BC Nanofibers Research Articles

Simultaneously depositing polyaniline onto bacterial cellulose nanofibers and graphene nanosheets toward electrically conductive nanocomposites

In this study, we report the construction of a ternary flexible nanocomposite of bacterial cellulose/graphene/polyaniline (BC/GE/PANI) via a facile two-step strategy. Bacterial cellulose/graphene (BC/GE) is first prepared by a novel in situ membrane-liquid-interface method, in which the three-dimensional continuous BC nanofibers can be maintained and the introduced GE can improve the mechanical properties mainly due to the uniform dispersion of GE in the BC matrix. To construct the effectively interconnected conductive paths between separated GE nanosheets, polyaniline (PANI) is simultaneously deposited on the surfaces of both BC nanofibers and GE nanosheets to obtain BC/GE/PANI with excellent electrical conductivity. It is found that the as-prepared BC/GE/PANI has an electrical conductivity of 1.7 ± 0.1 S cm−1, which is higher than most of PANI-based composites. It is believed that the BC/GE/PANI nanocomposite possesses great potential for applications in electromagnetic shielding and flexible electrodes.

Fabrication and enhanced mechanical properties of porous PLA/PEG copolymer reinforced with bacterial cellulose nanofibers for soft tissue engineering applications

A new class of polylactic acid (PLA)/polyethylene glycol (PEG) copolymer reinforced with bacterial cellulose nanofibers (BC) was prepared using a solvent casting and particulate leaching methods. Four weight fractions of BC (1, 2.5, 5, and 10 wt%) were incorporated into copolymer via silane coupling agent. Mechanical properties were evaluated using response surface method (RSM) to optimize the impact of pore size, porosity, and BC contents. Compressive strength obtained for PLA/PEG-5 BC wt% was 9.8 MPa, which significantly dropped after developing a porous structure to 4.9 MPa. Nielson model was applied to investigate the BC stress concentration on the PLA/PEG. Likewise, krenche and Hapli-Tasi model were employed to investigate the BC nanofiber reinforcement and BC orientation into PLA/PEG chains. The optimal parameters of the experiment results found to be 5 wt% for BC, 230 μm for pore size, and 80% for porosity. Scanning electron microscopy (SEM) micrograph indicates that uniform pore size and regular pore shape were achieved after an addition of BC-5% into PLA/PEG. The weight loss of copolymer-BC with scaffolds enhanced to the double values, compared with PLA/PEG-BC % without scaffolds. Differential Scanning Calorimetric (DSC) results revealed that the BC nanofiber improved glass transition temperature (Tg) 57 °C, melting temperature (Tm) 171 °C, and crystallinity (χ %) 43% of PLA/PEG reinforced-BC-5%.

Preparation of Pd/Bacterial Cellulose Hybrid Nanofibers for Dopamine Detection.

Palladium nanoparticle-bacterial cellulose (PdBC) hybrid nanofibers were synthesized by in-situ chemical reduction method. The obtained PdBC nanofibers were characterized by a series of analytical techniques. The results revealed that Pd nanoparticles were evenly dispersed on the surfaces of BC nanofibers. Then, the as-prepared PdBC nanofibers were mixed with laccase (Lac) and Nafion to obtain mixture suspension, which was further modified on electrode surface to construct novel biosensing platform. Finally, the prepared electrochemical biosensor was employed to detect dopamine. The analysis result was satisfactory, the sensor showed excellent electrocatalysis towards dopamine with high sensitivity (38.4 µA·mM−1), low detection limit (1.26 µM), and wide linear range (5–167 µM). Moreover, the biosensor also showed good repeatability, reproducibility, selectivity and stability and was successfully used in the detection of dopamine in human urine, thus providing a promising method for dopamine analysis in clinical application.

Superior hybrid hydrogels of polyacrylamide enhanced by bacterial cellulose nanofiber clusters

Hybrid polyacrylamide/bacterial cellulose nanofiber clusters (PAM/BC) hydrogels with high strength, toughness and recoverability were synthesized by in situ polymerization of acrylamide monomer in BC nanofiber clusters suspension. The hybrid gels exhibited an extremely large elongation at break of 2200%, and a high fracture stress of 1.35MPa. Additionally, the original length of hydrogels could be recovered after releasing the tensile force. Compressive results showed that the PAM/BC hybrid gels could reach a strain of about 99% without break, and was able to completely recover its original shape immediately after releasing the compression force. The compressive stress at 99% reached as high as 30MPa. Nearly no hysteresis in cyclic compressive tests was observed with these hybrid gels. The FT-IR, XRD and TGA analysis showed that hydrogen bonds between the PAM chains and BC nanofiber clusters mainly contributed to the superior mechanical properties of hybrid hydrogels. The cell viability results suggested that PAM/BC hybrid hydrogel was benign for biomedical application. These PAM/BC hydrogels offer a great promise as biomaterials such as bone and cartilage repair materials.

A facile synthesis method and electrochemical studies of a hierarchical structured MoS2/C-nanocomposite

A facile synthesis of MoS2 nanosheet coated BC nanofiber network as an additive free anode for LIBs has been reported. The strong interaction between the nanosheets and the carbon fibers endures it with enhanced cycling and rate performances.

A simple method for creating molecularly imprinted polymer-coated bacterial cellulose nanofibers

AbstractMolecularly imprinted polymer-coated bacterial cellulose nanofibers have been prepared by immersing solvent treated-bacterial cellulose into a dilute pre-polymerization mixture solution prior to the polymerization process. The quercetin-imprinted polymer coating bacterial cellulose (QIP-BC) nanofibers show discrete nanoparticles encapsulated along the BC nanofibers. The binding capacity of dried QIP-BC was approximately 3 mg per gram of the polymer. The obtained results indicated that QIP-BC nanofibers provided a three fold higher recognition ability for quercetin than quercetin-imprinted nanospheres. This technique can be easily used to combine two fascinating materials like BC nanofibers and molecularly imprinted polymers (MIPs) to afford promising polymer composites that are useful in various innovative applications in biomedical, pharmaceutical, and industrial sectors.

In situ synthesis of silver-nanoparticles/bacterial cellulose composites for slow-released antimicrobial wound dressing

Bacterial cellulose has attracted increasing attention as a novel wound dressing material, but it has no antimicrobial activity, which is one of critical skin-barrier functions in wound healing. To overcome such deficiency, we developed a novel method to synthesize and impregnate silver nanoparticles on to bacterial cellulose nanofibres (AgNP-BC). Uniform spherical silver nano-particles (10–30nm) were generated and self-assembled on the surface of BC nano-fibers, forming a stable and evenly distributed Ag nanoparticles coated BC nanofiber. Such hybrid nanostructure prevented Ag nanoparticles from dropping off BC network and thus minimized the toxicity of nanoparticles. Regardless the slow Ag+ release, AgNP-BC still exhibited significant antibacterial activities with more than 99% reductions in Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Moreover, AgNP-BC allowed attachment and growth of epidermal cells with no cytotoxicity emerged. The results demonstrated that AgNP-BC could reduce inflammation and promote wound healing.

Conductive polypyrrole–bacterial cellulose nanocomposite membranes as flexible supercapacitor electrode

Conductive nanocomposite membranes of polypyrrole/bacterial cellulose (PPy/BC) were fabricated in situ by oxidative polymerization of pyrrole with iron (III) chloride as an oxidant and BC as a template. The morphology of the PPy/BC membrane indicated that PPy nanoparticles deposited on the BC surface connected to form a continuous nanosheath structure by taking along the BC nanofiber. The flexible PPy/BC membrane obtained with the optimized reaction condition exhibited a high electrical conductivity of 3.9Scm−1, which was hardly affected by bending stress. The PPy/BC membrane could be directly used as flexible supercapacitor electrodes, with a maximum discharge capacity of 101.9mAhg−1 (459.5Fg−1) at 0.16Ag−1 current density. The capacity decreased with charge/discharge cycling, which is attributed to mechanical degradation of PPy as evidenced by scanning electron microscopy (SEM).

Flexible magnetic membranes based on bacterial cellulose and its evaluation as electromagnetic interference shielding material

Flexible magnetic membranes with high proportion of magnetite were successfully prepared by previous impregnation of the never dried bacterial cellulose pellicles with ferric chloride followed by reduction with sodium bisulfite and alkaline treatment for magnetite precipitation. Membranes were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating magnetometer, field emission scanning electron microscopy (FEG-SEM) and impedance spectroscopy. Microwave properties of these membranes were investigated in the X-band (8.2 to 12.4GHz). FEG-SEM micrographs show an effective coverage of the BC nanofibers by Fe3O4 nanoparticles. Membranes with up to 75% in weight of particles have been prepared after 60min of reaction. Magnetite nanoparticles in the form of aggregates well adhered to the BC fibers were observed by SEM. The average crystal sizes of the magnetic particles were in the range of 10±1 to 13±1nm (estimated by XRD). The magnetic particles in the BC pellicles presented superparamagnetic behavior with a saturation magnetization in the range of 60emug−1 and coercive force around 15Oe. These magnetic pellicles also displayed high electrical permittivity and a potential application as microwave absorber materials.

Nanostructured Composites Obtained by ATRP Sleeving of Bacterial Cellulose Nanofibers with Acrylate Polymers

Novel nanostructured composite materials based on bacterial cellulose membranes (BC) and acrylate polymers were prepared by in situ atom transfer radical polymerization (ATRP). BC membranes were functionalized with initiating sites, by reaction with 2-bromoisobutyryl bromide (BiBBr), followed by atom transfer radical polymerization of methyl methacrylate (MMA) and n-butyl acrylate (BA), catalyzed by copper(I) bromide and N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDETA), using two distinct initiator amounts and monomer feeds. The living characteristic of the system was proven by the growth of PBA block from the BC-g-PMMA membrane. The BC nanofiber sleeving was clearly demonstrated by SEM imaging, and its extent can be tuned by controlling the amount of initiating sites and the monomer feed. The ensuing nanocomposites showed high hydrophobicity (contact angles with water up to 134°), good thermal stability (initial degradation temperature in the range 241-275 °C), and were more flexible that the unmodified BC membranes.

Enhanced mechanical properties of silk fibroin-based composite plates for fractured bone healing

We successfully fabricated bacterial cellulose/silk fibroin (BC/SF) composite plates having similar strength to that of human cortical bone (12.8–17.7 GPa). The mechanical properties of the BC/SF composite plates were investigated at various BC nanofiber contents. The BC nanofibers acted as good reinforcements for the stress transfer produced by the interactions between the BC nanofibers and the SF matrix, as confirmed by the molecular deformation of the BC nanofibers. The BC/SF composite plates have a promising potential as a replacement material for existing metal bone plate.

Chemical modifications and characteristic changes in bacterial cellulose treated with different media

Bacterial cellulose membranes have attracted a great deal of attention as novel biomedical materials. In this paper, bacterial cellulose was treated with acidic, alkaline, and redox solutions to investigate the subsequent changes in the characteristics of the cellulose. The chemical structure, crystalline state, water-holding capacity, and micromorphology of each modified BC were characterized by FTIR, SEM, and XRD. After these treatments, the intermolecular or intramolecular hydrogen bonds of the BC were broken and the water bound to the BC was released from the BC hydrogel. During these processes, the crystallinity and surface morphology of the BC were also modified. Meanwhile, the crystalline form of the BC changed from cellulose I to II in alkaline medium. In particular, the BC nanofiber hydrogel broke into floccules when treated with highly concentrated NaOH solution at a temperature of −5 °C, but these floccules congregated into a bulk state again after removing the NaOH.

Mechanical, moisture absorption, and photodegradation behaviors of bacterial cellulose nanofiber‐ reinforced unsaturated polyester composites

AbstractBacterial cellulose (BC) fiber reinforced unsaturated polyester (UPE) composites were fabricated using the resin transfer molding method. The mechanical properties, moisture absorption behavior, and photodegradation of the composites were studied. Scanning electron microscopy observations indicated that BC nanofibers surface‐treated with silane exhibited higher fiber–resin adhesion strength in comparison to original BC. It was noted that the process of moisture absorption of the BC/UPE composites could be described by using Fick's law and an oxidative degradation took place when the composite is exposed to ultraviolet radiation. © 2011 Wiley Periodicals, Inc. Adv Polym Techn 30: 249–256, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20220

Solvent-free acetylation of bacterial cellulose under moderate conditions

Bacterial cellulose preserving the microfibrillar morphology was partially acetylated by the solvent-free acetylation method using acetic anhydride in the presence of iodine as a catalyst. The results showed that within the range of catalyst amounts studied, the overall degree of substitution increased as the amount of iodine used increased. We also found that the reaction time and temperature had an active influence on the extent of acetylation. X-ray diffraction profiles indicated that acetylation proceeded from the surface to the interior of BC nanofibers, and scanning electron microscopy images revealed that even low levels of acetylation were effective to make the nanofibers separated from each other. NMR analysis indicated the regio-nonselective reactivity of the OH groups in the glucose units in the acetylation process. The obtained acetylated BC membrane shows more hydrophobic surface and good mechanical properties which is in favor of enhancing the hydrophobic non-polar polymeric matrix.

Preparation of Novel Ag/Bacterial Cellulose Hybrid Nanofibers for Antimicrobial Wound Dressing

In this work, we describe a novel facile method to prepare long one-dimensional hybrid nanofibers by using hydrated bacterial cellulose nanofibers (BCF) as template. Silver (Ag) nanoparticles with an average diameter of 1.5 nm were well dispersed on BC nanofibers via a simple in situ chemical-reduction between AgNO3 and NaBH4 at relatively low temperature. The bare BCF and as-prepared Ag/BCF hybrid nanofibers were characterized by a range of analytical techniques including transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV–vis absorption spectra (UV–vis). The results reveal that Ag nanoparticles were homogeneously precipitated on the BCF surface. The results indicate that Ag/BCF hybrid nanofibers are promising candidate materials for functional antimicrobial agents.

Biotemplated Synthesis of Gold Nanoparticle–Bacteria Cellulose Nanofiber Nanocomposites and Their Application in Biosensing

AbstractBacteria cellulose (BC) nanofibers are used as robust biotemplates for the facile fabrication of novel gold nanoparticle (NP)–bacteria cellulose nanofiber (Au–BC) nanocomposites via a one‐step method. The BC nanofibers are uniformly coated with Au NPs in aqueous suspension using poly(ethyleneimine) (PEI) as the reducing and linking agent. With the addition of different halides, Au–BC nanocomposites with different Au shell thicknesses are formed, and a possible formation mechanism is proposed by taking into account the special role played by PEI. A novel H2O2 biosensor is constructed using the obtained Au–BC nanocomposites as excellent support for horseradish peroxidase (HRP) immobilization, which allows the detection of H2O2 with a detection limit lower than 1 µM. The Au–BC nanocomposites could be further used for the immobilization of many other enzymes, and thus, may find potential applications in bioelectroanalysis and bioelectrocatalysis.

Effect of coupling treatment on mechanical properties of bacterial cellulose nanofibre-reinforced UPR ecocomposites

Bacterial cellulose nanofiber-reinforced unsaturated polyester resin composites (BC/UPR) were prepared using vinyl-triethoxy silane coupling modified BC fibres by the method of resin transfer molding (RTM) and subjected to mechanical tests in order to study the effect of surface treatment on the properties of composites. The results show that coupling treatment did not change the morphology of BC nanofibers, while it changed the chemical states of the BC fiber's surface. The XPS result indicates that chemical bonding was formed at the interface between UPR matrix and BC fibers after surface treatment, which enhanced the mechanical properties of composites. After treatment, tensile strength, flexure strength, shear strength and tensile modulus of the composites with a fiber volume fraction ( V f) of 10% were increased by 117.7%, 38.4%, 38.7% and 27.6%, respectively.