Negatively charged hydrophobic nanoparticles inhibit amyloid β-protein fibrillation: The presence of an optimal charge density

Exogenous prion-like proteins and their potential to trigger cognitive dysfunction

The gut is exposed to a wide range of proteins, including ingested proteins and those produced by the resident microbiota. While ingested prion-like proteins can propagate across species, their implications for disease development remain largely unknown. Here, we apply a multidisciplinary approach to examine the relationship between the biophysical properties of exogenous prion-like proteins and the phenotypic consequences of ingesting them. Through computational analysis of gut bacterial proteins, we identified an enrichment of prion-like sequences in Helicobacter pylori. Based on these findings, we rationally designed a set of synthetic prion-like sequences that form amyloid fibrils, interfere with amyloid-beta-peptide aggregation, and trigger prion propagation when introduced in the yeast Sup35 model. When C. elegans were fed bacteria expressing these prion-like proteins, they lost associative memory and exhibited increased lipid oxidation. These data suggest a link between memory impairment, the conformational state of aggregates, and oxidative stress. Overall, this work supports gut microbiota as a reservoir of exogenous prion-like sequences, especially H. pylori, and the gut as an entry point for molecules capable of triggering cognitive dysfunction.

Probing the effect of the molecular interface of gold nanoparticles on the disassembly of insulin amyloid fibrils

Aberrant protein aggregation into amyloid fibrils underlies the onset of several degenerative pathologies, requiring increasing efforts to identify ever newer approaches to prevent their formation and to disassemble toxic amyloid structures. In this context, gold nanoparticles (AuNPs) show great promise, thanks to their ability to chemically interact with proteins while simultaneously serving as local spectroscopic probes due to their peculiar optical properties. Here, we investigate the role of the surface chemistry of AuNPs in the disassembly of insulin amyloid fibrils. By taking advantage of the remarkable sensitivity and spatial resolution of surface enhanced Raman spectroscopy, we elucidate the molecular mechanisms driving fibril-AuNP interaction at the nanoscale, identifying the amino acids directly involved. The obtained results will serve as a benchmark for developing novel diagnostic and therapeutic strategies employing AuNPs for the treatment of amyloid-related diseases.

Targeting Amyloids with Coated Nanoparticles: A Review on Potential Combinations of Nanoparticles and Bio-Compatible Coatings

Amyloidosis is the major cause of many neurodegenerative diseases, such as, Alzheimer's and Parkinson's where the misfolding and deposition of a previously functional protein make it inept for carrying out its function. The genesis of amyloid fibril formation and the strategies to inhibit it have been studied extensively, although some parts of this puzzle still remain unfathomable to date. Many classes of molecules have been explored as potential drugs in vitro, but their inability to work in vivo by crossing the blood-brain-barrier has made them an inadequate treatment option. In this regard, nanoparticles (NPs) have turned out to be an exciting alternative because they could overcome many drawbacks of previously studied molecules and provide advantages, such as, greater bioavailability of molecules and target-specific delivery of drugs. In this paper, we present an overview on several coated NPs which have shown promising efficiency in inhibiting fibril formation. A hundred and thirty papers published in the past two decades have been comprehensively reviewed, which majorly encompass NPs comprising different materials like gold, silver, iron-oxide, poly(lactic-co-glycolic acid), polymeric NP, etc., which are coated with various molecules of predominantly natural origin, such as different types of amino acids, peptides, curcumin, drugs, catechin, etc. We hope that this review will shed light on the advancement of symbiotic amalgamation of NPs with molecules from natural sources and will inspire further research on the tremendous therapeutic potential of these combinations for many amyloid-related diseases.

Microfluidic Synthesis of Ultrasmall Chitosan/Graphene Quantum Dots Particles for Intranasal Delivery in Alzheimer's Disease Treatment

Nanoparticles (NPs) based therapies for Alzheimer's disease (AD) attract interest due to their ability to pass across or bypass the blood-brain barrier. Chitosan (CS) NPs or graphene quantum dots (GQDs) are promising drug carriers with excellent physicochemical and electrical properties. The current study proposes the combination of CS and GQDs in ultrasmall NP form not as drug carriers but as theranostic agents for AD. The microfluidic-based synthesis of the CS/GQD NPs with optimized characteristics makes them ideal for transcellular transfer and brain targeting after intranasal (IN) delivery. The NPs have the ability to enter the cytoplasm of C6 glioma cells in vitro and show dose and time-dependent effects on the viability of the cells. IN administration of the NPs to streptozotocin (STZ) induced AD-like models lead to a significant number of entrances of the treated rats to the target arm in the radial arm water maze (RAWM) test. It shows the positive effect of the NPs on the memory recovery of the treated rats. The NPs are detectable in the brain via in vivo bioimaging due to GQDs as diagnostic markers. The noncytotoxic NPs localize in the myelinated axons of hippocampal neurons. They do not affect the clearance of amyloid β (Aβ) plaques at intercellular space. Moreover, they showed no positive impact on the enhancement of MAP2 and NeuN expression as markers of neural regeneration. The memory improvement in treated AD rats may be due to neuroprotection via the anti-inflammation effect and regulation of the brain tissue microenvironment that needs to be studied.

Stabilization of lysozyme in aqueous dispersion of graphene oxide sheets

This study examines the effect of surface oxygen groups upon ability of graphene oxide (GO) sheets in suppressing the fibrillation of lysozyme (LYZ). Graphite was oxidized using 6 and 8 wt equivalents of KMnO₄, and as produced sheets were abbreviated as GO-06 and GO-08, respectively. Particulate characteristics of sheets were characterized by light scattering and electron microscopic techniques, and their interaction with LYZ was analysed by circular dichroism (CD) spectroscopy. After ascertaining acid-driven conversion of LYZ to fibrillary form, we have shown that the fibrillation of dispersed protein can be prevented by adding GO sheets. Inhibitory effect could be attributed to binding of LYZ over the sheets via noncovalent forces. A comparison between GO-06 and GO-08 samples showed superior binding affinity of the latter. Higher aqueous dispersibility and density of oxygenated groups in GO-08 sheets would have facilitated the adsorption of protein molecules, thus making them unavailable for aggregation. Pre-treatment of GO sheets with Pluronic 103 (P103, a nonionic triblock copolymer), caused reduction in the adsorption of LYZ. P103 aggregates would have rendered the sheet surface unavailable for the adsorption of LYZ. Based on these observations, we conclude that fibrillation of LYZ can be prevented in association with graphene oxide sheets.

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

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

Impact of nanoparticles on amyloid β-induced Alzheimer's disease, tuberculosis, leprosy and cancer: a systematic review

Nanotechnology is an interdisciplinary domain of science, technology and engineering that deals with nano-sized materials/particles. Usually, the size of nanoparticles lies between 1 and 100 nm. Due to their small size and large surface area-to-volume ratio, nanoparticles exhibit high reactivity, greater stability and adsorption capacity. These important physicochemical properties attract scientific community to utilize them in biomedical field. Various types of nanoparticles (inorganic and organic) have broad applications in medical field ranging from imaging to gene therapy. These are also effective drug carriers. In recent times, nanoparticles are utilized to circumvent different treatment limitations. For example, the ability of nanoparticles to cross the blood-brain barrier and having a certain degree of specificity towards amyloid deposits makes themselves important candidates for the treatment of Alzheimer's disease. Furthermore, nanotechnology has been used extensively to overcome several pertinent issues like drug-resistance phenomenon, side effects of conventional drugs and targeted drug delivery issue in leprosy, tuberculosis and cancer. Thus, in this review, the application of different nanoparticles for the treatment of these four important diseases (Alzheimer's disease, tuberculosis, leprosy and cancer) as well as for the effective delivery of drugs used in these diseases has been presented systematically. Although nanoformulations have many advantages over traditional therapeutics for treating these diseases, nanotoxicity is a major concern that has been discussed subsequently. Lastly, we have presented the promising future prospective of nanoparticles as alternative therapeutics. In that section, we have discussed about the futuristic approach(es) that could provide promising candidate(s) for the treatment of these four diseases.

Influencing factors and characterization methods of nanoparticles regulating amyloid aggregation

Human disorders associated with amyloid aggregation, such as Alzheimer's disease and Parkinson's disease, afflict the lives of millions worldwide. When peptides and proteins in the body are converted to amyloids, which have a tendency to aggregate, the toxic oligomers produced during the aggregation process can trigger a range of diseases. Nanoparticles (NPs) have been found to possess surface effects that can modulate the amyloid aggregation process and they have potential application value in the treatment of diseases related to amyloid aggregation and fibrillary tangles. In this review, we discuss recent progress relating to studies of nanoparticles that regulate amyloid aggregation. The review focuses on the factors influencing this regulation, which are important as guidelines for the future design of NPs for the treatment of amyloid aggregation. We describe the characterization methods that have been utilized so far in such studies. This review provides research information and characterization methods for the rational design of NPs, which should result in therapeutic strategies for amyloid diseases.

Formulation and Optimization of Silymarin Encapsulated Binary Micelles for Enhanced Amyloid Disaggregation Activity

Purpose-Silymarin (SLY) is natural hydrophobic polyphenol which possess antioxidant and amyloid fibril (Aβ_1-42) inhibition activity, but its activity hinders due to low aqueous solubility. In this study, SLY is encapsulated in Binary micelle (SLY-BM) that have been utilized to enhance the Aβ_1-42 fibril disaggregation. To enhance the aqueous solubility and SLY payload in micelles were optimized using Box Behnken Design (BBD) to increase the efficiency of Aβ_1-42 fibril disaggregation. BBD was employed to investigate the effect of ratio of Solutol HS15: Poloxamer-188, amount of acetone and hydration volume on critical quality attributes (CQA), particle size and entrapment efficiency for SLY-BM. Further SLY-BM was characterized for its physical and drug release properties. The Aβ_1-42 fibril disaggregation and antioxidant studies was monitored using spectroscopic and microscopic techniques. BBD optimized the particle size <50 nm with % EE >80% and solubility factor of SLY-BM was enhanced to 460 folds than free SLY. Inhibitory concentration 50% (IC₅₀) value of SLY-BM was (19.67 µg/mL) compared to free SLY (30.06 µg/mL) in diphenylpicrahydrazyl (DPPH) assay. SLY-BM increased the Aβ _1-42 disaggregation compared to free SLY observed via thioflavin -T (ThT) assay, photon correlation spectroscopy (PCS), and Circular dichorism (CD). Further morphological evaluation of Aβ_1-42 disaggregation was monitored microscopy which showed SLY-BM disaggregated the fibrils in 48h. According to our findings, we concluded that SLY-BM micelles potential candidates for delivery of neuroprotective agents.

Conformational Tuning of Amylin by Charged Styrene-Maleic-Acid Copolymers

Human amylin forms structurally heterogeneous amyloids that have been linked to type-2 diabetes. Thus, understanding the molecular interactions governing amylin aggregation can provide mechanistic insights in its pathogenic formation. Here, we demonstrate that fibril formation of amylin is altered by synthetic amphipathic copolymer derivatives of the styrene-maleic-acid (SMAQA and SMAEA). High-speed AFM is used to follow the real-time aggregation of amylin by observing the rapid formation of de novo globular oligomers and arrestment of fibrillation by the positively-charged SMAQA. We also observed an accelerated fibril formation in the presence of the negatively-charged SMAEA. These findings were further validated by fluorescence, SOFAST-HMQC, DOSY and STD NMR experiments. Conformational analysis by CD and FT-IR revealed that the SMA copolymers modulate the conformation of amylin aggregates. While the species formed with SMAQA are α-helical, the ones formed with SMAEA are rich in β-sheet structure. The interacting interfaces between SMAEA or SMAQA and amylin are mapped by NMR and microseconds all-atom MD simulation. SMAEA displayed π-π interaction with Phe23, electrostatic π-cation interaction with His18 and hydrophobic packing with Ala13 and Val17; whereas SMAQA showed a selective interaction with amylin's C terminus (residues 31-37) that belongs to one of the two β-sheet regions (residues 14-19 and 31-36) involved in amylin fibrillation. Toxicity analysis showed both SMA copolymers to be non-toxic in vitro and the amylin species formed with the copolymers showed minimal deformity to zebrafish embryos. Together, this study demonstrates that chemical tools, such as copolymers, can be used to modulate amylin aggregation, alter the conformation of species.

Polyglutamine-Specific Gold Nanoparticle Complex Alleviates Mutant Huntingtin-Induced Toxicity

Huntington's disease (HD) belongs to protein misfolding disorders associated with polyglutamine (polyQ)-rich mutant huntingtin (mHtt) protein inclusions. Currently, it is indicated that the aggregation of polyQ-rich mHtt participates in neuronal toxicity and dysfunction. Here, we designed and synthesized a polyglutamine-specific gold nanoparticle (AuNP) complex, which specifically targeted mHtt and alleviated its toxicity. The polyglutamine-specific AuNPs were prepared by decorating the surface of AuNPs with an amphiphilic peptide (JLD1) consisting of both polyglutamine-binding sequences and negatively charged sequences. By applying the polyQ aggregation model system, we demonstrated that AuNPs-JLD1 dissociated the fibrillary aggregates from the polyQ peptide and reduced its β-sheet content in a concentration-dependent manner. By further integrating polyethyleneimine (PEI) onto AuNPs-JLD1, we generated a complex (AuNPs-JLD1-PEI). We showed that this complex could penetrate cells, bind to cytosolic mHtt proteins, dissociate mHtt inclusions, reduce mHtt oligomers, and ameliorate mHtt-induced toxicity. AuNPs-JLD1-PEI was also able to be transported to the brain and improved the functional deterioration in the HD Drosophila larva model. Our results revealed the feasibility of combining AuNPs, JLD1s, and cell-penetrating polymers against mHtt protein aggregation and oligomerization, which hinted on the early therapeutic strategies against HD.

Modulation of α-Synuclein Fibrillation by Ultrasmall and Biocompatible Gold Nanoclusters

Parkinson's disease (PD) is the second most common neurodegenerative disorder, the pathogenesis of which is closely linked to the misfolding and aggregation of the neuronal protein α-Synuclein (A-Syn). Numerous molecules that inhibit/modulate the pathogenic aggregation of A-Syn in an effort to tackle PD pathogenesis have been reported, but none so far have been successful in treating the disease at the clinic. One major reason for this is the poor blood-brain barrier (BBB) permeability of most of the molecules being used. Therefore, using BBB-permeable (and biocompatible) nanomaterials as fibrillation modulators is gaining importance. In the present work, we show how nontoxic and ultrasmall gold nanoclusters (AuNCs) can systematically modulate the pathogenic fibrillation of A-Syn in vitro, based on the chemical nature of their capping agents, using two reported easily synthesizable AuNCs as models. In addition, we detect the BBB permeability in mice of one of these AuNCs solely by making use of its intrinsic fluorescence. Thus, our work exemplifies how AuNCs can be potential therapeutics against PD; while also acting as fluorescent probes for their own BBB permeability.

Protein corona: Dr. Jekyll and Mr. Hyde of nanomedicine

Nanomedicine is an interdisciplinary field of research, comprising science, engineering, and medicine. Many are the clinical applications of nanomedicine, such as molecular imaging, medical diagnostics, targeted therapy, and image-guided surgery. Despite major advances during the past 20 years, many efforts must be done to understand the complex behavior of nanoparticles (NPs) under physiological conditions, the kinetic and thermodynamic principles, involved in the rational design of NP. Once administrated in physiological environment, NPs interact with biomolecules and they are surrounded by protein corona (PC) or biocorona. PC can trigger an immune response, affecting NPs toxicity and targeting capacity. This review aims to provide a detailed description of biocorona and of parameters that are able to control PC formation and composition. Indeed, the review provides an overview about the role of PC in the modulation of both cytotoxicity and immune response as well as in the control of targeting capacity.

Silymarin encapsulated nanoliquid crystals for improved activity against beta amyloid induced cytotoxicity

Silymarin (SLY) a natural Aβ aggregation inhibitor, antioxidant and act as neuroprotectant. In the present study, we have prepared nano liquid crystals (NLCs) of negatively charged glycerylmonooleate (GMO) loaded with SLY for enhancing activity against Aβ_1-42 induced toxicity. SLY-NLCs are characterized for physicochemical parameters such as particle size, zeta potential, and drug-loading. The average particle size, zeta potential and % DL were found ≤200 nm, -22 mV, and 8.73% respectively. The amorphous form and entrapment of SLY in NLC were confirmed using DSC and FTIR analysis. The cubosomal SLY-NLCs shape was characterized by SEM and TEM. The cumulative drug release of SLY was ~76% at pH 7.4 (cerebrospinal fluid) from lyophilized SLY-NLC in 48 h. In order to understand the Aβ_1-42 aggregation inhibition due to SLY-NLC ThT (Thioflavin T) kinetic binding assay was also performed. The cell viability assessment of SLY-NLC was performed on SHSY5Y cell line that showed the highest viability in comparison to free SLY treated groups. ROS and apoptosis activity study SLY-NLCs reduced the Aβ_1-42 induced free radical with cell death. Cellular uptake study proved enhanced intracellular internalization of FITC tagged NLCs in 24 h. SLY-NLCs can offer great prospects in the field of drug delivery for neuroprotection.

Recent advances in the design and applications of amyloid-β peptide aggregation inhibitors for Alzheimer's disease therapy

Alzheimer's disease (AD) is an irreversible neurological disorder that progresses gradually and can cause severe cognitive and behavioral impairments. This disease is currently considered a social and economic incurable issue due to its complicated and multifactorial characteristics. Despite decades of extensive research, we still lack definitive AD diagnostic and effective therapeutic tools. Consequently, one of the most challenging subjects in modern medicine is the need for the development of new strategies for the treatment of AD. A large body of evidence indicates that amyloid-β (Aβ) peptide fibrillation plays a key role in the onset and progression of AD. Recent studies have reported that amyloid hypothesis-based treatments can be developed as a new approach to overcome the limitations and challenges associated with conventional AD therapeutics. In this review, we will provide a comprehensive view of the challenges in AD therapy and pathophysiology. We also discuss currently known compounds that can inhibit amyloid-β (Aβ) aggregation and their potential role in advancing current AD treatments. We have specifically focused on Aβ aggregation inhibitors including metal chelators, nanostructures, organic molecules, peptides (or peptide mimics), and antibodies. To date, these molecules have been the subject of numerous in vitro and in vivo assays as well as molecular dynamics simulations to explore their mechanism of action and the fundamental structural groups involved in Aβ aggregation. Ultimately, the aim of these studies (and current review) is to achieve a rational design for effective therapeutic agents for AD treatment and diagnostics.

Efficient Modulation of β-Amyloid Peptide Fibrillation with Polymer Nanoparticles Revealed by Super-Resolution Optical Microscopy

β-Amyloid peptide (Aβ) aggregation is the essential hallmark of neurodegenerative disorders such as Alzheimer's disease. Efficient inhibitors are highly desired for the prevention of Aβ assembly that has been considered as the primary therapeutic strategy for neurodegenerative diseases. Apart from this, visualization of the aggregates and morphology at high spatial resolution is widely considered of crucial significance on biological treatment. In this work, we have developed small-sized (with diameter of ∼4.7 nm) and positively charged fluorescent conjugated polymer nanoparticles (CPNPs) with strong inhibition effect on Aβ_1-40 peptides fibrillation. Interestingly, the CPNPs also possess excellent photophysical properties, including high photon counts, robust blinking, and repetitive fluorescence switching, that are especially suitable for localization-based super-resolution imaging. Spatial resolution of ∼20 nm for these blinking CPNPs is readily achieved. According to the optical microscopic results, it was found that binding of CPNPs to the terminal of seed fibrils can effectively inhibit the fibrillation process. Owing to these attractive biological and unique photophysical properties, the small-sized CPNPs show high potential in a variety of super-resolution based biological applications.

A health concern regarding the protein corona, aggregation and disaggregation

Nanoparticle (NP)-protein complexes exhibit the "correct identity" of NP in biological media. Therefore, protein-NP interactions should be closely explored to understand and modulate the nature of NPs in medical implementations. This review focuses mainly on the physicochemical parameters such as dimension, surface chemistry, morphology of NPs, and influence of pH on the formation of protein corona and conformational changes of adsorbed proteins by different kinds of techniques. Also, the impact of protein corona on the colloidal stability of NPs is discussed. Uncontrolled protein attachment on NPs may bring unwanted impacts such as protein denaturation and aggregation. In contrast, controlled protein adsorption by optimal concentration, size, pH, and surface modification of NPs may result in potential implementation of NPs as therapeutic agents especially for disaggregation of amyloid fibrils. Also, the effect of NPs-protein corona on reducing the cytotoxicity and clinical implications such as drug delivery, cancer therapy, imaging and diagnosis will be discussed. Validated correlative physicochemical parameters for NP-protein corona formation frequently derived from protein corona fingerprints of NPs which are more valid than the parameters obtained only on the base of NP features. This review may provide useful information regarding the potency as well as the adverse effects of NPs to predict their behavior in vivo.

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

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

Modulation of amyloid β peptide aggregation by hydrophilic polymers

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

Charge effects of self-assembled chitosan-hyaluronic acid nanoparticles on inhibiting amyloid β-protein aggregation

Amyloid β-protein (Aβ) aggregation is crucial for the pathogenesis of Alzheimer's disease, and surface charge of nanoparticles (NPs) has been recognized as an important factor influencing Aβ aggregation. Herein, we report a systematic study on the issue with a series of self-assembled chitosan-hyaluronic acid composite (CH) NPs of different surface charges (CH1 to CH7, zeta potentials from +38 to -35 mV). Both the positive and negative CH NPs inhibited Aβ aggregation and the inhibitory effect increased with increasing the surface charges density. Circular dichroism spectroscopy and atomic force microscopy revealed the difference in their working mechanisms. Studies at different pH values further confirmed the importance of electrostatic interactions in Aβ aggregation and presented that the effects of CH NPs changed due to the change of Aβ charge property with pH. This work has thus provided new insight into the surface charge effects on Aβ aggregation.

Iminodiacetic acid-conjugated nanoparticles as a bifunctional modulator against Zn2+-mediated amyloid β-protein aggregation and cytotoxicity

Alzheimer's disease is characterized by the accumulation of amyloid β-protein (Aβ) fibrils in human brain, and the binding of metal ions, such as Zn²⁺, is closely associated with the aggregation and cytotoxicity of Aβ. Here, we designed and synthesized iminodiacetic acid-conjugated nanoparticles (IDA-NP) to modulate Aβ₄₂ aggregation and reduce the cytotoxicity accelerated by Zn²⁺. Results showed that IDA-NP enabled high metal-chelate capacity (752μmol/g) and potent inhibition capability against Aβ₄₂ fibrillation. Zn²⁺ ions could be completely removed by chelating to IDA-NP, which leads to the recovery of on-pathway Aβ₄₂ fibrillation. Then, the special surface character of IDA-NP inhibited Aβ₄₂ fibrillation. As a result, IDA-NP protected SH-SY5Y cells from the cytotoxicity induced by Zn²⁺-Aβ₄₂ species, as evidenced by about 80% (from 47.6% to 86.3%) increase of the cell viability. The research proved that IDA-NP was a potent bifunctional nano-modulator for preventing Zn²⁺-mediated Aβ aggregation and cytotoxicity.

Nanoparticulate strategies for the treatment of polyglutamine diseases by halting the protein aggregation process

Polyglutamine (polyQ) diseases are a class of neurodegenerative disorders that cause cellular dysfunction and, eventually, neuronal death in specific regions of the brain. Neurodegeneration is linked to the misfolding and aggregation of expanded polyQ-containing proteins, and their inhibition is one of major therapeutic strategies used commonly. However, successful treatment has been limited to date because of the intrinsic properties of therapeutic agents (poor water solubility, low bioavailability, poor pharmacokinetic properties), and difficulty in crossing physiological barriers, including the blood-brain barrier (BBB). In order to solve these problems, nanoparticulate systems with dimensions of 1-1000 nm able to incorporate small and macromolecules with therapeutic value, to protect and deliver them directly to the brain, have recently been developed, but their use for targeting polyQ disease-mediated protein misfolding and aggregation remains scarce. This review provides an update of the polyQ protein aggregation process and the development of therapeutic strategies for halting it. The main features that a nanoparticulate system should possess in order to enhance brain delivery are discussed, as well as the different types of materials utilized to produce them. The final part of this review focuses on the potential application of nanoparticulate system strategies to improve the specific and efficient delivery of therapeutic agents to the brain for the treatment of polyQ diseases.