Development of Vitamin C-Loaded Electrospun Nanofibers of Mixture of Polysaccharides of Pullulan/Xanthan Gum for Fast Dissolving Oral Film Applications.

In this study, polysaccharide-based nanofibrous fast dissolving oral films (FDOFs) were developed using pullulan (PUL) and xanthan gum (XG) via electrospinning. The edible, continuous, and bead-free nanofibers with average diameters ranging from 181.17 nm to 260.84 nm were prepared. The morphological, thermal, mechanical, and water-soluble properties of the nanofibrous FDOFs were characterized. For prospective future applications of the developed PUL/XG FDOFs, a model nutrient of vitamin C (VC) was encapsulated into the FDOFs. The success of VC encapsulation was confirmed by Fourier transform infrared spectroscopy. The encapsulation efficiency of VC was above 85% by ultraviolet-visible spectrophotometer. The amorphous structure of PUL/XG in the nanofibers film was demonstrated by X-ray diffractometer. In addition, the edible FDOFs could dissolve in water within 3 s. The nanofibers film we prepared could be used as nutrient or drug carriers and edible packaging film.

Mesostructured Fibrils Exfoliated in Deep Eutectic Solvent as Building Blocks of Collagen Membranes.

The mesoscale components of collagen (nanofibrils, fibrils, and fiber bundles) are well organized in native tissues, resulting in superior properties and diverse functions. In this paper, we present a simple and controlled liquid exfoliation method to directly extract medium-sized collagen fibers ranging from 102 to 159 nm in diameter from bovine Achilles tendon using urea/hydrochloric acid and a deep eutectic solvent (DES). In situ observations under polarized light microscopy (POM) and molecular dynamics simulations revealed the effects of urea and GuHCl on tendon collagen. FTIR study results confirmed that these fibrils retained the typical structural characteristics of type I collagen. These shed collagen fibrils were then used as building blocks to create independent collagen membranes with good and stable mechanical properties, excellent barrier properties, and cell compatibility. A new method for collagen processing is provided in this work by using DES-assisted liquid exfoliation for constructing robust collagen membranes with mesoscale collagen fibrils as building blocks.

Substantial and efficient adsorption of heavy metal ions based on protein and polyvinyl alcohol nanofibers by electrospinning.

The adverse effects of heavy metal pollutants in wastewater have threatened human health in recent decades. Therefore, the development of absorbents for such pollutants is essential to overcome these problems. Electrospun nanofibers are often used for wastewater treatment owing to their high porosity and high specific surface area. Zein from plants and collagen from animals are vulnerable to moisture, which limits its broad application in practice. However fully biodegradable polyvinyl alcohol (PVA), which is soluble in water, can be mixed with protein individually to overcome the limitation. In this work, the two proteins described above and PVA were combined to prepare protein nanofibers by electrospinning technology, which could achieve adsorption of Cu2+. As the protein content increased, the adsorption properties of the obtained nanofibers for Cu2+ showed a rising and then decreasing trend, with the highest point at 50 % of protein content, especially the collagen nanofibers, which reached 24.62 mg/g. Both protein nanofibers reached adsorption equilibrium after 15 h, but overall, collagen nanofibers showed a superior adsorption performance for Cu2+ than that by zein nanofibers. In the process of Cu2+ adsorption by protein nanofibers, both physical and chemical effect existed, and the physical effect played the leading role.

High-performance thermoplastic starch/poly(butylene adipate-co-terephthalate) blends through synergistic plasticization of epoxidized soybean oil and glycerol.

Utilizing starch, an abundant polysaccharide, as the renewable filler to blend with poly(butylene adipate-co-terephthalate) (PBAT) is a feasible tactic to construct cost-effective and high-performance biodegradable materials. It's worth noting that the thermal processing properties of starch can be manipulated by its plasticized behavior. Herein, epoxidized soybean oil (ESO) and glycerol were used as the plasticizer for native corn starch and the plasticized starch was integrated with PBAT to manufacture starch-based biodegradable blend films. ESO breaks the hydrogen bonds between starch chains through the fatty chains grafting reaction and increases the distance between starch molecular chains due to the large molecular weight of ESO. Meanwhile, glycerol molecules are incorporated into the starch molecular chains, and fatty chains grafted starch chains, effectively reducing the intermolecular forces of molecular chains. On account of the synergistic plasticization of ESO and glycerol which possess good compatibility with PBAT, the PSG20E10 blend film achieved a tensile strength, an elongation at break of 16.11 MPa and 612.09 %, and the balanced water and oxygen permeability properties.

Chitosan-Grafted Carbon Oxynitride Nanoparticles: Investigation of Photocatalytic Degradation and Antibacterial Activity.

In this work, a series of chitosan (CS)-grafted carbon oxynitride (OCN) nanoparticles (denoted as CS-OCN) were successfully synthesized for the first time by thermal polycondensation and subsequent esterification. The structure and photocatalytic performance of CS-OCN nanoparticles were investigated. The XPS spectra of CS-OCN-3 showed the presence of amino bonds. The optimal photocatalytic degradation efficiency of the synthesized CS-OCN-3 could reach 94.3% within 390 min, while the photocurrent response intensity was about 150% more than that of pure OCN. The improved photocatalytic performance may be mainly attributed to the enhanced photogenerated carrier's separation and transportation and stronger visible light response after CS grafting. In addition, the inhibition diameter of CS-OCN-3 reached 23 mm against E. coli within 24 h under visible light irradiation, exhibiting excellent photocatalytic bactericidal ability. The results of bacterial inhibition were supported by absorbance measurements (OD600) studies of E. coli. In a word, this work provided a rational design of an efficient novel metal-free photocatalyst to remove bacterial contamination and accelerate the degradation of organic dyes.

Microcrystalline cellulose grafted hyperbranched polyester with roll comb structure for synergistic toughening and strengthening of microbial PHBV/bio-based polyester elastomer composites.

The brittle feature of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is the major challenge that strongly restricts its application at present. Successfully synthesized bio-based engineering polyester elastomers (BEPE) were combined with PHBV to create entirely bio-composites with the intention of toughening PHBV. Herein, the 2,2-Bis(hydroxymethyl)-propionic acid (DMPA) was grafted onto microcrystalline cellulose (MCC) and then further transformed into hyperbranched polyester structure via polycondensation. The modified MCC, named MCHBP, had plenty of terminal hydroxyl groups, which get dispersed between PHBV and BEPE. Besides, a large number of terminal hydroxyl groups of MCHBP can interact with the carbonyl groups of PHBV or BEPE in a wide range of hydrogen bonds, and subsequently increase the adhesion and stress transfer between the PHBV and BEPE. The tensile toughness and the elongation at break of the PHBV/BEPE composites with 0.5phr MCHBP were improved by 559.7 % and 221.8 % in comparison to those of PHBV/BEPE composites. Results also showed that MCHBP can play a heterogeneous nucleation effect on the crystallization of PHBV. Therefore, this research can address the current issue of biopolymers' weak mechanical qualities and may have uses in food packaging.

Fabrication and characterization of natural polyphenol and ZnO nanoparticles loaded protein-based biopolymer multifunction electrospun nanofiber films, and application in fruit preservation.

To extend the shelf life of sweet cherries (Prunus avium L.) and considering the environmental problems caused by traditional packaging materials, novel Zein/Gelatin-proanthocyanidins-zinc oxide nanoparticles (ZE/GE-PC-ZnO) and Zein/Gelatin-gallic acid-zinc oxide nanoparticles (ZE/GE-GA-ZnO) protein-based composite nanofiber films were prepared by electrospinning. According to the results, ZE/GE-PC-ZnO and ZE/GE-GA-ZnO films' contact angles were higher than those of Zein/Gelatin film by 28.91% and 21.27%, and their antioxidant activities were 5 and 9 times higher, respectively. Moreover, ZE/GE-PC-ZnO film showed good inhibitory activity against B. cinerea. On the eleventh day of the cherry packaging test, compared to unwrapped cherries, the losses of weight and firmness of wrapped fruit were reduced by more than 20% and 60%, respectively. Respiration time was delayed by 5 days, and the peak of ethylene release was decreased by nearly half. In conclusion, these two nanofiber films were viable packaging materials that fulfilled global strategies for green development.

Fabrication of cellulose/rectorite composite films for sustainable packaging.

In order to reduce the environmental pollution caused by plastic packaging, the development of biodegradable high-performance packaging materials has become a research hotspot. Cellulose is a promising food packaging material, but it usually lacks sufficient ultraviolet (UV) shielding property and mechanical strength. In this work, rectorite microplates were incorporated into the cellulose matrix by a facile blending method to fabricate the composite films. The structure and properties of the composite films were characterized by FT-IR, X-ray diffraction, scanning electron microscopy, UV-vis and mechanical properties test etc. The results indicated that rectorite microplates were uniformly distributed in the cellulose matrix. The blocking percentages for UVA and UVB for the cellulose/rectorite composite film with 14 wt% rectorite content (RCRF-14) could reach as high as 97.8 % and 96.0 %, respectively, showing a good UV shielding property. Meanwhile, the addition of rectorite obviously improved the mechanical properties and decreased the water vapor and oxygen permeabilities of the cellulose film, showing a potential application as a sustainable food packaging material.

Electrospun natural polypeptides based nanofabrics enriched with antioxidant polyphenols for active food preservation.

In order to overcome the environmental problems posed by traditional packaging materials and taking into account the degradation factors, a natural polypeptides-based nanofiber rich in different polyphenols was prepared by electrospinning technique and has been explored as an active food packaging material. The results showed that the introduction of polyphenols improved the hydrophobicity and oxidation resistance of the natural polypeptides based nanofabric. The antioxidant value was 82.5% after incorporation of 15% gallic acid, which was ten times more than that of the natural polypeptides-based nanofabrics without polyphenols. Through the packaging test of wrapped cherries, it was found that the nanofabric films greatly improved the preservation performance of cherries. Water loss, hardness and gas release were significantly enhanced when compared with those of unwrapped cherries. In this work, the zein/gelatin film with 15% gallic acid or 10% procyanidins polyphenols exhibited the best fresh-keeping performance and remarkable effect thus leading to potential application aspect.

PDMS/PVDF Electrospinning Membranes for Water-in-Oil Emulsion Separation and UV Protection.

With industry development, the separation of oily wastewater is becoming more critical. Inspired by organisms such as lotus leaves, biomimetic superhydrophobic surfaces with micro-nano structures have shown great potential in this regard. In this work, PDMS/PVDF oil-water separation membranes with designed microstructures were prepared by electrospinning technology. The membrane-forming effect of electrospinning with different ratios of PDMS and PVDF was studied. The study found that membranes with high PDMS content were more likely to form microspheres, and PDMS tended to concentrate on the microspheres. The results also showed that the microspheres would bring better hydrophobicity to the membrane. When the ratio of PDMS to PVDF is 1:2, the membrane has a water contact angle of up to 150° and an oil contact angle of 0°. At this ratio, the separation efficiency of the membrane for the water-in-oil emulsion is 98.7%, and it can still maintain more than 98% after ten separation cycles, which is a good candidate for oil-water separation. Furthermore, microspheres enable the membrane to achieve macroscopic uniformity and microscopic phase separation so that the membranes have both good elongation and fracture strength. In addition, the PDMS/PVDF membranes also exhibit excellent UV resistance, and their UV protection factor is greater than 185, making them a potential UV protective material.

Improved piezoelectricity of porous cellulose material via flexible polarization-initiate bridge for self-powered sensor.

Self-powered piezoelectric sensors based on cellulose nanocrystal (CNC) porous materials are light-weight and portable, whereas using unmodified CNCs can hardly obtain enough piezoelectric properties without external strong polarization due to its irreversible deformation caused by low toughness. Here, we bonded rod-like CNCs with a soft polymer, poly ethylene glycol (PEG), and hypothesized that PEG could toughen the material and its dielectric signal could induce the CNC polarization. We further adsorbed graphene (GR) as surface electrodes to prepare a CNC-PEG-GR piezoelectric porous material with density of 0.096 g·cm-3. The voltage output reached maximum when the frequency matched the dielectric relaxation frequency of PEG. We also increased the length-diameter ratio of porous material pores from 1.1 to 3.3 by adjusting its freeze-drying process, and the voltage output could reach to 0.7 V at a moderate ratio. They could be conveniently integrated into portable self-powered sensors applied to the intelligent wearable electronic devices.

Production of Xylooligosaccharides from Jiuzao by Autohydrolysis Coupled with Enzymatic Hydrolysis Using a Thermostable Xylanase.

The production of xylooligosaccharides (XOS) from Jiuzao was studied using a two-stage process based on autohydrolysis pretreatment followed by enzymatic hydrolysis. Jiuzao was autohydrolyzed under conditions where temperature, time, particle size, and solid-liquid ratio were varied experimentally. Optimal XOS production was obtained from Jiuzao with a >20 mesh particle size treated at 181.5 °C for 20 min with a 1:13.6 solid-liquid ratio. Subsequently, optimal enzymatic hydrolysis conditions for xylanase XynAR were identified as 60 °C, pH 5, and xylanase XynAR loading of 15 U/mL. Using these conditions, a yield of 34.2% XOS was obtained from Jiuzao within 2 h. The process developed in the present study could enable effective and ecofriendly industrial production of XOS from Jiuzao.

Tailoring compatibility and toughness of microbial poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/bio-based polyester elastomer blends by epoxy-terminated hyperbranched polyester.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a type of promising bio-based thermoplastic for food packaging but find restricted industrial applications due to its brittleness and poor processability that is caused by its large spherulite sizes. In this study, for the purpose of toughening PHBV, bio-based engineering polyester elastomers (BEPE) were synthesized and blended with PHBV to prepare fully bio-based blends. In order to improve the compatibility and toughness of the BEPE/PHBV blends, epoxy-terminated hyperbranched polyesters (EHBP) were synthesized, which could be homogeneously dispersed into the PHBV/BEPE blends and improve the compatibility between the two phases of the matrix. The results showed that compared to those of the PHBV/BEPE blends, the elongation at break, impact strength and tensile toughness of the PHBV/BEPE blends with 3.0phr EHBP were enhanced by 134.2 %, 76.8 %, and 123.5 %, respectively. The crystallization study demonstrated the crystallization rate of PHBV/BEPE blends decreased due to the addition of EHBP. The reasons lied in that the addition of EHBP leads to chemical cross-linking between PHBV and BEPE. Meanwhile, the formation of hydrogen bonding, co-crystallization and chain entanglement increased the adhesion between PHBV and BEΡE, which generated the superior toughness of the blends.

An Electrospun Sandwich-Type Lipase-Membrane Bioreactor for Hydrolysis at Macroscopic Oil-Water Interfaces.

The core task for lipase catalytic system design is to construct a suitable oil-water interface for lipase distribution. In comparison to the micro-oil-water interface, the macro-oil-water interface (top oil-bottom water) served as a simplified lipase catalytic system that is more in line with industrial applications but limited in catalytic efficiency. Based on the assumption that one potential carrier can help lipase reach to the macro-oil-water interface, in the current work, sandwich-type lipase-membrane bioreactors (SLMBs) fabricated by a facile layer-by-layer electrospinning process were reported. These SLMBs were composed of a hydrophilic polyamide 6 nanofibrous membrane (NFM) as the bottom layer, a blended electrospun lipase/PVA NFM as the middle layer, and a hydrophobic EC/PU NFM as the top layer. The lipase loading can be controlled by altering the electrospinning time of the middle layer. Under the optimized conditions, the catalytic efficiency of the SLMBs was 2.05 times higher than that of free lipase. In addition, the SLMBs exhibit much better pH (high activity over a broad pH range of 5-10), temperature (retained 62% at 80 °C), storage stability (no loss of activity after being stored at 4 °C for 11 days), and reusability (retained 23% after five cycles) than free lipase.

A Novel Branched Al2O3/Silicon Rubber Composite with Improved Thermal Conductivity and Excellent Electrical Insulation Performance.

In this paper, we report a thermal conductive polymer composite that consists of silicone rubber (SR) and branched Al2O3 (B-Al2O3). Owing to the unique two-dimensional branched structure, B-Al2O3 particles form a continuous three-dimensional network structure by overlapping each other in the matrix, serving as a continuous heat conductive pathway. As a result, the polymer composite with a 70 wt% filler achieves a maximum thermal conductivity of 1.242 Wm-1 K-1, which is equivalent to a significant enhancement of 521% compared to that of a pure matrix. In addition, the composite maintains a high volume resistivity of 7.94 × 1014 Ω·cm with the loading of 70 wt%, indicating that it meets the requirements in the field of electrical insulation. Moreover, B-Al2O3 fillers are well dispersed (no large agglomerates) and form a strong interfacial adhesion with the matrix. Therefore, the thermal decomposition temperature, residual mass, tensile strength, modulus and modulus of toughness of composites are significantly improved simultaneously. This strategy provides new insights for the design of high-performance polymer composites with potential application in advanced thermal management in modern electronics.

Characterization and antibacterial properties of epsilon-poly- l-lysine grafted multi-functional cellulose beads.

In recent years, harmful microorganisms in water pose great harm to ecological environment and human health. To solve this problem, epsilon-poly-l-lysine (EPL) grafted cellulose beads were prepared via 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) mediated oxidation and carbodiimide mediated cross-linking reaction. Hydroxyl groups on C6 of cellulose were oxidized to carboxyl groups by TEMPO and grafting reaction was achieved between newly formed carboxyl groups of cellulose and amino of EPL. The beads were characterized by FTIR, SEM, XRD and TGA. The crystalline form of cellulose transformed from cellulose I to cellulose II after being dissolved and regenerated. The grafted cellulose beads showed good antibacterial activities against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus and Alicyclobacillus acidoterrestris with 10 h. The beads could be biodegraded in soil after 28 days. It is expected that the bio-based composite beads could have potential applications in water purification and food treatment fields.

Fabrication and characterization of antibacterial epsilon-poly-L-lysine anchored dicarboxyl cellulose beads.

Pathogens in the food and environment pose a great threat to human health. To solve this problem, we described a novel route to synthesize antibacterial epsilon-poly-L-lysine (EPL) anchored dicarboxyl cellulose beads. Cellulose beads were prepared via a sol-gel transition method and oxidized by sodium periodate and sodium chlorite to form carboxyl groups. EPL was anchored on the beads using carbodiimide mediated amidation. The structure and morphology of beads were characterized by FTIR, XPS, XRD, SEM, and TGA. After dissolution and regeneration, the crystalline form of cellulose is transformed from cellulose I to cellulose II. The thermal degradation temperature of the beads is 200∼300 °C.The samples displayed excellent antimicrobial activity against Staphylococcus aureus, Alicyclobacillus acidoterrestris and Escherichia coli within 12 h. The beads could be biodegraded in soil after 20 days. The biodegradable beads exhibited great potential in food and environmental applications.

Fabrication of branching poly (butylene succinate)/cellulose nanocrystal foams with exceptional thermal insulation.

Branching poly (butylene succinate) (BPBS) nanocomposite foams incorporated with cellulose nanocrystals (CNCs) were prepared by supercritical CO2. Surface modification of CNCs by acetylation was achieved through replacing hydrophilic hydroxyl groups with hydrophobic acetyl groups, which improved the dispersibility of CNCs significantly. The crystallite sizes of CNCs and acetylated CNCs were calculated by Scherrer's formula as 25 and 19 nm, respectively. The initial crystallization temperature of diverse poly (butylene succinate) (PBS) specimens, a crucial factor for regulating cell nucleation type, increased remarkably by 11.8 °C as well as their storage modulus increased by 2 orders of magnitudes, due to branching reaction and bio-filler addition. BPBS/CNCs foam possessed a high volume expansion ratio as 37.1 times and displayed an exceptional thermal conductivity as 0.021 W(m K)-1. This study provided a promising potential strategy to develop exceptional thermal-insulation polymer foams for composite structures, energy conservation and environment protection.

Preparation of Lipase-Electrospun SiO2 Nanofiber Membrane Bioreactors and Their Targeted Catalytic Ability at the Macroscopic Oil-Water Interface.

Lipase is one of the most widely used enzymes in biocatalysis. Because of the special structure of the catalytic active center, lipases show high catalytic activity at oil-water interfaces. Hence, the interface plays a key role in activating and modulating lipase biocatalysis. Compared with traditional catalytic systems that offer interfaces, such as emulsions, a lipase-membrane bioreactor exhibits many obvious advantages when at the macroscopic oil-water system. In our current research, a series of new Burkholderia cepacia lipase (BCL)-SiO2 nanofiber membrane (NFM) bioreactors prepared via combined electrospinning and immobilization strategies were reported. These SiO2 NFMs assisted BCL in reaching the oil-water interface for efficient catalysis. The enzyme loading capacity and catalytic efficiency of BCL-SiO2 NFMs varied with the surface hydrophobicity of the electrospun NFMs. As the hydrophobicity increased, the activity decreased from 2.43-fold to 0.74-fold that of free BCL. However, the lipase-loading capacity increased obviously when the hydrophobicity of the SiO2 NFMs increased from 0 to 143°, and no significant change was observed when the hydrophobicity of the SiO2 NFMs increased from 143 to 153°. The gel trapping technique proved that the hydrolytic activity of the different BCL-SiO2 NFM bioreactors depends on the contact area of the membrane at the oil-water interface. BCL-SiO2 NFM, BCL-SiO2 NFM-C12, and BCL-SiO2 NFM-C18 retained 32, 83, and 42% of activity, respectively, after five cycles of reuse. The current work was a useful exploration of the construction and modification of lipase-membrane reactors based on electrospun inorganic silicon.

Universal preparation of cellulose-based colorimetric sensor for heavy metal ion detection.

A simple and universal strategy was developed to prepare cellulose/dye composite film, as colorimetric sensor for heavy metal ions (HMIs) detection. After regenerating cellulose solution in ethanol, the regenerated films were further soaking in dye/ethanol solution followed by hot-pressing, to obtain cellulose/dye composite films. 1-(2-pyridylazo)-2-naphthol (PAN) was used as an example, and the resultant cellulose/PAN composite films (CPs) possessed robust mechanical property (tensile strength of 52.9 MPa), light transmittance, and thermodynamic stability. PAN distributed uniformly as nanoparticles of 30 nm on cellulose because of the interaction between N of azo group of PAN and cellulose. When used as colorimetric sensor for Zn2+ detection, the detection limit of CP was as low as 100 ppb, and the color change was distinguishable after testing with tap water. Moreover, two more dyes including 1-(2-thiazolylazo)-2-naphthol (TAN) and dithizone (Dith) were also immobilized successfully on cellulose, and the resultant films were effective colorimetric sensor for HMIs like Zn2+ and Cu2+. This work provided a facile and universal method to prepare cellulose-based colorimetric sensor or HMI detection, demonstrating great potential in water treatment and natural resources utilization.