Short Fibrils Research Articles

Plasma-assisted fibrillation and surface-modification of microfibrillar cellulose

The combination of microcrystalline cellulose (MCC) with maleic anhydride (MA) allowed for in-situ fibrillation and surface modification during pulsed plasma polymerization. Under optimized plasma parameters, the microfibrillated cellulose (MFC) morphology could be tuned according to the positioning in the reactor from small and short fibrils towards more elongated and crystallite structures in relation to the complex interactions between activated species. The chemical surface esterification was verified and resulted in good dispersion and higher water contact angle of the fibrils. The proposed route is an attractive ‘green’ and low-energy alternative for traditional mechanical processing and modification of nanocelluloses.

Glycosylation of a Nonfibrillizing Appendage Alters the Self-Assembly Pathway of a Synthetic β-Sheet Fibrillizing Peptide.

Owing to their biocompatibility and biodegradability, short synthetic peptides that self-assemble into elongated β-sheet fibers (i.e., peptide nanofibers) are widely used to create biomaterials for diverse medical and biotechnology applications. Glycosylation, which is a common protein post-translational modification, is gaining interest for creating peptide nanofibers that can mimic the function of natural carbohydrate-modified proteins. Recent reports have shown that glycosylation can disrupt the fibrillization of natural amyloid-forming peptides. Here, using transmission electron microscopy, fluorescence microscopy, and thioflavin T spectroscopy, we show that glycosylation at a site external to the fibrillization domain can alter the self-assembly pathway of a synthetic fibrillizing peptide, NSGSGQQKFQFQFEQQ (NQ11). Specifically, an NQ11 variant modified with N-linked N-acetylglucosamine, N(GlcNAc)SGSG-Q11 (GQ11), formed β-sheet nanofibers more slowly than NQ11 in deionized water (pH 5.8), which correlated to the tendency of GQ11 to form a combination of short fibrils and nonfibrillar aggregates, whereas NQ11 formed extended nanofibers. Acidic phosphate buffer slowed the rate of GQ11 fibrillization and altered the morphology of the structures formed yet had no effect on NQ11 fibrillization rate or morphology. The buffer ionic strength had no effect on the fibrillization rate of either peptide, while the diphosphate anion had a similar effect on the rate of fibrillization of both peptides. Collectively, these data demonstrate that a glycan moiety located external to the β-sheet fibrillizing domain can alter the pH-dependent self-assembly pathway of a synthetic peptide, leading to significant changes in the fibril mass and morphology of the structures formed. These observations add to the understanding of the effect of glycosylation on peptide self-assembly and should guide future efforts to develop biomaterials from synthetic β-sheet fibrillizing glycopeptides.

Ex-post correction of pacemaker mode switch episodes in undersensed atrial fibrillation

BackgroundInformation about short Atrial Fibrillation (AF) episodes can be gathered from the diagnostic records of cardiac implantable electronic devices (CIEDs). CIEDs are not accurate when detecting short arrhythmia episodes. The correlation between mode switching events and AF episodes is significant for long events but prone to errors for short episodes. MethodsExpectation-maximization algorithms are used to estimate the parameters of a mathematical model from a list of AF episodes produced by the CIED. The durations of some of the episodes may be missing. Abnormal mode changes are detected and short episodes are joined into longer events when appropriate. The proposed method does not require that the sensitivity parameters of the device are altered. Post-processing of the data is limited to the detection of false negatives, thus paroxysmal arrhythmia diagnostic evaluations are safer. ResultsA three year-long study was carried out with patients with dual-chamber pacemakers (PM) at the Hospital Universitario Central de Asturias (Spain) between 2012 and 2015. The number of patients in which the proposed algorithm altered the final histogram was 40 out of 76. On average, the algorithm removes 2.79% of episodes shorter than 1 min in length and finds that 1% of the previously unaccounted episodes are longer than 30 min, of which 16% are longer than 24 h. ConclusionThe method is stable and guarantees that long arrhythmia episodes are never eliminated, and at the same time it is the most similar to the human expert in finding new long episodes.

Amyloid-β-Derived Peptidomimetics Inhibits Tau Aggregation.

The aggregation of tau protein is one of the hallmarks for Alzheimer’s disease, resulting in neurodegeneration. The peptidomimetics strategy to prevent tau aggregation is more specific over other small molecules. In the present study, we analyzed the effect of amyloid-β-derived peptidomimetics for inhibiting heparin-induced tau aggregation in vitro. These peptides and their derivatives were known to prevent aggregation of amyloid-β. KLVFF is a hydrophobic sequence of the pentapeptide that prevented tau aggregation as observed by thioflavin S fluorescence, transmission electron microscopy, and circular dichroism spectroscopy. P4 and P5 also prevented assembly of tau into aggregates and formed short fibrils. The β-sheet breaker LPFFD was however ineffective in preventing tau aggregation. The peptides further demonstrated reversal of tau-induced cytotoxicity in a dose-dependent manner. Our results suggested that these peptides can also be used to inhibit tau aggregation and also, toxicity induced by tau could be considered as potential molecules that have an effect on tau as well as amyloid-β.

The release of toxic oligomers from \u03b1-synuclein fibrils induces dysfunction in neuronal cells

The self-assembly of α-synuclein (αS) into intraneuronal inclusion bodies is a key characteristic of Parkinson’s disease. To define the nature of the species giving rise to neuronal damage, we have investigated the mechanism of action of the main αS populations that have been observed to form progressively during fibril growth. The αS fibrils release soluble prefibrillar oligomeric species with cross-β structure and solvent-exposed hydrophobic clusters. αS prefibrillar oligomers are efficient in crossing and permeabilize neuronal membranes, causing cellular insults. Short fibrils are more neurotoxic than long fibrils due to the higher proportion of fibrillar ends, resulting in a rapid release of oligomers. The kinetics of released αS oligomers match the observed kinetics of toxicity in cellular systems. In addition to previous evidence that αS fibrils can spread in different brain areas, our in vitro results reveal that αS fibrils can also release oligomeric species responsible for an immediate dysfunction of the neurons in the vicinity of these species.

Low Embolic Risk from Short Duration Atrial Fibrillation following Anatomic Lung Resection

Objectives
 There is no consensus regarding the merits of anticoagulation following short duration atrial arrhythmia and anatomic lung resection. We hypothesized that the risk of embolic event following episodes of atrial fibrillation (AF) lasting less than 48 hours is low and even with an elevated CHA2DS2-VASC score should not incur the risk of long-term full dose anticoagulation contrary to recommendations.
 Design & Intervention
 A retrospective review was performed of a prospectively maintained database of all patients undergoing anatomic lung resection at a single institution from 2014 to 2019. Patients who had new onset post-operative atrial fibrillation (POAF) were queried as to their co-morbidities, the length of arrhythmia, discharge with anticoagulation, and any post-operative embolic events.
 Main Outcome Measures
 There were 565 patients who underwent anatomic lung resection. 40 patients (7.1%) developed new POAF that lasted a median of one day. In 32 patients (80%), POAF lasted for less than 48 hours. There were 28 males and 12 females, median age of 73 years. These patients underwent segmentectomy (2/40), lobectomy (24/40) and pneumonectomy (14/40). Twenty-nine patients were discharged home without anticoagulation. Median follow-up was 22 month (range 1.3 – 62.8 month). Two patients had embolic events and these two were discharged home without anticoagulation. The overall incidence rate of thromboembolic events was 3.2% per person year.
 Conclusions
 Our data suggest that the risk of arterial embolic events is low in patients with new, short duration atrial fibrillation post anatomical lung resection. Anticoagulation may not be necessary in these patients and can be given selectively.

Effect of packing density of lipid vesicles on the Aβ42 fibril polymorphism

The aggregation of amyloid-β 1–42 (Aβ42) on lipid membranes is closely related to the pathology of Alzheimer’s disease (AD). Herein, we demonstrated the effect of the packing density of lipid vesicles on the Aβ42 fibrillation kinetics and fibril morphology. We used three distinct phosphatidylcholine (PC) lipids, containing different numbers of cis-double bonds in acyl chains, and therefore, a different packing density in the lipid vesicles. Our results showed that the fibrillation of Aβ42 was greatly enhanced and the formed fibrils became shorter as the number of double bonds in lipids increased. Due to the low-density characteristics of dioleoyl phosphatidylcholine (DOPC), Aβ42 monomers were able to interact with the hydrophobic acyl chain of lipids exposed to the aqueous phase, thereby inducing rapid fibrillation and short fibril morphologies. Furthermore, the effects of the anionic lipids dioleoyl phosphatidylserine (DOPS) and dioleoyl phosphatidylglycerol (DOPG), and mixed vesicles of DOPC/DOPS and DOPC/DOPG on Aβ42 fibrillations were investigated. The tight binding of Aβ42 to the lipid head groups via electrostatic interactions was able to suppress the modulation of Aβ42 fibrillations compared to accelerated fibrillations on loosely packed membranes. Our proposed mechanism regarding the influence of lipid packing density on Aβ42 fibrillations provides an advanced understanding of lipid-associated amyloid fibrillations.

Umbral chromospheric fine structure and umbral flashes modelled as one: The corrugated umbra

Context.The chromosphere of the umbra of sunspots features an assortment of dynamic fine structures that are poorly understood and often studied separately. Small-scale umbral brightenings (SSUBs), umbral microjets, spikes or short dynamic fibrils (SDFs), and umbral dark fibrils are found in any observation of the chromosphere with sufficient spatial resolution performed at the correct umbral flash stage and passband. Understanding these features means understanding the dynamics of the umbral chromosphere.Aims.We aim to fully understand the dynamics of umbral chromosphere through analysis of the relationships between distinct observed fine features and to produce complete models that explain both spectral profiles and the temporal evolution of the features. We seek to relate such understanding to umbral flashes.Methods.We studied the spatial and spectral co-evolution of SDFs, SSUBs, and umbral flashes in Ca II8542 Å spectral profiles. We produced models that generate the spectral profiles for all classes of features using non-local thermodynamic equilibrium radiative transfer with a recent version of the NICOLE inversion code.Results.We find that both bright SSUBs and dark SDF structures are described with a continuous feature in the parameter space that is distinct from the surroundings even in pixel-by-pixel inversions. We find a phase difference between such features and umbral flashes in both inverted line-of-sight velocities and timing of the brightenings. For umbral flashes themselves we resolve, for the first time in inversion-based semi-empirical modelling, the pre-flash downflows, post-flash upflows, and the counter-flows present during the umbral flash phase. We further present a simple time-dependent cartoon model that explains the dynamics and spectral profiles of both fine structure, dark and bright, and umbral flashes in umbral chromospheres.Conclusions.The similarity of the profiles between the brightenings and umbral flashes, the pattern of velocities obtained from the inversions, and the phase relationships between the structures all lead us to put forward that all dynamic umbral chromospheric structures observed to this date are a locally delayed or locally early portion of the oscillatory flow pattern that generates flashes, secondary to the steepening large-scale acoustic waves at its source. Essentially, SSUBs are part of the same shock or merely compression front responsible for the spatially larger umbral flash phenomenon, but out of phase with the broader oscillation.

High-resolution Chromospheric Observations of a Solar Minifilament: Formation and Destabilization

Abstract Using H α line core and off-band imaging data from the New Vacuum Solar Telescope in China, we present a high-resolution observation on the entire life cycle of a solar minifilament from its birth to its final eruption. We find that the minifilament originates from a series of cascade-like reconfigurations of chromospheric fine structures. During which, owing to strong photospheric shearing and converging flows near its polarity inversion line, basic short chromospheric fibrils first slowly coalesce to elongated dark threads, and then further create a longer filament channel in a “head-to-tail” linkage scenario. In this course, obvious magnetic flux cancelation simultaneously proceeds below it, and further facilitates its destabilization. In its onset phase, clear clues indicate that the minifilament first starts to rise without brightening signals; instead, after a slow-to-fast acceleration, obvious runaway reconnection soon takes over its final jet-like eruption. Besides, off-band observations further reveal that the formed minifilament has a possible flux-rope configuration, and chromospheric upflows that detected in its early forming phase persistently supplies cool plasma into its channel. This observation is consistent with earlier observations and supports the view that both miniature and large-scale filaments may share analogous formation and destabilization mechanisms.

4138 Development of an Antibiofilm Resorbable Membrane for Treating Peri-implantitis

OBJECTIVES/GOALS: Peri-implantitis is the inflammation of peri-implant mucosa and subsequent loss of supporting bone. Its treatment is only <40% successful mainly due to persistent bacterial infection. The goal of this project is to increase success rates by developing a robust antibiofilm multi-biomolecular membrane that can be placed around implant surfaces. METHODS/STUDY POPULATION: A collagen membrane was soaked in the antimicrobial peptide GL13K solution overnight to form an interpenetrating fibrillary network. The nanostructure of the membrane was imaged with scanning electron microscope (SEM). The hydrophobicity of the membrane was analyzed by water contact angle (WCA) measurements. The biodegradability was tested in a 0.01 mg/mL Type I collagenase solution for up to 5 weeks. The antimicrobial activity of the membrane was assessed with Gram-positive oral bacteria Streptococcus gordonii. The cytotoxicity was evaluated by culturing human gingival fibroblasts (HGF), and the osteogenesis was assessed using preosteoblasts MC3T3. Pure collagen membrane was used as the control. Statistical significance (p<0.05) was determined by one-way ANOVA with Tukey’s HSD test. RESULTS/ANTICIPATED RESULTS: The antimicrobial peptide GL13K self-assembled to short fibrils (< 1 µm long), which entangled with the larger collagen fibers (around 200 nm in diameter). The collagen fibers presented characteristic periodic banding structures, which provided biomimetic cues for cell behavior as extracellular matrix. The interpenetrated GL13K fibrils turned the highly hydrophilic collagen membrane to a hydrophobic membrane (WCA = 135 °) and significantly reduced the rate of degradation by collagenases. The developed membrane was efficient in preventing the attachment of S. gordonii. A large portion of the attached bacteria was killed on the surface of the membrane. The incorporation of GL13K did not affect the cytocompatibility of the membrane for HGF. DISCUSSION/SIGNIFICANCE OF IMPACT: We developed an antibiofilm membrane with interpenetrating collagen and antimicrobial peptide fibrils. The strong antimicrobial activity and low cytotoxicity support its further translational evaluation as scaffolds for increasing success rate in treating peri-implantitis.

InVivo Bioengineering of Fluorescent Conductive Protein-Dye Microfibers.

SummaryEngineering protein-based biomaterials is extremely challenging in bioelectronics, medicine, and materials science, as mechanical, electrical, and optical properties need to be merged to biocompatibility and resistance to biodegradation. An effective strategy is the engineering of physiological processes in situ, by addition of new properties to endogenous components. Here we show that a green fluorescent semiconducting thiophene dye, DTTO, promotes, in vivo, the biogenesis of fluorescent conductive protein microfibers via metabolic pathways. By challenging the simple freshwater polyp Hydra vulgaris with DTTO, we demonstrate the stable incorporation of the dye into supramolecular protein-dye co-assembled microfibers without signs of toxicity. An integrated multilevel analysis including morphological, optical, spectroscopical, and electrical characterization shows electrical conductivity of biofibers, opening the door to new opportunities for augmenting electronic functionalities within living tissue, which may be exploited for the regulation of cell and animal physiology, or in pathological contexts to enhance bioelectrical signaling.

Structural-rheological characteristics of Chaplin E peptide at the air/water interface; a comparison with β-lactoglobulin and β-casein

The Chaplin E peptide is a surface-active agent that can adsorb to the air/water interface and form interfacial films that display distinct interfacial properties as a function of pH. The ~2 nm thick homogeneous Chaplin E film formed under acidic conditions contains ordered structures that give a high dilatational elasticity. In contrast, the heterogeneous film formed under basic conditions contained fibrils resulting in a rough ~17 nm thick film with predominantly viscoelastic properties, probably due to the reduced intermolecular interactions. These fibrils were also susceptible to breakage, fragmenting into shorter fibrils, which gave a greater elasticity. The fibrils also lead to a greater shear viscosity compared to the ordered structures aligned within the Chaplin E film at pH 3.0. A higher stability was observed for the foam formed by the Chaplin E compared to the foam formed by β-lactoglobulin, consistent with the greater rheological properties observed for the Chaplin E film at the interface. Our findings suggest that Chaplin E has potential to provide long time stability to dispersions in food, consumer goods or pharmaceutical applications, forming films with greater rheological properties and at least similar thickness to those formed by other surface-active proteins such as β-casein and β-lactoglobulin.

Duration of Persistent Atrial Fibrillation Is Associated with Alterations in Human Gut Microbiota and Metabolic Phenotypes.

Atrial fibrillation (AF) has been shown to be associated with disordered gut microbiota (GM). The underlying factors governing persistent AF (psAF) are not well understood, and the association between AF duration and GM profiles remains to be characterized. Thus, the present study aimed at investigating the dysbiosis of GM in patients with short and long psAF duration and illuminating the relationship between the GM and psAF maintenance. Based on metagenomic sequencing and metabolomic analyses, we assessed the metabolic and GM signature in 12 patients with psAF of <12 months (Pers<12m), eight patients with psAF of >12 months (Pers>12m), and 20 controls. We found that the GM in patients with both Pers<12m and Pers>12m was significantly perturbed, with an elevated microbial diversity, distinct structure, and discrepant composition. Although Pers<12m and Pers>12m patients shared a large number of common bacteria with controls, including 84 genera and 404 species, certain bacteria were differently enriched at different AF durations. Furthermore, disturbance in gut microbial function and GM-linked metabolic alterations were detected in both the Pers<12m and Pers>12m groups. The connection of GM and metabolites with psAF is consistent with interaction and potential modulation of host metabolic pathways due to GM dysbiosis with AF persistence. Our results showed that patients of the Pers<12m and Pers>12m groups shared many common disordered GM and metabolic features, which might occur in early disease, while prolonged psAF duration was related to certain unique alterations. Preventative strategies targeting GM and microbial metabolites for early intervention to treat AF patients are highly warranted.IMPORTANCE Atrial fibrillation was associated with a disordered gut microbiota in previous research. However, the gut microbiota signature of patients at different stages of atrial fibrillation remains largely unknown. We sought to determine whether the shift in the gut microbiota and metabolic profiles occurs early and remains stable or develops gradually during atrial fibrillation. We found that patients with persistent atrial fibrillation of <12 months and persistent atrial fibrillation of >12 months shared most of the common features of gut microbiota dysbiosis. However, some distinctive and progressive alterations in the gut microbiota and metabolic structure, which may contribute to the progression of atrial fibrillation, were identified. The present study provides a comprehensive description of the dysbiotic gut microbiota and metabolic profiles in patients of short and long persistent atrial fibrillation, and our findings may help identify therapeutic strategies targeting the gut microbiota to treat atrial fibrillation at an early stage.

Characterization of stitch adhesions: Fibronectin-containing cell-cell contacts formed by fibroblasts

Fibronectin is a multifunctional, extracellular matrix glycoprotein that exists either as an insoluble multimeric fibrillar component of the extracellular matrix or as a soluble monomer. Cells attach to fibronectin through transmembrane integrin receptors and form a variety of cell-matrix contacts. Here we show that primary fibroblasts can use fibronectin to organize a specific cell-cell contact – “stitch adhesions.” This contact is formed by short parallel fibronectin fibrils connecting adjacent cells above the level of the focal adhesions that attach the cells to the substrate. Stitch adhesions contain integrin α5β1 but not αVβ3, align with actin filament bundles, and contain talin, tensin, α-actinin, vinculin, paxillin and a phosphorylated form of focal adhesion kinase. This combination of components differs from the described constituents of the known cell adhesions. Stitch adhesions are organized when protein synthesis and secretion are inhibited by cycloheximide and exogenous fibronectin is provided to the cells. The adhesion stitches described here provide an attractive model system for studying fibronectin fibrillogenesis and the mechanisms governing the formation of cellular adhesions.

In vitro digestion and stability under environmental stresses of ovotransferrin nanofibrils

The objectives of this study were to investigate in vitro digestion and stability under environmental stresses of ovotransferrin (OVT) nanofibrils. Gastrointestinal digestion of OVT nanofibrils was characterized by thioflavin T (ThT) fluorescence and atomic force microscopy (AFM). Most of OVT nanofibrils were disrupted during gastrointestinal digestion, and some OVT nanofibrils showed resistance to proteolytic digestion in vitro. Long-term storage stability of OVT nanofibrils over a wide pH range was studied at room temperature, and storage stability of β-lactoglobulin (BLG) nanofibrils as function of pH was also studied. AFM data showed that these protein nanofibrils were stable at pHs below isoelectric point, but they were unstable at pHs above isoelectric point. It was worthwhile to note that this was the first study that relationships between long-term storage stability and zeta potential of food protein nanofibrils were clarified, which could advance understandings about long-term preservation of food protein nanofibrils. Negligible decrease in ThT fluorescence revealed that OVT nanofibrils suffered little loss of fibrillar structures after frozen storage−lyophilization−rehydration. AFM data demonstrated that OVT nanofibrils were fractured into short and curly fibrils after high-speed shearing, and ThT fluorescence measurement showed that few fibrillar structures were destroyed during shear treatment, indicating that high-speed shearing was a reliable and cost-effective strategy to tailor OVT nanofibrils for specific needs. Hopefully, this study could provide new insight about in vitro digestion and stability under environmental stresses of protein nanofibrils.

Nature of Amorphous Hydrophilic Block Affects Self-Assembly of an Artificial Viral Coat Polypeptide.

Consensus motifs for sequences of both crystallizable and amorphous blocks in silks and natural structural analogues of silks vary widely. To design novel silklike polypeptides, an important question is therefore how the nature of either the crystallizable or the amorphous block affects the self-assembly and resulting physical properties of silklike polypeptides. We address herein the influence of the amorphous block on the self-assembly of a silklike polypeptide that was previously designed to encapsulate single DNA molecules into rod-shaped viruslike particles. The polypeptide has a triblock architecture, with a long N-terminal amorphous block, a crystallizable midblock, and a C-terminal DNA-binding block. We compare the self-assembly behavior of a triblock with a very hydrophilic collagen-like amorphous block (GXaaYaa)132 to that of a triblock with a less hydrophilic elastin-like amorphous block (GSGVP)80. The amorphous blocks have similar lengths and both adopt a random coil structure in solution. Nevertheless, atomic force microscopy revealed significant differences in the self-assembly behavior of the triblocks. If collagen-like amorphous blocks are used, there is a clear distinction between very short polypeptide-only fibrils and much longer fibrils with encapsulated DNA. If elastin-like amorphous blocks are used, DNA is still encapsulated, but the polypeptide-only fibrils are now much longer and their size distribution partially overlaps with that of the encapsulated DNA fibrils. We attribute the difference to the more hydrophilic nature of the collagen-like amorphous block, which more strongly opposes the growth of polypeptide-only fibrils than the elastin-like amorphous blocks. Our work illustrates that differences in the chemical nature of amorphous blocks can strongly influence the self-assembly and hence the functionality of engineered silklike polypeptides.

Dynamic Properties of Human α-Synuclein Related to Propensity to Amyloid Fibril Formation

α-Synuclein (αSyn) is an intrinsically disordered protein that can form amyloid fibrils. Fibrils of αSyn are implicated with the pathogenesis of Parkinson's disease and other synucleinopathies. Elucidating the mechanism of fibril formation of αSyn is therefore important for understanding the mechanism of the pathogenesis of these diseases. Fibril formation of αSyn is sensitive to solution conditions, suggesting that fibril formation of αSyn arises from the changes in its inherent physico-chemical properties, particularly its dynamic properties because intrinsically disordered proteins such as αSyn utilize their inherent flexibility to function. Characterizing these properties under various conditions should provide insights into the mechanism of fibril formation. Here, using the quasielastic neutron scattering and small-angle x-ray scattering techniques, we investigated the dynamic and structural properties of αSyn under the conditions, where mature fibrils are formed (pH 7.4 with a high salt concentration), where clumping of short fibrils occurs (pH 4.0), and where fibril formation is not completed (pH 7.4). The small-angle x-ray scattering measurements showed that the extended structures at pH 7.4 with a high salt concentration become compact at pH 4.0 and 7.4. The quasielastic neutron scattering measurements showed that both intra-molecular segmental motions and local motions such as side-chain motions are enhanced at pH 7.4 with a high salt concentration, compared to those at pH 7.4 without salt, whereas only the local motions are enhanced at pH 4.0. These results imply that fibril formation of αSyn requires not only the enhanced local motions but also the segmental motions such that proper inter-molecular interactions are possible.

Graphene oxide containing self-assembling peptide hybrid hydrogels as a potential 3D injectable cell delivery platform for intervertebral disc repair applications

Cell-based therapies have shown significant promise in tissue engineering with one key challenge being the delivery and retention of cells. As a result, significant efforts have been made in the past decade to design injectable biomaterials to host and deliver cells at injury sites. Intervertebral disc (IVD) degeneration, a major cause of back pain, is a particularly relevant example where a minimally-invasive cellular therapy could bring significant benefits specifically at the early stages of the disease, when a cell-driven process starts in the gelatinous core of the IVD, the nucleus pulposus (NP).In this present study we explore the use of graphene oxide (GO) as nano-filler for the reinforcement of FEFKFEFK (β-sheet forming self-assembling peptide) hydrogels. Our results confirm the presence of strong interactions between FEFKFEFK and GO flakes with the peptide coating and forming short thin fibrils on the surface of the flakes. These strong interactions were found to affect the bulk properties of hybrid hydrogels. At pH 4 electrostatic interactions between the peptide fibres and the peptide-coated GO flakes are thought to govern the final bulk properties of the hydrogels while at pH 7, after conditioning with cell culture media, electrostatic interactions are removed leaving the hydrophobic interactions to govern hydrogel final properties. The GO-F820 hybrid hydrogel, with mechanical properties similar to the NP, was shown to promote high cell viability and retained cell metabolic activity in 3D over the 7 days of culture and therefore shown to harbour significant potential as an injectable hydrogel scaffold for the in-vivo delivery of NP cells. Statement of SignificanceShort self-assembling peptide hydrogels (SAPHs) have attracted significant interest in recent years as they can mimic the natural extra-cellular matrix, holding significant promise for the ab initio design of cells’ microenvironments. Recently the design of hybrid hydrogels for biomedical applications has been explored through the incorporation of specific nanofillers. In this study we exploited graphene oxide (GO) as nanofiller to design hybrid injectable 3Dscaffolds for the delivery of nucleus pulposus cells (NPCs) for intervertebral disc regeneration. Our work clearly shows the presence of strong interactions between peptide and GO, mimicking the mechanical properties of the NP tissue and promoting high cell viability and metabolic activity. These hybrid hydrogels therefore harbour significant potential as injectable scaffolds for the in vivo delivery of NPCs.

Improving the production of nanofibrillated cellulose from bamboo pulp by the combined cellulase and refining treatment

AbstractBACKGROUNDNanofibrillated cellulose (NFC) has shown great potential for wide applications in various fields and industries such as food, coatings, daily chemicals, superabsorbent high‐strength materials, and other high‐value products. Bamboo, with a chemical composition and fibre properties comparable to wood, is considered as an ideal nonwood material for the production of high‐quality NFC. However, the normally used two‐step process [TEMPO‐mediated oxidation and high‐pressure homogenization (HPH)] not only requires high amounts of energy, but also results in high heterogeneity of the resultant nanocellulose products.RESULTSIn this study, we proposed a sequential treatment method combining cellulase treatment followed by mechanical refining to improve the process for NFC production from bleached bamboo kraft pulp. The results showed that cellulase treatment using an enzyme dosage of 7 U g−1 cellulose followed by mechanical refining for 5000 revolutions increased the content of carboxyl group in treated pulp from 0.46 to 0.90 mmol g−1cellulose following TEMPO‐mediated oxidation. The effect of cellulase treatment and mechanical refining on the fibre properties was investigated in terms of freeness, fibre length, water retention value, pore volume and other fibrillation characteristics, such as the diameter of the NFC fibrils. Finally, we also found that, using the above‐proposed process, ca. 85 g high‐quality NFC could be produced from 100 g bleached bamboo pulp.CONCLUSIONSThis study demonstrated that the combination of cellulase treatment and mechanical refining is a promising strategy to produce high‐quality NFC with short fibril diameter while increasing NFC yield and reducing energy consumption during HPH. © 2019 Society of Chemical Industry

Novel model of secreted human tau protein reveals the impact of the abnormal N-glycosylation of tau on its aggregation propensity

Alzheimer’s disease (AD) is the most common neurodegenerative disorder and has no disease-modifying treatment yet. The hallmarks of AD are two amyloidogenic proteins: tau and amyloid β (Aβ). Tau undergoes several posttranslational modifications, including N-glycosylation. Tau was reported to be N-glycosylated in AD brains, but not in healthy counterparts, which may affect AD etiology. Here, we aimed to examine the effect of N-glycosylation on aggregation propensity of tau. To that end, a novel SH-SY5Y cell-based model was generated in which recombinant human tau (htau) is forced to be secreted from the cells. Secreted htau was found to localize in the secretory pathway compartments and to undergo N-glycosylation. Following N-glycan cleavage of the secreted htau, various biophysical results collectively indicated that the untreated N-glycosylated secreted htau is markedly less aggregative, contains thinner and shorter fibrils, as compared to treated de-glycosylated secreted htau. This finding shows that N-glycans attached to htau may affect its aggregation. This could help to better understand the effect of N-glycosylated htau on AD progression.