Fibrillar Morphology Research Articles

Aqueous-Based Polyimine Functionalization of Cellulose Nanofibrils for Effective Drying and Polymer Composite Reinforcement

A simple strategy was developed to synthesize polyimine-coated cellulose nanofibrils (CNF) for effective CNF drying and composite reinforcement. The polyimine was synthesized in an aqueous medium using a selective hydrophilic and hydrophobic component that forces the polyimine to precipitate, which prevents the reverse imine reaction. The polyimine coating allowed the CNF to be easily oven-dried while maintaining a fibrillar morphology to provide mechanical reinforcement in poly(ethylene terephthalate glycol) (PETG) composites. In comparison, poor mechanical performance and a heterogeneous fracture surface were observed when the coated CNF were incorporated into poly(l-lactide) (PLA) composites. It is hypothesized that intermolecular aromatic–aromatic interactions are formed at the interface between fibers and the polymer matrix in the PETG system, while no such phenomena occur in the PLA system. Overall, this facile strategy to produce modified, easily dried CNF can be adapted to produce polyimine-coated CNF with unique functionalities that are useful in a range of applications.

High-performance organic photodetectors enabled by a refined fibrillar multiphase morphology

Film morphology of donor:acceptor blend layers plays a critical role in photon-to-current efficiency and dark/noise current of organic photodetectors (OPDs). One effective approach to manipulate crystallization and mesoscale phase separation of such blend layers is sequential casting (SC). However, the guiding strategies to control the morphology and the impacts on OPD performance of the SC films remain elusive, as the film structural evolution during SC is different from conventional blend casting (BC). Here, a refined fibrillar multiphase morphology is demonstrated by SC in an NT812:IEICO-4F blend film, where the high-quality IEICO-4F crystallites infiltrate the robust NT812 fibril network from the surface to the bulk. Such a morphology leads to improved charge generation and collection, reduced trap states, and enhanced charge block capability of resultant device, enabling simultaneous achievement of high external quantum efficiency and low dark/noise current. A maximum special detectivity of 5 × 1013 Jones is achieved at 860 nm under –0.1 V, which is among the highest detectivities for vis-to-NIR OPDs. The linear dynamic range and response speed are also improved. Such enhancements are parallelly observed from OPD devices based on other blend systems with similar fibrillar refinement, which provides guidelines for film structure manipulation towards high OPD performance.

Central Unit Fluorination of Non-Fullerene Acceptors Enables Highly Efficient Organic Solar Cells with Over 18 % Efficiency.

Halogenation of terminal of acceptors has been shown to give dramatic improvements in power conversion efficiencies (PCEs) of organic solar cells (OSCs). Similar significant results could be expected from the halogenation of the central units of state-of-the-art Y-series acceptors. Herein, a pair of acceptors, termed CH6 and CH4, featuring a conjugation-extended phenazine central unit with and without fluorination, have been synthesized. The fluorinated CH6 has enhanced molecular interactions and crystallinity, superior fibrillar network morphology and improved charge generation and transport in blend films, thus affording a higher PCE of 18.33 % for CH6-based binary OSCs compared to 16.49 % for the non-fluorinated CH4. The new central site offers further opportunities for structural optimization of Y-series molecules to afford better-performed OSCs and reveals the effectiveness of fluorination on central units.

Central Unit Fluorination of Non‐Fullerene Acceptors Enables Highly Efficient Organic Solar Cells with Over 18 % Efficiency

AbstractHalogenation of terminal of acceptors has been shown to give dramatic improvements in power conversion efficiencies (PCEs) of organic solar cells (OSCs). Similar significant results could be expected from the halogenation of the central units of state‐of‐the‐art Y‐series acceptors. Herein, a pair of acceptors, termed CH6 and CH4, featuring a conjugation‐extended phenazine central unit with and without fluorination, have been synthesized. The fluorinated CH6 has enhanced molecular interactions and crystallinity, superior fibrillar network morphology and improved charge generation and transport in blend films, thus affording a higher PCE of 18.33 % for CH6‐based binary OSCs compared to 16.49 % for the non‐fluorinated CH4. The new central site offers further opportunities for structural optimization of Y‐series molecules to afford better‐performed OSCs and reveals the effectiveness of fluorination on central units.

The oil absorption capacity of polypropylene porous absorbents fabricated through iPP/EVA in situ microfibrillar composites: effect of fibrillar morphology

The oil absorption capacity of polypropylene porous absorbents fabricated through iPP/EVA in situ microfibrillar composites: effect of fibrillar morphology

Three-dimensional tailor-made collagen-like proteins hydrogel for tissue engineering applications.

Despite the potential tunable properties of blank slate collagen-like proteins (CLP), an alternative to animal-originated collagen, assembling them into a stable 3D hydrogel to mimic extracellular matrix is a challenge. To address this constraint, the CLP (without hydroxyproline, CLPpro) and its variants encoding functional unnatural amino acids such as hydroxyproline (CLPhyp) and 3,4-dihydroxyphenylalanine (CLPdopa) were generated through genetic code engineering for 3D hydrogel development. The CLPhyp and CLPdopa were chosen to enhance the intermolecular hydrogen bond interaction through additional hydroxyl moiety and thereby facilitate the self-assembly into a fibrillar network of the hydrogel. Hydrogelation was induced through genipin as a cross-linker, enabling intermolecular cross-linking to form a hydrogel. Spectroscopic and rheological analyses confirmed that CLPpro and its variants maintained native triple-helical structure, which is necessary for its function, and viscoelastic nature of the hydrogels, respectively. Unlike CLPpro, the varients (CLPhyp and CLPdopa) increased pore size formation in the hydrogel scaffold, facilitating 3T3 fibroblast cell interactions. DSC analysis indicated that the stability of the hydrogels got increased upon the genetic incorporation of hydroxyproline (CLPhyp) and dopa (CLPdopa) in CLPpro. In addition, CLPdopa hydrogel was found to be relatively stable against collagenase enzyme compared to CLPpro and CLPhyp. It is the first report on 3D biocompatible hydrogel preparation by tailoring CLP sequence with non-natural amino acids. These next-generation tunable CLP hydrogels open a new venue to design synthetic protein-based biocompatible 3D biomaterials for tissue engineering applications.

Amyloidogenesis of SARS-CoV-2 Spike Protein.

SARS-CoV-2 infection is associated with a surprising number of morbidities. Uncanny similarities with amyloid-disease associated blood coagulation and fibrinolytic disturbances together with neurologic and cardiac problems led us to investigate the amyloidogenicity of the SARS-CoV-2 spike protein (S-protein). Amyloid fibril assays of peptide library mixtures and theoretical predictions identified seven amyloidogenic sequences within the S-protein. All seven peptides in isolation formed aggregates during incubation at 37 °C. Three 20-amino acid long synthetic spike peptides (sequence 192–211, 601–620, 1166–1185) fulfilled three amyloid fibril criteria: nucleation dependent polymerization kinetics by ThT, Congo red positivity, and ultrastructural fibrillar morphology. Full-length folded S-protein did not form amyloid fibrils, but amyloid-like fibrils with evident branching were formed during 24 h of S-protein coincubation with the protease neutrophil elastase (NE) in vitro. NE efficiently cleaved S-protein, rendering exposure of amyloidogenic segments and accumulation of the amyloidogenic peptide 194–203, part of the most amyloidogenic synthetic spike peptide. NE is overexpressed at inflamed sites of viral infection. Our data propose a molecular mechanism for potential amyloidogenesis of SARS-CoV-2 S-protein in humans facilitated by endoproteolysis. The prospective of S-protein amyloidogenesis in COVID-19 disease associated pathogenesis can be important in understanding the disease and long COVID-19.

Proteins Do Not Replicate, They Precipitate: Phase Transition and Loss of Function Toxicity in Amyloid Pathologies.

Simple SummaryAmyloid aggregation of proteins in disease has been known for over a hundred years; however, effective therapeutics for amyloid pathologies such as Alzheimer’s disease and Parkinson’s disease are still lacking. This review divides the amyloid phenomenon into four major questions: What are amyloids? How do amyloids form? Can proteins replicate? How do amyloids cause toxicity? The aim is to answer these questions within a unified physicochemical framework that links the structural biology of amyloids to the thermodynamics of amyloid formation and the pathophysiology of amyloid aggregates in different diseases. We illustrate that the thermodynamics of protein aggregation does not support the prion protein-only replication hypothesis, and how the structural biology of amyloids makes them largely domainless, generic, and inert. The implications of this understanding for the etiology, pathogenesis and potential therapeutics of amyloid diseases are briefly discussed.Protein aggregation into amyloid fibrils affects many proteins in a variety of diseases, including neurodegenerative disorders, diabetes, and cancer. Physicochemically, amyloid formation is a phase transition process, where soluble proteins are transformed into solid fibrils with the characteristic cross-β conformation responsible for their fibrillar morphology. This phase transition proceeds via an initial, rate-limiting nucleation step followed by rapid growth. Several well-defined nucleation pathways exist, including homogenous nucleation (HON), which proceeds spontaneously; heterogeneous nucleation (HEN), which is catalyzed by surfaces; and seeding via preformed nuclei. It has been hypothesized that amyloid aggregation represents a protein-only (nucleic-acid free) replication mechanism that involves transmission of structural information via conformational templating (the prion hypothesis). While the prion hypothesis still lacks mechanistic support, it is also incompatible with the fact that proteins can be induced to form amyloids in the absence of a proteinaceous species acting as a conformational template as in the case of HEN, which can be induced by lipid membranes (including viral envelopes) or polysaccharides. Additionally, while amyloids can be formed from any protein sequence and via different nucleation pathways, they invariably adopt the universal cross-β conformation; suggesting that such conformational change is a spontaneous folding event that is thermodynamically favorable under the conditions of supersaturation and phase transition and not a templated replication process. Finally, as the high stability of amyloids renders them relatively inert, toxicity in some amyloid pathologies might be more dependent on the loss of function from protein sequestration in the amyloid state rather than direct toxicity from the amyloid plaques themselves.

Disaggregation of Islet Amyloid Polypeptide Fibrils as a Potential Anti-Fibrillation Mechanism of Tetrapeptide TNGQ.

Islet amyloid polypeptide (IAPP) fibrillation has been commonly associated with the exacerbation of type 2 diabetes prognosis. Consequently, inhibition of IAPP fibrillation to minimize β-cell cytotoxicity is an important approach towards β-cell preservation and type 2 diabetes management. In this study, we identified three tetrapeptides, TNGQ, MANT, and YMSV, that inhibited IAPP fibrillation. Using thioflavin T (ThT) fluorescence assay, circular dichroism (CD) spectroscopy, dynamic light scattering (DLS), and molecular docking, we evaluated the potential anti-fibrillation mechanism of the tetrapeptides. ThT fluorescence kinetics and microscopy as well as transmission electron microscopy showed that TNGQ was the most effective inhibitor based on the absence of normal IAPP fibrillar morphology. CD spectroscopy showed that TNGQ maintained the α-helical conformation of monomeric IAPP, while DLS confirmed the presence of varying fibrillation species. Molecular docking showed that TNGQ and MANT interact with monomeric IAPP mainly by hydrogen bonding and electrostatic interaction, with TNGQ binding at IAPP surface compared to YMSV, which had the highest docking score, but interact mainly through hydrophobic interaction in IAPP core. The highly polar TNGQ was the most active and appeared to inhibit IAPP fibrillation by disaggregation of preformed IAPP fibrils. These findings indicate the potential of TNGQ in the development of peptide-based anti-fibrillation and antidiabetic nutraceuticals.

Structure modeling and quantitative X-ray diffraction of C-(A)-S-H.

Quantitative X-ray diffraction of nanocrystalline calcium silicate hydrate (C-S-H) and its aluminium-substituted variants (C-A-S-H) has so far been limited by a lack of appropriate structure models. In this study, atomistic structure models derived from tobermorite were combined with a supercell approach using TOPAS. By accounting for nanostructural features such as isolated layers, turbostratic disorder and, for the first time, fibrils, characteristic reflections and asymmetric bands were more accurately simulated than before, providing the means for phase quantification and refinement of structural sites. This improved methodology is applied to autoclaved aerated concrete and the experimental study of related hydrothermal reactions. Scanning electron microscopy indicated a fibrillar morphology for intermediate C-(A)-S-H, and energy-dispersive X-ray spectroscopy constrained its Ca/Si ratio to 1.31-1.35. As a first step, the direct quantification of C-(A)-S-H via structure models was assessed by a series of X-ray diffraction measurements using corundum as an internal standard. Secondly, the verified structure model was applied to evaluate in situ X-ray diffraction experiments at 457, 466 and 473 K (1.1, 1.35 and 1.55 MPa, respectively). Finally, a quantitative study of industrially produced autoclaved aerated concrete was conducted, determining 20-30 wt% C-(A)-S-H at Ca/Si ratios < 1.0. In general, the developed structure models advance the study of Portland cement concrete and related materials, including autoclaved aerated concrete, and the supercell approach may be universally applicable to other nanocrystalline materials.

Cancer cell migration on straight, wavy, loop and grid microfibre patterns

Cell migration plays an important role in physiological and pathological processes where the fibrillar morphology of extracellular matrices (ECM) could regulate the migration dynamics. To mimic the morphological characteristics of fibrillar matrix structures, low-voltage continuous electrospinning was adapted to construct straight, wavy, looped and gridded fibre patterns made of polystyrene (of fibre diameter ca. 3 μm). Cells were free to explore their different shapes in response to the directly-adhered fibre, as well as to the neighbouring patterns. For all the patterns studied, analysing cellular migration dynamics of MDA-MB-231 (a highly migratory breast cancer cell line) demonstrated two interesting findings: first, although cells dynamically adjust their shapes and migration trajectories in response to different fibrillar environments, their average step speed is minimally affected by the fibre global pattern; secondly, a switch in behaviour was observed when the pattern features approach the upper limit of the cell body’s minor axis, reflecting that cells’ ability to divert from an existing fibre track is limited by the size along the cell body’s minor axis. It is therefore concluded that the upper limit of cell body’s minor axis might act as a guide for the design of microfibre patterns for different purposes of cell migration.

High-Performance Organic Photodetectors Enabled by a Refined Fibrillar Multiphase Morphology

High-Performance Organic Photodetectors Enabled by a Refined Fibrillar Multiphase Morphology

Estimating the Dimensions of Nanocrystalline Elements of the Polyethylene Structure by Differential Scanning Calorimetry

A method is proposed for calculating the dimension distribution of nanocrystalline elements of the lamellar and fibrillar morphologies of a polymer. Calorimetric data were used to calculate the distribution of the longitudinal size of these elements in lamellae and microfibrils of ultrahigh molecular weight polyethylene. The calculation results are consistent with the data obtained by the X-ray method.. Keywords: heat capacity, dimension effect, lamella, microfibril, polyethylene.

Оценка размеров нанокристаллических элементов структуры полиэтилена методом дифференциальной сканирующей калориметрии

A method is proposed for calculating the dimension distribution of nanocrystalline elements of the lamellar and fibrillar morphologies of a polymer. Calorimetric data were used to calculate the distribution of the longitudinal size of these elements in lamellae and microfibrils of ultrahigh molecular weight polyethylene. The calculation results are consistent with the data obtained by the X-ray method. V. M. Egorov1, A. K. Borisov1, V. A. Marikhin1, L. P. Myasnikova1, S. A. Gureva1, E. M. Ivan’kova2 1 Ioffe Institute, 26 Polytechnicheskaya, St. Petersburg 194021, Russia 2 Institute of Macromolecular Compounds, 31 Bolshoy pr., St. Petersburg 199004, Russia

Morphology, Rheological and Mechanical Properties of Isotropic and Anisotropic PP/rPET/GnP Nanocomposite Samples.

The effect of graphene nanoplatelets (GnPs) on the morphology, rheological, and mechanical properties of isotropic and anisotropic polypropylene (PP)/recycled polyethylene terephthalate (rPET)-based nanocomposite are reported. All the samples were prepared by melt mixing. PP/rPET and PP/rPET/GnP isotropic sheets were prepared by compression molding, whereas the anisotropic fibers were spun using a drawing module of a capillary viscometer. The results obtained showed that the viscosity of the blend is reduced by the presence of GnP due to the lubricating effect of the graphene platelets. However, the Cox–Merz rule is not respected. Compared to the PP/rPET blend, the GnP led to a slight increase in the elastic modulus. However, it causes a slight decrease in elongation at break. Morphological analysis revealed a poor adhesion between the PP and PET phases. Moreover, GnPs distribute around the droplets of the PET phase with a honey-like appearance. Finally, the effect of the orientation on both systems gives rise not only to fibers with higher modulus values, but also with high deformability and a fibrillar morphology of the dispersed PET phase. A fragile-ductile transition driven by the orientation was observed in both systems.

β-Barrels and Amyloids: Structural Transitions, Biological Functions, and Pathogenesis.

Insoluble protein aggregates with fibrillar morphology called amyloids and β-barrel proteins both share a β-sheet-rich structure. Correctly folded β-barrel proteins can not only function in monomeric (dimeric) form, but also tend to interact with one another—followed, in several cases, by formation of higher order oligomers or even aggregates. In recent years, findings proving that β-barrel proteins can adopt cross-β amyloid folds have emerged. Different β-barrel proteins were shown to form amyloid fibrils in vitro. The formation of functional amyloids in vivo by β-barrel proteins for which the amyloid state is native was also discovered. In particular, several prokaryotic and eukaryotic proteins with β-barrel domains were demonstrated to form amyloids in vivo, where they participate in interspecies interactions and nutrient storage, respectively. According to recent observations, despite the variety of primary structures of amyloid-forming proteins, most of them can adopt a conformational state with the β-barrel topology. This state can be intermediate on the pathway of fibrillogenesis (“on-pathway state”), or can be formed as a result of an alternative assembly of partially unfolded monomers (“off-pathway state”). The β-barrel oligomers formed by amyloid proteins possess toxicity, and are likely to be involved in the development of amyloidoses, thus representing promising targets for potential therapy of these incurable diseases. Considering rapidly growing discoveries of the amyloid-forming β-barrels, we may suggest that their real number and diversity of functions are significantly higher than identified to date, and represent only “the tip of the iceberg”. Here, we summarize the data on the amyloid-forming β-barrel proteins, their physicochemical properties, and their biological functions, and discuss probable means and consequences of the amyloidogenesis of these proteins, along with structural relationships between these two widespread types of β-folds.

Bioscaffold Stiffness Mediates Aerosolized Nanoparticle Uptake in Lung Epithelial Cells.

In this study, highly porous, ultrasoft polymeric mats mimicking human tissues were formed from novel polyurethane soft dendritic colloids (PU SDCs). PU SDCs have a unique fibrillar morphology controlled by antisolvent precipitation. When filtered from suspension, PU SDCs form mechanically robust nonwoven mats. The stiffness of the SDC mats can be tuned for physiological relevance. The unique physiochemical characteristics of the PU SDC particles dictate the mechanical properties resulting in tunable elastic moduli ranging from 200 to 800 kPa. The human lung A549 cells cultured on both stiff and soft PU SDC membranes were found to be viable, capable of supporting the air-liquid interface (ALI) cell culture, and maintained barrier integrity. Furthermore, A549 cellular viability and uptake efficiency of aerosolized tannic acid-coated gold nanoparticles (Ta-Au) was found to depend on elastic modulus and culture conditions. Ta-Au nanoparticle uptake was twofold and fourfold greater on soft PU SDCs, when cultured at submerged and ALI conditions, respectively. The significant increase in endocytosed Ta-Au resulted in a 20% decrease in viability, and a 4-fold increase in IL-8 cytokine secretion when cultured on soft PU SDCs at ALI. Common tissue culture materials exhibit super-physiological elastic moduli, a factor found to be critical in analyzing nanomaterial cellular interactions and biological responses.

Amyloids as Building Blocks for Macroscopic Functional Materials: Designs, Applications and Challenges.

Amyloids are self-assembled protein aggregates that take cross-β fibrillar morphology. Although some amyloid proteins are best known for their association with Alzheimer’s and Parkinson’s disease, many other amyloids are found across diverse organisms, from bacteria to humans, and they play vital functional roles. The rigidity, chemical stability, high aspect ratio, and sequence programmability of amyloid fibrils have made them attractive candidates for functional materials with applications in environmental sciences, material engineering, and translational medicines. This review focuses on recent advances in fabricating various types of macroscopic functional amyloid materials. We discuss different design strategies for the fabrication of amyloid hydrogels, high-strength materials, composite materials, responsive materials, extracellular matrix mimics, conductive materials, and catalytic materials.

Systematic Investigation of Solution-State Aggregation Effect on Electrical Conductivity in Doped Conjugated Polymers

Systematic Investigation of Solution-State Aggregation Effect on Electrical Conductivity in Doped Conjugated Polymers

Fluorination of the π-bridge in a polymer skeleton enables a significant improvement in photovoltaic performance

An easy and efficient approach for the synthesis of an important photoelectric intermediate 3-fluoro-2-iodithiophene is developed. Therefrom, a polymer J52FF, featuring fluorination of the π-bridges on the backbone and side chains of the classical polymer, J52, is synthesized. J52FF displays a coplanar molecular configuration with the dihedral angles smaller than 2° in skeleton, a low-lying HOMO energy level of −5.62 eV, which is nearly aligned with the acceptor IT-4F, and a broad absorption range from 300 nm to 650 nm. The J52FF:IT-4F (1:0.8) blend shows a strong and complementary spectral absorption, a uniform fibrillar textured morphology and high and balanced charge mobilities. The inverted device based on J52FF:IT-4F blend obtained an encouraging power conversion efficiency (PCE) of 14.83% with the open-circuit voltage (Voc) of 0.90 V, the short circuit current (Jsc) of 23.21 mA cm−2, and the fill factor (FF) of 0.71 under the optimal conditions, which is one of the best PCE value among the ever reported BDT-alt-BTz derivatives or IT-4F based non-fullerene organic solar cells (NF–OSCs). It demonstrates that fluorination of polymer in skeleton is an efficient strategy for obtaining high performance.