efforts are still needed to overcome the inconsistencies and safety concerns. This review evaluated the current understanding of how various SPIONs interact with AD models and explored the discrepancies in their efficacy and safety.

Polystyrene nanoparticles trigger aberrant condensation of TDP-43 and amyotrophic lateral sclerosis-like symptoms

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the dysfunction and progressive death of cerebral and spinal motor neurons. Preliminary epidemiological research has hinted at a relationship between environmental risks and the escalation of ALS, but the underlying reasons remain mostly mysterious. Here we show that nanosize polystyrene plastics (PS) induce ALS-like symptoms and illustrate the related molecular mechanism. When exposed to PS, cells endure internal oxidative stress, which leads to the aggregation of TAR DNA-binding protein 43 kDa (TDP-43), triggering ALS-like characteristics. In addition, the oxidized heat shock protein 70 fails to escort TDP-43 back to the nucleus. The cytoplasmic accumulation of TDP-43 facilitates the formation of a complex between PS and TDP-43, enhancing the condensation and solidification of TDP-43. These findings are corroborated through in silico and in vivo assays. Altogether, our work illustrates a unique toxicological mechanism induced by nanoparticles and provides insights into the connection between environmental pollution and neurodegenerative disorders.

Surface effects on functional amyloid formation

Functional amyloids formed by the protein FapC in Pseudomonas bacteria are key structural components of Pseudomonas biofilms, which mediate chronic infections and also contribute to antimicrobial resistance. Here, we combine kinetic experiments with mechanistic modelling to probe the role of surfaces in FapC functional amyloid formation. We find that nucleation of new fibrils is predominantly heterogeneous in vitro, being catalysed by reaction vessel walls but not by the air/water interface. Removal of such interfaces by using microdroplets greatly slows heterogeneous nucleation and reveals a hitherto undetected fibril surface-catalysed "secondary nucleation" reaction step. We tune the degree of catalysis by varying the interface chemistry of the reaction vessel and by adding nanoparticles with tailored surface properties that catalyse fibril nucleation. In so doing, we discover that the rate of nucleation is controlled predominantly by the strength with which FapC binds to the catalytic sites on the interface, and by its surface area. Surprisingly, neither primary nucleation rate nor catalytic site binding strength appear closely correlated to the charge and hydrophilicity of the interface. This indicates the importance of considering experimental design in terms of surface chemistry of the reaction container while also highlighting the notion that fibril nucleation during protein aggregation is a heterogeneous process.

Multifunctional magneto-plasmonic lipogel based on peptide hydrogel for application in combined cancer therapy

Supramolecular hydrogels, particularly low-molecular-weight peptide hydrogels, are promising drug delivery systems due to their ability to change the solubility, targeting, metabolism and toxicity of drugs. Magneto-plasmonic liposomes, in addition to being remotely controllable with the application of an external magnetic field, also increase the efficiency of encapsulated drug release through thermal stimulation, for example, with magnetic and optical hyperthermia. Thus, the combination of those two materials-giving magneto-plasmonic lipogels-brings together several functionalities, among which are hyperthermia and spatiotemporally controlled drug delivery. In this work, a novel dehydrodipeptide hydrogelator was synthesised, and the respective hydrogel was functionalized with magneto-plasmonic liposomes. After individually characterising the components with regard to their rheological, spectroscopic and magnetic properties, the magneto-plasmonic lipogel was equally characterised and evaluated concerning its ability to deliver drugs in a controlled fashion. To this end, the response of the 5(6)-carboxyfluorescein-loaded magneto-plasmonic lipogel to near-infrared light was assessed. The results showed that the system is a proper carrier of hydrophilic drugs and allows to envisage photo-responsive drug delivery. These facts, together with the magnetic guidance and hyperthermia capabilities of the developed composite gel, may pave the way to a new era in the treatment of cancer and other diseases.

Single-domain magnetic particles with motion behavior under electromagnetic AC and DC fields are a fatal cargo in Metropolitan Mexico City pediatric and young adult early Alzheimer, Parkinson, frontotemporal lobar degeneration and amyotrophic lateral sclerosis and in ALS patients

Metropolitan Mexico City (MMC) children and young adults exhibit overlapping Alzheimer and Parkinsons' diseases (AD, PD) and TAR DNA-binding protein 43 pathology with magnetic ultrafine particulate matter (UFPM) and industrial nanoparticles (NPs). We studied magnetophoresis, electron microscopy and energy-dispersive X-ray spectrometry in 203 brain samples from 14 children, 27 adults, and 27 ALS cases/controls. Saturation isothermal remanent magnetization (SIRM), capturing magnetically unstable FeNPs ~ 20nm, was higher in caudate, thalamus, hippocampus, putamen, and motor regions with subcortical vs. cortical higher SIRM in MMC ≤ 40y. Motion behavior was associated with magnetic exposures 25-100 mT and children exhibited IRM saturated curves at 50-300 mT associated to change in NPs position and/or orientation in situ. Targeted magnetic profiles moving under AC/AD magnetic fields could distinguish ALS vs. controls. Motor neuron magnetic NPs accumulation potentially interferes with action potentials, ion channels, nuclear pores and enhances the membrane insertion process when coated with lipopolysaccharides. TEM and EDX showed 7-20 nm NP Fe, Ti, Co, Ni, V, Hg, W, Al, Zn, Ag, Si, S, Br, Ce, La, and Pr in abnormal neural and vascular organelles. Brain accumulation of magnetic unstable particles start in childhood and cytotoxic, hyperthermia, free radical formation, and NPs motion associated to 30-50 μT (DC magnetic fields) are critical given ubiquitous electric and magnetic fields exposures could induce motion behavior and neural damage. Magnetic UFPM/NPs are a fatal brain cargo in children's brains, and a preventable AD, PD, FTLD, ALS environmental threat. Billions of people are at risk. We are clearly poisoning ourselves.

A comprehensive investigation of the interactions of human serum albumin with polymeric and hybrid nanoparticles

Nanoparticles (NPs) engineered as drug delivery systems continue to make breakthroughs as they offer numerous advantages over free therapeutics. However, the poor understanding of the interplay between the NPs and biomolecules, especially blood proteins, obstructs NP translation to clinics. Nano-bio interactions determine the NPs' in vivo fate, efficacy and immunotoxicity, potentially altering protein function. To fulfill the growing need to investigate nano-bio interactions, this study provides a systematic understanding of two key aspects: (i) protein corona (PC) formation and (ii) NP-induced modifications on protein's structure and stability. A methodology was developed by combining orthogonal techniques to analyze both quantitative and qualitative aspects of nano-bio interactions, using human serum albumin (HSA) as a model protein. Protein quantification via liquid chromatography-mass spectrometry, and capillary zone electrophoresis (CZE) clarified adsorbed protein quantity and stability. CZE further unveiled qualitative insights into HSA forms (native, glycated HSA and cysteinylated), while synchrotron radiation circular dichroism enabled analyzing HSA's secondary structure and thermal stability. Comparative investigations of NP cores (organic vs. hybrid), and shells (with or without polyethylene glycol (PEG)) revealed pivotal factors influencing nano-bio interactions. Polymeric NPs based on poly(lactic-co-glycolic acid) (PLGA) and hybrid NPs based on metal-organic frameworks (nanoMOFs) presented distinct HSA adsorption profiles. PLGA NPs had protein-repelling properties while inducing structural modifications on HSA. In contrast, HSA exhibited a high affinity for nanoMOFs forming a PC altering thereby the protein structure. A shielding effect was gained through PEGylation for both types of NPs, avoiding the PC formation as well as the alteration of unbound HSA structure.

Nanoparticle-assisted tubulin assembly is environment dependent

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

Dissimilar effects of the hydrophilic carbon dots on the amyloid aggregation of two model proteins and the mechanism discussion

Many proteins could aggregate into amyloid fibrils under certain conditions. However, the aggregation process and morphology of the fibrils may be significantly different because of the distinct protein structure. In this article, the hydrophilic carbon dots (Lys-CA-CDs) were prepared using lysine (Lys) and citric acid (CA) as reactant under the assistance of a microwave. The dissimilar modulation effect of Lys-CA-CDs on the aggregation process of distinct structure protein was further investigated, where bovine serum albumin (BSA) and hen egg white lysozyme (HEWL) were chosen as model proteins. All results showed that Lys-CA-CDs displayed the contrary influence on the aggregation process of BSA and HEWL. Lys-CA-CDs could induce BSA to aggregate into more wormlike fibrils and inhibit the aggregation of HEWL into hair-like fibrils. The influence on the aggregation process of BSA may be assigned to the increased concentration of BSA around the Lys-CA-CDs caused by their interaction. However, inserting of Lys-CA-CDs into the inner structure of HEWL led to the change of protein secondary structure. The change of secondary structure further made it difficult for HEWL to aggregate into fibrils and Lys-CA-CDs showed the inhibition effect on HEWL aggregation.

The role of shear forces in primary and secondary nucleation of amyloid fibrils

Shear forces affect self-assembly processes ranging from crystallization to fiber formation. Here, the effect of mild agitation on amyloid fibril formation was explored for four peptides and investigated in detail for A[Formula: see text]42, which is associated with Alzheimer's disease. To gain mechanistic insights into the effect of mild agitation, nonseeded and seeded aggregation reactions were set up at various peptide concentrations with and without an inhibitor. First, an effect on fibril fragmentation was excluded by comparing the monomer-concentration dependence of aggregation kinetics under idle and agitated conditions. Second, using a secondary nucleation inhibitor, Brichos, the agitation effect on primary nucleation was decoupled from secondary nucleation. Third, an effect on secondary nucleation was established in the absence of inhibitor. Fourth, an effect on elongation was excluded by comparing the seeding potency of fibrils formed under idle or agitated conditions. We find that both primary and secondary nucleation steps are accelerated by gentle agitation. The increased shear forces facilitate both the detachment of newly formed aggregates from catalytic surfaces and the rate at which molecules are transported in the bulk solution to encounter nucleation sites on the fibril and other surfaces. Ultrastructural evidence obtained with cryogenic transmission electron microscopy and free-flow electrophoresis in microfluidics devices imply that agitation speeds up the detachment of nucleated species from the fibril surface. Our findings shed light on the aggregation mechanism and the role of detachment for efficient secondary nucleation. The results inform on how to modulate the relative importance of different microscopic steps in drug discovery and investigations.

Mechanistic Insights Behind the Self-Assembly of Human Insulin under the Influence of Surface-Engineered Gold Nanoparticles

Elucidating the underlying principles of amyloid protein self-assembly at nanobio interfaces is extremely challenging due to the diversity in physicochemical properties of nanomaterials and their physical interactions with biological systems. It is, therefore, important to develop nanoscale materials with dynamic features and heterogeneities. In this work, through engineering of hierarchical polyethylene glycol (PEG) structures on gold nanoparticle (GNP) surfaces, tailored nanomaterials with different surface properties and conformations (GNPs-PEG) are created for modulating the self-assembly of a widely studied protein, insulin, under amyloidogenic conditions. Important biophysical studies including thioflavin T (ThT) binding, circular dichroism (CD), surface plasmon resonance (SPR), and atomic force microscopy (AFM) showed that higher-molecular weight GNPs-PEG triggered the formation of amyloid fibrils by promoting adsorption of proteins at nanoparticle surfaces and favoring primary nucleation rate. Moreover, the modulation of fibrillation kinetics reduces the overall toxicity of insulin oligomers and fibrils. In addition, the interaction between the PEG polymer and amyloidogenic insulin examined using MD simulations revealed major changes in the secondary structural elements of the B chain of insulin. The experimental findings provide molecular-level descriptions of how the PEGylated nanoparticle surface modulates protein adsorption and drives the self-assembly of insulin. This facile approach provides a new avenue for systematically altering the binding affinities on nanoscale surfaces by tailoring their topologies for examining adsorption-induced fibrillogenesis phenomena of amyloid proteins. Together, this study suggests the role of nanobio interfaces during surface-induced heterogeneous nucleation as a primary target for designing therapeutic interventions for amyloid-related neurodegenerative disorders.

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

Background

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

Materials and Methods

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

Results

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

Conclusion

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

Neurotoxicities induced by micro/nanoplastics: A review focusing on the risks of neurological diseases

Pollution of micro/nano-plastics (MPs/NPs) is ubiquitously prevalent in the environment, leading to an unavoidable exposure of the human body. Despite the protection of the blood-brain barrier, MPs/NPs can be transferred and accumulated in the brain, which subsequently exert negative effects on the brain. Nevertheless, the potential neurodevelopmental and/or neurodegenerative risks of MPs/NPs remain largely unexplored. In this review, we provide a systematic overview of recent studies related to the neurotoxicity of MPs/NPs. It covers the environmental hazards and human exposure pathways, translocation and distribution into the brain, the neurotoxic effects, and the possible mechanisms of environmental MPs/NPs. MPs/NPs are widely found in different environment matrices, including air, water, soil, and human food. Ambient MPs/NPs can enter the human body by ingestion, inhalation and dermal contact, then be transferred into the brain via the blood circulation and nerve pathways. When MPs/NPs are present in the brain, they can initiate a series of molecular or cellular reactions that may harm the blood-brain barrier, cause oxidative stress, trigger inflammatory responses, affect acetylcholinesterase activity, lead to mitochondrial dysfunction, and impair autophagy. This can result in abnormal protein folding, loss of neurons, disruptions in neurotransmitters, and unusual behaviours, ultimately contributing to the initiation and progression of neurodegenerative changes and neurodevelopmental abnormalities. Key challenges and further research directions are also proposed in this review as more studies are needed to focus on the potential neurotoxicity of MPs/NPs under realistic conditions.

Fluorescence study of the interaction between albumin and layered double hydroxides

Layered double hydroxides nanoparticles (LDH-NP) are increasingly studied for biomedical applications. Nevertheless, their interaction with biomolecules such as proteins needs further exploration for an effective application. In this work, the adsorption of bovine serum albumin (BSA) on LDH-NP and the conformation changes of the protein upon adsorption were characterized using fluorescence spectroscopy. First, the quenching of tryptophan residues of BSA by chloride-intercalated LDH-NP was explored and the BSA adsorption capacity of LDH-NP were determined. Then, the structural conformation of the protein was analyzed by fluorescence spectroscopy (including synchronous, polarization and quenching studies) at different surface coverages. Finally, the proclivity of adsorbed BSA molecules to assemble as amyloid fibril was evaluated. Due to the positive charging and low curvature of LDH-NP, BSA molecules were strongly adsorbed, which produced a quenching of the protein fluorescence and a large adsorption capacity. The effect on BSA conformation was dependent on surface coverage (SC): at low values ,t he tryptophan residues were in more hydrophobic environments and more accessible to quenchers than al high ones. At low SC, there is space between the BSA molecules to spread on the surface, which led to a conformation change. Contrarily, the native conformation around tryptophan residues of BSA was preserved at high SC due to the tight packing of the adsorbed protein molecules. As a result, BSA molecules are stabilized against the formation of amyloid fibrils at high SC, while at low SC they present a similar fibrillation than free BSA.

Systematic review of the osteogenic effect of rare earth nanomaterials and the underlying mechanisms

Rare earth nanomaterials (RE NMs), which are based on rare earth elements, have emerged as remarkable biomaterials for use in bone regeneration. The effects of RE NMs on osteogenesis, such as promoting the osteogenic differentiation of mesenchymal stem cells, have been investigated. However, the contributions of the properties of RE NMs to bone regeneration and their interactions with various cell types during osteogenesis have not been reviewed. Here, we review the crucial roles of the physicochemical and biological properties of RE NMs and focus on their osteogenic mechanisms. RE NMs directly promote the proliferation, adhesion, migration, and osteogenic differentiation of mesenchymal stem cells. They also increase collagen secretion and mineralization to accelerate osteogenesis. Furthermore, RE NMs inhibit osteoclast formation and regulate the immune environment by modulating macrophages and promote angiogenesis by inducing hypoxia in endothelial cells. These effects create a microenvironment that is conducive to bone formation. This review will help researchers overcome current limitations to take full advantage of the osteogenic benefits of RE NMs and will suggest a potential approach for further osteogenesis research.

The presymptomatic treatment with 3HFWC nanosubstance decreased plaque load in 5XFAD mouse model of Alzheimer's disease

INTRODUCTION

In the present study, we assessed the effects of the hyper-harmonized-hydroxylated fullerene-water complex (3HFWC) on Alzheimer's disease (AD) neuropathological hallmarks in 5XFAD mice, an AD animal model.

METHODS

The 3-week-old 5XFAD mice were exposed to 3HFWC water solution ad libitum for 3 months in the presymptomatic phase of pathology. The functional effects of the treatment were confirmed through near-infrared spectroscopy (NIRS) analysis through machine learning (ML) using artificial neural networks (ANNs) to classify the control and 3HFWC-treated brain tissue samples. The effects of 3HFWC treatment on amyloid-β (Aβ) accumulation, plaque formation, gliosis, and synaptic plasticity in cortical and hippocampal tissue were assessed.

RESULTS

The 3HFWC treatment significantly decreased the amyloid-β plaque load in specific parts of the cerebral cortex. At the same time, 3HFWC treatment did not induce the activation of glia (astrocytes and microglia) nor did it negatively affect synaptic protein markers (GAP-43, synaptophysin, and PSD-95).

CONCLUSION

The obtained results point to the potential of 3HFWC, when applied in the presymptomatic phase of AD, to interfere with amyloid plaque formation without inducing AD-related pathological processes such as neuroinflammation, gliosis, and synaptic vulnerability.

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

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

Interactions of Turmeric- and Curcumin-Functionalized Gold Nanoparticles with Human Serum Albumin: Exploration of Protein Corona Formation, Binding, Thermodynamics, and Antifibrillation Studies

In order to better understand the bioavailability and biocompatibility of polyphenol-assisted surface-modified bioengineered nanoparticles in nanomedicine applications, here, we address a series of photophysical experiments to quantify the binding affinity of serum albumin toward polyphenol-capped gold nanoparticles. For this, two different gold nanoparticles (AuNPs) were synthesized via the green synthesis approach, where curcumin and turmeric extract act as reducing as well as capping agents. The size, surface charge, and surface plasmon bands of the AuNPs were highly affected by the adsorption of human serum albumin (HSA) during protein corona formation, which was investigated using dynamic light scattering (DLS), ξ-potential, ultraviolet-visible (UV-vis) spectroscopy, and transmission electron microscopy (TEM) measurements. Fluorescence-based methods, absorbance, and SERS experiments were carried out to evaluate the binding aspects of AuNPs with HSA. We found that the AuNPs show moderate binding affinity toward HSA (Kb ∼ 104 M-1), irrespective of the capping agents on the surface. Hydrophobic association, along with some contribution of electrostatic interaction, played a key role in the binding process. The binding interaction was more toward the subdomain IIA region of HSA, as indicated by the competitive displacement studies using site-specific binders (warfarin and flufenamic acid). Because of the large surface curvature of small-sized AuNPs, the secondary structural conformations of HSA were slightly altered, as revealed by circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy, and surface-enhanced Raman scattering (SERS) measurements. Additionally, the findings of the binding interactions were re-evaluated using molecular dynamics (MD) simulation studies by determining the root-mean-square deviation (RMSD), root-mean-square fluctuation (RMSF), radius of gyration (Rg), and changes in the binding energy of HSA upon complexation with AuNPs. To determine the tentative evidence for pharmacokinetic administration, these biocompatible AuNPs were applied to inhibit the amyloid fibril formation of HSA and monitored by using the thioflavin T (ThT) assay, ANS fluorescence assay, fluorescence microscopic imaging, and FESEM. AuNPs were found to show better resistance toward fibrillation of the adsorbed protein.

Nano-Osmolyte Conjugation: Tailoring the Osmolyte-Protein Interactions at the Nanoscale

Osmolytes are small organic compounds accumulated at higher concentrations in the cell under various stress conditions like high temperature, high salt, high pressure, etc. Osmolytes mainly include four major classes of compounds including sugars, polyols, methylamines, and amino acids and their derivatives. In addition to their ability to maintain protein stability and folding, these osmolytes, also termed as chemical chaperones, can prevent protein misfolding and aggregation. Although being efficient protein folders and stabilizers, these osmolytes exhibit certain unavoidable limitations such as nearly molar concentrations of osmolytes being required for their effect, which is quite difficult to achieve inside a cell or in the extracellular matrix due to nonspecificity and limited permeability of the blood-brain barrier system and reduced bioavailability. These limitations can be overcome to a certain extent by using smart delivery platforms for the targeted delivery of osmolytes to the site of action. In this context, osmolyte-functionalized nanoparticles, termed nano-osmolytes, enhance the protein stabilization and chaperone efficiency of osmolytes up to 105 times in certain cases. For example, sugars, polyols, and amino acid functionalized based nano-osmolytes have shown tremendous potential in preventing protein aggregation. The enhanced potential of nano-osmolytes can be attributed to their high specificity at low concentrations, high tunability, amphiphilicity, multivalent complex formation, and efficient drug delivery system. Keeping in view the promising potential of nano-osmolytes conjugation in tailoring the osmolyte-protein interactions, as compared to their molecular forms, the present review summarizes the recent advancements of the nano-osmolytes that enhance the protein stability/folding efficiency and ability to act as artificial chaperones with increased potential to prevent protein misfolding disorders. Some of the potential nano-osmolyte aggregation inhibitors have been highlighted for large-scale screening with future applications in aggregation disorders. The synthesis of nano-osmolytes by numerous approaches and future perspectives are also highlighted.

Nanocellulose aerogels as 3D amyloid templates

Proteins in solution tend to coat solid surfaces upon exposure. Depending on the nature of the surface, the environmental conditions, and the nature of the protein these adsorbed proteins may self-assemble into ordered, fibre-like structures called amyloids. Nanoparticulate surfaces, with their high surface to volume ratio, are particularly favourable to amyloid formation. Most prior research has focussed on either inorganic or organic nanoparticles in solution. In this research, we instead focus on aerogels created from TEMPO-oxidized cellulose nanofibers (TO-CNF) to serve as bio-based, three-dimensional amyloid templates with a tuneable surface chemistry. Previous research on the use of cellulose as a protein adsorption template has shown no evidence of a change in the secondary protein structure. Herein, however, with the aid of the reducing agent TCEP, we were able to induce the formation of amyloid-like 'worms' on the surface of TO-CNF aerogels. Furthermore, we demonstrate that the addition of the TO-CNF aerogel can also induce bulk aggregation under conditions where it previously did not exist. Finally, we show that the addition of the aerogel increases the rate of 'worm' formation in conditions where previous research has found a long lag-phase. Therefore, TO-CNF aerogels are shown to be excellent templates for inducing ordered protein aggregation.

Elegant Nematodes Improve Our Understanding of Human Neuronal Diseases, the Role of Pollutants and Strategies of Resilience

The prevalence of neurodegenerative disorders such as Alzheimer's and Parkinson's disease are rising globally. The role of environmental pollution in neurodegeneration is largely unknown. Thus, this perspective advocates exposome research in C. elegans models of human diseases. The models express amyloid proteins such as Aβ, recapitulate the degeneration of specifically vulnerable neurons and allow for correlated neurobehavioral phenotyping throughout the entire life span of the nematode. Neurobehavioral traits like locomotion gaits, rigidity, or cognitive decline are quantifiable and carefully mimic key aspects of the human diseases. Underlying molecular pathways of neurodegeneration are elucidated in pollutant-exposed C. elegans Alzheimer's or Parkinson's models by transcriptomics (RNA-seq), mass spectrometry-based proteomics and omics addressing other biochemical traits. Validation of the identified disease pathways can be achieved by genome-wide association studies in matching human cohorts. A consistent One Health approach includes isolation of nematodes from contaminated sites and their comparative investigation by imaging, neurobehavioral profiling and single worm proteomics. C. elegans models of neurodegenerative diseases are likewise well-suited for high throughput methods that provide a promising strategy to identify resilience pathways of neurosafety and keep up with the number of pollutants, nonchemical exposome factors, and their interactions.

Adsorption behavior of serum proteins on anodized titanium is driven by surface nanomorphology

Protein adsorption behavior can play a critical role in defining the outcome of a material by affecting the subsequent in vivo response to it. To date, the effect of surface properties on protein adsorption behavior has been mainly focused on surface chemistry, but research on the effect of nanoscale surface topography remains limited. In this study, the adsorption behavior of human serum albumin, immunoglobulin G, and fibrinogen in terms of the adsorbed amount and conformational changes were investigated on bare and anodized titanium (Ti) samples (40 and 60 V applied voltages). While the surface chemistry, RMS surface roughness, and arithmetic surface roughness of the anodized samples were similar, they had distinctly different nanomorphologies identified by atomic force microscopy and scanning electron microscopy, and the surface statistical parameters, surface skewness Ssk and kurtosis Sku. The Feret pore size distribution was more uniform on the 60 V sample, and surface nanostructures were more symmetrical with higher peaks and deeper pores. On the other hand, the 40 V sample surface presented a nonuniform pore size distribution and asymmetrical surface nanostructures with lower peaks and shallower pores. The amount of surface-adsorbed protein increased on the sample surfaces in the order of Ti < 40 V < 60 V with the predominant factor affecting the amount of surface-adsorbed protein being the increased surface area attained by pore formation. The secondary structure of all adsorbed proteins deviated from that of their native counterparts. While comparing the secondary structure components of proteins on anodized surfaces, it was observed that all three proteins retained more of their secondary structure composition on the surface with more uniform and symmetrical nanofeatures than the surface having asymmetrical nanostructures. Our results suggest that the nanomorphology of the peaks and outer walls of the nanotubes can significantly influence the conformation of adsorbed serum proteins, even for surfaces having similar roughness values.

Inhibitory effect of plain and functionalized graphene nanoplateles on hen egg white lysozyme fibrillation

Protein fibrillation is a phenomenon associated with misfolding and the production of highly ordered nanofibrils, which may cause serious degenerative diseases such as Parkinson's disease, Alzheimer's disease, and type 2 diabetes. Upon contact with biological fluids, the nanomaterials are immediately covered by proteins and interact with them. In this study, the effects of Graphene NanoPlateles (Plain-GNPs) and their modified forms with a carboxyl group (GNPs -COOH) and an amine group (GNPs -NH2) are evaluated on the fibrillation process of Hen Egg White Lysozyme (HEWL). The fibrillation process of HEWL was studied using thioflavin-T, Circular Dichroism spectrometry, and Atomic Force Microscopy. Plain-GNPs significantly decreased the fibrillation process at different stages, including nucleation, exponential fibrillation phases, and end-mature fibril products. However, GNPs-COOH and GNPs-NH2 affected the final fluorescence of ThT. The species formed in the presence of Plain-GNPs showed less toxicity in SH-SY5Y cells, which could be applicable for therapeutic purposes.

Aggregation of an Amyloidogenic Peptide on Gold Surfaces

Solid surfaces have been shown to affect the aggregation and assembly of many biomolecular systems. One important example is the formation of protein fibrils, which can occur on a range of biological and synthetic surfaces. The rate of fibrillation depends on both the protein structure and the surface chemistry, with the different molecular and oligomer structures adopted by proteins on surfaces likely to be crucial. In this paper, the aggregation of the model amyloidogenic peptide, Aβ(16-22), corresponding to a hydrophobic segment of the amyloid beta protein on a gold surface is studied using molecular dynamics simulation. Previous simulations of this peptide on gold surfaces have shown that it adopts conformations on surfaces that are quite different from those in bulk solution. These simulations show that this then leads to significant differences in the oligomer structures formed in solution and on gold surfaces. In particular, oligomers formed on the surface are low in beta-strands so are unlike the structures formed in bulk solution. When oligomers formed in solution adsorb onto gold surfaces they can then restructure themselves. This can then help explain the inhibition of Aβ(16-22) fibrillation by gold surfaces and nanoparticles seen experimentally.

Stability of DNA Origami Nanostructures in Physiological Media: The Role of Molecular Interactions

Programmable, custom-shaped, and nanometer-precise DNA origami nanostructures have rapidly emerged as prospective and versatile tools in bionanotechnology and biomedicine. Despite tremendous progress in their utilization in these fields, essential questions related to their structural stability under physiological conditions remain unanswered. Here, DNA origami stability is explored by strictly focusing on distinct molecular-level interactions. In this regard, the fundamental stabilizing and destabilizing ionic interactions as well as interactions involving various enzymes and other proteins are discussed, and their role in maintaining, modulating, or decreasing the structural integrity and colloidal stability of DNA origami nanostructures is summarized. Additionally, specific issues demanding further investigation are identified. This review - through its specific viewpoint - may serve as a primer for designing new, stable DNA objects and for adapting their use in applications dealing with physiological media.

Direct observation of secondary nucleation along the fibril surface of the amyloid β 42 peptide

Alzheimer's disease is a neurodegenerative condition which involves heavy neuronal cell death linked to oligomers formed during the aggregation process of the amyloid β peptide 42 (Aβ42). The aggregation of Aβ42 involves both primary and secondary nucleation. Secondary nucleation dominates the generation of oligomers and involves the formation of new aggregates from monomers on catalytic fibril surfaces. Understanding the molecular mechanism of secondary nucleation may be crucial in developing a targeted cure. Here, the self-seeded aggregation of WT Aβ42 is studied using direct stochastic optical reconstruction microscopy (dSTORM) with separate fluorophores in seed fibrils and monomers. Seeded aggregation proceeds faster than nonseeded reactions because the fibrils act as catalysts. The dSTORM experiments show that monomers grow into relatively large aggregates on fibril surfaces along the length of fibrils before detaching, thus providing a direct observation of secondary nucleation and growth along the sides of fibrils. The experiments were repeated for cross-seeded reactions of the WT Aβ42 monomer with mutant Aβ42 fibrils that do not catalyze the nucleation of WT monomers. While the monomers are observed by dSTORM to interact with noncognate fibril surfaces, we fail to notice any growth along such fibril surfaces. This implies that the failure to nucleate on the cognate seeds is not a lack of monomer association but more likely a lack of structural conversion. Our findings support a templating role for secondary nucleation, which can only take place if the monomers can copy the underlying parent structure without steric clashes or other repulsive interactions between nucleating monomers.

Surface-modified cerium dioxide nanoparticles with improved anti-amyloid and preserved nanozymatic activity

Cerium dioxide nanoparticles (CeO₂ NPs) are used increasingly in nanotechnology and particularly in biotechnology and bioresearch. Thus, CeO₂ NPs have been successfully tested in vitro as a potential therapeutic agent for various pathologies associated with oxidative stress, including the formation of protein amyloid aggregates. In this study, to increase the anti-amyloidogenic efficiency and preserve the antioxidant potential, the surface of the synthesized CeO₂ NPs is modified with a nonionic, sugar-based surfactant, dodecyl maltoside (DDM), which is known for its high anti-amyloidogenic activity and biocompatibility. Dynamic light scattering and Fourier transform infrared spectroscopy demonstrated successful modification by DDM. The apparent hydrodynamic diameters of CeO₂ NPs and DDM-modified NPs (CeO₂@DDM NPs) are found to be ⁓180 nm and ⁓260 nm, respectively. A positive zeta potential value of + 30.5 mV for CeO₂ NPs and + 22.5 mV for CeO₂ @DDM NPs suggest sufficient stability and good dispersion of NPs in an aqueous solution. A combination of Thioflavin T fluorescence analysis and atomic force microscopy is used to assess the effect of nanoparticles on the formation of insulin amyloid fibrils. Results show that the fibrillization of insulin is inhibited by both, naked and modified NPs in a dose-dependent manner. However, while the IC₅₀ of naked NPs is found to be ∼270 ± 13 µg/mL, the surface-modified NPs are 50% more efficient with IC₅₀ equaled to 135 ± 7 µg/mL. In addition, both, the naked CeO₂ NPs and DDM-modified NPs displayed an antioxidant activity expressed as oxidase-, catalase- and SOD-like activity. Therefore, the resulting nanosized material is very well suited to prove or disprove the hypothesis that oxidative stress plays a role in the formation of amyloid fibrils.

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.

Effect of Albumin Corona Conformation on In Vitro and In Vivo Profiles of Intravenously Administered Nanoparticles

Under physiological conditions, nanoparticles (NPs) inevitably interact with proteins, resulting in extensive protein adsorption and the formation of a protein corona. Recent studies have shown that the different surface properties of NPs lead to varying degrees of conformational changes of adsorbed proteins. However, the impact of corona protein conformation on the in vitro and in vivo profiles of NPs remain largely unexplored. Herein, d-α-tocopherol polyethylene glycol 1000 succinate-based NPs with natural human serum albumin (HSA_N) corona or thermally denatured HSA (HSA_D) corona were synthesized following a previously established method. We then conducted a systematic study of the protein conformation as well as adsorption behaviors. Additionally, the impact of protein corona conformation on the NPs profiles in vitro and in vivo were elucidated to gain insight into its biological behaviors as a targeted delivery system for renal tubule diseases. Overall, NPs modified by HSA_N corona showed improved serum stability, greater cell uptake efficiency, better renal tubular targetability, and therapeutic efficacy on acute kidney injury in rats than NPs modified by HSA_D corona. Hence, the conformation of protein adsorbed on the surface of NPs may impact the in vitro and in vivo profiles of NPs.

Mechanistic Understanding of Protein Corona Formation around Nanoparticles: Old Puzzles and New Insights

Although a wide variety of nanoparticles (NPs) have been engineered for use as disease markers or drug delivery agents, the number of nanomedicines in clinical use has hitherto remained small. A key obstacle in nanomedicine development is the lack of a deep mechanistic understanding of NP interactions in the bio-environment. Here, the focus is on the biomolecular adsorption layer (protein corona), which quickly enshrouds a pristine NP exposed to a biofluid and modifies the way the NP interacts with the bio-environment. After a brief introduction of NPs for nanomedicine, proteins, and their mutual interactions, research aimed at addressing fundamental properties of the protein corona, specifically its mono-/multilayer structure, reversibility and irreversibility, time dependence, as well as its role in NP agglomeration, is critically reviewed. It becomes quite evident that the knowledge of the protein corona is still fragmented, and conflicting results on fundamental issues call for further mechanistic studies. The article concludes with a discussion of future research directions that should be taken to advance the understanding of the protein corona around NPs. This knowledge will provide NP developers with the predictive power to account for these interactions in the design of efficacious nanomedicines.

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.

The protein corona from nanomedicine to environmental science

The protein corona spontaneously develops and evolves on the surface of nanoscale materials when they are exposed to biological environments, altering their physiochemical properties and affecting their subsequent interactions with biosystems. In this Review, we provide an overview of the current state of protein corona research in nanomedicine. We next discuss remaining challenges in the research methodology and characterization of the protein corona that slow the development of nanoparticle therapeutics and diagnostics, and we address how artificial intelligence can advance protein corona research as a complement to experimental research efforts. We then review emerging opportunities provided by the protein corona to address major issues in healthcare and environmental sciences. This Review details how mechanistic insights into nanoparticle protein corona formation can broadly address unmet clinical and environmental needs, as well as enhance the safety and efficacy of nanobiotechnology products.

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.

In Silico Analysis of Nanoplastics' and β-amyloid Fibrils' Interactions

Plastic pollution has become a global environmental threat, which leads to an increasing concern over the consequences of plastic exposition on global health. Plastic nanoparticles have been shown to influence the folding of proteins and influence the formation of aberrant amyloid proteins, therefore potentially triggering the development of systemic and local amyloidosis. This work aims to study the interaction between nanoplastics and β-amyloid fibrils to better understand the potential role of nanoplastics in the outbreak of neurodegenerative disorders. Using microsecond-long coarse-grained molecular dynamics simulations, we investigated the interactions between neutral and charged nanoparticles made of the most common plastic materials (i.e., polyethylene, polypropylene, and polystyrene) and β-amyloid fibrils. We observe that the occurrence of contacts, region of amyloid fibril involved, and specific amino acids mediating the interaction depend on the type and charge of the nanoparticles.

Sleep matters: Neurodegeneration spectrum heterogeneity, combustion and friction ultrafine particles, industrial nanoparticle pollution, and sleep disorders-Denial is not an option

Sustained exposures to ubiquitous outdoor/indoor fine particulate matter (PM_2.5), including combustion and friction ultrafine PM (UFPM) and industrial nanoparticles (NPs) starting in utero, are linked to early pediatric and young adulthood aberrant neural protein accumulation, including hyperphosphorylated tau (p-tau), beta-amyloid (Aβ_{1 - 42}), α-synuclein (α syn) and TAR DNA-binding protein 43 (TDP-43), hallmarks of Alzheimer's (AD), Parkinson's disease (PD), frontotemporal lobar degeneration (FTLD), and amyotrophic lateral sclerosis (ALS). UFPM from anthropogenic and natural sources and NPs enter the brain through the nasal/olfactory pathway, lung, gastrointestinal (GI) tract, skin, and placental barriers. On a global scale, the most important sources of outdoor UFPM are motor traffic emissions. This study focuses on the neuropathology heterogeneity and overlap of AD, PD, FTLD, and ALS in older adults, their similarities with the neuropathology of young, highly exposed urbanites, and their strong link with sleep disorders. Critical information includes how this UFPM and NPs cross all biological barriers, interact with brain soluble proteins and key organelles, and result in the oxidative, endoplasmic reticulum, and mitochondrial stress, neuroinflammation, DNA damage, protein aggregation and misfolding, and faulty complex protein quality control. The brain toxicity of UFPM and NPs makes them powerful candidates for early development and progression of fatal common neurodegenerative diseases, all having sleep disturbances. A detailed residential history, proximity to high-traffic roads, occupational histories, exposures to high-emission sources (i.e., factories, burning pits, forest fires, and airports), indoor PM sources (tobacco, wood burning in winter, cooking fumes, and microplastics in house dust), and consumption of industrial NPs, along with neurocognitive and neuropsychiatric histories, are critical. Environmental pollution is a ubiquitous, early, and cumulative risk factor for neurodegeneration and sleep disorders. Prevention of deadly neurological diseases associated with air pollution should be a public health priority.

Comment on "Optimal centrifugal isolating of liposome-protein complexes from human plasma" by L. Digiacomo, F. Giulimondi, A. L. Capriotti, S. Piovesana, C. M. Montone, R. Z. Chiozzi, A. Laganá, M. Mahmoudi, D. Pozzi and G. Caracciolo, Nanoscale Adv., 2021, , 3824

In a recent paper in Nanoscale Advances, Digiacomo et al. conclude that centrifugation should be the method of choice for researchers who want to investigate the protein corona of liposomes for drug delivery in human plasma. In this Comment, we however propose the opposite - that centrifugation, in most cases, is unsuitable for isolating liposomes from human plasma. Our conclusion is based on the bulk literature on this and similar topics, and new experimental data based on formulations and protocols like the ones used by Digiacomo et al.

Polyphenols-Based Nanosheets of Propolis Modulate Cytotoxic Amyloid Fibril Assembly of α-Synuclein

Natural compounds with anti-aggregation capacity are increasingly recognized as viable candidates against neurodegenerative diseases. Recently, the polyphenolic fraction of propolis (PFP), a complex bee product, has been shown to inhibit amyloid aggregation of a model protein especially in the nanosheet form. Here, we examine the aggregation-modulating effects of the PFP nanosheets on α-synuclein (α-syn), an intrinsically disordered protein involved in the pathogenesis of Parkinson's disease. Based on a range of biophysical data including intrinsic and extrinsic fluorescence, circular dichroism (CD) data, and nuclear magnetic resonance spectroscopy, we propose a model for the interaction of α-syn with PFP nanosheets, where the positively charged N-terminal and the middle non-amyloid component regions of α-syn act as the main binding sites with the negatively charged PFP nanosheets. The Thioflavin T (ThT) fluorescence, Congo red absorbance, and CD data reveal a prominent dose-dependent inhibitory effect of PFP nanosheets on α-syn amyloid aggregation, and the microscopy images and MTT assay data suggest that the PFP nanosheets redirect α-syn aggregation toward nontoxic off-pathway oligomers. When preformed α-syn amyloid fibrils are present, fluorescence images show co-localization of PFP nanosheets and ThT, further confirming the binding of PFP nanosheets with α-syn amyloid fibrils. Taken together, our results demonstrate the binding and anti-aggregation activity of PFP nanosheets in a disease-related protein system and propose them as potential nature-based tools for probing and targeting pathological protein aggregates in neurodegenerative diseases.

Amyloidogenesis: What Do We Know So Far?

The study of protein aggregation, and amyloidosis in particular, has gained considerable interest in recent times. Several neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's (PD) show a characteristic buildup of proteinaceous aggregates in several organs, especially the brain. Despite the enormous upsurge in research articles in this arena, it would not be incorrect to say that we still lack a crystal-clear idea surrounding these notorious aggregates. In this review, we attempt to present a holistic picture on protein aggregation and amyloids in particular. Using a chronological order of discoveries, we present the case of amyloids right from the onset of their discovery, various biophysical techniques, including analysis of the structure, the mechanisms and kinetics of the formation of amyloids. We have discussed important questions on whether aggregation and amyloidosis are restricted to a subset of specific proteins or more broadly influenced by the biophysiochemical and cellular environment. The therapeutic strategies and the significant failure rate of drugs in clinical trials pertaining to these neurodegenerative diseases have been also discussed at length. At a time when the COVID-19 pandemic has hit the globe hard, the review also discusses the plausibility of the far-reaching consequences posed by the virus, such as triggering early onset of amyloidosis. Finally, the application(s) of amyloids as useful biomaterials has also been discussed briefly in this review.

Quantitative comparison of the protein corona of nanoparticles with different matrices

Nanoparticles (NPs) are paving the way for improved treatments for difficult to treat diseases diseases; however, much is unknown about their fate in the body. One important factor is the interaction between NPs and blood proteins leading to the formation known as the “protein corona” (PC). The PC, consisting of the Hard (HC) and Soft Corona (SC), varies greatly based on the NP composition, size, and surface properties. This highlights the need for specific studies to differentiate the PC formation for each individual NP system. This work focused on comparing the HC and SC of three NPs with different matrix compositions: a) polymeric NPs based on poly(lactic-co-glycolic) acid (PLGA), b) hybrid NPs consisting of PLGA and Cholesterol, and c) lipidic NPs made only of Cholesterol. NPs were formulated and characterized for their physico-chemical characteristics and composition, and then were incubated in human plasma. In-depth purification, identification, and statistical analysis were then performed to identify the HC and SC components. Finally, similar investigations demonstrated whether the presence of a targeting ligand on the NP surface would affect the PC makeup. These results highlighted the different PC fingerprints of these NPs, which will be critical to better understand the biological influences of the PC and improve future NP designs.

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NPs with different matrices were formulated: PLGA, Cholesterol, or mixed PLGA-Chol hybrids.

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The hard and soft corona of each formulation was quantified and compared.

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The PC seems to be more strongly affected by the polymer rather than the lipid in mixed NPs.

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The soft corona depends more on the hard corona composition than on the matrix.

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Surface modification with a targeting ligand did not influence PC composition.

Influence of denaturants on amyloid β42 aggregation kinetics

Amyloid formation is linked to devastating neurodegenerative diseases, motivating detailed studies of the mechanisms of amyloid formation. For Aβ, the peptide associated with Alzheimer's disease, the mechanism and rate of aggregation have been established for a range of variants and conditions in vitro and in bodily fluids. A key outstanding question is how the relative stabilities of monomers, fibrils and intermediates affect each step in the fibril formation process. By monitoring the kinetics of aggregation of Aβ42, in the presence of urea or guanidinium hydrochloride (GuHCl), we here determine the rates of the underlying microscopic steps and establish the importance of changes in relative stability induced by the presence of denaturant for each individual step. Denaturants shift the equilibrium towards the unfolded state of each species. We find that a non-ionic denaturant, urea, reduces the overall aggregation rate, and that the effect on nucleation is stronger than the effect on elongation. Urea reduces the rate of secondary nucleation by decreasing the coverage of fibril surfaces and the rate of nucleus formation. It also reduces the rate of primary nucleation, increasing its reaction order. The ionic denaturant, GuHCl, accelerates the aggregation at low denaturant concentrations and decelerates the aggregation at high denaturant concentrations. Below approximately 0.25 M GuHCl, the screening of repulsive electrostatic interactions between peptides by the charged denaturant dominates, leading to an increased aggregation rate. At higher GuHCl concentrations, the electrostatic repulsion is completely screened, and the denaturing effect dominates. The results illustrate how the differential effects of denaturants on stability of monomer, oligomer and fibril translate to differential effects on microscopic steps, with the rate of nucleation being most strongly reduced.

Micro- and Nanoplastics’ Effects on Protein Folding and Amyloidosis

A significant portion of the world’s plastic is not properly disposed of and, through various processes, is degraded into microscopic particles termed micro- and nanoplastics. Marine and terrestrial faunae, including humans, inevitably get in contact and may inhale and ingest these microscopic plastics which can deposit throughout the body, potentially altering cellular and molecular functions in the nervous and other systems. For instance, at the cellular level, studies in animal models have shown that plastic particles can cross the blood–brain barrier and interact with neurons, and thus affect cognition. At the molecular level, plastics may specifically influence the folding of proteins, induce the formation of aberrant amyloid proteins, and therefore potentially trigger the development of systemic and local amyloidosis. In this review, we discuss the general issue of plastic micro- and nanoparticle generation, with a focus on their effects on protein folding, misfolding, and their possible clinical implications.

Effects of air pollution on human health - Mechanistic evidence suggested by in vitro and in vivo modelling

Airborne particulate matter (PM) comprises both solid and liquid particles, including carbon, sulphates, nitrate, and toxic heavy metals, which can induce oxidative stress and inflammation after inhalation. These changes occur both in the lung and systemically, due to the ability of the small-sized PM (i.e. diameters ≤2.5 μm, PM_2.5) to enter and circulate in the bloodstream. As such, in 2016, airborne PM caused ∼4.2 million premature deaths worldwide. Acute exposure to high levels of airborne PM (eg. during wildfires) can exacerbate pre-existing illnesses leading to hospitalisation, such as in those with asthma and coronary heart disease. Prolonged exposure to PM can increase the risk of non-communicable chronic diseases affecting the brain, lung, heart, liver, and kidney, although the latter is less well studied. Given the breadth of potential disease, it is critical to understand the mechanisms underlying airborne PM exposure-induced disorders. Establishing aetiology in humans is difficult, therefore, in-vitro and in-vivo studies can provide mechanistic insights. We describe acute health effects (e.g. exacerbations of asthma) and long term health effects such as the induction of chronic inflammatory lung disease, and effects outside the lung (e.g. liver and renal change). We will focus on oxidative stress and inflammation as this is the common mechanism of PM-induced disease, which may be used to develop effective treatments to mitigate the adverse health effect of PM exposure.

Adsorption free energy predicts amyloid protein nucleation rates

Primary nucleation is the fundamental event that initiates the conversion of proteins from their normal physiological forms into pathological amyloid aggregates associated with the onset and development of disorders including systemic amyloidosis, as well as the neurodegenerative conditions Alzheimer's and Parkinson's diseases. It has become apparent that the presence of surfaces can dramatically modulate nucleation. However, the underlying physicochemical parameters governing this process have been challenging to elucidate, with interfaces in some cases having been found to accelerate aggregation, while in others they can inhibit the kinetics of this process. Here we show through kinetic analysis that for three different fibril-forming proteins, interfaces affect the aggregation reaction mainly through modulating the primary nucleation step. Moreover, we show through direct measurements of the Gibbs free energy of adsorption, combined with theory and coarse-grained computer simulations, that overall nucleation rates are suppressed at high and at low surface interaction strengths but significantly enhanced at intermediate strengths, and we verify these regimes experimentally. Taken together, these results provide a quantitative description of the fundamental process which triggers amyloid formation and shed light on the key factors that control this process.

Lanthanum oxide nanoparticle-collagen bio matrix induced endothelial cell activation for sustained angiogenic response for biomaterial integration

Rare earth lanthanum oxide nanoparticle reinforced collagen biomatrix that elicited the endothelial cell activation to promote angiogenesis for biomaterial integration was developed and evaluated in the present study. The structural integrity of collagen was not compromised on crosslinking of lanthanum oxide nanoparticle to collagen biomolecule. As-synthesised collagen biomatrix was shown to have improved mechanical strength, a lesser susceptibility to proteolytic degradation and good swelling properties. Superior cytocompatibility, hemocompatibility and minimal ROS generation was observed with Lanthanum oxide nanoparticle reinforced collagen bio matrix. The Lanthanum oxide nanoparticle reinforced collagen bio matrix elicited endothelial cell activation eliciting pro-angiogensis as observed in tube formation and aortic arch assays. The bio-matrix promoted the infiltration and proliferation of endothelial cells which is an unexplored domain in the area of tissue engineering that is very essential for biomaterial integration into host tissue. The wound healing effect of Lanthanum oxide nanoparticle stabilized collagen showed enhanced cell migration in vitro in cells maintained in Lanthanum oxide nanoparticle reinforced collagen bio matrix. The study paves the way for developing rare earth-based dressing materials which promoted biomatrix integration by enhancing vascularisation for tissue regenerative applications in comparison with traditional biomaterials.

Camouflaged Fluorescent Silica Nanoparticles Target Aggregates and Condensates of the Amyloidogenic Protein Tau

Intrinsically disordered proteins (IDPs) are increasingly found to be associated with irreversible neurodegenerative disorders. The protein tau is a prototypical IDP whose abnormal aggregation into insoluble filaments is a major hallmark of Alzheimer's disease. The view has emerged that aggregation may proceed via alternative pathways involving oligomeric intermediates or phase-separated liquid droplets. Nanoparticles (NPs) offer significant potential for probing the mechanisms of protein fibrillation and may be capable of redirecting conformational transitions. Here, we camouflaged dye-doped silica NPs through functionalization with tau molecules to impart them the ability to associate with protein assemblies such as aggregates or condensates. The prepared NP-tau conjugates showed little influence on the aggregation kinetics and morphology of filamentous aggregates of tau but were found to associate with the filaments. Moreover, NP-tau conjugates were recruited and concentrated into polyanion-induced condensates of tau, driven by multivalent electrostatic interactions, thereby illuminating liquid droplets and their time-dependent transformation, as observed by fluorescence microscopy. NP-tau conjugates were capable of entering human neuroglioma cells and were not cytotoxic. Hence, we propose that NP-tau conjugates could serve as nanotracers for in vitro and in-cell studies to target and visualize tau assemblies and condensates, contributing to an explanation for the molecular mechanisms of abnormal protein aggregation.

Differential cascading cellular and subcellular toxicity induced by two sizes of nanoplastics

Nanoplastics (NPs) can be potentially accumulated by living organisms, but how they interact with cells at the cellular or subcellular level in the physiological environment is still largely unknown. In this study, time-resolved flow cytometry coupled with confocal imaging as well as other biomolecular approaches were used to investigate the cellular and subcellular responses to amine-modified polystyrene NPs of two different sizes (100 nm and 1000 nm). We first demonstrated that the two sizes of NPs displayed contrasting cytotoxicity to embryonic zebrafish fibroblast cell lines ZF4. Using the fluorescent-labeled NPs, the differentially internalized patterns between the two-sized NPs in a time-resolved manner were observed. Confocal images showed that the two sizes of NPs were deposited in lysosomes but could escape through lysosomal rupture, as evidenced by the induction of lysosomal acidification (for 1000 nm) and alkalization (for 100 nm) as well as permeabilization. Subsequent deposition of 100-NPs in the cytosol induced loss of mitochondrial membrane potential and significant reactive oxygen species production, and finally stimulated the activation of caspases, disrupted the mitochondrial mitophagy, leading to irreversible cell death. In contrast, 1000-NPs toxicity in ZF4 cells did not involve lysosomal permeabilization and loss of mitochondrial membrane potential. Lysosomal deposition of such larger sized nanoplastics mainly induced lysosome acidification, activated the autophagy as well as disrupted the integrity of cell membrane, but at the same time provoked the activation of caspases and finally triggered the apoptosis. Our study demonstrated a complicated relationship among lysosome damage, autophagy activation, and apoptosis, leading to contrasting toxicity of NPs of different sizes.

Chrysin-Loaded Chitosan Nanoparticle-Mediated Neuroprotection in Aβ1-42-Induced Neurodegenerative Conditions in Zebrafish

Amyloid β plaques and neurofibrillary tangles are the characteristic features of Alzheimer's disease (AD). Plaques of amyloid β play a pivotal role in affecting cognitive functions and memory. Alzheimer's disease is a progressive neurodegenerative disease and is one of the leading causes of dementia worldwide. Several treatment strategies focusing on the amyloid cascade have been implemented to treat AD. The blood-brain barrier (BBB) poses the main obstructive barrier by refraining drugs from penetrating the brain. Nanotechnology is a promising research field for brain drug delivery using nanosized particles. Zebrafish is emerging as a model of interest to elaborate on brain targeting and nanotechnology-based therapeutics for neurodegenerative diseases. In the current study, we have synthesized and characterized chrysin-loaded chitosan nanoparticles (Chr-Chi NPs) and evaluated them for neuroprotection against amyloid-β-induced toxicity. We find that treatment with Chr-Chi NPs helps to retain memory, cognition, and synaptic connections, which are otherwise compromised due to Aβ_1-42 toxicity. The NPs further help in reducing aggregates of amyloid β, thus decreasing neuronal death and generation of reactive oxygen species (ROS). Taken together, our study brings to light a novel strategy for treating AD by a combined action on the neurons and amyloid aggregates mediated by chrysin and chitosan, respectively. Chr-Chi NPs, therefore, have the potential to provide a beneficial combinatorial treatment strategy for AD.