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Abstract: The experimental study of polymer growth on spatially unconstrained flat silica surfaces is presented for propylene and ethylene polymerization in liquid and gas phases with high activity metallocene catalyst (rac‐Et(Indenyl)2ZrCl2/ methylaluminoxane at 30–70 °C and 30–50 psig. The study shows a surprisingly rich spectrum of nascent morphologies for each polymer synthesized in two different reaction phases. In propylene polymerization in a liquid phase, polypropylene nanofibrils are first formed at the catalyst sites and quickly develop into microglobular morphology, whereas in ethylene polymerization in a liquid phase, polyethylene nanofibrils formed at the catalyst sites grow to a ribbon‐like morphology. In gas phase polymerization where polymerization rate is much lower due to low monomer concentration, both polymers grow to compact aggregates of globules. Unlike in liquid phase polymerization, no ribbon‐like structure is formed in ethylene polymerization. The sequential polymerization of these olefin monomers has also been carried out and the experimental data show two distinct regions of corresponding polymers as observed in separate ethylene and propylene homopolymerization experiments. [ABSTRACT FROM AUTHOR]

Regenerated Silk biomaterials are usually pre-formed from silk fibroin solutions. However, the dissolution of silk fibroin in proper solvents by a simple and low cost way is still a challenge. Here, we employed a CaCl 2 -methanol solvent system with a very low CaCl 2 concentration of 6 wt% to dissolve silk fibroin. During the dissolution process, the evaporation of methanol cause the changing of solvation sheath of ions in the solvent. The remaining solvent with the incomplete solvation sheath is absorbed by the silk fiber and interacts with fibroin chains to complete the solvation sheath, which accounts for the dissolution of silk fibroin. Silk fibroin dissolution stops as all the solvation sheaths are complete. The final CaCl 2 concentration is ca. 26% and silk fibroin is completely dissolved with a yield of about 90%. Silk fibroin is dissolved into multi-scale nanofibrils solution which is potential for producing regenerated silk fibroin materials for functional applications. [ABSTRACT FROM AUTHOR]

Natural silk fibers represent one of the most advanced blueprints for (bio)polymer scientists, displaying highly optimized mechanical properties due to their hierarchical structures. Biotechnological production of silk proteins and implementation of advanced processing methods enabled harnessing the potential of these biopolymer not just based on the mechanical properties. In addition to fibers, diverse morphologies can be produced, such as nonwoven meshes, films, hydrogels, foams, capsules and particles. Among them, nanoscale fibrils and fibers are particularly interesting concerning medical and technical applications due to their biocompatibility, environmental and mechanical robustness as well as high surface‐to‐volume ratio. Therefore, we introduce here self‐assembly of silk proteins into hierarchically organized structures such as supramolecular nanofibrils and fabricated materials based thereon. As an alternative to self‐assembly, we also present electrospinning a technique to produce nanofibers and nanofibrous mats. Accordingly, we introduce a broad range of silk‐based dopes, used in self‐assembly and electrospinning: natural silk proteins originating from natural spinning glands, natural silk protein solutions reconstituted from fibers, engineered recombinant silk proteins designed from natural blueprints, genetic fusions of recombinant silk proteins with other structural or functional peptides and moieties, as well as hybrids of recombinant silk proteins chemically conjugated with nonproteinaceous biotic or abiotic molecules. We highlight the advantages but also point out drawbacks of each particular production route. The scope includes studies of the natural self‐assembly mechanism during natural silk spinning, production of silk fibrils as new nanostructured non‐native scaffolds allowing dynamic morphological switches, as well as studying potential applications. This article is categorized under:  Biology‐Inspired Nanomaterials > Peptide‐Based Structures  Nanotechnology Approaches to Biology > Nanoscale Systems in Biology  Biology‐Inspired Nanomaterials > Protein and Virus‐Based Structures [ABSTRACT FROM AUTHOR]

Abstract: Marine macrofoulers (e.g., barnacles, tubeworms, mussels) create underwater adhesives capable of attaching themselves to almost any material. The difficulty in removing these organisms frustrates maritime and oceanographic communities, and fascinates biomedical and industrial communities seeking synthetic adhesives that cure and hold steadfast in aqueous environments. Protein analysis can reveal the chemical composition of natural adhesives; however, developing synthetic analogs that mimic their performance remains a challenge due to an incomplete understanding of adhesion processes. Here, it is shown that acorn barnacles (Amphibalanus (=Balanus) amphitrite) secrete a phase‐separating fluid ahead of growth and cement deposition. This mixture consists of a phenolic laden gelatinous phase that presents a phase rich in lipids and reactive oxygen species at the seawater interface. Nearby biofilms rapidly oxidize and lift off the surface as the secretion advances. While phenolic chemistries are ubiquitous to arthropod adhesives and cuticles, the findings demonstrate that A. amphitrite uses these chemistries in a complex surface‐cleaning fluid, at a substantially higher relative abundance than in its adhesive. The discovery of this critical step in underwater adhesion represents a missing link between natural and synthetic adhesives, and provides new directions for the development of environmentally friendly biofouling solutions. [ABSTRACT FROM AUTHOR]

Abstract: A sustainable packaging system with excellent liquid- and gas-barrier properties and enhanced strength properties was highlighted by a composite coating containing a mixture of cellulose nanocrystals (CNC), a high-aspect ratio nano-filler montmorillonite clay, an amphiphilic binder soy protein, and a surface-active agent alkyl ketene dimer. They were tested on various surfaces of commercially available packaging papers and compared with the appropriate control (i.e., CNC-only coating) to determine surface morphology, chemical composition, barrier, and mechanical properties. Scanning electron microscopy image analysis showed a compact matrix whose defects (cracks) were significantly attenuated compared to the control while FTIR showed fewer exposed hydroxyl (-OH) groups. The compact structure and reduced proportion of -OH groups are attributed to the plate-like structure, high aspect ratio of clay, and uniform distribution of additives to help inhibit gas, moisture, water, oil, and grease permeation. The base paper used also had a significant impact on how coatings interacted with various fluids. Overall, sustainable CNC-composite barrier coatings with relatively low-cost additives were fabricated and showed improved barrier and strength characteristics with a strong potential as barrier coatings for packaging.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The functional attributes of globular proteins can be extended by controlling the nature of the aggregates they form. In this study, the effect of thermal treatment (85°C/20 min) and high pressure microfluidization (20,000 psi, 1 pass) on the physical properties of whey protein isolate solutions (5–9%; pH 2) was investigated. Heating solutions of native whey protein isolate (8 wt%) under these acidic conditions led to the formation of highly viscous solutions (η = 306 mPa s) with low turbidity (τ = 0.04 cm −1 ), which was attributed to the formation of protein fibrils (effective d = 310 nm). Microfluidization of these protein fibrils decreased their length (effective d = 97 nm) leading to a substantial reduction in solution viscosity (η = 3.8 mPa s), and a slight reduction in turbidity (τ < 0.03 cm −1 ). The impact of solution pH (2–7) on the appearance and rheology of native, heated, and heated-microfluidized whey protein isolate solutions was then examined. For all systems, highly turbid solutions (τ > 1 cm −1 ) were formed at pH values close to the isoelectric point of the whey proteins (pH 4.5) due to protein self-association caused by reduction of the electrostatic repulsion between the protein molecules. Highly viscous or gelled solutions were formed for the heated and heated-microfluidized proteins across a wide pH range, which was attributed to the presence of fibrils. The study showed that the functional attributes of whey proteins can be modulated by thermal and high-pressure homogenization treatment. [ABSTRACT FROM AUTHOR]

Somatostatin-14 is a native neuropeptide with widespread functions in the body. Self-assembly of somatostatin-14 into amyloid-like nanofibrils has been previously demonstrated in aqueous media. We here hypothesize that the somatostatin nanofibrils can form a stable depot that release monomers in a controlled manner. This study aims to investigate if somatostatin monomers are released from physical hydrogels formed in water and in the presence of electrolytes. The release kinetics of the somatostatin monomers is investigated for the first time. This is correlated with the rheological properties of the hydrogels formed. We demonstrate that at the concentrations tested, there is release of somatostatin monomers from the hydrogels following a novel hybrid model of zero-order and first-order release. In the presence of electrolytes, somatostatin hydrogels demonstrated higher elastic moduli (G′) which correlates to the narrower and higher density of nanofibrils observed with TEM. The presence of electrolytes resulted in a slower release of the somatostatin monomers and in a lower cumulative percentage released over 48 hrs. It is questionable that the concentrations released will be therapeutically effective. However, self-assembled somatostatin hydrogels have the potential to act as a depot for ocular drug delivery. [ABSTRACT FROM AUTHOR]

Amyloid-like aggregation of natural proteins or polypeptides is an important process involved in many human diseases as well as some normal biological functions. Plenty of works have been done on this ubiquitous phenomenon, but the molecular mechanism of amyloid-like aggregation has not been fully understood yet. In this study, we showed that a series of designer bolaamphiphilic peptides could undergo amyloid-like aggregation even though they didn't possess typical β-sheet secondary structure. Through systematic amino acid substitution, we found that for the self-assembling ability, the number and species of amino acid in hydrophobic section could be variable as long as enough hydrophobic interaction is provided, while different polar amino acids as the hydrophilic heads could change the self-assembling nanostructures with their aggregating behaviors affected by pH value change. Based on these results, novel self-assembling models and aggregating mechanisms were proposed, which might provide new insight into the molecular basis of amyloid-like aggregation. [ABSTRACT FROM AUTHOR]

Development of strong cellulose nanofibril (CNF) networks for advanced applications, such as in the biomedical field, is of high importance owing to the biocompatible nature and plant-based origin of cellulose nanofibrils. Nevertheless, lack of mechanical strength and complex synthesis methods hinder the application of these materials in areas where both toughness and manufacturing simplicity are required. In this work, we introduce a facile method for the synthesis of a low solid content (< 2 wt%), covalently crosslinked CNF hydrogel where Poly (N-isopropylacrylamide) (NIPAM) chains are utilized as crosslinks between the nanofibrils. The resulting networks have the capability to fully recover the shape in which they were formed after various drying and rewetting cycles. Characterization of the hydrogel and its constitutive components was performed using X-ray scattering, rheological investigations and uniaxial testing in compression. Influence of covalent crosslinks was compared with networks crosslinked by the addition of CaCl 2. Among other things the results show that the mechanical properties of the hydrogels can be tuned by controlling the ionic strength of the surrounding medium. Finally, a mathematical model was developed based on the experimental results, which describes and predicts to a decent degree the large-deformation, elastoplastic behavior, and fracture of these networks. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, a novel technology involving radio frequency heating (RF) was applied to promote the production of whey protein isolate (WPI) nanofibrils. As the prolonged treatment time, gradual increases were observed in the conversion rate (>16 h with the conventional processes), fluorescence intensity, and free amino acid content of WPI. During the fibrillation process, WPI was hydrolyzed into small molecular weight peptides that self-assembled into fibrils, resulting in a significant increase in the ζ-potential and surface hydrophobicity. Conformational and structural changes that favored an increased content of β-sheets were confirmed by Fourier transform infrared and circular dichroism spectroscopy. A linear fibril structure with a proper aspect ratio (length/diameter, 35.50 ± 0.39) formed at 7 h. Moreover, the good resistance to proteolytic digestion (especially gastric stage) of certain fibrils makes them suitable for application as nutraceutical delivery vehicles. Our findings move a step forward for WPI fibrillation by RF heating. [Display omitted] • Whey protein isolate (WPI) nanofibril was formed via radio frequency (RF) heating. • RF induced a reduction in fibrillation time and degree of browning in WPI. • RF treatments led to an increase in surface hydrophobicity and β-sheet level. • The longer and more flexible fibrils were observed by 7 h fibrillation process. • Some nanofibrils exhibited resistance to proteolytic digestion in vitro. [ABSTRACT FROM AUTHOR]

The present review article is intended to direct attention to the technological advances made in the 2010–2014 quinquennium for the isolation and manufacture of nanofibrillar chitin and chitosan. Otherwise called nanocrystals or whiskers, n-chitin and n-chitosan are obtained either by mechanical chitin disassembly and fibrillation optionally assisted by sonication, or by e-spinning of solutions of polysaccharides often accompanied by poly(ethylene oxide) or poly(caprolactone). The biomedical areas where n-chitin may find applications include hemostasis and wound healing, regeneration of tissues such as joints and bones, cell culture, antimicrobial agents, and dermal protection. The biomedical applications of n-chitosan include epithelial tissue regeneration, bone and dental tissue regeneration, as well as protection against bacteria, fungi and viruses. It has been found that the nano size enhances the performances of chitins and chitosans in all cases considered, with no exceptions. Biotechnological approaches will boost the applications of the said safe, eco-friendly and benign nanomaterials not only in these fields, but also for biosensors and in targeted drug delivery areas.

Cellulose nanofibril foams are cellulose-based porous materials with outstanding mechanical properties, resulting from the high strength-to-weight ratio of nanofibrils. Here we report the development of an optimized fabrication process for highly porous cellulose foams, based on a well-controlled freeze-thawing-drying (FTD) process at ambient pressure. This process enables the fabrication of foams with ultra-high porosity, up to 99.4%, density of 10 mg/cm3, and liquid (such as oil) absorption capacity of 100 L/kg. The proposed approach is based on the ice-templating of nanocellulose suspension in water, followed by thawing in ethanol and drying at environmental pressures. As such, the proposed fabrication route overcomes one of the major bottle-necks of the classical freeze-drying approach, by eliminating the energy-demanding vacuum drying step required to avoid wet foam collapse upon drying. As a result, the process is simple, environmentally friendly, and easily scalable. Details of the foam development fabrication process and functionalization are thoroughly discussed, highlighting the main parameters affecting the process, e.g., the concentration of nanocellulose and additives used to control the ice nucleation. The foams are also characterized by mechanical tests and oil absorption measurements, which are used to assess the foam absorption capability as well as the foam porosity. Compound water-in-oil drop impact experiments are used to demonstrate the potential of immiscible liquid separation using cellulose foams.

Soy protein isolate (SPI) was isolated from Indonesian soybean var. Grobogan and converted into protein nanofibrils. Their functionalities as a food thickener and building blocks for microcapsules were investigated and compared with those of commercial whey protein isolate (WPI). The isolation yield was about 58% with SPI's protein content of about 90% on dry basis. Long, curved, and branched SPI fibrils with a few nanometers of diameter were obtained by heating SPI suspension at pH 2.0. The solution of SPI fibrils was shear thinning with much higher viscosity than the unheated SPI which was Newtonian. The fibrils showed a good potential as building blocks of microcapsules prepared by layer-by-layer adsorption method, which were similar to WPI fibrils. [ABSTRACT FROM AUTHOR]

An oil-in-water (o/w) emulsion is a system where the oil droplets are dispersed within a watery phase. The most important function of emulsions is their ability to incorporate lipophilic components into food matrices. Thus, it is crucial to develop an emulsion that is highly stable. This work was aimed at developing a palm olein o/w emulsion stabilized by a whey protein isolate nanofibrils-alginate complex, as well as evaluating the influence of oil load and the homogenization process (both pressure and cycle) on the characteristics of the o/w emulsions. Emulsions were analyzed for droplet size, zeta potential, viscosity, creaming stability, and morphology. The results showed that an increase in oil load led to a larger droplet size, less negative zeta potential, and emulsions that were more viscous and less stable. On the other hand, increasing homogenization pressure and the number of homogenization cycles resulted in a smaller droplet size, more negative zeta potential, and emulsions that were less viscous and more stable. Emulsions with a smaller droplet size and better stability resulted from lower oil load, high homogenization pressure and more homogenization cycles. [ABSTRACT FROM AUTHOR]

The ability to tune the inter-subunit interaction within the virus capsid may be critical to assembly and biological function. This process was extended here with peptide/DNA co-assembled viral mimics. The resulting co-assemblies, formed and stabilized by both peptide nanofibril–DNA and peptide nanofibril–nanofibril interactions, were tuned through hydrophobic packing interactions of the peptide sequences. By strengthening peptide side-chain complementarity and/or elongating the peptide chain (from 4 to 8 residues), we report strengthening the inter-nanofibril interaction to create stable nanococoons that give high gene-transfection efficacy. [ABSTRACT FROM AUTHOR]

A hybrid catalyst was prepared using cellulose nanofibrils and magnetite to degrade organic compounds. Cellulose nanofibrils were isolated by mechanical defibrillation producing a suspension used as a matrix for magnetite particles. The solution of nanofibrils and magnetite was dried and milled resulting in a catalyst with a 1:1 ratio of cellulose and magnetite that was chemically and physically characterized using light, scanning electron and transmission electron microscopies, specific surface area analysis, vibrating sample magnetometry, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, catalytic potential and degradation kinetics. Results showed good dispersion of the active phase, magnetite, in the mat of cellulosic nanofibrils. Leaching and re-use tests showed that catalytic activity was not lost over several cycles. The hybrid material produced was tested for degradation of methylene blue dye in Fenton-like reactions resulting in a potential catalyst for use in degradation of organic compounds. [ABSTRACT FROM AUTHOR]

The effects of using (NH 4 ) 2 SO 4 as a carbonization promoter for producing cellulose-derived carbon aerogels (CAG) was studied. The effects of pretreatment on the textural, morphological, and chemical properties of pristine cellulose nanofibers (CNF) were analyzed through N 2 adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), elemental analysis, inductively coupled plasma optical emission spectrometry (ICP-OES), and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the thermal behaviors of raw CNF and those impregnated with (NH 4 ) 2 SO 4 were investigated by coupling thermogravimetric analysis with mass spectrometry (TGA-MS). The results suggested that the pretreatment did not cause any morphological/structural changes in the nanofibers. However, the presence of (NH 4 ) 2 SO 4 affected their pyrolysis by favoring intermolecular dehydration, thereby reducing the formation of levoglucosan and increasing the carbon yield during pyrolysis. Interestingly, above certain impregnation level, the concentration of sulfate-derived species in the gas phase increased. This phenomenon was attributed to an excess of salt within the fiber structure and on their surfaces. Consequently, the levoglucosan-to-carbon route was inhibited, and the mechanisms of intra- and inter-molecular dehydration, chain scission, and crosslinking reactions were affected, leading to a reduced char yield. The chemical effects of ammonia-based salts is elucidated supported on the interpretation of MS signals and kinetic modeling results. [ABSTRACT FROM AUTHOR]

Green low-cost synthesis and efficient recyclability are two major hindrances for Au nanocrystals as catalysts applying in diverse industrial reaction processes. By the use of low-cost α-zein (i.e. a major storage protein of corn) as the reductant, capping agent and stabilizer, Au nanocrystals with tunable catalytic activity were synthesized in a wet-chemical approach. Fibrillation of α-zein further enhanced its reducing ability due to larger specific surface area and more hydrophilic groups exposed on the surfaces. The obtained Au nanocrystals had biocompatibility, high stability in various solvents, unique solubility in aqueous alcohol and high catalytic ability, being able to detect ethanol composition in aqueous ethanol as well as H 2 O 2 for diagnosis of diabetes mellitus. These advantages also enable efficient recyclability of Au nanocrystals with continuous flow catalysis in different solvents and environments. Thus, the use of α-zein offered Au nanocrystals not only with green low-cost synthesis, but also with tunable catalytic activities, ethanol-responsiveness and efficient recyclability, which may be applicable in diverse fields. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) with its inherent nanofibrils framework is an attractive building block for the fabrication of sustainable bioelectronics, but there still lacks an effective and green strategy to regulate the hydrogen-bonding topological structure of BC to improve its optical transparency and mechanical stretchability. Herein, we report an ultra-fine nanofibril-reinforced composite hydrogel by utilizing gelatin and glycerol as hydrogen-bonding donor/acceptor to mediate the rearrangement of the hydrogen-bonding topological structure of BC. Attributing to the hydrogen-bonding structural transition, the ultra-fine nanofibrils were extracted from the original BC nanofibrils, which reduced the light scattering and endowed the hydrogel with high transparency. Meanwhile, the extracted nanofibrils were connected with gelatin and glycerol to establish an effective energy dissipation network, leading to an increase in stretchability and toughness of hydrogels. The hydrogel also displayed tissue-adhesiveness and long-lasting water-retaining capacity, which acted as bio-electronic skin to stably acquire the electrophysiological signals and external stimuli even after the hydrogel was exposing to air condition for 30 days. Moreover, the transparent hydrogel could also serve as a smart skin dressing for optical identification of bacterial infection and on-demand antibacterial therapy after combined with phenol red and indocyanine green. This work offers a strategy to regulate the hierarchical structure of natural materials for designing skin-like bioelectronics toward green, low cost, and sustainability. [ABSTRACT FROM AUTHOR]

Recently developed technology permits to optimize simultaneously surface area, porosity, density, rigidity and surface morphology of chitin-derived materials of biomedical interest. Safe and ecofriendly disassembly of chitin has superseded the dangerous acid hydrolysis and provides higher yields and scaling-up possibilities: the chitosan nanofibrils are finding applications in reinforced bone scaffolds and composite dressings for dermal wounds. Electrospun chitosan nanofibers, in the form of biocompatible thin mats and non-wovens, are being actively studied: composites of gelatin + chitosan + polyurethane have been proposed for cardiac valves and for nerve conduits; fibers are also manufactured from electrospun particles that self-assemble during subsequent freeze-drying. Ionic liquids (salts of alkylated imidazolium) are suitable as non-aqueous solvents that permit desirable reactions to occur for drug delivery purposes. Gel drying with supercritical CO2 leads to structures most similar to the extracellular matrix, even when the chitosan is crosslinked, or in combination with metal oxides of interest in orthopedics.

Ammonium persulfate has been known as an agent for obtaining nanocellulose in recent years, however most research has focused on producing cellulose nanocrystals. A lack of research about combined ammonium persulfate oxidation and common mechanical treatment in order to obtain cellulose nanofibrils has been identified. The objective of this research was to obtain and investigate carboxylated cellulose nanofibrils produced by ammonium persulfate oxidation combined with ultrasonic and mechanical treatment. Light microscopy, atomic force microscopy (AFM), powder X-Ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Zeta potential measurements were applied during this research. The carboxylated cellulose suspension of different fractions including nanofibrils, microfibrils and bundles were produced from bleached birch Kraft pulp fibers using chemical pretreatment with ammonium persulfate solution and further defibrillation using consequent mechanical treatment in a high shear laboratory mixer and ultrasonication. The characteristics of the obtained nanofibrils were: diameter 20–300 nm, crystallinity index 74.3%, Zeta potential −26.9 ± 1.8 mV, clear FTIR peak at 1740 cm−1 indicating the C=O stretching vibrations, and lower thermostability in comparison to the Kraft pulp was observed. The proposed method can be used to produce cellulose nanofibrils with defined crystallinity.

A post-esterification with a high degree of substitution (hDS) mechanical treatment (Pe(hDS)M) approach was used for the production of highly hydrophobic cellulose nanoparticles (CNPs). The process has the advantages of substantially reducing the mechanical energy input for the production of CNPs and avoiding CNP aggregation through drying or solvent exchange. A conventional esterification reaction was carried out using a mixture of acetic anhydride, acetic acid, and concentrated sulfuric acid, but at temperatures of 60–85 °C. The successful hDS esterification of bleached eucalyptus kraft pulp fibers was confirmed by a variety of techniques, such as Fourier transform infrared (FTIR), solid state 13C NMR, X-ray photoelectron spectroscopy (XPS), elemental analyses, and X-ray diffraction (XRD). The CNP morphology and size were examined by atomic force microscopy (AFM) as well as dynamic light scattering. The hydrophobicity of the PeM-CNP was confirmed by the redispersion of freeze-dried CNPs into organic solvents and water contact-angle measurements. Finally, the partial conversion of cellulose I to cellulose II through esterification improved PeM-CNP thermal stability.

Cellulose has a complex, multi-level supermolecular architecture. This natural polymer is built from superfine fibrils having diameters in the nano scale, and each such nanofibril contains ordered nanocrystallites and low-ordered nano-domains. In this review, the nano-structure of cellulose and its influence on various properties of the polymer is discussed. In particular, the ability of nano-scale crystallites to undergo lateral co-crystallization and aggregation, as well as to undergo phase transformation through dissolution, alkalization, and chemical modifica-tion of cellulose has been the subject of investigation. The recent investigations pave the way for development of highly reactive cellulosic materials. Methods for preparation nanofibrillated cellulose and free nano-particles are described. Some application areas of the nanostruc-tured and nano-cellulose are discussed.

Nature regulates cellular interactions through the cell-surface molecules and plasma membranes. Despite advances in cell-surface engineering with diverse ligands and reactive groups, modulating cell-cell interactions through scaffolds of the cell-binding cues remains a challenging endeavor. Here, we assembled peptide nanofibrils on live cell surfaces to present the ligands that bind to the target cells. Surprisingly, with the same ligands, reducing the thermal stability of the nanofibrils promoted cellular interactions. Characterizations of the system revealed a thermally induced fibril disassembly and reassembly pathway that facilitated the complexation of the fibrils with the cells. Using the nanofibrils of varied stabilities, the cell-cell interaction was promoted to different extents with free-to-bound cell conversion ratios achieved at low (31%), medium (54%), and high (93%) levels. This study expands the toolbox to generate desired cell behaviors for applications in many areas and highlights the merits of thermally less stable nanoassemblies in designing functional materials.

In recent years the nanocellulose has become an important topic for several research fields due to its renewability, availability, biocompatibility and different awesome properties. As occurs with first and second generation bioethanol, the investigation on nanocellulose is gradually going towards the indirect use of lignocellulosic biomass, i.e. the exploitation of different cellulosic residues and wastes produced from agricultural and industrial activities because of the wide availability and renewable character of these feedstocks. In the present review, an exhaustive bibliographic study was performed to prove the increasing interest on these new cellulose sources. Furthermore, and according to existing literature about nanocellulose obtaining, the new properties and possibilities that this new feedstock offers were discussed, and the advantages due to the use of this kind of raw materials were presented. Finally, overlooking the valorization of existing agricultural activities and industrial processes, a scheme of the proper use of these agricultural and industrial wastes as a future nanocellulose supply chain was proposed. [ABSTRACT FROM AUTHOR]

Poly(1-amino-5-chloroanthraquinone) (PACA) nanofibrils were applied as new nano-adsorbents for heavy metal removal from aqueous solutions. Adsorption properties including adsorption capacity, selectivity, kinetics, mechanism, and isotherm of PACA nanofibrils were studied in detail. The competitive adsorption of the nanofibrils for Pb(II) and Cr(III) in binary mixture systems was investigated. The results showed that Pb(II) and Cr(III) were adsorbed preferentially over the other metal ions including Hg(II), Cr(VI), Zn(II), Cd(II), Fe(III) and Cu(II), under competitive conditions. Kinetic data indicated that the adsorption process of PACA nanofibrils for Pb(II) and Cr(III) achieved equilibrium within 2 h following a pseudo-second-order rate equation and exhibiting a three-stage intraparticle diffusion mode. The adsorption mechanism of PACA nanofibrils for Pb(II) and Cr(III) was investigated by Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses. The adsorption isotherms of Pb(II) and Cr(III) fitted well with the Langmuir model, exhibiting superb adsorption capacity of 4.27 and 4.22 mmol of metal per gram of adsorbent, respectively. Furthermore, adsorption–desorption experiments demonstrated that the PACA nano-adsorbents could be easily recycled without considerable changes in the adsorption capacity. [ABSTRACT FROM AUTHOR]

Salt-acid system has been proved to be of high efficiency for silk fibroin dissolution. Using salt-acid system to dissolve silk, native silk fibrils can be preserved in the regenerated solution. Increasing experiments indicate that acquirement of silk fibrils in solution is strongly associated with the degumming process. In this study, the effect of sodium carbonate degumming concentration on solution properties based on lithium bromide-formic acid dissolution system was systematically investigated. Results showed that the morphology transformation of silk fibroin in solution from nanospheres to nanofibrils is determined by sodium carbonate concentration during the degumming process. Solutions containing different silk fibroin structure exhibited different rheological behaviors and different electrospinnability, leading to different electrospun nanofibre properties. The results have guiding significance for preparation and application of silk fibroin solutions. [ABSTRACT FROM AUTHOR]

Huntington's disease (HD) is recognized as a currently incurable, inherited neurodegenerative disorder caused by the accumulation of misfolded polyglutamine (polyQ) peptide aggregates in neuronal cells. Yet, the mechanism by which newly formed polyQ chains interact and assemble into toxic oligomeric structures remains a critical, unresolved issue. In order to shed further light on the matter, our group elected to investigate the folding of polyQ peptides – examining glutamine repeat lengths ranging from 3 to 44 residues. To characterize these aggregates we employed a diverse array of technologies, including: nuclear magnetic resonance; circular dichroism; Fourier transform infrared spectroscopy; fluorescence resonance energy transfer (FRET), and atomic force microscopy. The data we obtained suggest that an increase in the number of glutamine repeats above 14 residues results in disordered loop structures, with different repeat lengths demonstrating unique folding characteristics. This differential folding manifests in the formation of distinct nano-sized fibrils, and on this basis, we postulate the idea of 14 polyQ repeats representing a critical loop length for neurotoxicity – a property that we hope may prove amenable to future therapeutic intervention. Furthermore, FRET measurements on aged assemblages indicate an increase in the end-to-end distance of the peptide with time, most probably due to the intermixing of individual peptide strands within the nanofibril. Further insight into this apparent time-dependent reorganization of aggregated polyQ peptides may influence future disease modeling of polyQ-related proteinopathies, in addition to directing novel clinical innovations. [ABSTRACT FROM AUTHOR]

Fabricating alginate fibers of high strength and toughness remains a great challenge because of the difficulty in improving both strength and toughness simultaneously. Herein, this work reported the hierarchical assembly of sodium alginate nano-helix and its potential application as a new reinforcing unit for alginate fibers. Contributed from the hierarchical structures of α-helix, β-sheet and tertiary helical alignment of nanofibrils, nano-helix improved the tensile strength of fibers with enhanced modulus, and prolonged elongation through unravelling the tertiary structures. Thus, the strength, elongation and toughness of alginate fibers were all enhanced by >200 %, solving the tradeoff of strength and toughness. The mechanical performance of nano-helix engineered alginate fibers is superior to present alginate fibers and even some other biomass-based fibers. The assembly of nano-helix provides a feasible reinforcing strategy for polysaccharide based materials, achieving simultaneous improvement of strength and toughness. [Display omitted] • Hierarchical nano-helix is composed of α-helix, β-sheet and tertiary structure of helical alignment of nanofibrils. • Hierarchical nano-helix is prepared through three stages of assembly with reorganized secondary structures. • Hierarchical nano-helix is a structural reinforcing unit for simultaneous improvement of strength and toughness. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ ethylene-propylene-diene terpolymer (EPDM) nanofibrils were achieved. • UV-crosslinking was able to freeze in-situ fibrillated EPDM nanofibrils. • EPDM nanofibril-reinforced polylactic acid (PLA) showed ductile fracture behavior. • PLA/EPDM foams with outstanding insulating performance were prepared. Polylactic acid (PLA) is a promising biomass and biodegradable polymer but suffers from its brittle feature and poor foaming ability. Thus, many ductile polymers have been used to modify PLA through compounding. Although some of them can improve the toughness, the strength and rigidness of PLA are seriously scarified due to the large dosage, poor dispersion, and see-island structures. Herein, UV-crosslinking-assisted in-situ fibrillation was developed to fabricate ethylene-propylene-diene terpolymer (EPDM) nanofibril-reinforced PLA composites. Twin-screw compounding followed by melt blowing was used to stretch EPDM phase into nanofibrils, while UV-crosslinking was proposed to stabilize the EPDM nanofibrils in the final PLA/EPDM composites. Thanks to UV-crosslinking, EPDM nanofibrils with an average diameter of 94.3 nm were achieved in PLA. Due to the heterogeneous nucleating effect of UV-crosslinked EPDM nanofibrils, the crystallization rate of PLA was significantly enhanced, and refined crystal morphology with fibrous structures was obtained. Surprisingly, merely 3 wt% of UV-crosslinked EPDM nanofibrils remarkably enhanced the mechanical properties of PLA. The tensile toughness and impact strength were increased by 620% and 440%, respectively, without sacrificing strength and rigidness. Moreover, the UV-crosslinked EPDM nanofibrils also significantly improved the foaming ability of PLA. The PLA/UV-crosslinked EPDM foam with an expansion ratio of up to 28-fold was achieved for the first time by mold-opening microcellular injection molding. With the presence of UV-crosslinked EPDM nanofibrils, the expansion ratio and cell population density of the foams can be increased by 470% and 5 orders of magnitude, respectively. Owing to the super-high expansion ratio and unique micro/nanoscale structures on cell walls, the 28-fold expanded PLA/EPDM foam exhibited outstanding thermally insulating performance with a thermal conductivity of as low as 26.3 mW/m∙K. [ABSTRACT FROM AUTHOR]

In order to achieve the regulation preparation of sulfated cellulose nanofibrils, a series of sulfated conditions was carried out to investigate the features and the potential application in nanoparticles dispersion. The morphology and surface features of the sulfated cellulose nanofibrils were characterized by means of Fourier transform infrared spectroscopy, atomic force microscope, transmission electron microscope, X-ray diffraction, elemental analysis, thermo-gravimetric analysis, etc. The results showed that the yield of the obtained sulfated cellulose nanofibrils can be high up to 96.9%. Besides, the sulfated cellulose nanofibrils showed a width and length in range of 3–8 nm and 200–800 nm, respectively, exhibiting the aspect ratio of about 100. Moreover, the zeta potential, degree of substitution and degree of polymerization were in range of − 57.5–−79.1 mV, 0.11–0.48, and 131–570, respectively, and could be tailored by variation of reagent molar ratio, reaction temperature and time during sulfation pretreatment. Notably, the sulfated cellulose nanofibrils showed great potential to be served as good dispersions for nanoparticles, which could make the dispersion of carbon nanotubes and nano zinc oxide stable for more than half a month. • A high yield up to 96.9 % of nanofibrils sulfated by sulfamic acid was obtained. • The features of sulfated nanofibrils were regulated by the sulfation conditions. • The sulfated nanofibrils showed an excellent dispersity for CNTs and nano ZnO. [ABSTRACT FROM AUTHOR]

While silk fibers produced by silkworms and spiders are frequently described as a network of amorphous protein chains reinforced by crystalline β-sheet nanodomains, the importance of higher-order, self-assembled structures has been recognized for advanced modeling of mechanical properties. General acceptance of hierarchical structural models is, however, currently limited by lack of experimental results. Indeed, X-ray scattering studies of spider's dragline-type fibers have been particularly limited by low crystallinities. Here we are reporting on probing the local structure of exceptionally crystalline bagworm silk fibers by X-ray nanobeam scattering. Probing the comparable thickness of cross sections with an X-ray nanobeam allows removing the strong scattering background from the outer sericin layer and reveals a hidden structural organization due to a radial gradient in diameters of mesoscale nanofibrillar bundles in the fibroin phase. Our results provide direct support for lateral interactions between nanofibrils.

This work aimed to evaluate the effect of including different concentrations of bamboo nanofibrils on physical, mechanical, morphological and structural properties of nanocomposites from cassava starch and polyvinyl alcohol (PVA). Nanocomposites were prepared with blends of starch/PVA and nanofibrils of bamboo. Chemical pre-treatments and mechanical defibrillation were used to obtain the nanofibrils. The mixture containing 3% of starch and 4% of PVA in the proportion of 20/80 (starch/PVA) were chosen after preliminary testing. Atomic force microscopy (AFM) and transmission electronic microscopy (TEM) were used to characterize the bamboo nanofibrils. Microstructure of the nanocomposites was evaluated using scanning electron microscopy (SEM) and X-ray diffractrometry (XRD). Physical and mechanical properties were also evaluated. Results showed that pre-chemical treatments increased the content of the alpha-cellulose in bleached pulp by approximately 112% in relation to the native fiber. Increasing the number of passages through the defibrillator reduced the average diameter of the bamboo nanofibrils (from 82 ± 29 nm to 10 ± 6 nm). Addition of 6.5% nanofibrils improved the tensile strength and elongation at the break of the nanocomposite by 24 and 51%, respectively, but reduced the tensile modulus by 40% in relation to control (unreinforced) blend. Nanofibrils decreased the transparency of the nanocomposite films. The water vapor permeability and water solubility of the nanocomposite containing high contents of nanofibrils decreased up to 20% and 30%, respectively, in relation to the control blend. [ABSTRACT FROM AUTHOR]

Performance enhancement of polymer solar cells (PSCs) is achieved by expanding the absorption of the active layer of devices. To better match the spectrum of solar radiation, two polymers with different band gaps are used as the donor material to fabricate ternary polymer cells. Ternary blend PSCs exhibit an enhanced short-circuit current density and open-circuit voltage in comparison with the corresponding HD-PDFC-DTBT (HD)- and DT-PDPPTPT (DPP)-based binary polymer solar cells, respectively. Ternary PSCs show a power conversion efficiency (PCE) of 6.71%, surpassing the corresponding binary PSCs. This work demonstrates that the fabrication of ternary PSCs by using two polymers with complementary absorption is an effective way to improve the device performance. [ABSTRACT FROM AUTHOR]

Amyloids are highly ordered protein/peptide aggregates associated with human diseases as well as various native biological functions. Given the diverse range of physiochemical properties of amyloids, we hypothesized that higher order amyloid self-assembly could be used for fabricating novel hydrogels for biomaterial applications. For proof of concept, we designed a series of peptides based on the high aggregation prone C-terminus of Aβ42, which is associated with Alzheimer's disease. These Fmoc protected peptides self assemble to β sheet rich nanofibrils, forming hydrogels that are thermoreversible, non-toxic and thixotropic. Mechanistic studies indicate that while hydrophobic, π–π interactions and hydrogen bonding drive amyloid network formation to form supramolecular gel structure, the exposed hydrophobic surface of amyloid fibrils may render thixotropicity to these gels. We have demonstrated the utility of these hydrogels in supporting cell attachment and spreading across a diverse range of cell types. Finally, by tuning the stiffness of these gels through modulation of peptide concentration and salt concentration these hydrogels could be used as scaffolds that can drive differentiation of mesenchymal stem cells. Taken together, our results indicate that small size, ease of custom synthesis, thixotropic nature makes these amyloid-based hydrogels ideally suited for biomaterial/nanotechnology applications. [ABSTRACT FROM AUTHOR]

Fibroin nanofibrils were synthesized by a pH-controlled heat denaturation method. The nanofibrils were then applied to the surface of a carbon paste electrode to prepare a novel and biocompatible electrode for electrical double-layer supercapacitor applications. The capacity per surface area at a charge/discharge current of 1.0 A was obtained as 4.68 mF cm. The electrode showed improved capability and charge/discharge behavior. [ABSTRACT FROM AUTHOR]

Present study illustrates the preparation of chitin nanofibrils (CNF) reinforced carrageenan nanocomposite films by the solution-casting technique. CNF was prepared by acid hydrolysis of chitin, followed by high speed homogenization and sonication. FTIR result demonstrated that the chemical structure of chitin had not changed after acid hydrolysis. However, the crystalinity of CNF was found to be higher than chitin. The crystallite size of chitin and CNF was 4.73 and 6.27 nm, respectively. The char content at 600 °C of chitin (19.2%) was lower than the CNF (25%). The carrageenan/CNF composite films were smooth and flexible and the CNF was dispersed uniformly in the carrageenan polymer matrix. The tensile strength and modulus of carrageenan film were increased significantly ( p < 0.05) after CNF reinforcement with up to 5 wt%, however, elongation at break, water vapor permeability, and transparency decreased slightly. Carrageenan/CNF nanocomposite films showed strong antibacterial activity against a Gram-positive food-borne pathogen, Listeria monocytogenes. [ABSTRACT FROM AUTHOR]