Smart coating by thermo-sensitive Pluronic F-127 for enhanced corneal healing via delivery of biological macromolecule progranulin.

As a leading cause of vision impairment and blindness, corneal alkali burns lead to long-term visual deterioration or even permanent visual impairment while effective treatment strategies remain a challenge. Herein, a thermo-sensitive hydrogel with the combination of multi-functional protein progranulin (PGRN), a biological macromolecule consisting of several hundred amino acids and possessing a high molecular weight, is efficiently prepared through a convenient stirring and mixing at the low temperature. The hydrogel can be easily administrated to the ocular surface contacting with the cornea, which can be immediately transformed into gel-like state due to the thermo-responsive behavior, realizing a site-specific coating to isolate further external stimulation. The smart coating not only exhibits excellent transparency and biocompatibility, but also presents a constant delivery of PGRN, creating a nutritious and supportive micro-environment for the ocular surface. The results show that the prepared functional hydrogel can efficiently suppress inflammation, accelerate re-epithelization, and intriguingly enhance axonal regeneration via modulation of multiple signaling pathways, indicating the novel designed HydrogelPGRN is a promising therapy option for serious corneal injury.

Stretchable, Ultratough, and Intrinsically Self-Extinguishing Elastomers with Desirable Recyclability.

Advanced elastomers are increasingly used in emerging areas, for example, flexible electronics and devices, and these real-world applications often require elastomers to be stretchable, tough and fire safe. However, to date there are few successes in achieving such a performance portfolio due to their different governing mechanisms. Herein, a stretchable, supertough, and self-extinguishing polyurethane elastomers by introducing dynamic π-π stacking motifs and phosphorus-containing moieties are reported. The resultant elastomer shows a large break strain of ≈2260% and a record-high toughness (ca. 460 MJ m-3 ), which arises from its dynamic microphase-separated microstructure resulting in increased entropic elasticity, and strain-hardening at large strains. The elastomer also exhibits a self-extinguishing ability thanks to the presence of both phosphorus-containing units and π-π stacking interactions. Its promising applications as a reliable yet recyclable substrate for strain sensors are demonstrated. The work will help to expedite next-generation sustainable advanced elastomers for flexible electronics and devices applications.

Nanocellulose implantation enriched the pore structure of aerogel for effective particulate matter removal.

Particulate matter (PM) pollution poses a serious threat to public health, disposable and degradable filter materials are expected to handle the problem in the future. Here, polyvinyl alcohol (PVA)/borax/cellulose nanofibrils (CNF) aerogels were implanted on a biodegradable corrugated paper to form composite air filters for the first time via freeze-drying the coated composite hydrogels. The low content of CNF and PVA could be cross-linked by borax to form hydrogels, which enhanced its maneuverability for surface implanting on the substrate. More importantly, the addition of CNF greatly enriched the pore structure of aerogels, which provided a structural basis for PM capture. The as-prepared composite air filters exhibited excellent filtration efficiencies of 92 % and 96 % toward PM1.0 and PM3.0, respectively. Moreover, the addition of dimethylol-5,5-dimethylhydantoin endowed the filters with an antibacterial property. This work shows a new possibility for the design of degradable and functional filter materials.

A biodegradable composite filter made from electrospun zein fibers underlaid on the cellulose paper towel.

Conventional petroleum-based synthetic polymeric fiber filter materials for separation may cause secondary pollution to the environment due to their non-degradable properties. Herein, we report a facile method of preparation of a biodegradable composite filter that can achieve filtration for air by underlaying the commercialized cellulose paper towel under electrospun zein fibers. The morphology of zein fibers was successfully steered via varying the weight ratios of ethanol/deionized water mixture solvent, as a result, the round or flat ribbon fibers were obtained. The effect of zein fiber morphology on air filtration performance was investigated both experimentally and theoretically. It was found that the flat ribbon fiber filter had a higher filtration efficiency (99%) for PM0.3 removal and a lower pressure drop (109 Pa) compared with the round zein fiber filter. Notably, the as-prepared composite filter can be biodegradable easily, contributing to green ecological environment. This work shows an efficient way to develop biodegradable filtration materials with the cheap price, easy availability of component materials, exhibiting a great potential application in air filtration area.

Insight into levofloxacin loaded biocompatible electrospun scaffolds for their potential as conjunctival substitutes.

The rehabilitation of visual acuity with severe conjunctival fibrosis depends on ocular reconstruction with suitable conjunctival substitutes. In this study, we have developed poly(lactic acid) (PLA) electrospun nanofibrous membranes (EFMs) surface coated by cellulose nanofibrils (CNF) and/or silk peptide (SP). The CNF coating improved the hydrophilicity and the SP coating proliferated conjunctival epithelial cells (CjECs). To prevent post-operative infections, the composite scaffolds were loaded with levofloxacin (LF), constantly exerting efficient bactericidal effects. In in vivo evaluations, the PLA EFMs presented excellent therapeutic effects by promoting structural and functional restoration of conjunctiva after transplant. Even with reduced topical administration of antibiotics, the coloboma treated with LF loaded scaffolds presented no infections. It could be deduced that the potent bacterial inhibition feature could save troubles for patients by minimizing the application of antibiotics post-surgery. Hence, the developed PLA EFMs loaded with LF could be promising conjunctival substitutes.

Three-dimensional fast elemental mapping by soft X-ray dual-energy focal stacks imaging.

The three-dimensional (3D) dual-energy focal stacks (FS) imaging method has been developed to quickly obtain the spatial distribution of an element of interest in a sample; it is a combination of the 3D FS imaging method and two-dimensional (2D) dual-energy contrast imaging based on scanning transmission soft X-ray microscopy (STXM). A simulation was firstly performed to verify the feasibility of the 3D elemental reconstruction method. Then, a sample of composite nanofibers, polystyrene doped with ferric acetylacetonate [Fe(acac)3], was further investigated to quickly reveal the spatial distribution of Fe(acac)3 in the sample. Furthermore, the data acquisition time was less than that for STXM nanotomography under similar resolution conditions and did not require any complicated sample preparation. The novel approach of 3D dual-energy FS imaging, which allows fast 3D elemental mapping, is expected to provide invaluable information for biomedicine and materials science.

Hierarchically Structured Nanocellulose-Implanted Air Filters for High-Efficiency Particulate Matter Removal.

Fine particulate matter (PM) air pollution has increasingly become a global problem; thus, high-performance air filtration materials are in great demand. Herein, we first prepared a biodegradable hierarchically structured nanocellulose-implanted air filter with a high filtration capacity using a freeze-drying technique. In this hierarchically structured air filter, porous structures of corrugated paper and cellulose nanofibrils (CNFs) were used as a frame and functional fillers, respectively. The self-assembled structure of the CNF fillers could be controlled by changing the freezing temperature, CNF sizes, concentrations, and base weights. Only the CNFs with a smaller size and concentration of 0.05 wt % were able to self-assemble to well-dispersed fibril networks. With constant optimization of conditions, when the base weight went up to only 0.25 g/m2, the coverage of the corrugated paper fibers with CNF networks became perfect, and a high efficiency of 94.6% for PM0.3 removal was achieved, while maintaining a relatively low pressure drop of 174.2 Pa. All of the raw materials we used are biodegradable, nonpetroleum-based materials, contributing to sustainable development. We believe that such excellent biodegradable high-performance cellulose-based air filtration materials will provide a new direction for the application of nanocellulose in air filtration.

A tunable alkaline/oxidative process for cellulose nanofibrils exhibiting different morphological, crystalline properties.

This study describes a two-step alkali/oxidation process to efficiently convert waste sugarcane bagasse (SCB) into cellulose nanofibrils (CNF) whose structures have been characterized using a range of analytical techniques (SR-WAXS, IR, TEM and DLS). Increasing the concentration of the NaOH solution from 10 to 16 wt% in the first step results in a gradual increase in cellulose II content from 0 to >99 %, which also produces a corresponding increase in fiber crystallinity index from 32 to 61 %. Varying the concentration of NaClO used in the second oxidative step enables the morphologies of the CNF to be reliably controlled, with fiber lengths decreasing from micrometer to nanometer levels as the amount of NaClO oxidant used is increased. This simple two-step alkaline/oxidative treatment process enables SCB to be converted into CNF exhibiting different polymorphic and morphological properties, thus enabling their economic and reproducible production as nanostructured materials for numerous applications.

Surface modified electrospun poly(lactic acid) fibrous scaffold with cellulose nanofibrils and Ag nanoparticles for ocular cell proliferation and antimicrobial application.

Corneal and conjunctival infections are common ocular diseases, sometimes, causing severe and refractory drug-resistant bacteria infections. Fungal keratitis is a leading cause for blindness and traditional medical treatment is unsatisfactory. Thus, there is an urge to develop a new therapy to deal with these cases. In this study, we developed surface modified poly(lactic acid) (PLA) electrospun nanofibrous membranes (EFMs) with silver nanoparticles (AgNPs) and cellulose nanofibrils (CNF) as scaffolds for cell proliferation and antimicrobial application. The AgNPs with a very low content (below 0.1%) were easily anchored on the surface of PLA EFMs by CNF, which endowed the scaffold with hydrophilicity and antibacterial ability. The in-vitro cell co-culture experiments showed that the scaffold had great biocompatibility to ocular epithelial cells, especially the scaffolds coated by CNF, which significantly proliferated cells. Furthermore, the antibacterial activity could reach >95% inhibiting Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) due to the implantation of AgNPs, and the antifungal activity was also outstanding with most of the Fusarium spp. inhibited. Hence, the developed PLA EFMs with CNF and AgNPs are promising ocular bandages to promote cell proliferation and kill infectious pathogens, exhibiting potential applications in ocular wound healing in the future.

Isolation of hierarchical cellulose building blocks from natural flax fibers as a separation membrane barrier.

Cellulose nanofibrils (CNF) is a natural nanomaterial composed of biomacromolecules that can be extracted from plants and has great potential applications in many fields due to its excellent regenerative, sustainable, and biodegradable properties. In this work, the flax CNF with hierarchical scales was obtained by using the flax fibers (FF) treated with different concentrations of alkaline solution, followed by the TEMPO-mediated ternary oxidation and mechanical treatment. Subsequently, the resultant CNF was implanted on the commercial filter paper as a surface barrier for oil/water preparation. The changes of cellulose crystal form and crystallinity caused by alkali treatment on FF were studied by Fourier transform infrared spectroscopy and X-ray diffraction. Morphological changes of FF before and after alkali treatment were observed. The morphology of obtained CNF was examined. Moreover, the transmittance of the prepared CNF suspension and films was also investigated by a UV spectroscopy. The prepared modified filter paper can effectively separate the oil/water mixture, which gives themselves promise as candidates in practical applications of oil/water separation.

Facile and quick formation of cellulose nanopaper with nanoparticles and its characterization.

Cellulose nanofibrils (CNF) is a suitable functional material as its lightweight, huge availability and biodegradable advantages. A direct-evaporation method was employed to prepare the CNF nanopapers with or without Fe3O4 and TiO2 nanoparticles (NPs) in the form of films, which is more facile and efficient in comparison with the methods of vacuum-filtration and cast drying. A combination of three-dimensional (3D) focal stacks and dual-energy imaging method was firstly used to characterize the CNF nanopapers embedded with Fe3O4 and TiO2 NPs, where the locations of the NPs can be clearly and exactly distinguished. Furthermore, the thickness, transparency, magnetism and tensile properties of the CNF nanopapers were characterized. This work shows a facile method for the preparation of CNF nanopapers with or without addition. More importantly, the combination of focal stacks and dual-energy imaging method offers a superior means of characterizing the spatial structures and 3D elemental visualization.

Coiled Plant Tendril Bioinspired Fabrication of Helical Porous Microfibers for Crude Oil Cleanup.

Fabrication of the helical fibers with sheath/core structure comprising 3D interconnected porous polystyrene (PS) and ductile polyvinylidene fluoride is inspired by coiled plant tendril. The key innovation point applied in this study is to produce a helical porous system based on sheath/core structure that can come into being a huge storage space in the sorption process for crude oil. More importantly, the mechanical properties confirm to have a more excellent improvement than that of the initial PS fibers, which make it become a possible candidate for the large-area sorption and reuse of crude oil from the ocean or industry. The bioinspired fabricating strategy opens a significant avenue between the coaxial electrospinning and crude oil contamination cleanup. It is also expected that the unique structure can make it a promising candidate for applications in energy conversion, tissue engineering, and intelligent devices.

Cellulose nanofibrils extracted from the byproduct of cotton plant.

Cotton stalk bark, as the byproduct of cotton plant, was usually discarded and/or combusted, leading to waste of resources and environment pollution. How to efficiently utilize this kind of cellulosic materials is of significative to energy saving and environment protection. Herein, we report on the extraction of cellulose nanofibrils (CNF) from the cotton stalk bark for the first time by a combination of TEMPO-oxidation and mechanical disintegration method. The obtained CNF showed a yield more than 20 wt%. The morphologies, crystalline structures and thermal properties of CNF were extensively investigated by the transmission electron microscopy, scanning electron microscopy, synchrotron radiation wide-angle X-ray scattering, Fourier transform infrared spectra and differential scanning calorimetry, respectively. The results showed that the final extracted CNF have similar polymorphs with their starting materials and a significantly increased crystallinity. This work will provide a new way to utilize the cotton stalk barks.

Bioinspired Thermoresponsive Photonic Polymers with Hierarchical Structures and Their Unique Properties.

Thermoresponsive photonic materials having hierarchical structures are created by combining a template of Morpho butterfly wings with poly(N-isopropylacrylamide) (PNIPAM) through a chemical bonding and polymerization route. These materials show temperature-induced color tunability. Through reacting with both NIPAM monomers and the amino groups of chitosan in wing scales, glutaraldehyde workes as a bridge by creating chemical bonding between the biotemplate and the PNIPAM. The corresponding reflection peaks red-shift with increase in temperature-an opposite phenomenon to previous studies, demonstrating a thermoresponsive photonic property. This unique phenomenon is caused by the refractive index change due to the volume change of PNIPAM during the temperature rising. This work sets up an efficient strategy for the fabrication of stimuli-responsive photonic materials with hierarchical structures toward extensive applications in science and technology.

Pectin/lysozyme bilayers layer-by-layer deposited cellulose nanofibrous mats for antibacterial application.

Positively charged lysozyme (LZ) and negatively charged pectin, were alternately deposited on the surface of the cellulose nanofibrous mats by layer-by-layer (LBL) self-assembly technique. Scanning electron microscopy images showed that the nanofibers were orderly and compactly arrayed after LBL. Besides, as the number of LZ/pectin bilayers increased, the average diameter of nanofibers increased. LZ has assembled on the cellulose mats successfully, which was confirmed by X-ray photoelectron spectroscopy analysis. Thermal gravimetric analysis results showed that the thermal properties of LZ/pectin films coated mats was better than that of the unmodified cellulose mats. Importantly, the results of the bacterial inhibition test for LBL structured mats and cellulose mats indicated that the nanofibrous mats coated by 10.5 LZ/pectin bilayers (with LZ on the outmost layer) possessed the strongest inhibitory effect against both Escherichia coli and Staphylococcus aureus.

Cellulose nanofibrils aerogels generated from jute fibers.

In this work, we report the cellulose nanofibrils extracted from the pristine jute fibers via the pretreatments followed by the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and mechanical disintegration. The effects of pretreatments by using the NaOH solution and dimethyl sulfoxide solvent on the fiber morphology and macro/micro-structures were investigated by polarizing microscope and synchrotron radiation wide/small-angle X-ray scattering (WAXS/SAXS). The cellulose nanofibrils exhibit a diameter ranging from 5 nm to 20 nm and a length of several micrometers, which have been assembled into cellulose aerogels by the lyophilization of as-prepared nanofibrils dispersions with various concentrations. The results indicated that the hierarchical structures of as-prepared cellulose aerogels were dependent on the dispersion concentrations. The WAXS results show that the typical cellulose aerogels are coexistence of cellulose I and cellulose II, which has a great promise for many potential applications, such as pharmaceutical, liquid filtration, catalysts, bio-nanocomposites, and tissue engineering scaffolds.

Structure and properties of novel regenerated cellulose fibers prepared in NaOH complex solution.

Novel spinning solution, prepared by dissolving hydroxyethyl cellulose (HEC) owning a low molar substitution (MS) into NaOH/urea/thiouea aqueous solution with a specific weight ratio of 8:8:6.5, was employed to fabricate a new type of regenerated fibers by wet-spun method. The structure and properties of the resultant HEC fibers were characterized by (13)C NMR, FTIR, synchrotron WAXS, SEM, and tensile tester. The results showed that HEC fibers exhibited structure identical with HEC because of the physical dissolution and coagulation processes, but quite different from native cellulose due to partial breakage of hydrogen bonds and crystal transformation from cellulose I to cellulose II during cellulose modification. The resultant HEC fibers with relatively dense and homogenous structure displayed good moisture related properties and stayed stable in alkali solution with low concentration. Moreover, the novel fibers owned good dry mechanical properties in spit of their slightly poor wet mechanical properties comparable to viscose rayon, showing great potential in substituting the traditional viscose fibers.

Co-axial electrospun polystyrene/polyurethane fibres for oil collection from water surface.

The pollution arising from oil spills is a matter of great concern due to its damaging impacts on the ecological environment, which has created a tremendous need to find more efficient materials for oil spill cleanup. In this work, we reported a sorbent for oil soak-up from a water surface with a high sorption capacity, good selectivity, and excellent reusability based on the hydrophobic-oleophilic fibrous mats that were fabricated via co-axial electrospinning polystyrene (PS) solution as the shell solution and polyurethane (PU) solution as the core solution. The fine structures of as-prepared fibers were regulated by manipulating the spinning voltages, core solution concentrations, and solvent compositions in shell solutions, which were also characterized by field emission scanning electron microscopy, transmission electron microscopy, nitrogen adsorption method, and synchrotron radiation small-angle X-ray scattering. The effects of inter-fiber voids and intra-fiber porosity on oil sorption capacities were well studied. A comparison of oil sorption capacity for the single fiber with different porous structures was also investigated with the help of scanning transmission X-ray microscopy. The results showed that the sorption capacities of the as-prepared sorbent with regards to motor oil and sunflower seed oil can be 64.40 and 47.48 g g(-1), respectively, approximately 2-3 times that of conventional polypropylene (PP) fibers for these two same oils. Even after five sorption cycles, a comparable oil sorption capacity with PP fibers was still maintained, exhibiting an excellent reusability. We believe that the composite PS-PU fibrous mats have a great potential application in wastewater treatment, oil accident remediation and environmental protection.

Facile control of intra-fiber porosity and inter-fiber voids in electrospun fibers for selective adsorption.

We report a facile method to control intra-fiber porosity via varying the relative humidity and inter-fiber voids through the blending of two different polymeric fibers via multi-nozzles spinning of electrospun fibers for selective adsorption of oil from water.

Subtle regulation of the micro- and nanostructures of electrospun polystyrene fibers and their application in oil absorption.

In this study, we conducted a subtle regulation of micro- and nanostructures of electrospun polystyrene (PS) fibers via tuning the molecular weights of the polymers with different sources, solvent compositions, and solution concentration. The surface morphology and porous structures of as-prepared PS fibers were characterized, and a full and intuitive observation of the porous structures as well as a tentative account of the formation of porous structures was presented. Additionally, the porous PS fibrous mats showed much higher oil absorption capacities than those of commercial polypropylene fibers in the form of a non-woven fabric, which displays a bight future for oil spill cleanups. We believe that such regulation of micro- and nanostructures of the PS fibers will widen the range of their applications in self-cleaning materials, ultra-high sensitivity sensors, tissue engineering, ion exchange materials, etc.