Polyoxometalates as Inhibitors of the Aggregation of Amyloid β Peptides Associated with Alzheimer’s Disease

Self-assembling peptide and protein amyloids: from structure to tailored function in nanotechnology

Self-assembled peptide and protein amyloid nanostructures have traditionally been considered only as pathological aggregates implicated in human neurodegenerative diseases. In more recent times, these nanostructures have found interesting applications as advanced materials in biomedicine, tissue engineering, renewable energy, environmental science, nanotechnology and material science, to name only a few fields. In all these applications, the final function depends on: (i) the specific mechanisms of protein aggregation, (ii) the hierarchical structure of the protein and peptide amyloids from the atomistic to mesoscopic length scales and (iii) the physical properties of the amyloids in the context of their surrounding environment (biological or artificial). In this review, we will discuss recent progress made in the field of functional and artificial amyloids and highlight connections between protein/peptide folding, unfolding and aggregation mechanisms, with the resulting amyloid structure and functionality. We also highlight current advances in the design and synthesis of amyloid-based biological and functional materials and identify new potential fields in which amyloid-based structures promise new breakthroughs.

Using Multifunctional Peptide Conjugated Au Nanorods for Monitoring β-amyloid Aggregation and Chemo-Photothermal Treatment of Alzheimer's Disease

Development of sensitive detectors of Aβ aggregates and effective inhibitors of Aβ aggregation are of diagnostic importance and therapeutic implications for Alzheimer's disease (AD) treatment. Herein, a novel strategy has been presented by self-assembly of peptide conjugated Au nanorods (AuP) as multifunctional Aβ fibrillization detectors and inhibitors. Our design combines the unique high NIR absorption property of AuNRs with two known Aβ inhibitors, Aβ15-20 and polyoxometalates (POMs). The synthesized AuP can effectively inhibit Aβ aggregation and dissociate amyloid deposits with NIR irradiation both in buffer and in mice cerebrospinal fluid (CSF), and protect cells from Aβ-related toxicity upon NIR irradiation. In addition, with the shape and size-dependent optical properties, the nanorods can also act as effective diagnostic probes to sensitively detect the Aβ aggregates. This is the first report to integrate 3 segments, an Aβ-targeting element, a reporter and inhibitors, in one drug delivery system for AD treatment.

N-Methyl Mesoporphyrin IX as an Effective Probe for Monitoring Alzheimer's Disease β-Amyloid Aggregation in Living Cells

Formation of amyloid fibrils by amyloid-β peptide (Aβ) is an important step in Alzheimer's disease (AD) progression. Screening and designing of new molecules which can monitor the amyloidosis process especially in cells are diagnostically and therapeutically important. Utilizing Thioflavin T (ThT), the commonly used amyloid dye, is the most standardized way to monitor amyloid. However, with the green fluorescence emission and small Stokes shift, the fluorescence of ThT can overlap with that arising from other intrinsic fluorescent components in the cells, making it not suitable for detection of protein aggregates in vivo. Therefore, it is urgent for developing amyloid probes with large Stokes shifts and red-shifted fluorescence emission to detect Aβ aggregates in cells. In this report, we found that N-methyl mesoporphyrin IX (NMM), a widely used G-quadruplex DNA specific fluorescent binder, can be an efficient probe for monitoring Aβ fibrillation in living cells. NMM is nonfluorescent in aqueous solution or monomeric Aβ environments. However, through stacking with the Aβ assemblies, NMM emits strong fluorescence. Furthermore, the large Stokes shift and stable photoluminescence make it an ideal probe for detecting Aβ aggregates in highly fluorescent environments and cell culture. Our results provide a new sight to design and screen new reagents for monitoring the diseases associated with protein conformational disorders.

Chemical Methods to Knock Down the Amyloid Proteins

Amyloid proteins are closely related with amyloid diseases and do tremendous harm to human health. However, there is still a lack of effective strategies to treat these amyloid diseases, so it is important to develop novel methods. Accelerating the clearance of amyloid proteins is a favorable method for amyloid disease treatment. Recently, chemical methods for protein reduction have been developed and have attracted much attention. In this review, we focus on the latest progress of chemical methods that knock down amyloid proteins, including the proteolysis-targeting chimera (PROTAC) strategy, the "recognition-cleavage" strategy, the chaperone-mediated autophagy (CMA) strategy, the selectively light-activatable organic and inorganic molecules strategy and other chemical strategies.

Genotoxicity and acute and subchronic toxicity studies of a bioactive polyoxometalate in Wistar rats

Background

Cs₂K₄Na [SiW₉Nb₃O₄₀] (POM93) is a novel broad-spectrum antiviral agent with high activity, high stability, and low toxicity in vitro. Most toxicity studies for POM93 have been performed in cultured cell lines rather than in animals. Like other POMs, there is a lack of evidence for in vivo toxicity limits, oral bioavailability, and therapeutic applications.

Methods

The toxic properties of POM93 were evaluated comprehensively in vivo, including the acute and subchronic oral toxicity studies and genotoxicity tests.

Results

The acute toxicity study showed no abnormal changes or mortality in rats treated with POM93 even at the single high dose of 5000 mg/kg body weight. In the subchronic toxicity study, regardless of the body weight, the organ weight, and the hematological parameters, similar results were observed between the control group and the experimental groups. POM93 produced mild changes in rare hematological parameters in the liver and kidneys, but did not induce the clinical symptoms of liver or kidneys injury in rats as confirmed by histopathological analysis. Moreover, neither mutagenicity nor clastogenicity was caused by POM93 treatment in vitro and in vivo.

Conclusions

The present study demonstrates that the oral administration of POM93 is presumed safe and poses a low risk of potential health risks.

Electronic supplementary material

The online version of this article (doi:10.1186/s40360-017-0133-x) contains supplementary material, which is available to authorized users.

Hematite-Based Photoelectrode Materials for Photoelectrocatalytic Inhibition of Alzheimer's β-Amyloid Self-Assembly

A visible light-active, hematite-based photoelectrode platform for suppressing β-amyloid (Aβ) self-assembly in vitro is reported. Upon illumination of a light-emitting diode with an anodic bias, the hematite photoanode generates reactive radical species, such as superoxide ions and hydroxyl radicals, via photoelectrocatalytic process. According to our analyses, the hematite photoanode exhibited a strong inhibitory effect on Aβ aggregation under visible light illumination and anodic bias. We found that hole-derived radicals played a significant role of oxidizing Aβ peptides, which effectively blocked further aggregation. The efficacy of photoelectrocatalytic inhibition on Aβ aggregation was enhanced by introducing cobalt phosphate (Co-Pi) as a co-catalyst on the hematite photoanode, which facilitated the separation of electron-hole pairs. We verified that both bare and Co-Pi@hematite photoanodes are biocompatible and effective in reducing Aβ aggregation-induced cytotoxicity.

Dual-functional selenium nanoparticles bind to and inhibit amyloid β fiber formation in Alzheimer's disease

LPFFD/TGN modified SeNPs could cross the BBB and selectively bind to Aβ species. This binding might disrupted Aβ₄₀nucleation, and finally decrease Aβ₄₀fibrillation and their corresponding neurotoxicity in PC12 cells.

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.

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.

Heteropoly acids triggered self-assembly of cationic peptides into photo- and electro-chromic gels

A series of cationic peptides with alternating lysines and hydrophobic residues were designed and synthesized. These kinds of short peptides with protonated lysines can complex with anionic heteropoly acids (HPAs) to form a stable gel in water/ethanol mixed solution. Circular dichroism spectroscopy showed that the short peptides adopted a mixed conformation (β-sheet and random-coil) within the gel matrix. Scanning and transmission electron microscopy revealed that the heteropoly acids, acting as nanosized cross-linkers, first initiated the self-assembly of the cationic peptides into spherical nanostructures. Then these nanospheres accumulated with each other through hydrogen bonds and hydrophobic interactions to form large sheet-like assemblies, which further interconnected with each other forming continuous 3D network structures. Fourier-transform infrared spectroscopy showed that the structural integrity of the HPAs was maintained during the gelation process. The resultant hybrid gels showed reversible photo- and elecrtro-chromic properties. X-ray photoelectron spectroscopy revealed that the hybrid gels, capable of persistent and reversible changes of their colour, are attributed to the intervalence charge-transfer transition of the HPAs. Reversible information writing and erasing were demonstrated through a repeated photo-lithograph or electric stimuli without significant loss of the gel performance.

Photoactive g-C3 N4 Nanosheets for Light-Induced Suppression of Alzheimer's β-Amyloid Aggregation and Toxicity

Graphitic carbon nitride (g-C3 N4 ) has a suppressive capability toward Alzheimer's Aβ aggregation under light-illumination. Photoinduced electrons of g-C3 N4 generate reactive oxygen resulting in photooxidation of amyloid peptides that blocks Aβ aggregation. Fe doping of g-C3 N4 frameworks results in enhanced optical properties and even stronger inhibition of Aβ aggregation.

Irreversible destruction of amyloid fibril plaques by conjugated polymer based fluorogenic nanogrenades

Supramolecular assembly between conjugated polymers and fluorescent dyes produces a unique class of fluorogenic "nanogrenades". These nanomaterials have shown the ability to image as well as irreversibly destruct amyloid β fibril plaques by simple light irradiation.

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.

Morphology-Specific Inhibition of β-Amyloid Aggregates by 17β-Hydroxysteroid Dehydrogenase Type 10

A major hallmark of Alzheimer's disease (AD) is the formation of toxic aggregates of the β-amyloid peptide (Aβ). Given that Aβ peptides are known to localise within mitochondria and interact with 17β-HSD10, a mitochondrial protein expressed at high levels in AD brains, we investigated the inhibitory potential of 17β-HSD10 against Aβ aggregation under a range of physiological conditions. Fluorescence self-quenching (FSQ) of Aβ(1-42) labelled with HiLyte Fluor 555 was used to evaluate the inhibitory effect under conditions established to grow distinct Aβ morphologies. 17β-HSD10 preferentially inhibits the formation of globular and fibrillar-like structures but has no effect on the growth of amorphous plaque-like aggregates at endosomal pH 6. This work provides insights into the dependence of the Aβ-17β-HSD10 interaction with the morphology of Aβ aggregates and how this impacts enzymatic function.

Graphene quantum dots for the inhibition of β amyloid aggregation

The aggregation of Aβ peptides is a crucial factor leading to Alzheimer's disease (AD). Inhibiting the Aβ peptide aggregation has become one of the most essential strategies to treat AD. In this work, efficient and low-cytotoxicity inhibitors, graphene quantum dots (GQDs) are reported for their application in inhibiting the aggregation of Aβ peptides. Compared to other carbon materials, the low cytotoxicity and great biocompatibility of GQDs give an advantage to the clinical research for AD. In addition, the GQDs may cross the blood-brain barrier (BBB) because of the small size. It is believed that GQDs may be therapeutic agents against AD. This work provides a novel insight into the development of Alzheimer's drugs.

Inhibition of Beta-Amyloid Fibrillation by Luminescent Iridium(III) Complex Probes

We report herein the application of kinetically inert luminescent iridium(III) complexes as dual inhibitors and probes of beta-amyloid fibrillogenesis. These iridium(III) complexes inhibited Aβ_1–40 peptide aggregation in vitro, and protected against Aβ-induced cytotoxicity in neuronal cells. Furthermore, the complexes differentiated between the aggregated and unaggregated forms of Aβ_1–40 peptide on the basis of their emission response.

Modulation of Amyloid-β Fibrils into Mature Microrod-Shaped Structure by Histidine Functionalized Water-Soluble Perylene Diimide

Alzheimer's disease (AD) is associated with different types of amyloid peptide aggregates including senile plaques, fibrils, protofibrils, and oligomers. Due to these difficulties, a powerful strategy is needed for the disaggregation of amyloid aggregates by modulating their self-aggregation behavior. Herein, we report a unique approach toward transforming the aggregated amyloidogenic peptides using an amino acid functionalized perylene diimide as a molecular modulator, which is a different nondestructive approach as compared to inhibiting the aggregation of peptides. The histidine functionalized perylenediimide (PDI-HIS) molecule could coassemble with amyloid β (Aβ) peptides via hydrogen bonding that leads to the enhancement in the π-π interactions between Aβ and PDI-HIS moieties. The Thioflavin T (ThT) assay and various spectroscopic and microscopic techniques establish that the PDI-HIS molecules accelerate the Aβ1-40 and the amyloid aggregates in CSF into micro size coassembled structures. These results give rise to a new and unique complementary approach for modulating the biological effects of the aggregates in amyloidogenic peptides.

Effective Amyloid Defibrillation by Polyhydroxyl-Substituted Squaraine Dyes

With an objective to develop β-amyloid destabilizing agents, we have investigated the interactions of a few water-soluble near-infrared (NIR)-absorbing squaraine dyes 1-3 with lysozyme and its amyloid aggregates through photophysical and biophysical techniques. These dyes exhibited strong interactions with lysozyme and β-amyloids in addition to serum albumins as evidenced by the absorption and emission changes. The interactions were found to be spontaneous with association constant values in the range of approximately 10(4)-10(5)  m(-1), as confirmed through half-reciprocal analysis and isothermal calorimetric measurements. Uniquely, such effective interactions of the dyes have led to the complete disassembly of the β-amyloid fibrillar structures to form spherical particles approximately 350 nm in size, as confirmed through photophysical, thioflavin assay, circular dichroism (CD), atomic force microscopy (AFM), TEM, and selected-area electron diffraction (SAED) techniques. These results demonstrate that the squaraine dyes 1-3 under investigation act as effective protein-labelling and destabilizing agents of the protein amyloidogenesis.

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.

Chemical perturbation of an intrinsically disordered region of TFIID distinguishes two modes of transcription initiation

Intrinsically disordered proteins/regions (IDPs/IDRs) are proteins or peptide segments that fail to form stable 3-dimensional structures in the absence of partner proteins. They are abundant in eukaryotic proteomes and are often associated with human diseases, but their biological functions have been elusive to study. In this study, we report the identification of a tin(IV) oxochloride-derived cluster that binds an evolutionarily conserved IDR within the metazoan TFIID transcription complex. Binding arrests an isomerization of promoter-bound TFIID that is required for the engagement of Pol II during the first (de novo) round of transcription initiation. However, the specific chemical probe does not affect reinitiation, which requires the re-entry of Pol II, thus, mechanistically distinguishing these two modes of transcription initiation. This work also suggests a new avenue for targeting the elusive IDRs by harnessing certain features of metal-based complexes for mechanistic studies, and for the development of novel pharmaceutical interventions.

DOI:http://dx.doi.org/10.7554/eLife.07777.001

DNA contains instructions to make all the proteins and other molecules that drive essential processes in cells. To issue such specific sets of instructions, a section of DNA—called a gene—is first copied to make molecules of messenger ribonucleic acid (or mRNA for short) in a process called transcription. This process is tightly regulated in all living organisms so that only a subset of genes are actively transcribed at any time in a given cell.

A group or ‘complex’ of proteins called TFIID plays an essential role in starting the transcription of genes that encode proteins in humans and other eukaryotic organisms. However, it is tricky to study how TFIID works because mutant cells that are missing individual components of the complex are unable to properly transcribe the required genes and soon die. Consequently, many studies of TFIID have used purified proteins in artificial systems where it is possible to examine particular aspects of TFIID activity in depth.

Here, Zhang et al. used a combination of chemistry, biochemistry, and molecular biology techniques to identify a new molecule that can selectively bind to the TFIID complex. In an artificial system containing purified proteins and other molecules, this molecule ‘locks’ TFIID onto DNA and prevents a change in shape that is required for transcription to start. The experiments show that this rearrangement is only required to make the first mRNA copy of a gene because the molecule had no effect on initiating further rounds of transcription on the same DNA.

Zhang et al.'s findings reveal that TFIID is very dynamic in controlling transcription, and that subsequent rounds of transcription follow a different path to make mRNAs. The next steps are to use new techniques such as single-molecule imaging to directly visualize the molecules involved in transcription, and to use the new molecule to block the start of transcription in living cells.

DOI:http://dx.doi.org/10.7554/eLife.07777.002

Gold-nanoparticle-based multifunctional amyloid-β inhibitor against Alzheimer's disease

Targeting amyloid-β (Aβ)-induced complex neurotoxicity has received considerable attention in the therapeutic and preventive treatment of Alzheimer's disease (AD). The complex pathogenesis of AD suggests that it requires comprehensive treatment, and drugs with multiple functions against AD are more desirable. Herein, AuNPs@POMD-pep (AuNPs: gold nanoparticles, POMD: polyoxometalate with Wells-Dawson structure, pep: peptide) were designed as a novel multifunctional Aβ inhibitor. AuNPs@POMD-pep shows synergistic effects in inhibiting Aβ aggregation, dissociating Aβ fibrils and decreasing Aβ-mediated peroxidase activity and Aβ-induced cytotoxicity. By taking advantage of AuNPs as vehicles that can cross the blood-brain barrier (BBB), AuNPs@POMD-pep can cross the BBB and thus overcome the drawbacks of small-molecule anti-AD drugs. Thus, this work provides new insights into the design and synthesis of inorganic nanoparticles as multifunctional therapeutic agents for treatment of AD.

Chiral metallohelical complexes enantioselectively target amyloid β for treating Alzheimer's disease

Stereochemistry is a very important issue for the pharmaceutical industry and can determine drug efficacy. The design and synthesis of small molecules, especially chiral molecules, which selectively target and inhibit amyloid-β (Aβ) aggregation, represent valid therapeutic strategies for treatment of Alzheimer's disease (AD). Herein we report that two triple-helical dinuclear metallosupramolecular complexes can act as a novel class of chiral amyloid-β inhibitors. Through targeting α/β-discordant stretches at the early steps of aggregation, these metal complexes can enantioselectively inhibit Aβ aggregation, which is demonstrated using fluorescent living cell-based screening and multiple biophysical and biochemical approaches. To the best of our knowledge, this is the first report of enantioselective inhibition of Aβ aggregation. Intriguingly, as a promising candidate for AD treatment, the chiral metal complex can cross the blood-brain barrier and have superoxide dismutase activity. It is well-known that chiral discrimination is important for understanding chiral drug action. Generally, one enantiomer is pharmaceutically active while the other is inactive or exerts severe side effects. Chiral discrimination should be important for AD treatment. Our work provides new insights into chiral inhibition of Aβ aggregation and opens a new avenue for design and screening of chiral agents as Aβ inhibitors against AD.

Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors

Background

SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of polyoxometalates as specific SOX transcription factor drugs.

Results

The residual DNA-binding activities of 15 different transcription factors were measured after treatment with a panel of diverse polyoxometalates. Polyoxometalates belonging to the Dawson structural class were found to be more potent inhibitors than the Keggin class. Further, organically modified Dawson polyoxometalates were found to be the most potent in inhibiting transcription factor DNA binding activity. The size of the polyoxometalates and its derivitization were found to be the key determinants of their potency.

Conclusion

Polyoxometalates are highly potent, nanomolar range inhibitors of the DNA binding activity of the Sox-HMG family. However, binding assays involving a limited subset of structurally diverse polyoxometalates revealed a low selectivity profile against different transcription factor families. Further progress in achieving selectivity and deciphering structure-activity relationship of POMs require the identification of POM binding sites on transcription factors using elaborate approaches like X-ray crystallography and multidimensional NMR. In summary, our report reaffirms that transcription factors are challenging molecular architectures and that future polyoxometalate chemistry must consider further modification strategies, to address the substantial challenges involved in achieving target selectivity.

New insights into Alzheimer's disease amyloid inhibition: nanosized metallo-supramolecular complexes suppress aβ-induced biosynthesis of heme and iron uptake in PC12 cells

Nanosized metallo-supramolecular compounds, [Ni2 L3 ](4+) and [Fe2 L3 ](4+) , can not only strongly inhibit Aβ aggregation but also reduce the peroxidase activity of Aβ-heme. Further studies demonstrate that through blocking the heme-binding site, these two compounds can suppress Aβ-induced biosynthesis of heme and iron uptake in PC12 cells. This work provides new insights into molecular mechanisms of Aβ inhibitors on Aβ-mediated neurotoxicity.

Artificial evolution of graphene oxide chemzyme with enantioselectivity and near-infrared photothermal effect for cascade biocatalysis reactions

It is highly desirable and challenging when the chemzyme can be not only simply duplicating and imitating the properties of natural enzymes, but also introducing additional new features for practical applications. Herein, we report a zinc-finger-protein like α-helical chiral metallo-supramolecular complex ([Fe2L3](4+)) functionalized graphene oxide (GO-COOH) as a peroxidase mimic. This artificial enzyme integrates the characteristics of both chiral metallo-supramolecular complex and GO-COOH, and shows excellent catalytic activity. More intriguingly, the novel chemzyme turn out to have enantioselectivity and near-infrared photothermal effect. To the best of our knowledge, this is the first example that the chemzyme has such new features. Based on these properties, we have demonstrated three examples for the applications of our designed enzyme: 1) Intracellular H2O2 detection in PC12 cells against Alzheimer's disease; 2) Discrimination between the chiral drug, Levodopa (L-dopa), the gold standard for treating Parkinson's disease and its enantiomer, D-dopa. This is important because L-dopa is the most effective drug at present used to combat Parkinson's disease while D-dopa is inactive and can even cause side effects, thus for drug efficacy it must be free of D-dopa in the formulation; 3) Remote control of enzyme cascade biocatalysis reactions using high transparent, bio-friendly near-infrared (NIR) light. NIR allows remote activation with relatively high spatial and temporal precision. Our work will provide new insights into design and construction of novel chemzyme with more advanced features beyond intrinsic enzyme property.

Transition-metal-substituted polyoxometalate derivatives as functional anti-amyloid agents for Alzheimer's disease

Inhibitions of amyloid β (Aβ) aggregation and Aβ-haem peroxidase-like activity have received much attention because these two symptoms can be the primary targets of therapeutic strategies for Alzheimer's disease (AD). Recently, our group found that polyoxometalate (POM) with a Wells-Dawson structure can efficiently inhibit Aβ aggregation. However, the interaction between POMs and Aβ is robust, but still needs to improve Aβ binding affinity. More importantly, it is unclear whether POMs can cross the blood-brain barrier and decrease Aβ-haem peroxidase-like activity. Here we show that our designed series of transition metal-functionalized POM derivatives with a defined histidine-chelated binding site have much better Aβ inhibition and peroxidase-like activity inhibition effects than the parent POM. More intriguingly, we show that these compounds can cross the blood-brain barrier and are metabolized after 48 h. Our work provides insights into the design, synthesis and screening of inorganic metal compounds as multifunctional therapeutic agents against AD.

Unprecedented high-nuclear transition-metal-cluster-substituted heteropolyoxoniobates: synthesis by {V8 } ring insertion into the POM matrix and antitumor activities

Reactions of hexaniobate with vanadate in the presence of Ni(2+) , Zn(2+) , or Cu(2+) have furnished three high-nuclear vanadium cluster-substituted heteropolyoxoniobates (HPNs): {Ni(en)3 }5 H{V(V) Nb8 V(IV) 8 O44 }⋅9 H2 O (1), (H2 en)Na2 [{Zn(en)2 (Hen)}{Zn(en)2 (H2 O)}2 {PNb8 V(IV) 8 O44 }]⋅11 H2 O (2), and Na{Cu(en)2 }3 {[Cu(en)2 ]2 [PNb8 V(IV) 8 O44 ]}⋅11 H2 O (3) (en=1,2-diaminoethane). Their structures have been determined and characterized by single-crystal X-ray diffraction analysis, thermogravimetric analysis (TGA), and elemental analysis. Structural analysis has revealed that compounds 1-3 contain similar {V8 }-substituted [X(V) Nb8 V(IV) 8 O44 ](11-) (X=P, V) clusters, obtained by inserting a {V8 } ring into tetravacant HPN [XNb8 O36 ](27-) . To the best of our knowledge, compounds 1-3 represent the first high-nuclear vanadium cluster-substituted HPNs, and compound 1 is the largest vanadoniobate cluster yet obtained in HPN chemistry. Nickel and zinc cations have been introduced into HPNs for the first time, which might promise a more diverse set of structures in this family. Antitumor studies have indicated that compounds 1 and 2 exhibit high activity against human gastric cancer SGC-7901 cells, SC-1680 cells, and MG-63 cells.

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

Amyloid fibril formation is a critical step in Alzheimer's disease (AD) pathogenesis. Inhibition of Aβ aggregation has shown promising against AD and has been used in clinic trials. Here, a novel strategy is reported for the self-assembly of polyoxometalate-peptide (POM@P) hybrid particles as bifunctional Aβ inhibitors. The two-in-one bifunctional POM@P nanoparticles show an enhanced inhibition effect on amyloid aggregation in mice cerebrospinal fluid. Incorporating a clinically used Aβ fibril-staining dye, congo red (CR), into the hybrid colloidal spheres, the nanoparticles can also act as an effective fluorescent probe to monitor the inhibition process of POM@P via CR fluorescence change in real time. It is believed that such flexible organic-inorganic hybrid systems may prompt the design of new multifunctional materials for AD treatment.

Glyconanoparticle aided detection of β-amyloid by magnetic resonance imaging and attenuation of β-amyloid induced cytotoxicity

The development of a noninvasive method for the detection of Alzheimer's disease is of high current interest, which can be critical in early diagnosis and in guiding treatment of the disease. The aggregates of β-amyloid are a pathological hallmark of Alzheimer's disease. Carbohydrates such as gangliosides have been shown to play significant roles in initiation of amyloid aggregation. Herein, we report a biomimetic approach using superparamagnetic iron oxide glyconanoparticles to detect β-amyloid. The bindings of β-amyloid by the glyconanoparticles were demonstrated through several techniques including enzyme linked immunosorbent assay, gel electrophoresis, tyrosine fluorescence assay, and transmission electron microscopy. The superparamagnetic nature of the nanoparticles allowed easy detection of β-amyloid both in vitro and ex vivo by magnetic resonance imaging. Furthermore, the glyconanoparticles not only were nontoxic to SH-SY5Y neuroblastoma cells but also greatly reduced β-amyloid induced cytotoxicity to cells, highlighting the potential of these nanoparticles for detection and imaging of β-amyloid.

sym-Triazines for directed multitarget modulation of cholinesterases and amyloid-β in Alzheimer's disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder marked by numerous causative factors of disease progression, termed pathologies. We report here the synthesis of a small library of novel sym-triazine compounds designed for targeted modulation of multiple pathologies related to AD, specifically human acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and Aβ aggregation. Rational targeting of AChE was achieved by the incorporation of acetylcholine substrate analogues into a sym-triazine core in either a mono-, di-, or trisubstituted regime. A subset of these derivatives demonstrated improved activity compared to several commercially available cholinesterase inhibitors. High AChE/BuChE selectivity was characteristic of all derivatives, and AChE steady-state kinetics indicated a mixed-type inhibition mechanism. Further integration of multiple hydrophobic phenyl units allowed for improved β-sheet intercalation into amyloid aggregates. Several highly effective structures exhibited fibril inhibition greater than the previously reported β-sheet-disrupting penta-peptide, iAβ5p, evaluated by thioflavin T fluorescence spectroscopy and transmission electron microscopy. Highly effective sym-triazines were shown to be well tolerated by differentiated human neuronal cells, as demonstrated by the absence of adverse effects on cellular viability at a wide range of concentrations. Parallel targeting of multiple pathologies using sym-triazines is presented here as an effective strategy to address the complex, multifactorial nature of AD progression.

In situ monitoring Alzheimer's disease β-amyloid aggregation and screening of Aβ inhibitors using a perylene probe

A cationic perylene tetracarboxylic acid diimide derivative (1) is employed as a probe for in situ monitoring of Aβ aggregation and screening Aβ inhibitors. The assay is based on the fluorescence change through the aggregation of compound 1 following Aβ assembly. Importantly, this probe, compared with the well known amyloid-staining compound thioflavin T (ThT), is more sensitive to Aβ oligomer, which is highly toxic and plays a crucial role in the early stages of Alzheimer's disease.

New horizons for diagnostics and therapeutic applications of graphene and graphene oxide

Graphene, a one-atom-thick two-dimensional (2D) layer of sp(2) -bonded carbon, has received worldwide attention owing to its extraordinary physical and chemical properties. Recently, great efforts have been devoted to explore potential applications of graphene and its oxide in life science, especially in disease-related diagnostics, near-Infrared (NIR) phototherapy and imaging. Here we will introduce recent advances and new horizons in this area, and focus on the rising progress on NIR photothermal therapy for cancer and Alzheimer's disease (AD), human telomerase detection, stem cell proliferation and differentiation on graphene substrate, diagnosis of cancer cell and related biomarkers, drug/nucleotide/peptide delivery and cell imaging, which have not been comprehensively reviewed. We hope to provide an outlook to the applications of graphene and its oxide, especially on the new horizons in this field, and inspire broader interests across various disciplines.