Self-assembled peptide-polyoxometalate hybrid nanospheres: two in one enhances targeted inhibition of amyloid β-peptide aggregation associated with Alzheimer's disease

Influence of reaction conditions on the self-assembly of the natural silk sericin protein

In the past years, the self-assembly of specific proteins has been paid more and more attention due to their significant role in human health and fabrication of new materials. In this article, we explore the effect of reaction conditions on the self-assembly of natural silk sericin protein, including the molecular weight and the concentration of sericin, pH, and metal ions in the reaction system. The results indicate that all these factors, especially species and concentration of metal ions, could influence the self-assembly process of the silk sericin protein. A series of assemblies with various morphologies can be fabricated by modulating the reaction condition. The article may provide some clue for the understanding of the protein self-assembly in the body and a method to fabricate new organic materials with different morphology. Microsc. Res. Tech. 80:298-304, 2017. © 2016 Wiley Periodicals, Inc.

Rationally Designed Peptides and Peptidomimetics as Inhibitors of Amyloid-β (Aβ) Aggregation: Potential Therapeutics of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease with no clinically accepted treatment to cure or halt its progression. The worldwide effort to develop peptide-based inhibitors of amyloid-β (Aβ) aggregation can be considered an unplanned combinatorial experiment. An understanding of what has been done and achieved may advance our understanding of AD pathology and the discovery of effective therapeutic agents. We review here the history of such peptide-based inhibitors, including those based on the Aβ sequence and those not derived from that sequence, containing both natural and unnatural amino acid building blocks. Peptide-based aggregation inhibitors hold significant promise for future AD therapy owing to their high selectivity, effectiveness, low toxicity, good tolerance, low accumulation in tissues, high chemical and biological diversity, possibility of rational design, and highly developed methods for analyzing their mode of action, proteolytic stability (modified peptides), and blood-brain barrier (BBB) permeability.

Neuroprotective effect of single-wall carbon nanotubes with built-in peroxidase-like activity against β-amyloid-induced neurotoxicity

Carbon nanotubes (CNTs) have emerged as a leading nanomaterial for biomedical applications because of their extraordinary properties, which make them useful as delivery vehicles for drugs, proteins, and DNA into cells. However, the numerous applications of carbon nanotubes inevitably increase the potential risk of this nanomaterial. To address this issue, it is necessary to develop protocols for the effective and safe degradation of CNTs. In this study, we demonstrate a self-degradation route for single-wall carbon nanotubes mediated by the built-in peroxidase-like activity of bacterial magnetic nanoparticles (BMPs). Biocompatible BMPs which originated from Magnetospirillum sp. AMB-1 were directly conjugated through covalent bonding to functionalized SWNTs (f-SWNTs) without any additional functionalization processes. This SWNT-BMP hybrid was proven to exhibit highly synergetic peroxidase-like activity, and BMPs act as a highly effective intrinsic peroxidase for the self-degradation of BMP-decorated SWNTs. Moreover, it was shown to be an inhibitor that reduces the formation of β-amyloid (Aβ) fibrils, which are considered a key element in Alzheimer's disease. Thereby the SWNT-BMP hybrid exerts neuroprotective effects against β-amyloid (Aβ) fibrillation-induced neurotoxicity in SH-SY5Y human neuroblastoma cells. These results suggest that the SWNT-BMP hybrid could offer a new approach for treating or preventing neurodegenerative diseases.

Facile synthesis and shape evolution of well-defined phosphotungstic acid potassium nanocrystals as a highly efficient visible-light-driven photocatalyst

Uniform and hollow rhombic dodecahedral, rhombic dodecahedral, spherical, and semi-hollow K₃PW₁₂O₄₀·nH₂O nanocrystals are fabricated without any surfactants or templating agents in mild hydrothermal conditions. The shape evolution and growth of these crystals are studied by changing different reaction parameters, such as the reagent, time and temperature. It is found that the temperature and time have significant effects on the possible growth processes of these nanostructures. More importantly, according to photocatalytic results, due to the specific nanostructure-hollow rhombic dodecahedral structure, the hollow rhombic dodecahedral K₃PW₁₂O₄₀·nH₂O particles with nanopores are shown to be the most effective at activating H₂O₂, degrading dye pollutants completely after 90 minutes of visible light radiation. What's more, the good recycle lifetime for the hollow rhombic dodecahedral K₃PW₁₂O₄₀·nH₂O particles makes them practical for industrial applications. Possible mechanisms for the photocatalysis reaction are further discussed.

A survey of the different roles of polyoxometalates in their interaction with amino acids, peptides and proteins

This perspective provides a comprehensive description of the different roles of POMs in their interaction with relevant biological molecules.

Co-assembly of polyoxometalates and peptides towards biological applications

The synergistic self-assembly of biomolecules with polyoxometalates (POMs) has recently been considered as an effective approach to construct nano-biomaterials with diverse structures and morphologies towards applications in drug delivery, controlled release, tissue engineering scaffolds, and biomineralization, due to the unique features of the clusters in addition to many well-known inorganic nanoparticles. This review presents an overview of recent work focusing on the noncovalent co-assembly of peptides and POMs as well as their biological applications. In the co-assemblies triggered by the interaction between the components significant advantages are observed that POMs or peptides alone do not possess; examples include chiral recognition of hybrid metal oxides, the quick hydrolysis of peptides, and enhanced inhibition of Aβ aggregation. Finally, we outline a brief perspective on possible unresolved issues and future opportunities in this field.

Degradable Organically-Derivatized Polyoxometalate with Enhanced Activity against Glioblastoma Cell Line

High efficacy and low toxicity are critical for cancer treatment. Polyoxometalates (POMs) have been reported as potential candidates for cancer therapy. On accounts of the slow clearance of POMs, leading to long-term toxicity, the clinical application of POMs in cancer treatment is restricted. To address this problem, a degradable organoimido derivative of hexamolybdate is developed by modifying it with a cleavable organic group, leading to its degradation. Of note, this derivative exhibits favourable pharmacodynamics towards human malignant glioma cell (U251), the ability to penetrate across blood brain barrier and low toxicity towards rat pheochromocytoma cell (PC12). This line of research develops an effective POM-based agent for glioblastoma inhibition and will pave a new way to construct degradable anticancer agents for clinical cancer therapy.

Penetratin Peptide-Functionalized Gold Nanostars: Enhanced BBB Permeability and NIR Photothermal Treatment of Alzheimer's Disease Using Ultralow Irradiance

The structural changes of amyloid-beta (Aβ) from nontoxic monomers into neurotoxic aggregates are implicated with pathogenesis of Alzheimer's disease (AD). Over the past decades, weak disaggregation ability and low permeability to the blood-brain barrier (BBB) may be the main obstacles for major Aβ aggregation blockers. Here, we synthesized penetratin (Pen) peptide loaded poly(ethylene glycol) (PEG)-stabilized gold nanostars (AuNS) modified with ruthenium complex (Ru@Pen@PEG-AuNS), and Ru(II) complex as luminescent probes for tracking drug delivery. We revealed that Ru@Pen@PEG-AuNS could obviously inhibit the formation of Aβ fibrils as well as dissociate preformed fibrous Aβ under the irradiation of near-infrared (NIR) due to the NIR absorption characteristic of AuNS. More importantly, this novel design could be applied in medicine as an appropriate nanovehicle, being highly biocompatible and hemocompatible. In addition, Ru@Pen@PEG-AuNS had excellent neuroprotective effect on the Aβ-induced cellular toxicity by applying NIR irradiation. Meanwhile, Pen peptide could effectively improve the delivery of nanoparticles to the brain in vitro and in vivo, which overcame the major limitation of Aβ aggregation blockers. These consequences illustrated that the enhanced BBB permeability and efficient photothermolysis of Ru@Pen@PEG-AuNS are promising agents in AD therapy.

Ceria/POMs hybrid nanoparticles as a mimicking metallopeptidase for treatment of neurotoxicity of amyloid-β peptide

Protein misfolding to amyloid aggregates is the hallmark for neurodegenerative disease. While much attention has been paid to screen natural proteases that can degrade amyloid-β peptides (Aβ), it is difficult to apply them in the clinics with the intractable problem of immunogenicity in living organisms. Herein, we rationally designed an artificial nanozyme, Ceria/Polyoxometalates hybrid (CeONP@POMs) with both proteolytic and superoxide dismutase (SOD) activities. Our results indicated that CeONP@POMs could efficiently degrade Aβ aggregates and reduce intracellular reactive oxygen species (ROS). More importantly, CeONP@POMD could not only promote PC12 cell proliferation and can cross blood-brain barrier (BBB), but also inhibit Aβ-induced BV2 microglial cell activation which was demonstrated by immunoluorescence assay and flow cytometry measurements. In vivo studies further indicated that CeONP@POMD as nanozyme possessed good biocompatibility, evidenced by a detailed study of their biodistribution, body weight change, and in vivo toxicology. Therefore, our results pave the way for design of multifunctional artificial nanozyme for treatment of neurotoxicity of amyloid-β peptide.

Controlled H2O2 release via long-lived electron-hole separation mediated to induce tumor cell apoptosis

Flexible films of polytungstate (PT) as active ingredients were fabricated in PDMS as a "band-Aid" to achieve controllable H₂O₂ release. In these different systems of an amorphous PT building block, the lengthened lifetime (bleaching process) of photo-electron-hole separation is attributed to the electron trapping of the PT network and the existence of hole scavengers. The hole scavengers further prevent recombination of electrons and holes, so that the long-lived photoelectron could provide sustainable reactive oxygen species (ROS) by trapped electrons. Transient absorption illustrates the kinetic competition between the process of photohole induced bleaching and coloration induced by weak irradiation, which suggests that the hole scavenger is vital for ROS generation. The signals of electron spin resonance further confirm the existence of ROS. The profiles of controllable H₂O₂ with various release efficiency were obtained via fluorescence studies. The results indicate that the H₂O₂ release efficiency is related to both the hole scavenger and the tungstate cluster. The released H₂O₂ on the responses of tumor cells were evaluated. Compared with a cancer drug, the controllable and reversible released H₂O₂ delivery is highly efficient in preventing the proliferation and inducing apoptosis of A375 melanoma cells.

Chiral Metallo-Supramolecular Complex Directed Enantioselective Self-Assembly of β-Sheet Breaker Peptide for Amyloid Inhibition

Chiral recognition plays an important role for biomacromolecules involved self-assembly and further affects their biological functions. Herein, it is demonstrated that two chiral metal complexes can enantioselectively bind with Aβ15-20, leading to the formation of different self-assembled nanostructures. With the ability of both metal complexes and Aβ15-20 to inhibit Aβ1-40 aggregation, the NiM@P hybrid particles can act as bifunctional Aβ inhibitors.

Nanotherapeutic strategies for the treatment of Alzheimer's disease

Alzheimer's disease (AD), the most common form of dementia, is now representing one of the largest unmet medical needs. However, no effective treatment is now available to impede the progression of AD or delay its onset. There are two major challenges for the development of effective therapy for AD. First, the exact cause for AD onset is still unknown. Second, brain drug delivery is significantly hindered by the blood-brain barrier (BBB). In this review, we will summarize the pathological understanding about AD and the related treatments, compare BBB and its effect on brain drug delivery under normal and AD conditions and review the nanotherapeutic strategies that have been developed for AD therapy in recent years.

Design of LVFFARK and LVFFARK-functionalized nanoparticles for inhibiting amyloid β-protein fibrillation and cytotoxicity

Aggregation of amyloid β-protein (Aβ) into amyloid oligomers and fibrils is pathologically linked to Alzheimer's disease (AD). Hence, the inhibition of Aβ aggregation is essential for the prevention and treatment of AD, but the development of potent agents capable of inhibiting Aβ fibrillogenesis has posed significant challenges. Herein, we designed Ac-LVFFARK-NH2 (LK7) by incorporating two positively charged residues, R and K, into the central hydrophobic fragment of Aβ17-21 (LVFFA) and examined its inhibitory effect on Aβ42 aggregation and cytotoxicity by extensive physical, biophysical, and biological analyses. LK7 was observed to inhibit Aβ42 fibrillogenesis in a dose-dependent manner, but its strong self-assembly characteristic also resulted in high cytotoxicity. In order to prevent the cytotoxicity that resulted from the self-assembly of LK7, the peptide was then conjugated to the surface of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) to fabricate a nanosized inhibitor, LK7@PLGA-NPs. It was found that LK7@PLGA-NPs had little cytotoxicity because the self-assembly of the LK7 conjugated on the NPs was completely inhibited. Moreover, the NPs-based inhibitor showed remarkable inhibitory capability against Aβ42 aggregation and significantly alleviated its cytotoxicity at a low LK7@PLGA-NPs concentration of 20 μg/mL. At the same peptide concentration, free LK7 showed little inhibitory effect. It is considered that several synergetic effects contributed to the strong inhibitory ability of LK7@PLGA-NPs, including the enhanced interactions between Aβ42 and LK7@PLGA-NPs brought on by inhibiting LK7 self-assembly, restricting conformational changes of Aβ42, and thus redirecting Aβ42 aggregation into unstructured, off-pathway aggregates. The working mechanisms of the inhibitory effects of LK7 and LK7@PLGA-NPs on Aβ42 aggregation were proposed based on experimental observations. This work provides new insights into the design and development of potent NPs-based inhibitors against Aβ aggregation and cytotoxicity.

A novel organic–inorganic hybrid polyoxometalate for the selective adsorption/isolation of β-lactoglobulin

A novel polyoxometalate (POM)-based organic–inorganic hybrid is preparedviaa one-pot hydrothermal reaction between Keggin POM and a star-like N-donor ligand. The hybrid exhibits excellent adsorption performance towards β-lactoglobulin with a favorable sorption capacity.

Mo polyoxometalate nanoclusters capable of inhibiting the aggregation of Aβ-peptide associated with Alzheimer's disease

A neuropathological hallmark of Alzheimer's disease (AD) is aggregation of a forty-residue peptide known as amyloid beta forty (Aβ40). While past work has indicated that blocking Aβ40 aggregation could be an effective strategy for the treatment of AD, developing therapies with this goal has been met with limited success. Polyoxometalates (POMs) have been previously investigated for their anti-viral and anti-tumoral properties and we report here that three representative POM nanoclusters have been synthesized for use against Aβ40 aggregation. Through the use of thioflavin T fluorescence, turbidity, circular dichroism spectroscopy, and transmission electron microscopy (TEM), we found that all three POM complexes can significantly inhibit both natural Aβ40 self-aggregation and metal-ion induced Aβ40 aggregation. We also evaluated the protective effect of POM complexes on Aβ40-induced neurotoxicity in cultured PC12 cells and found that treatment with POM complexes can elevate cell viability, decrease levels of intracellular reactive oxygen species, and stabilize mitochondrial membrane potential. These findings indicate that all three representative POM complexes are capable of inhibiting Aβ40 aggregation and subsequent neurotoxicity. While a complete mechanistic understanding remains to be elucidated, the synthesized POM complexes may work through a synergistic interaction with metal ions and Aβ40. These data indicate that POM complexes have high therapeutic potential for use against one of the primary neuropathological features of AD.

Amyloid-β aggregation with gold nanoparticles on brain lipid bilayer

Understanding and manipulating amyloid-β (Aβ) aggregation provide key knowledge and means for the diagnosis and cure of Alzheimer's disease (AD) and the applications of Aβ-based aggregation systems. Here, we studied the formation of various Aβ aggregate structures with gold nanoparticles (AuNPs) and brain total lipid extract-based supported lipid bilayer (brain SLB). The roles of AuNPs and brain SLB in forming Aβ aggregates were studied in real time, and the structural details of Aβ aggregates were monitored and analyzed with the dark-field imaging of plasmonic AuNPs that allows for long-term in situ imaging of Aβ aggregates with great structural details without further labeling. It was shown that the fluid brain SLB platform provides the binding sites for Aβ and drives the fast and efficient formation of Aβ aggregate structures and, importantly, large Aβ plaque structures (>15 μm in diameter), a hallmark for AD, were formed without going through fibril structures when Aβ peptides were co-incubated with AuNPs on the brain SLB. The dark-field scattering and circular dichroism-correlation data suggest that AuNPs were heavily involved with Aβ aggregation on the brain SLB and less α-helix, less β-sheet and more random coil structures were found in large plaque-like Aβ aggregates.

Nanoparticles in relation to peptide and protein aggregation

Over the past two decades, there has been considerable research interest in the use of nanoparticles in the study of protein and peptide aggregation, and of amyloid-related diseases. The influence of nanoparticles on amyloid formation yields great interest due to its small size and high surface area-to-volume ratio. Targeting nucleation kinetics by nanoparticles is one of the most searched for ways to control or induce this phenomenon. The observed effect of nanoparticles on the nucleation phase is determined by particle composition, as well as the amount and nature of the particle's surface. Various thermodynamic parameters influence the interaction of proteins and nanoparticles in the solution, and regulate the protein assembly into fibrils, as well as the disaggregation of preformed fibrils. Metals, organic particles, inorganic particles, amino acids, peptides, proteins, and so on are more suitable candidates for nanoparticle formulation. In the present review, we attempt to explore the effects of nanoparticles on protein and peptide fibrillation processes from both perspectives (ie, as inducers and inhibitors on nucleation kinetics and in the disaggregation of preformed fibrils). Their formulation and characterization by different techniques have been also addressed, along with their toxicological effects, both in vivo and in vitro.

Pharmacogenomics of Alzheimer's disease: novel therapeutic strategies for drug development

Alzheimer's disease (AD) is a major problem of health and disability, with a relevant economic impact on our society. Despite important advances in pathogenesis, diagnosis, and treatment, its primary causes still remain elusive, accurate biomarkers are not well characterized, and the available pharmacological treatments are not cost-effective. As a complex disorder, AD is a polygenic and multifactorial clinical entity in which hundreds of defective genes distributed across the human genome may contribute to its pathogenesis. Diverse environmental factors, cerebrovascular dysfunction, and epigenetic phenomena, together with structural and functional genomic dysfunctions, lead to amyloid deposition, neurofibrillary tangle formation, and premature neuronal death, the major neuropathological hallmarks of AD. Future perspectives for the global management of AD predict that genomics and proteomics may help in the search for reliable biomarkers. In practical terms, the therapeutic response to conventional drugs (cholinesterase inhibitors, multifactorial strategies) is genotype-specific. Genomic factors potentially involved in AD pharmacogenomics include at least five categories of gene clusters: (1) genes associated with disease pathogenesis; (2) genes associated with the mechanism of action of drugs; (3) genes associated with drug metabolism (phase I and II reactions); (4) genes associated with drug transporters; and (5) pleiotropic genes involved in multifaceted cascades and metabolic reactions. The implementation of pharmacogenomic strategies will contribute to optimize drug development and therapeutics in AD and related disorders.