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1.
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.  相似文献   

2.
The self‐assembly of human islet amyloid polypeptide (hIAPP) into β‐sheet‐rich nanofibrils is associated with the pathogeny of type 2 diabetes. Soluble hIAPP is intrinsically disordered with N‐terminal residues 8–17 as α‐helices. To understand the contribution of the N‐terminal helix to the aggregation of full‐length hIAPP, here the oligomerization dynamics of the hIAPP fragment 8–20 (hIAPP8‐20) are investigated with combined computational and experimental approaches. hIAPP8‐20 forms cross‐β nanofibrils in silico from isolated helical monomers via the helical oligomers and α‐helices to β‐sheets transition, as confirmed by transmission electron microscopy, atomic force microscopy, circular dichroism spectroscopy, Fourier transform infrared spectroscopy, and reversed‐phase high performance liquid chromatography. The computational results also suggest that the critical nucleus of aggregation corresponds to hexamers, consistent with a recent mass‐spectroscopy study of hIAPP8‐20 aggregation. hIAPP8‐20 oligomers smaller than hexamers are helical and unstable, while the α‐to‐β transition starts from the hexamers. Converted β‐sheet‐rich oligomers first form β‐barrel structures as intermediates before aggregating into cross‐β nanofibrils. This study uncovers a complete picture of hIAPP8‐20 peptide oligomerization, aggregation nucleation via conformational conversion, formation of β‐barrel intermediates, and assembly of cross‐β protofibrils, thereby shedding light on the aggregation of full‐length hIAPP, a hallmark of pancreatic beta‐cell degeneration.  相似文献   

3.
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.  相似文献   

4.
Amyloidogenic peptides can self‐assemble into highly ordered nanostructures consisting of cross β‐sheet‐rich networks that exhibit unique physicochemical properties and high stability. Light‐harvesting amyloid nanofibrils are constructed by employing insulin as a building block and thioflavin T (ThT) as a amyloid‐specific photosensitizer. The ability of the self‐assembled amyloid scaffold to accommodate and align ThT in high density on its surface allows for efficient energy transfer from the chromophores to the catalytic units in a similar way to natural photosystems. Insulin nanofibrils significantly enhance the photoactivity of ThT by inhibiting nonradiative conformational relaxation around the central C? C bonds and narrowing the distance between ThT molecules that are bound to the β‐sheet‐rich amyloid structure. It is demonstrated that the ThT‐amyloid hybrid nanostructure is suitable for biocatalytic solar‐to‐chemical conversion by integrating the light‐harvesting amyloid module (for nicotinamide cofactor regeneration) with a redox biocatalytic module (for enzymatic reduction).  相似文献   

5.
The unfolding, misfolding, and aggregation of proteins lead to a variety of structural species. One form is the amyloid fibril, a highly aligned, stable, nanofibrillar structure composed of β‐sheets running perpendicular to the fibril axis. β‐Lactoglobulin (β‐Lg) and κ‐casein (κ‐CN) are two milk proteins that not only individually form amyloid fibrillar aggregates, but can also coaggregate under environmental stress conditions such as elevated temperature. The aggregation between β‐Lg and κ‐CN is proposed to proceed via disulfide bond formation leading to amorphous aggregates, although the exact mechanism is not known. Herein, using a range of biophysical techniques, it is shown that β‐Lg and κ‐CN coaggregate to form morphologically distinct co‐amyloid fibrillar structures, a phenomenon previously limited to protein isoforms from different species or different peptide sequences from an individual protein. A new mechanism of aggregation is proposed whereby β‐Lg and κ‐CN not only form disulfide‐linked aggregates, but also amyloid fibrillar coaggregates. The coaggregation of two structurally unrelated proteins into cofibrils suggests that the mechanism can be a generic feature of protein aggregation as long as the prerequisites for sequence similarity are met.  相似文献   

6.
The inhibition of amyloid‐β (Aβ) aggregation by photo‐oxygenation has become an effective way of treating Alzheimer's disease (AD). New near‐infrared (NIR) activated treatment agents, which not only possess high photo‐oxygenation efficiency, but also show low biotoxicity, are urgently needed. Herein, for the first time, it is demonstrated that NIR activated black phosphorus (BP) could serve as an effective nontoxic photo‐oxidant for amyloid?β peptide in vitro and in vivo. The nanoplatform BP@BTA (BTA: one of thioflavin‐T derivatives) possesses high affinity to the Aβ peptide due to specific amyloid selectivity of BTA. Importantly, under NIR light, BP@BTA can significantly generate a high quantum yield of singlet oxygen (1O2) to oxygenate Aβ, thereby resulting in inhibiting the aggregation and attenuating Aβ‐induced cytotoxicity. In addition, BP could finally degrade into nontoxic phosphate, which guarantees the biosafety. Using transgenic Caenorhabditis elegans CL2006 as AD model, the results demonstrate that the 1O2‐generation system could dramatically promote life‐span extension of CL2006 strain by decreasing the neurotoxicity of Aβ.  相似文献   

7.
Peptide self‐assembly is an attractive route for the synthesis of intricate organic nanostructures that possess remarkable structural variety and biocompatibility. Recent studies on peptide‐based, self‐assembled materials have expanded beyond the construction of high‐order architectures; they are now reporting new functional materials that have application in the emerging fields such as artificial photosynthesis and rechargeable batteries. Nevertheless, there have been few reviews particularly concentrating on such versatile, emerging applications. Herein, recent advances in the synthesis of self‐assembled peptide nanomaterials (e.g., cross β‐sheet‐based amyloid nanostructures, peptide amphiphiles) are selectively reviewed and their new applications in diverse, interdisciplinary fields are described, ranging from optics and energy storage/conversion to healthcare. The applications of peptide‐based self‐assembled materials in unconventional fields are also highlighted, such as photoluminescent peptide nanostructures, artificial photosynthetic peptide nanomaterials, and lithium‐ion battery components. The relation of such functional materials to the rapidly progressing biomedical applications of peptide self‐assembly, which include biosensors/chips and regenerative medicine, are discussed. The combination of strategies shown in these applications would further promote the discovery of novel, functional, small materials.  相似文献   

8.
Senile plaques, the extracellular deposit of amyloid‐β (Aβ) peptides, are one of the neuropathological hallmarks found in Alzheimer's disease (AD) brain. The current method of brain imaging of amyloid plaques based on positron emission tomography (PET) is expensive and invasive with low spatial resolution. Thus, the development of sensitive and nonradiative amyloid‐β (Aβ)‐specific contrast agents is highly important and beneficial to achieve early AD detection, monitor the disease progression, and evaluate the effectiveness of potential AD drugs. Here a neuroprotective dual‐modal nanoprobe developed by integrating highly Aβ‐specific and turn‐on fluorescence cyanine sensors with superparamagnetic iron oxide nanoparticles as an effective near‐infrared imaging (NIRI)/magnetic resonance imaging (MRI) contrast agent for imaging of Aβ species in vivo is reported. This Aβ‐specific probe is found not only nontoxic and noninvasive, but also highly blood brain barrier permeable. It also shows a potent neuroprotective effect against Aβ‐induced toxicities. This nanoprobe is successfully applied for in vivo fluorescence imaging with high sensitivity and selectivity to Aβ species, and MRI with high spatial resolution in an APP/PS1 transgenic mice model. Its potential as a powerful in vivo dual‐modal imaging tool for early detection and diagnosis of AD in humans is affirmed.  相似文献   

9.
A self‐assembly approach for the design of multifunctional nanomaterials consisting of different nanoparticles (gold, iron oxide, and lanthanide‐doped LiYF4) is developed. This modular system takes advantage of the light‐responsive supramolecular host–guest chemistry of β‐cyclodextrin and arylazopyrazole, which enables the dynamic and reversible self‐assembly of particles to spherical nanoparticle aggregates in aqueous solution. Due to the magnetic iron oxide nanoparticles, the aggregates can be manipulated by an external magnetic field leading to the formation of linear structures. As a result of the integration of upconversion nanoparticles, the aggregates are additionally responsive to near‐infrared light and can be redispersed by use of the upconversion effect. By varying the nanoparticle and linker concentrations the composition, size, shape, and properties of the multifunctional nanoparticle aggregates can be fine‐tuned.  相似文献   

10.
Aggregation of amyloid‐β protein (Aβ) is a pathological hallmark of Alzheimer's disease (AD), so the inhibition of Aβ aggregation is an important strategy for the prevention and treatment of AD. Herein, we proposed to design molecular hybrids of peptide inhibitors by combining two peptide inhibitors, VVIA and LPFFD, into single sequences and examined their effects on Aβ42 aggregation and cytotoxicity. The hybrid peptides exhibit increased but moderate inhibitory activity as compared to their two precursors. By conjugating the peptides onto gold nanoparticles (AuNPs), however, the inhibition activity of the corresponding peptide@AuNPs against Aβ42 aggregation and cytotoxicity is greatly improved. Among them, VVIACLPFFD (VCD10)@AuNP is the most effective, which increases cell viability from 48% to 82% at a dosage as low as 0.1 nmol L?1 (NPs) or 40 nmol L?1 (peptide). The superior capacity of VCD10@AuNPs is considered due to its branched dual‐inhibitor sequence, and its special surface orientation and conformation. These structural features promote its synergetic interactions with Aβ on AuNP surface, leading to strong inhibitions of Aβ oligomerization and fibrillation and the cytotoxicity caused by the aggregation species. The findings suggest that potent inhibitors can be derived by hybridization of multiple peptide inhibitors with the hybrid products coupled onto nanoparticles.  相似文献   

11.
Nanomedicine is a rapidly growing field that has the potential to deliver treatments for many illnesses. However, relatively little is known about the biological risks of nanoparticles. Some studies have shown that nanoparticles can have an impact on the aggregation properties of proteins, including fibril formation. Moreover, these studies also show that the capacity of nanoscale objects to induce or prevent misfolding of the proteins strongly depends on the primary structure of the protein. Herein, light is shed on the role of the peptide primary structure in directing nanoparticle‐induced misfolding by means of two model peptides. The design of these peptides is based on the α‐helical coiled‐coil folding motif, but also includes features that enable them to respond to pH changes, thus allowing pH‐dependent β‐sheet formation. Previous studies showed that the two peptides differ in the pH range required for β‐sheet folding. Time‐dependent circular dichroism spectroscopy and transmission electron microscopy are used to characterize peptide folding and aggregate morphology in the presence of negatively charged gold nanoparticles (AuNPs). Both peptides are found to undergo nanoparticle‐induced fibril formation. The determination of binding parameters by isothermal titration calorimetry further reveals that the different propensities of both peptides to form amyloid‐like structures in the presence of AuNPs is primarily due to the binding stoichiometry to the AuNPs. Modification of one of the peptide sequences shows that AuNP‐induced β‐sheet formation is related to the structural propensity of the primary structure and is not a generic feature of peptide sequences with a sufficiently high binding stoichiometry to the nanoparticles.  相似文献   

12.
A nanolithographic approach based on hierarchical peptide self‐assembly is presented. An aromatic peptide of N‐(t‐Boc)‐terminated triphenylalanine is designed from a structural motif for the β‐amyloid associated with Alzheimer's disease. This peptide adopts a turnlike conformation with three phenyl rings oriented outward, which mediate intermolecular ππ stacking interactions and eventually facilitate highly crystalline bionanosphere assembly with both thermal and chemical stability. The self‐assembled bionanospheres spontaneously pack into a hexagonal monolayer at the evaporating solvent edge, constituting evaporation‐induced hierarchical self‐assembly. Metal nanoparticle arrays or embossed Si nanoposts could be successfully created from the hexagonal bionanosphere array masks in conjunction with a conventional metal‐evaporation or etching process. Our approach represents a bionanofabrication concept that biomolecular self‐assembly is hierarchically directed to establish a straightforward nanolithography compatible with conventional device‐fabrication processes.  相似文献   

13.
Accumulation of amyloid‐β (Aβ) peptides in the brain is regarded as a major contributor to the pathogenesis and progression of Alzheimer's disease (AD). However, development of clinically relevant techniques to reduce Aβ levels in AD patients is hindered by low efficiency and/or side effects. Here, an extracorporeal Aβ cleansing system, where multifunctional magnetite/ceria nanoparticle assemblies are used to remove Aβ peptides from flowing blood by specific capture and magnetic separation, is reported. The magnetite nanoparticles in the nanoassembly core enable the magnetic isolation of the captured Aβ peptides by generating a large attraction force under an external magnetic field. The ceria nanoparticles in the nanoassembly shell relieve oxidative stress by scavenging reactive oxygen species that are produced by immune response during the process. Blood Aβ cleansing treatment of 5XFAD transgenic mice not only demonstrates the decreased Aβ levels both in the blood and in the brain but also prevents the spatial working memory deficits, suggesting the potential of the method for AD prevention and therapy.  相似文献   

14.
The oligomerization and aggregation of amyloid β (Aβ) play central role in the pathogenesis of Alzheimer's disease (AD). Molecular binding agents for modulating the formation of Aβ oligomers and fibrils have promising application potential in AD therapies. By screening a peptoid library using surface plasmon resonance imaging, amyloid inhibitory peptoid 1 (AIP1) that has high affinity to Aβ42 is identified. AIP1 is demonstrated to inhibit Aβ42 oligomerization and fibrillation and to rescue Aβ42‐induced cytotoxicity through decreasing the content of Aβ42 oligomers that is related to cell membrane permeability. Molecular docking suggests that the binding sites of AIP1 may be at the N‐terminus of Aβ42. The blood‐brain barrier (BBB) permeability of AIP1 using an in vitro BBB model is also revealed. This work provides a strategy for the design and development of peptoid‐based antiamyloidogenic agents. The obtained amyloid inhibitory peptoid shows prospects in the therapeutic application in AD.  相似文献   

15.
The accumulation and formation of β‐amyloid (Aβ) plaques in the brain are distinctive pathological hallmarks of Alzheimer's disease (AD). Designing nanoparticle (NP) contrast agents capable of binding with Aβ highly selectively can potentially facilitate early detection of AD. However, a significant obstacle is the blood brain barrier (BBB), which can preclude the entrance of NPs into the brain for Aβ binding. In this work, bovine serum albumin (BSA) coated NPs are decorated with sialic acid (NP‐BSAx‐Sia) to overcome the challenges in Aβ imaging in vivo. The NP‐BSAx‐Sia is biocompatible with high magnetic relaxivities, suggesting that they are suitable contrast agents for magnetic resonance imaging (MRI). The NP‐BSAx‐Sia binds with Aβ in a sialic acid dependent manner with high selectivities toward Aβ deposited on brains and cross the BBB in an in vitro model. The abilities of these NPs to detect Aβ in vivo in human AD transgenic mice by MRI are evaluated without the need to coinject mannitol to increase BBB permeability. T2*‐weighted MRI shows that Aβ plaques in mouse brains can be detected as aided by NP‐BSAx‐Sia, which is confirmed by histological analysis. Thus, NP‐BSAx‐Sia is a promising new tool for noninvasive in vivo detection of Aβ plaques.  相似文献   

16.
Complex recombinant biomaterials that merge the self‐assembling properties of different (poly)peptides provide a powerful tool for the achievement of specific structures, such as hydrogel networks, by tuning the thermodynamics and kinetics of the system through a tailored molecular design. In this work, elastin‐like (EL) and silk‐like (SL) polypeptides are combined to obtain a silk‐elastin‐like recombinamer (SELR) with dual self‐assembly. First, EL domains force the molecule to undergo a phase transition above a precise temperature, which is driven by entropy and occurs very fast. Then, SL motifs interact through the slow formation of β‐sheets, stabilized by H‐bonds, creating an energy barrier that opposes phase separation. Both events lead to the development of a dynamic microstructure that evolves over time (until a pore size of 49.9 ± 12.7 µm) and to a delayed hydrogel formation (obtained after 2.6 h). Eventually, the network is arrested due to an increase in β‐sheet secondary structures (up to 71.8 ± 0.8%) within SL motifs. This gives a high bond strength that prevents the complete segregation of the SELR from water, which results in a fixed metastable microarchitecture. These porous hydrogels are preliminarily tested as biomimetic niches for the isolation of cells in 3D cultures.  相似文献   

17.
The pathological aggregation of some proteins is claimed to be highly related to several human diseases, such as β-amyloid 1–42 (Aβ42) to Alzheimer's disease (AD), islet amyloid polypeptide, and insulin to type 2 diabetes mellitus. Therefore, it is in desperate need to develop effective methods for detection of protein aggregates and inhibition of abnormal aggregation. Herein, to construct all-in-one probe with both diagnosis and treatment potentials for protein aggregation diseases, Congo red (CR), a classical staining reagent with red fluorescence signal output for protein aggregates, is deliberately adopted to react with three different reductive carbon sources and ammonium persulfate to generate three CR-derived carbon dots (CDs). The obtained CDs exhibit the capabilities of turn-on red fluorescence imaging of protein aggregates, and/or inhibition of protein aggregation as well as scavenging of free radicals. Among them, CA-CDs, using citric acid as the reductive carbon source, demonstrate the superiority to the other two studied CDs in integrating all of these functions, and particularly exert excellent cytoprotection effect against toxic Aβ42 species, possessing tremendous potential in diagnosis and treatment of AD for future study. The present study paves a new way to develop all-in-one CDs for the protein disease research.  相似文献   

18.
Peptides that self‐assemble into cross‐β‐sheet amyloid structures constitute promising building blocks to construct highly ordered proteinaceous materials and nanoparticles. Nevertheless, the intrinsic polymorphism of amyloids and the difficulty of controlling self‐assembly currently limit their usage. In this study, the effect of electrostatic interactions on the supramolecular organization of peptide assemblies is investigated to gain insights into the structural basis of the morphological diversities of amyloids. Different charged capping units are introduced at the N‐terminus of a potent β‐sheet‐forming sequence derived from the 20–29 segment of islet amyloid polypeptide, known to self‐assemble into polymorphic fibrils. By tuning the charge and the electrostatic strength, different mesoscopic morphologies are obtained, including nanorods, rope‐like fibrils, and twisted ribbons. Particularly, the addition of positive capping units leads to the formation of uniform rod‐like assemblies, with lengths that can be modulated by the charge number. It is proposed that electrostatic repulsions between N‐terminal positive charges hinder β‐sheet tape twisting, leading to a unique control over the size of these cytocompatible nanorods by protofilament growth frustration. This study reveals the high susceptibility of amyloid formation to subtle chemical modifications and opens to promising strategies to control the final architecture of proteinaceous assemblies from the peptide sequence.  相似文献   

19.
One of the fundamental challenges encountered in successful incorporation of directed self‐assembly in sub‐10 nm scale practical nanolithography is the process compatibility of block copolymers with a high Flory–Huggins interaction parameter (χ). Herein, reliable, fab‐compatible, and ultrafast directed self‐assembly of high‐χ block copolymers is achieved with intense flash light. The instantaneous heating/quenching process over an extremely high temperature (over 600 °C) by flash light irradiation enables large grain growth of sub‐10 nm scale self‐assembled nanopatterns without thermal degradation or dewetting in a millisecond time scale. A rapid self‐assembly mechanism for a highly ordered morphology is identified based on the kinetics and thermodynamics of the block copolymers with strong segregation. Furthermore, this novel self‐assembly mechanism is combined with graphoepitaxy to demonstrate the feasibility of ultrafast directed self‐assembly of sub‐10 nm nanopatterns over a large area. A chemically modified graphene film is used as a flexible and conformal light‐absorbing layer. Subsequently, transparent and mechanically flexible nanolithography with a millisecond photothermal process is achieved leading the way for roll‐to‐roll processability.  相似文献   

20.
Human islet amyloid polypeptide (hIAPP, or amylin) forms amyloid deposits in the islets of Langerhans, a phenomenon that is associated with type‐2 diabetes impacting millions of people worldwide. Accordingly, strategies against hIAPP aggregation are essential for the prevention and eventual treatment of the disease. Here, it is shown that generation‐3 OH‐terminated poly(amidoamine) dendrimer, a polymeric nanoparticle, can effectively halt the aggregation of hIAPP and shut down hIAPP toxicity in pancreatic MIN6 and NIT‐1 cells as well as in mouse islets. This finding is supported by high‐throughput dynamic light scattering experiment and thioflavin T assay, where the rapid evolution of hIAPP nucleation and elongation processes is halted by the addition of the dendrimer up to 8 h. Discrete molecular dynamics simulations further reveal that hIAPP residues bound strongly with the dendrimer near the c‐terminal portion of the peptide, where the amyloidogenic sequence (residues 22–29) locates. Furthermore, simulations of hIAPP dimerization reveal that binding with the dendrimer significantly reduces formation of interpeptide contacts and hydrogen bonds, thereby prohibiting peptide self‐association and amyloidosis. This study points to a promising nanomedicinal strategy for combating type‐2 diabetes and may have broader implications for targeting neurological disorders whose distinct hallmark is also amyloid fibrillation.  相似文献   

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