Yingfei Zhan

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.

Plasma treated polyethylene terephthalate/polypropylene films assembled with chitosan and various preservatives for antimicrobial food packaging.

In this study, polyethylene terephthalate/polypropylene (PET/PP) films were treated via atmospheric pressure plasma, assembled with chitosan and various preservatives and applied for antimicrobial food packaging. Surface properties of these obtained films were studied by contact angle measurement, atomic force microscopy (ATM), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FT-IR) and dynamic laser scattering (DLS). The above results showed that the surface hydrophilicity and roughness of the films increased after the plasma treatment. Besides, chitosan and the preservatives were successfully assembled onto the surface of the films. In addition, the antimicrobial activities of the films against three kinds of microorganisms (Staphylococcus aureus, Bacillus subtilis and Escherichia coli) were investigated and the results indicated that the inhibition ratios against B. subtilis and E. coli reached almost 100% while the inhibition ratios against S. aureus were lower than 85%. Moreover, the accumulative release profiles of the antimicrobial substances migrating from the assembled films into the release solutions revealed that their release speed increased with the increment of temperature and acidity, but decreased with enhancing the ionic strength regulated by sodium chloride or with lowering the ionic mobility regulated by sucrose.

Fabrication of rectorite-contained nanoparticles for drug delivery with a green and one-step synthesis method

The composite nanoparticles (NPs) consisted of quaternized chitosan (QC)/bovine serum albumin (BSA)/rectorite (REC) were prepared successfully just by adding BSA solution into QC-REC nanocomposites solution via electrostatic interactions. The average diameter of NPs increased with the accretion of REC, which was demonstrated with dynamic laser scattering (DLS) and transmission electron microscopy (TEM). The results of small angle X-ray diffraction (SAXRD) and selected area electron diffraction (SAED) demonstrated that the intercalated structure of REC was enlarged with the addition of REC. Besides, it can was proved that the interaction had occurred between QC and REC in NPs with fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). In addition, doxorubicin (DOX) was used to investigate the entrapment efficiency and release pattern in NPs. It turned out to be that the addition of REC could increase the encapsulation efficiency (EE) and loading capacity (LC). The results also exhibited that the drug release in simulated gastric fluid reduced apparently with the addition of REC, which could ensure more DOX released in intestines.

Controllable immobilization of naringinase on electrospun cellulose acetate nanofibers and their application to juice debittering

Electrospinning is a facile method to fabricate nanofibers, in terms of their high specific surface area and porous structure. Electrospun nanofibrous mats are excellent candidates for immobilization of enzymes. In this study, a simple route based on electrospinning and layer-by-layer (LBL) self-assembly processes has been developed to prepared naringinase/alginate multilayer coated electrospun cellulose acetate nanofibers. The content of immobilized naringinase could be tuned by adjusting the number of multilayers. XPS results indicated that naringinase was successfully immobilized on cellulose acetate nanofibers. SEM images showed the nanofibers maintain their sharp but became rougher after multilayer coating. Besides, the surface area of electrospun cellulose acetate nanofibers decreased and mesopores reduced. The major bitter components of grapefruit juice are naringin and limonin, naringin could be slightly removed by hydrolysis with naringinase and limonin might be removed by adsorption with cellulose acetate nanofibers.

Antimicrobial application of nanofibrous mats self-assembled with quaternized chitosan and soy protein isolate

Positively charged N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) and negatively charged soy protein isolate (SPI) were alternately assembled on cellulose acetate (CA) electrospun nanofibrous mats via electrostatic layer-by-layer self-assembly technique. CA nanofibrous mats coated with bilayers of HTCC and SPI possessed more orderly-arranged structure than uncoated CA mats according to the observation from scanning electron microscopy images. The average diameter of the nanofibers was enlarged by the increase of the bilayer number. X-ray photoelectron spectroscopy indicated that HTCC and SPI were coated on the surface of the CA mats successfully. The average diameters of inhibition zones of (HTCC/SPI)10.5-films-coated nanofibrous mats against Escherichia coli and Staphylococcus aureus were 9.6mm and 11.53mm, respectively, which demonstrated the highest antimicrobial activity among samples in presented study.

Pore volume and distribution regulation of highly nanoporous titanium dioxide nanofibers and their photovoltaic properties

By combining the initial solvent volatilization and ultimate calcination to form highly nanoporous polystyrene/titanium dioxide (PS/TiO2) composite nanofibrous mats were fabricated via electrospinning, then the PS was removed afterwards by calcination, and finally porous TiO2 nanofibers were formed successfully. The porous structure of the nanofibers was characterized by field emission scanning electron microscopy and Brunauer-Emmett-Teller measurements, which indicated that the size and the diameter of the pore and the ratio of the surface area to the volume of the mats were regulated by adjusting the weight ratios of tetrahydrofuran and N,N-dimethylformamide in the binary solvent mixtures. X-ray photoelectron spectroscopy and Raman analysis confirmed that the addition of TiO2 into the fibers was successful and that PS decomposed completely from fibers after calcination at 500°C. The photovoltaic measurements showed that the obtained TiO2 nanofibers were ideal candidates for the fabrication of the photoanodes on the dye-sensitized solar cells.

Production of thick uniform-coating films containing rectorite on nanofibers through the use of an automated coating machine

When an efficient automated coating machine is used to process layer-by-layer (LBL) deposited nanofibrous mats, it causes an obvious planar effect on the surface of the mats, which can be eliminated through ultimate immersion. During this process, chitosan (CS) - rectorite (REC) intercalated composite films are built on the surface of cellulose acetate (CA) nanofibrous mats by a coating machine. Then, the immersion process is utilized to allow positively charged CS or CS-REC intercalated composites to uniformly assemble on the surface of negatively charged CA nanofibers. An investigation into the morphology of the resultant scaffolds confirms that the uniquely small pore size, high specific surface area and typically three-dimensional (3D) structure of nanofibrous mats remain present. The results of Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) indicate that it is feasible to assemble nanofibrous mats using a coating machine. The intercalated structure of CS-REC is confirmed by the results of small-angle X-ray diffraction (SAXRD) and wide-angle X-ray diffraction (WAXRD). The results of the cell experiment and antibacterial test demonstrate that the addition of REC not only has little impact on the cytocompatibility of the mats but also enhances their ability to inhibit bacteria.

Regulating the gaps between folds on the surface of silk fibroin membranes via LBL deposition for improving their biomedical properties

Silk fibroin (SF) has become a promising biomaterial in guided bone regeneration (GBR). In an attempt to modify the size of the gaps on the surface of SF barrier membrane and improve its antibacterial activity, biological and mechanical properties, positively charged Lysozyme (LY)-Collagen Type-I (COL) composites and negatively charged SF were introduced to the negatively charged surface of SF substrates utilizing the electrostatic layer-by-layer (LBL) self-assembly technique. The morphology, chemical structures and element content of the LBL structured membranes were investigated. The results suggested that LY and COL were successfully assembled and the gaps between the folds on the surface of the membranes became smaller gradually with the increase of coated film numbers. Besides, the content of β-sheets of the membranes increased after deposition, which indicated the improvement of their mechanical properties. Moreover, the results of the measurement of immobilized LY and antibacterial assay not only revealed that the enzymatic catalysis and antibacterial activity of the samples enhanced with the increase of coated bilayer numbers but also implied that LBL modified membranes had better antibacterial activity when LY-COL was on the outermost layer. Furthermore, CCK-8 assay certified both SF membrane and LBL structured membranes could facilitate cell growth and proliferation, and the introduction of COL could further promote this ability. Finally, cell attachment and morphology examination provided intuitional evidence that SF membrane and LBL modified membranes have excellent biocompatibility.

Pectin based composite nanofabrics incorporated with layered silicate and their cytotoxicity.

Pectin based composite polymer nanofabrics incorporated with rectorite (REC) were fabricated via electrospinning. Continuous and uniform nanofibers were obtained by electrospinning poly (vinyl alcohol) (PVA)-Pectin (80/20) composite solution. REC was successfully introduced to the polymer composite nanofabrics, which was confirmed by Energy-dispersive X-ray spectroscopy and Fourier transform infrared spectra. Small angel X-ray diffraction demonstrated the REC in PVA-Pectin-REC composite nanofabrics was neither of an intercalated type nor of a completely exfoliated type. And organic-inorganic composite nanofabrics with enhanced thermal stability and cell viability were obtained, which was demonstrated by thermo-gravimetric analysis and cell cytotoxic evaluation results, respectively. High content of REC (≥1%) in composite nanofabrics could obviously reduce the cytotoxicity and improve the cell viability of the composite nanofabrics.

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.