Quantitative analysis of intermolecular forces in cellulose microfibrils and hemicellulose with AFM nano-colloidal probes.

It is an interesting research topic to study the interfacial interactions between hemicellulose and cellulose, specifically how hemicellulose's structure affects its binding to cellulose nanofibers. Our research proposes that dispersion interaction play an important role in this interfacial interaction, more so than electrostatic forces when considering the adherence of cellulose to xylan. To quantify these interactions, the Atomic Force Microscope (AFM) colloidal probe technique is applied to measure the intermolecular forces between cellulose nanofibers, which are attached to the probe and xylan. These measured forces are then analyzed in relation to the length, diameter and functional groups of the nanocellulose, as well as the molecular weight and side chains of the xylan. Moreover, the predominance of dispersion forces by contrasting the adhesive forces before and after the grafting of a large nonpolar group onto xylan. This modification significantly reduces contact between the cellulose and xylan backbone, thereby markedly diminishing the dispersion interactions. Parallel to the AFM experiments, molecular dynamics (MD) simulations corroborate the experimental results and support our hypotheses. Collectively, these findings contribute to a deeper understanding of polysaccharide interactions within lignocellulose.

Palm-based nanofibrillated cellulose (NFC) in carotenoid encapsulation and its incorporation into margarine-like reduced fat spread as fat replacer.

Nanofibrillated cellulose (NFC) from plant biomass is becoming popular, attributed to the protective encapsulation of bioactive compounds in Pickering emulsion, preventing degradation and stabilizing the emulsion. NFC, as a natural dietary fiber, is a prominent fat replacer, providing a quality enhancement to reduced-fat products. In this study, NFC Pickering emulsions were prepared at NFC concentrations of 0.2%, 0.4%, 0.6%, 0.8%, and 1% to encapsulate carotenoids. The NFC Pickering emulsions at NFC concentrations of 0.4%, 0.6%, 0.8%, and 1% were incorporated into margarine-like reduced fat (3%) spreads as the aqueous phase. Characterization of both NFC Pickering emulsion and the incorporated NFC Pickering emulsion, margarine-like reduced fat spreads, was conducted with mastersizer, rheometer, spectrophotometer, and texture analyzer. The particle size (73.67 ± 0.35 to 94.73 ± 2.21 nm), viscosity (138.36 ± 3.35 to 10545.00 ± 567.10 mPa s), and creaming stability (25% to 100% stable) of the NFC Pickering emulsions were increased significantly when increasing the NFC concentration, whereas the encapsulation efficiency was highest at NFC 0.4% and 0.6%. Although imitating the viscoelastic solid-like behavior of margarine was difficult, the NFC Pickering emulsion properties were still able to enhance hardness, slip melting point, and color of the reduced fat spreads compared to the full-fat margarine, especially at 0.6% of NFC. Overall, extensive performances of NFC can be seen in encapsulating carotenoids, especially at NFC concentrations of 0.4% and 0.6%, with the enhancement of Pickering emulsion stability while portraying futuristic possibilities as a fat replacer in margarine optimally at 0.6% of NFC concentration. PRACTICAL APPLICATION: Nanocellulose extracted from palm dried long fiber was utilized to encapsulate carotenoids and replace fats in margarine-like reduced fat (3%) spreads. Our study portrayed high encapsulation efficiency and successful fat replacement with promising stability performances. Hence, nanocellulose displayed extensive potential as encapsulating agents and fat replacers while providing quality and sustainability enhancements in reduced-fat food.

Unveiling the potential of cellulose, chitosan and polylactic acid as precursors for the production of green carbon nanofibers with controlled morphology and diameter.

Carbon nanofibers (CNFs) are very promising materials with application in many fields, such as sensors, filtration systems, and energy storage devices. This study aims to explore the use of eco-friendly biopolymers for CNF production, finding novel, suitable and sustainable precursors and thus prioritising environmentally conscious processes and ecological compatibility. Polymeric nanofibers (PNFs) using cellulose acetate, polylactic acid, and chitosan as precursors were successfully prepared via electrospinning. Rheological testing was performed to determine suitable solution concentrations for the production of PNFs with controlled diameter and appropriate morphology. Their dimensions and structure were found to be significantly influenced by the solution concentration and electrospinning flow rate. Subsequently, the electrospun green nanofibers were subject to stabilisation and carbonisation to convert them into CNFs. Thermal behaviour and chemical/structural changes of the nanofibers during stabilisation were investigated by means of thermogravimetric analysis and Fourier-transform infrared spectroscopy, while the final morphology of the fibers after stabilisation and carbonisation was examined through scanning electron microscopy to determine the optimal stabilisation parameters. The optimal fabrication parameters for cellulose and chitosan-based CNFs with excellent morphology and thermal stability were successfully established, providing valuable insight and methods for the sustainable and environmentally friendly synthesis of these promising materials.

Development of highly bacterial filtration efficient and antibacterial cellulose acetate/gum rosin composite nanofibers for facemask application.

Cellulose acetate (CA) is a non-toxic, renewable, and biodegradable polymeric material that can be effectively electrospuned into bacterial filtration efficient nanofiber membrane for face mask application. However, its fragile and non-antibacterial nature influenced its scalability. In this context, natural antibacterial gum rosin (GR) additive can be explored. Therefore, the present study aimed to produce a CA/GR composite nanofibers membrane for the finest bacterial filtration, excellent antibacterial moiety, and improved tensile properties for facemask application. Hence, in this work, we have studied the effect of GR concentrations (0-15 g) on the needleless electrospinning behavior and fibers' morphology through rheology, electrical conductivity, and SEM analysis. These analyses revealed that GR significantly affects the fibers' spinning behavior, morphology, and diameter of the produced fibers. Later, ATR-FTIR spectroscopy mapped the functional changes in the produced nanofibers that affirmed the integration of GR with CA polymer. This modification resulted in a 3-fold rise in tensile strength and an 11-fold decline in elongation% in 15 g CA/GR composite nanofibers membrane than the control sample. Furthermore, it has shown 98.79 ± 0.10% bacterial filtration efficiency and âˆ¼ 93 % reduction in Staphylococcus Aureus and Klebsiella Pneumoniae bacterial growth, elucidating a high-efficiency level for potential facemask application.

Pickering Emulsions and Hydrophobized Films of Amphiphilic Cellulose Nanofibers Synthesized in Deep Eutectic Solvent.

Herein, a dual-functioning deep eutectic solvent system based on triethylmethylammonium chloride and imidazole was harnessed as a swelling agent and a reaction medium for the esterification of cellulose with n-octyl succinic anhydride (OSA). The modified or amphiphilic cellulose nanofibers (ACNFs), synthesized using three different OSA-to-anhydroglucose unit molar ratios (0.5:1, ACNF-1; 1:1, ACNF-2; and 1.5:1, ACNF-3), were further converted into nanofibers with degree of substitution (DS) values of 0.24-0.66. The ACNFs possessed a lateral dimension of 4.24-9.22 nm and displayed surface activity due to the balance of hydrophobic and hydrophilic characteristics. The ACNFs made stable aqueous dispersions; however, the instability index of ACNF-3 (0.51) was higher than those of ACNF-1 (0.29) and ACNF-2 (0.33), which was attributed to the high DS-induced hydrophobicity, causing the instability in water. The amphiphilic nature of ACNFs promoted their performance as stabilizers in oil-in-water Pickering emulsions with average droplet sizes of 4.85 µm (ACNF-1) and 5.48 µm (ACNF-2). Self-standing films of ACNFs showed high contact angles for all the tested DS variants (97.48-114.12°), while their tensile strength was inversely related to DS values (ACNF-1: 115 MPa and ACNF-3: 49.5 MPa). Aqueous dispersions of ACNFs were also tested for coating fruits to increase their shelf life. Coatings improved their shelf life by decreasing oxygen contact and moisture loss.

Synergistic Enhancement of Filtering Efficiency and Antibacterial Performance of a Nanofiber Air Filter Decorated with Electropolarized Lithium-Doped ZnO Nanorods.

According to clinical case reports, bacterial co-infection with COVID-19 can significantly increase mortality, with Staphylococcus aureus (S. aureus) being one of the most common pathogens causing complications such as pneumonia. Thus, during the pandemic, research on imparting air filters with antibacterial properties was actively initiated, and several antibacterial agents were investigated. However, air filters with inorganic nanostructures on organic nanofibers (NFs) have not been investigated extensively. This study aimed to demonstrate the efficiency of electropolarized poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) NFs decorated with Li-doped ZnO nanorods (NRs) to improve the filtering ability and antibacterial activity of the ultrathin air filter. The surfactant was loaded onto the ZnO─known for its biocompatibility and low toxicity─nanoparticles (NPs) and transferred to the outer surface of the NFs, where Li-doped ZnO NRs were grown. The Li-doped ZnO NR-decorated NF effectively enhanced the physical filtration efficiency and antibacterial properties. Additionally, by exploiting the ferroelectric properties of Li-doped ZnO NRs and PVDF-TrFE NFs, the filter was electropolarized to increase its Coulombic interaction with PMs and S. aureus. As a result, the filter exhibited a 90% PM1.0 removal efficiency and a 99.5% sterilization rate against S. aureus. The method proposed in this study provides an effective route for simultaneously improving the air filter performance and antibacterial activity.

Antibacterial and antioxidant double-layered nanofibrous mat promotes wound healing in diabetic rats.

Diabetic wounds are problematic to heal owing to microbial infections as well as decreased proliferation and high concentrations of reactive oxygen species. In this study, a double-layered nanofibrous mat containing grape seed extract (GSE) and silver sulfadiazine (SSD) was fabricated. A synthetic biodegradable polymer, e.g., polycaprolactone (PCL), and a natural material (i.e., collagen) were employed as wound dressing substances. The results showed that GSE possesses antioxidant activity which can be helpful in reducing free radicals. The platform exhibited antibacterial activity against gram-positive and -negative bacteria. The double-layered nanofibrous mat containing GSE and SSD not only was not toxic but also amplified the cell proliferation compared to a pure mat, showing the effect of plant extract. After induction of a round wound, the animals were divided into three groups, namely (1) normal group (receiving + GSE/-GSE nanofiber), (2) diabetic group (receiving + GSE/-GSE nanofiber), and (3) control group (receiving gauze). In vivo evaluation demonstrated no significant differences in the healing process of normal rats. Surprisingly, fully repaired skin was observed on day 14 in the double-layered nanofibrous mat containing GSE in the normal and diabetic groups whereas the wound of diabetic rats treated with pure mat was not completely healed. The macroscopic and microscopic results after 14 days showed the following order in wound repair: Normal/ + GES > Diabetic/ + GSE > Normal/-GES > Diabetic/-GSE > control (with gauze) (p < 0.05). Accordingly, the double-layered nanofibrous mat containing GSE and SSD used in the present study could be considered as a suitable wound dressing in order to shorten healing time and prevent infection during the wound healing process.

Ondansetron/Cyclodextrin inclusion complex nanofibrous webs for potential orally fast-disintegrating antiemetic drug delivery.

Ondansetron (ODS) is an effective antiemetic drug which suffers from limited solubility and bioavailability during oral administration due to first-pass metabolism. However, these limitations can be mitigated through inclusion complexation with cyclodextrins (CDs). In this study, we have reported the electrospinning of polymer-free, free-standing ODS/CD nanofibrous webs (NW), a promising approach for developing a fast-disintegrating delivery system of an antiemetic drug molecule. Highly water soluble hydroxypropyl-beta-cyclodextrins (HPßCD) were used as both complexation agent and electrospinning matrix. The computational study revealed that the 1/2 (drug/CD) stoichiometry was more favorable compared to 1/1. The ODS/HPßCD NW was obtained with higher loading efficiency (∼96 %) compared to the control sample of ODS/polyvinyl alcohol (PVA) NW (∼80 %). The amorphous distribution of ODS raised by complexation and the highly water-soluble nature of HPßCD resulted into faster and better release profile and quite faster disintegration property (∼2 s) in artificial saliva than polymeric ODS/PVA NW. Here, ODS/HPßCD NW was generated in the absence of a toxic solvent or chemical to enable the drug loading in an amorphous state. From all reasons above, ODS/HPßCD NW might be a promising alternative to the polymeric based systems for the purpose of fast-disintegrating oral drug delivery.

Mucoadhesive Electrospun Nanofiber-Based Hybrid System with Controlled and Unidirectional Release of Desmopressin.

The sublingual mucosa is an attractive route for drug delivery, although challenged by a continuous flow of saliva that leads to a loss of drug by swallowing. It is of great benefit that drugs absorbed across the sublingual mucosa avoid exposure to the harsh environment of the gastro-intestinal lumen; this is especially beneficial for drugs of low physicochemical stability such as therapeutic peptides. In this study, a two-layered hybrid drug delivery system was developed for the sublingual delivery of the therapeutic peptide desmopressin. It consisted of peptide-loaded mucoadhesive electrospun chitosan/polyethylene oxide-based nanofibers (mean diameter of 183 ± 20 nm) and a saliva-repelling backing film to promote unidirectional release towards the mucosa. Desmopressin was released from the nanofiber-based hybrid system (approximately 80% of the loaded peptide was released within 45 min) in a unidirectional manner in vitro. Importantly, the nanofiber-film hybrid system protected the peptide from wash-out, as demonstrated in an ex vivo flow retention model with porcine sublingual mucosal tissue. Approximately 90% of the loaded desmopressin was retained at the surface of the ex vivo porcine sublingual mucosa after 15 min of exposure to flow rates representing salivary flow.

Bruch's-Mimetic Nanofibrous Membranes Functionalized with the Integrin-Binding Peptides as a Promising Approach for Human Retinal Pigment Epithelium Cell Transplantation.

BACKGROUND: This study aimed to develop an ultrathin nanofibrous membrane able to, firstly, mimic the natural fibrous architecture of human Bruch's membrane (BM) and, secondly, promote survival of retinal pigment epithelial (RPE) cells after surface functionalization of fibrous membranes. METHODS: Integrin-binding peptides (IBPs) that specifically interact with appropriate adhesion receptors on RPEs were immobilized on Bruch's-mimetic membranes to promote coverage of RPEs. Surface morphologies, Fourier-transform infrared spectroscopy spectra, contact angle analysis, Alamar Blue assay, live/dead assay, immunofluorescence staining, and scanning electron microscopy were used to evaluate the outcome. RESULTS: Results showed that coated membranes maintained the original morphology of nanofibers. After coating with IBPs, the water contact angle of the membrane surfaces varied from 92.38 ± 0.67 degrees to 20.16 ± 0.81 degrees. RPE cells seeded on IBP-coated membranes showed the highest viability at all time points (Day 1, p < 0.05; Day 3, p < 0.01; Days 7 and 14, p < 0.001). The proliferation rate of RPE cells on uncoated poly(ε-caprolactone) (PCL) membranes was significantly lower than that of IBP-coated membranes (p < 0.001). SEM images showed a well-organized hexa/polygonal monolayer of RPE cells on IBP-coated membranes. RPE cells proliferated rapidly, contacted, and became confluent. RPE cells formed a tight adhesion with nanofibers under high-magnification SEM. Our findings confirmed that the IBP-coated PCL membrane improved the attachment, proliferation, and viability of RPE cells. In addition, in this study, we used serum-free culture for RPE cells and short IBPs without immunogenicity to prevent graft rejection and immunogenicity during transplantation. CONCLUSIONS: These results indicated that the biomimic BM-IBP-RPE nanofibrous graft might be a new, practicable approach to increase the success rate of RPE cell transplantation.

Antibacterial, antioxidant and anti-inflammatory PLCL/gelatin nanofiber membranes to promote wound healing.

Epigallocatechin-3-O-gallate (EGCG) is a green biomedical agent for promoting wound healing, which possess excellent antibacterial, antioxidant and anti-inflammatory activities. For improving the low bioavailability challenges of EGCG in vivo, we had successful created a low-cost and simple wound dressing Poly (L-Lactic-co-caprolactone) (PLCL)/Gelatin/EGCG/Core-shell nanofiber membrane (PGEC) with drug sustained release capacity through coaxial electrospinning technology. In vitro experimental indicated that the core-shell structure wound dressing had excellent biocompatibility, antibacterial and antioxidant ability, which could support cell viability and proliferation, encourage re-epithelialization during the healing process, inhibit subsequent wound infection and thus promote wound regeneration. In vivo experimental demonstrated that PGEC wound dressing could promote wound healing, the histological results further demonstrated that PGEC not only facilitated early wound closure but also influenced cellular differentiation and tissue organization. Meanwhile, PGEC had excellent hemostatic ability. Taken all together, we believed that the PGEC wound dressing, which could localize delivery of EGCG, had high potential clinical application for promoting wound healing, hemostasis or other related clinical applications in the future.

Morphological study of electrospun chitosan/poly(vinyl alcohol)/glycerol nanofibres for skin care applications.

This study aimed to evaluate the influence of formulation and procedure parameters in obtaining thick and continuous chitosan/PVA/glycerol nanofibres to be applied in skin care. For that, the polymers were characterized by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and size-exclusion chromatography. After this, 96 chitosan/PVA/glycerol nanofibre scaffolds were prepared by electrospinning method, using factorial designs. The independent variables were crude and pure chitosan, 2 brands of PVA, 2 needle gauges, high and low polymer concentration, high and low glycerol concentration, and final solution with and without ultrafiltration. Morphological analysis was performed by scanning electron microscopy, atomic force microscopy, and confocal microscopy. The best sample (NF67) presented an average thickness of 268.3 nm, uniform distribution, and high yield. It was obtained at a 1:3.5 (crude chitosan: PVA with lower molecular weight, but more hydrolysed) ratio and lower glycerol concentration, suggesting that the degree of hydrolysis of the PVA is more important than its molecular weight for obtaining better quality nanofibres and that the glycerol also makes the electrospinning process difficult. Thus, it was possible to choose parameters that provide scaffolds that could be applied as a matrix extracellular-like material in wound healing.

Cellulose nanofibers aerogels functionalized with AgO: Preparation, characterization and antibacterial activity.

In the experiment, a chemical oxidation method was used to prepare nano-divalent silver oxide powder with a particle size of about 10 nm. Compared with silver nanoparticles and monovalent silver compounds, nano­silver oxide has better antibacterial properties. The cellulose antibacterial aerogel was prepared by combining it with cellulose nanofibrils and using freeze-thaw cycles and freeze-drying methods. The microscopic morphology, mechanical properties, in vitro release of silver ions, antibacterial properties and biodegradability of composite aerogels were studied. The porosity of the cellulose antibacterial aerogel can reach 94%, the swelling rate was greater than 1000%, and the pore size was between 13 and 15 nm, which showed a larger storage space and attachment site for the aerogel. The diameter of the inhibition zone of the aerogel against Escherichia coli and Staphylococcus aureus was 23 mm and 20 mm respectively, and the aerogels still exhibited significant antibacterial activities with more than 99.5% reductions in Escherichia coli and Staphylococcus aureus, which shows highly effective antibacterial properties. This research proposes an economical and novel preparation method of antibacterial cellulose aerogel, making it a candidate material with high efficiency, broad-spectrum antibacterial and more suitable for life needs.

Fabrication and in vitro evaluation of thermally cross-linked gelatin nanofibers for drug delivery applications.

In this study, four different nanofibers consisting of gelatin (Gel), doxorubicin (DOX) with gel (DOX@Gel), a composite of gel with poly(ethylene glycol) (PEGylated-gel), and DOX@PEGylated-gel were fabricated. Subsequently, the nanofibers were thermally cross-linked in order to offer a stable and biocompatible alternative for the biological applications of nanofibers such as drug delivery and tissue engineering. Nanofibers were characterized by scanning electron microscopy, Fourier Transform-Infrared Spectroscopy (FT-IR), and confocal microscopy. The formation of smooth, continuous, and uniform nanofibers was observed and the addition of PEG resulted in an increase whereas the incorporation of DOX into nanofibers had no significant change in the diameter of nanofibers. Crosslinking also enlarged the diameter of all nanofibers and the most dramatic increase was observed 53% by DOX@PEGylated-gel. Afterward, the biological performance of the nanofibers was investigated by drug release profile, cytotoxicity on A549 cell line as well as antimicrobial activity with E. coli and S. aureus. The results indicate an enhanced drug release profile, moderate antimicrobial activity, and reasonable cytotoxic efficiency for thermally cross-linked nanofibers compared to uncross-linked nanofibers.

Lipase immobilization on a novel class of Zr-MOF/electrospun nanofibrous polymers: Biochemical characterization and efficient biodiesel production.

In this study, due to the favorable properties of MOF compounds and fibrous materials, new nanostructures of Zr-MOF/PVP nanofibrous composites were synthesized by electrospinning procedure. The related features of these samples were characterized by relevant analyzes, including SEM, BET surface area analysis, XRD, and FTIR spectroscopy. The final product showed significant properties such as small particle size distribution, large surface area, and high crystallinity. This strategy for producing these nanostructures could lead to new compounds as novel alternative materials for biological applications. Lipase MG10 was successfully immobilized on the mentioned nanofibrous composites and biochemically characterized. The lipase activity of free and immobilized lipases was considered by measuring the absorbance of pNPP (500 µM in 40 mM Tris/HCl buffer, pH 7.8, and 0.01% Triton X100) at 37 °C for 30 min. Different concentrations of glutaraldehyde, different crosslinking times, different times of immobilization, different enzyme loading, and different pH values have been optimized. Results showed that the optimized immobilization condition was achieved in 2.5% glutaraldehyde, after 2 h of crosslinking time, after 6 h immobilization time, using 180 mg protein/g support at pH 9.0. The immobilized enzyme was also totally stable after 180 min incubation at 60 °C. The free enzyme showed the maximum activity at pH 9.0, but the optimal pH of the immobilized lipase was shifted about 1.5 pH units to the alkaline area. The immobilized lipase showed about 2.7 folds (78%) higher stability than the free enzyme at 50 °C. Some divalent metal ions, including Cu2+ (22%), Co2+ (37%), Mg2+ (12%), Hg2+ (11%), and Mn2+ (17%) enhanced the enzyme activity of immobilized enzyme. The maximum biodiesel production (27%) from R. communis oil was obtained after 18 h of incubation by lipase MG10. The immobilized lipase displayed high potency in biodiesel production, about 83% after 12 h of incubation. These results indicated the high potency of Zr-MOF/PVP nanofibrous composites for efficient lipase immobilization.

3D printing and properties of cellulose nanofibrils-reinforced quince seed mucilage bio-inks.

Plant-based hydrogels have attracted great attention in biomedical fields since they are biocompatible and based on natural, sustainable, cost-effective, and widely accessible sources. Here, we introduced new viscoelastic bio-inks composed of quince seed mucilage and cellulose nanofibrils (QSM/CNF) easily extruded into 3D lattice structures through direct ink writing in ambient conditions. The QSM/CNF inks enabled precise control on printing fidelity where CNF endowed objects with shape stability after freeze-drying and with suitable porosity, water uptake capacity, and mechanical strength. The compressive and elastic moduli of samples produced at the highest CNF content were both increased by ~100% (from 5.1 ± 0.2 kPa and 32 ± 1 kPa to 10.7 ± 0.5 and 64 ± 2 kPa, respectively). These values ideally matched those reported for soft tissues; accordingly, the cell compatibility of the printed samples was evaluated against HepG2 cells (human liver cancer). The results confirmed the 3D hydrogels as being non-cytotoxic and suitable to support attachment, survival, and proliferation of the cells. All in all, the newly developed inks allowed sustainable 3D bio-hydrogels fitting the requirements as scaffolds for soft tissue engineering.

Effects of cellulose nanofibrils and starch compared with polyacrylamide on fundamental properties of pulp and paper.

Bio-based additives received significant attention in pulp and paper properties improvement. For this, the most cited biochemical Cellulose Nano Fibrils (CNFs) and Cationic Starch (CS) were experimentally compared with the most declared synthetic chemical, Cationic Polyacrylamide (CPAM). SEM images showed better paper surface filling by the utilization of the chemicals. The three studied polymers, in solely or combination mechanism, improved mainly bagasse pulp and paper properties compared to the blank sample, except for pulp drainage, which decreased by CNFs to lower volumes presumably due to its intrinsic characteristics. Cationic polymers (CP) compared to CP/CNFs approaches increased pulp retention and drainage but decreased paper density and strengths. The best pulp retention and drainage achieved by CS followed by CPAM, while paper air persistency, density, and strength properties evaluated highest by CP/CNFs followed by CNFs. Generally, CS revealed a more significant improvement in pulp and paper properties than CPAM either with or without CNFs.

Surface analysis of novel fibroin films based on well-preserved crystalline structures.

We recently reported that a highly homogeneous aqueous suspension of fibroin nanofiber (FNF) can be simply obtained by mechanical water-grinding a heterogeneous aqueous fibroin slurry and that the FNF in the suspension preserves the native ß-sheet secondary structure during this mechanical treatment. The current study reports the surface properties of well-preserved crystalline structure novel FNF film from water-grinding preparation as compared with those of typical, conventionally prepared regenerated fibroin (RF) film. RF film was not treated with alcoholic solutions and was verified to be amorphous from a WAXD diffraction diagram. The air-side surfaces of the FNF semi-crystalline and RF amorphous films were studied to clarify differences using scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), static water contact angle, and X-ray photoelectron spectroscopy (XPS). The well-preserved crystalline in the FNF film was found to exist near a slightly deep surface region and to act as a physically cross-linking domain, governing the molecular motions of the amorphous polypeptide chains at the very shallow surface region.

Preparation and characterization of polylactic acid nanofiber films loading Perilla essential oil for antibacterial packaging of chilled chicken.

Biodegradable and eco-friendly food packaging materials have attracted attention. Novel blending films were prepared with polylactic acid (PLA) and Perilla essential oil (PEsO). The morphological features of the nanofibers were modulated by adjusting process parameters (e.g. PLA solution concentration, applied voltage and ultrasonic power). The optimal spinning concentrations, applied voltages and ultrasonic power of the PLA solutions were set at 15% (m/v), 20 kV and 640 W, respectively. Compared with the PLA films, the addition of PEsO increased the diameter of the nanofibers and solvent resistance and reduced the swelling rate of the PLA/PEsO films. The breakage elongation and the gas barrier properties significantly improved when 2% (w/w) PEsO was used. Fourier infrared spectroscopy, X-ray diffractometer, thermogravimetry and differential scanning were used in analyzing the potential interactions of the film matrices. The PLA/PEsO films had good biocompatibility and antibacterial and antioxidant properties. The PLA/PEsO (1:0.02) film loaded with 2% PEsO extended the shelf life of chilled chicken to 12 days, as indicated by the measured total volatile basic nitrogen (TVB-N), total viable count and pH value. Therefore, PLA/PEsO films have great potential as fresh-keeping packaging.

The effects of cellulose nanocrystal and cellulose nanofiber on the properties of pumpkin starch-based composite films.

Pumpkin starch (PS) was extracted from Cucurbita maxima and utilized to prepare films in combination with cellulose nanocrystal (CNC) and cellulose nanofiber (CNF), using a solvent casting strategy. The PS was characterized to contain 26.6% of amylose, exhibiting a "B"-type crystalline structure and high stability against thermal degradation. PS/CNF films showed better thermal stability than PS/CNC films, whereas the CNC was more effective than CNF for enhancing the tensile strength (TS) of the films. The nanocomposite films containing 1% CNC showed the highest TS of 30.32 MPa. Fourier transform infrared spectra revealed stronger hydrogen bonding in the PS/CNC films, likely contributing to the observed high mechanical strength. CNC and CNF both decreased the transparency of PS films, by 5.2% and 13.1%, respectively. Overall, the properties of PS composite films can be effectively modified by incorporating CNC and CNF, as PS/CNC films with high mechanical strength and PS/CNF films with good thermal stability. Our results indicate that PS is a suitable material for CNC/CNF composite film fabrication. These films are expected to be especially useful in food packaging applications.