Cellulose Mats Research Articles

Three-dimensional cellulose sponge: Fabrication, characterization, biomimetic mineralization, and in vitro cell infiltration

In this study, cellulose based scaffolds were produced by electrospinning of cellulose acetate (CA) solution followed by its saponification with NaOH/ethanol system for 24h. The resulting nonwoven cellulose mat was treated with sodium borohydride (SB) solution. In situ hydrolysis of SB solution into the pores of the membrane produced hydrogen gas resulting a three-dimensional (3D) cellulose sponge. SEM images demonstrated an open porous and loosely packed fibrous mesh compared to the tightly packed single-layered structure of the conventional electrospun membrane. 3D cellulose sponge showed admirable ability to nucleate bioactive calcium phosphate (Ca–P) crystals in simulated body fluid (SBF) solution. SEM-EDX and X-ray diffraction studies revealed that the minerals deposited on the nanofibers have the nonstoichiometric composition similar to that of hydroxyapatite, the mineralized component of the bone. 3D cellulose sponge exhibited the better cell infiltration, spreading and proliferation compared to 2D cellulose mat. Therefore, a facile fabrication of 3D cellulose sponge with improved mineralization represents an innovative strategy for the bone tissue engineering applications.

Adsorption and photocatalyst assisted dye removal and bactericidal performance of ZnO/chitosan coating layer

Pure chitosan and its zinc oxide composite coatings were applied on microfibriller cellulose mat (MCM) to prepare chitosan coated microfibriller cellulose (Chi-MCM) and zinc oxide/chitosan coated microfibriller cellulose (ZnO/Chi-MCM), respectively. X-ray diffraction (XRD), and scanning electron microscopy (SEM), were used to characterize the samples in this study. SEM images showed that dense chitosan solutions (3 and 5wt%) made a thick layer over MCM while diluted solution (1wt%) resulted in wrapping of the chitosan over the individual microfibers and avoided the thick layer formation. Removal of an azo dye methyl orange (MO) from aqueous solution using adsorption and combined adsorption with photodegradation activity of the Chi-MCM and ZnO/Chi-MCM were evaluated, respectively. Compared in the absence of UV light, ZnO/Chi-MCM showed faster and higher degree of dye removal by photocatalytic dissociation and adsorption under ultraviolet irradiation. Various parameters including pH of MO solution and its initial concentration were tested for the removal of MO dye. ZnO/Chi-MCM showed maximum adsorption capacity of 42.8mg/g. Antibacterial activities were also evaluated where ZnO/Chi-MCM displayed a remarkable performance inhibiting the Escherichia coli growth.

Enhanced growth of neural networks on conductive cellulose-derived nanofibrous scaffolds.

The problem of recovery from neurodegeneration needs new effective solutions. Tissue engineering is viewed as a prospective approach for solving this problem since it can help to develop healthy neural tissue using supportive scaffolds. This study presents effective and sustainable tissue engineering methods for creating biomaterials from cellulose that can be used either as scaffolds for the growth of neural tissue in vitro or as drug screening models. To reach this goal, nanofibrous electrospun cellulose mats were made conductive via two different procedures: carbonization and addition of multi-walled carbon nanotubes. The resulting scaffolds were much more conductive than untreated cellulose material and were used to support growth and differentiation of SH-SY5Y neuroblastoma cells. The cells were evaluated by scanning electron microscopy and confocal microscopy methods over a period of 15 days at different time points. The results showed that the cellulose-derived conductive scaffolds can provide support for good cell attachment, growth and differentiation. The formation of a neural network occurred within 10 days of differentiation, which is a promising length of time for SH-SY5Y neuroblastoma cells.

Production of cellulose from sugarcane molasses using Gluconacetobacter intermedius SNT-1: optimization & characterization

Cellulose production by Gluconacetobacter intermedius SNT-1 under static condition was compared using various carbon sources. The trend observed was: HS-glucose > HS-glucose + sucrose + fructose > HS-fructose > HS-sucrose. Molasses, an industrial byproduct also served as a feedstock for cellulose production. Cellulose yield of 12.6 g L−1 was obtained from 45.8 g L−1 of diluted (1:4) molasses after H2SO4-heat pre-treatment. Cellulose yields were comparable using corn-steep liquor or yeast extract as the nitrogen sources along with heat pretreated molasses. Cellulose production was decreased by 30% in the absence of polypeptone. The number of viable cells entrapped within bacterial cellulose mat was much higher in comparison to that present in the spent medium. Cellulose immobilized cells may be protected against toxicity of components present in molasses. Bacterial cellulose produced from pretreated molasses contained mixture of cellulose I and cellulose II types, was predominantly in Iα (∼60%) form, had high tensile strength. This study demonstrates the suitability of using molasses from sugar industries as cheap carbon source for production of bacterial cellulose, with characteristics similar to those obtained using expensive carbon sources such as glucose or fructose. Huge amount of molasses is produced worldwide annually and therefore it is a readily available resource for cellulose production. Cellulose produced by bacteria using molasses is relatively pure which does not require extensive chemical treatments as in Kraft pulping or bleaching. Bacterial production of cellulose causes lower impact on environment in terms of pollution load and energy consumption.

Antimicrobial activity and cytotoxicity of nanofibrous mats immobilized with polysaccharides-rectorite based nanogels

Rectorite (REC)-encapsulated lysozyme (LY)-alginate (ALG) nanogels (NGs) were prepared by adding ALG-REC composites suspensions into LY solutions at the mass ratio of 1:2. The morphology of the NGs and the NGs-assembled nanofibrous mats were studied by transmission electron microscope and field emission scanning electron microscopy, respectively. The composition of NGs-immobilized nanofibrous mats was detected by X-ray photoelectron spectroscopy. The NGs-assembled nanofibrous mats with the addition of REC could enhance the inhibition against Escherichia coli and Staphylococcus aureus. Additionally, NGs-coated mats reduced the toxicity of cellulose mats on mouse lung fibroblasts using MTT assay. Besides, the addition of REC in the NGs improved the cell compatibility of NGs-assembled nanofibrous mats.

Microfibrillated cellulose-SiO2 composite nanopapers produced by spray deposition

Microfibrillated cellulose (MFC)-SiO2 nanopapers were prepared using a rapid spray deposition technique. Large area (~310 cm2) composite nanopapers with thickness and SiO2 content varying from 16 to 92 µm and 0 to 33 %, respectively, were prepared in less than 30 min with nearly complete nanoparticle retention in the cellulose mat. In the presence of an excess of MFC, SiO2 nanoparticles formed large clusters embedded in a dense and continuous cellulose matrix which conferred to the composite an extremely low permeability to air, i.e., below 2 nm2. For silica mass fraction above 20 %, SiO2 clusters induced a net increase in air permeability and ionic conductivity up to 12 nm2 and 1.5 mS cm−1 for a SiO2 content of 33 %. Despite the addition of an inert phase, composite nanopapers displayed mechanical properties, viz. Young’s modulus and internal cohesion higher than 2.2 GPa and 913 J m−2, outperforming those of most conventional papers. This study demonstrates that MFC-SiO2 nanopapers fabricated by spray deposition can be an alternative to PE/PP membranes as separators in Li-ion batteries and, in general, that spray deposition is a promising method for the rapid fabrication of large area composite nanopapers.

Nano- and macroscale structural and mechanical properties of in situ synthesized bacterial cellulose/PEO-b-PPO-b-PEO biocomposites.

Highly transparent biocomposite based on bacterial cellulose (BC) mat modified with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymer (EPE) were fabricated in situ during biosynthesis of bacterial cellulose in a static culture from Gluconacetobacter xylinum. The effect of the addition to the culture medium of water-soluble EPE block copolymer on structure, morphology, crystallinity, and final properties of the novel biocomposites was investigated at nano- and macroscale. High compatibility between components was confirmed by ATR-FTIR indicating hydrogen bond formation between the OH group of BC and the PEO block of EPE block copolymer. Structural properties of EPE/BC biocomposites showed a strong effect of EPE block copolymer on the morphology of the BC mats. Thus, the increase of the EPE block copolymer content lead to the generation of spherulites of PEO block, clearly visualized using AFM and MO technique, changing crystallinity of the final EPE/BC biocomposites investigated by XRD. Generally, EPE/BC biocomposites maintain thermal stability and mechanical properties of the BC mat being 1 wt % EPE/BC biocomposite material with the best properties. Biosynthesis of EPE/BC composites open new strategy to the utilization of water-soluble block copolymers in the preparation of BC mat based biocomposites with tunable properties.

Structural characteristics of nanofibrillated cellulose mats: Effect of preparation conditions

Nanofibrillated cellulose (NFC) mats, which have porous or dense structures, were prepared in this study. The effects of the number of grinding passes, suspension solids content, and drying conditions on the structural changes of the NFC mats were investigated. Water removal in the NFC suspensions for forming the mats was carried out using pressurized dewatering equipment. The field-emission scanning electron microscope observation showed that the nanofibrils were preserved by solvent exchange drying, whereas the partial aggregation of nanofibrils occurred by freeze drying. Properties such as shrinkage, density, porosity, and specific surface areas of the NFC mats changed depending on the preparation conditions of the NFC mats. The NFC mats, which have low density and high porosity, could be prepared by solvent exchange drying and freeze drying. Porosity of the NFC mats varied from 76 % to 96 %. The specific surface area of the NFC mat increased to 175 m2/g with an increase in the number of grinding passes.

Layer-by-layer immobilization of quaternized carboxymethyl chitosan/organic rectorite and alginate onto nanofibrous mats and their antibacterial application.

Quaternized carboxymethyl chitosan (QCM-chitosan) and organic rectorite (OREC) immobilized nanofibrous mats are fabricated via layer-by-layer (LBL) technique in a self-assembly manner. The negatively charged cellulose nanofibrous mats hydrolyzed from electrospun cellulose acetate (CEL) mats are alternately modified with the positively charged QCM-chitosan and OREC intercalated composites and the negatively charged sodium alginate (ALG) via LBL technique. The morphology and antibacterial activity of the resultant mats are studied by changing the number of deposition bilayers, the compositions of dipping solutions and outermost layer. X-ray photoelectron spectroscopy results imply that QCM-chitosan and OREC are coated on cellulose mats. Besides, wide angle X-ray diffraction and small angle X-ray diffraction are applied to investigate the crystalline of the composite mats and the interlayer distance of OREC, respectively. The antibacterial activity of the mats increases with the incorporation of OREC into LBL films.

Natural ECM-Bacterial Cellulose Wound Healing—Dubai Study

Bacterial cellulose (BC) can be used in wide area of applied scientific, especially for tissue regeneration and regenerative medicine, lately, bacterial cellulose mats are used in the treatment of skin conditions such as burns and ulcers, because of the morphology of fibrous biopolymers serving as a support for cell proliferation, its pores allow gas exchange between the organism and the environment. Moreover, the nanostructure and morphological similarities with collagen make BC attractive for cell immobilization, cell support and Natural Extracellular Matrix (ECM) Scaffolds. In this scope, Natural ECM is the ideal biological scaffold since it contains all the components of the tissue. The development of mimicking biomaterials and hybrid biomaterial can further advance directed cellular differentiation without specific induction. The extracellular matrix (ECM) contains several signals that are received by cell surface receptors and contribute to cell adhesion and cell fate which control cellular activities such as proliferation, migration and differentiation. As such, regenerative medicine studies often rely on mimicking the natural ECM to promote the formation of new tissue by host cells, and characterization of natural ECM components is vital for the development of new biomimetic approaches. In this work, the bacterial cellulose fermentation process is modified by the addition of vegetal stem cell to the culture medium and natural materials before the bacteria are inoculated. In vivo behavior using natural ECM for regenerative medicine is presented.

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.

Antibacterial multilayer films fabricated by layer-by-layer immobilizing lysozyme and gold nanoparticles on nanofibers

Negatively charged gold nanoparticles (GNP) and positively charged lysozyme (Lys) were alternately deposited on negatively charged cellulose mats via layer-by-layer (LBL) self-assembly technique. The fabricated multilayer films were characterized by energy-dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FT-IR), and wide-angle X-ray diffraction (XRD). Morphology of the LBL film coated mats was observed by scanning electron microscopy (SEM). Thermal degradation properties were investigated by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Additionally, the result of microbial inhibition assay indicated that the composite nanofibrous mats had excellent antibacterial activity against Escherichia coli and Staphylococcus aureus, which could be used for antimicrobial packing, tissue engineering, wound dressing, etc.

Chitosan/phosvitin antibacterial films fabricated via layer-by-layer deposition

Negatively charged phosvitin (PV) and positively charged chitosan (CS) were alternately deposited on negatively charged cellulose mats via layer-by-layer (LBL) self-assembly technique. The deposition of PV and CS was confirmed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FT-IR), and wide-angle X-ray diffraction (XRD). Morphologies of the LBL films coating mats were observed by scanning electron microscope (SEM). Thermal degradation properties were investigated by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Additionally, the result of microbial inhibition assay indicated that the composite nanofibrous mats had excellent antibacterial activity against Escherichia coli and Staphylococcus aureus, which could be used for antimicrobial packing, tissue engineering, wound dressing, etc.

Effect of the Number of Passes through Grinder on the Pore Characteristics of Nanofibrillated Cellulose Mat

In this study, we investigated the effect of the number of passes through agrinder on the pore characteristics of nanofibrillated cellulose (NFC) mat. The beaten pulp suspension was used to make NFC suspension using a grinder. To evaluate the pore characteristics of a NFC mat, the surface morphology of the dried NFC mat was observed with FE-SEM and the specific surface area was analyzed with BET nitrogen gas adsorption. The structure of NFC mat was changed with the different number of passes and drying methods. The specific surface area of NFC mat increased with the increase in the number of passes. The 20-passed NFC mat had 20 times larger specific surface area (<TEX>$141m^2/g$</TEX>) compared to the 0-passed NFC mat. The specific surface area was strongly correlated with the average pore size in NFC mat. The average pore diameter in NFC mat was calculated from the gas sorption isotherms using BJH model. The value was 13 - 15 nm, indicating that the NFC mat had mesoporous structure.

Conductive Photoswitchable Vanadium Oxide Nanopaper based on Bacterial Cellulose

A bacterial cellulose mat was used as a template for the fabrication of conductive photoswitchable hybrid nanopaper by the incorporation of sol-gel synthesized vanadium nanoparticles. The resulting nanopaper, prepared through a green pathway, was able to photoinduce a reversible color change. Conductive properties at the nano- and macroscales were confirmed by electrostatic force microscopy and semiconductor analysis measurements, respectively.

Effect of water absorption on mechanical properties of soybean oil thermosets reinforced with natural fibers

Natural fiber composites are known to absorb more water than glass fiber reinforced composites. In this study, hybrid natural fiber composites were prepared by combining different fiber reinforcements, and both the water absorption and the mechanical properties were studied. Compression molding technique was used to manufacture composite laminates from a bio-based resin (acrylated epoxidized soybean oil) and natural fibers: non-woven and woven jute, non-woven regenerated cellulose mat (Lyocell and viscose), and woven glass fiber. The composite laminates were cured at 160–170°C and 40 bar, with a fiber content of 40 wt%. We investigated effect of pretreatment of regenerated cellulose fiber using 4% NaOH solution. The gravimetric water absorption was tested by exposure to water for 10 days. Specimens were cut from composites with laser-cutting technique according to ISO standards, and tested for tensile, flexural, and impact strength. To determine the influence of water absorption on the mechanical properties, specimens were immersed in distilled water for 10 days before testing. As a reference, dry specimens were tested. The results showed that water absorption was reduced by producing hybrid composites with jute fibers, glass fiber, and Lyocell fiber. The tensile, flexural, and impact properties were improved by inclusion of glass fiber and Lyocell in the composite. The tensile and flexural properties of natural fiber reinforced composites were mostly affected by the influence of water, but this was improved considerably by hybridization with glass and Lyocell fibers. The viscoelastic properties of the manufactured composites and hybrid composites were studied using dynamic mechanical thermal analysis.

Nanopores Structure in Electrospun Bacterial Cellulose

Bacterial cellulose (BC) has established to be a remarkably versatile biomaterial and can be used in wide variety of applied scientific endeavours, especially for medical devices, lately, bacterial cellulose mats are used in the treatment of skin conditions such as burns and ulcers, because of the morphology of fibrous biopolymers serving as a support for cell proliferation, its pores allow gas exchange between the organism and the environment. Moreover, the nanostructure and morphological similarities with collagen make BC attractive for cell immobilization and cell support. In this work, we obtain first electrospun bacterial cellulose mats after chemical treatment and without conductive additives. With DMA/LiClmechanism dissolution, modified bacterial cellulose was easily electrospun in chloroform/acetone solvents in comparison with BC unmodified. FTIR peaks results are consistent with proposed interactions between cellulose and DMA/LiCl solvent system.

Development of electrospun EVOH fibres reinforced with bacterial cellulose nanowhiskers. Part I: Characterization and method optimization

In the present study, hybrid electrospun EVOH fibres reinforced with bacterial cellulose nanowhiskers (BCNW) were developed and characterized. The nanowhiskers, obtained by sulphuric acid digestion of native bacterial cellulose mats generated by Gluconacetobacter xylinum, were morphologically characterized by SEM and optical microscopy with polarized light and revealed a highly crystalline structure of nanofibrils aggregates. XRD analyses suggested a crystalline structure corresponding to the cellulose I allomorph. It was also confirmed by means of FT-IR spectroscopy that amorphous regions were preferentially digested by the acid treatment, whereas TGA analyses showed a decrease in the thermal stability of the nanowhiskers most likely due to incorporation of sulphate groups and the inherent acidity remaining in the filler even after extensive washing cycles. A method was developed for improving the incorporation of BCNW within the EVOH electrospun fibres, consisting on the addition of the BCNW in the form of a centrifuged precipitate, versus the most conventionally employed freeze-dried nanowhiskers. DSC analyses showed a significant increase in the glass transition temperature of the composites during the second heating run, which may be related to the acidic character of the nanofiller. Finally, sonication was seen to enhance interfacial interaction but to reduce the incorporation of the filler in the matrix in the case of the centrifuged material.

Enhanced bacterial inhibition activity of layer-by-layer structured polysaccharide film-coated cellulose nanofibrous mats via addition of layered silicate

Organic rectorite (OREC) was used to prepare the intercalated composites with chitosan (CS). The negatively charged cellulose nanofibers hydrolyzed from electrospun cellulose acetate fibrous mats were modified with multilayers of the positively charged CS-OREC intercalated composite and the negatively charged sodium alginate (ALG) via layer-by-layer (LBL) technique. The morphology and antibacterial activity of the resultant samples were studied by regulating the number of deposition bilayers, the compositions of dipping solutions and outermost layer of films. Field emission scanning electron microscopy images indicated that the thickness of CS-OREC/ALG bilayer formed on fibers was estimated from 12 to 26 nm. Additionally, the energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy results indicated that CS and OREC were successfully deposited on cellulose fibers. The bacterial inhibition experiments demonstrated that LBL films modified fibrous cellulose mats with the addition of OREC can increase the degree of inhibition on Escherichia coli.

Self-assembly of phthalocyanine and polyacrylic acid composite multilayers on cellulose nanofibers

In this study, a novel nanocomposite multilayers was deposited on the electrospun nanofibrous mats by an electrostatic layer-by-layer (LBL) self-assembly technique. The positively charged water-insoluble 2,9,16,23-tetraaminophthalocyanine copper (CuTaPc) and the negatively charged water-soluble poly(acrylic acid) (PAA) were alternately deposited on the surface of negatively charged nanofibrous cellulose mats. The cationic CuTaPc was synthesized and characterized by UV–Vis and Fourier transform infrared (FT-IR) spectroscopy. The template nanofibrous cellulose mats were obtained from the alkaline hydrolysis of electrospun nanofibrous cellulose acetate mats. The resultant nanofibrous mats were characterized by scanning electron microscopy (SEM) and FT-IR spectroscopy. The SEM images showed that the composite LBL structured films were homogeneously deposited on the surface of the nanofibers. The diameters of nanofibers increased with the number of deposition bilayers. The average thickness of each CuTaPc/PAA bilayer is about 10 nm. Additionally, the FT-IR spectra results also indicated that the CuTaPc and PAA were coated on the nanofibrous cellulose mats.