Hongbing Deng

Quaternized chitosan-layered silicate intercalated composites based nanofibrous mats and their antibacterial activity.

Quaternized chitosan (HTCC)-organic rectorite (OREC) intercalated composites based electrospun nanofibrous mats were fabricated from HTCC-OREC/polyvinyl alcohol (PVA) solutions for the first time. The morphology, intercalated structure, and antibacterial activity of the as-spun mats were investigated. The transmission electron microscopy images taken from HTCC-OREC composites showed that HTCC chains were inside the OREC interlayer. Scanning electron microscopy results verified that more typical fibrous structure would be generated by adding OREC. Fourier transform infrared spectra and energy-dispersive X-ray spectroscopy results indicated that OREC existed in the HTCC-OREC/PVA nanofibrous mats. The intercalation structure in nanofibrous mats was confirmed by X-ray diffraction results, which confirmed that HTCC and PVA chains could intercalate into the interlayer of OREC. The antibacterial activity of the electrospun mats was enhanced when the amount of the OREC increased. Therefore, the novel ternary nanofibrous mats could be used in the field of food packaging and biomedical applications.

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.

Antibacterial activity of nanofibrous mats coated with lysozyme-layered silicate composites via electrospraying.

A mixture of positively charged lysozyme (LY) and rectorite (REC) composites was electrosprayed onto negatively charged electrospun cellulose acetate (CA) nanofibrous mats. The morphology and average diameter of CA mats and the mats coated with LY-REC were investigated by scanning electron microscopy. The composite mats were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy, and the results confirmed that LY and REC were successfully immobilized on the surface of CA mats via electrospraying technique. The small-angle X-ray diffraction results showed that the silicate layers of REC were completely exfoliated. The enzyme activity and bacterial inhibition analysis verified that the antimicrobial effect of the composite fibrous mats was enhanced with the addition of REC. The protein delivery properties and the bound enzyme activity after removal of unbound lysozyme from fibers were measured and showed that the electrospraying technique was suitable for enzyme immobilization.

Nanogels fabricated by lysozyme and sodium carboxymethyl cellulose for 5-fluorouracil controlled release.

Lysozyme (Ly) and sodium carboxymethyl cellulose (CMC) were used to fabricate nanogels by a convenient method without using any chemical treatment except simple heating to achieve the denaturation temperature of Ly. The prepared nanogels were characterized by dynamic laser scattering (DLS), rheological analysis, transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The nanogels are of spherical shape with average hydrodynamic diameter of 241 nm and the swelling ratio of nanogels is about 5. Then 5-fluorouracil was used as a model drug to investigate the entrapment efficiency and release ability in nanogels. It turned out to be that the release in simulated gastric fluid (SGF) was more slowly compared with that in simulated intestinal fluid (SIF), which could protect the 5-Fu in stomach and ensure it released in intestines.

A study of chitosan hydrogel with embedded mesoporous silica nanoparticles loaded by ibuprofen as a dual stimuli-responsive drug release system for surface coating of titanium implants

In this study, the complex pH and electro responsive system made of chitosan hydrogel with embedded mesoporous silica nanoparticles (MSNs) was evaluated as a tunable drug release system. As a model drug, ibuprofen (IB) was used; its adsorption in MSNs was evidenced by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). In order to prepare the complex drug release system, the loaded particles IB-MSNs were dispersed in chitosan solution and then the complex IB-MSNs/chitosan film of 2mm thickness was deposited as a hydrogel on the titanium electrode. The codeposition of components was performed under a negative biasing of the titanium electrode at -0.75 mA/cm2 current density during 30 min. The IB release from the IB-MSNs/chitosan hydrogel film was studied as dependent on pH of the release media and electrical conditions applied to the titanium plate. When incubating the complex hydrogel film in buffers with different pH, the IB release followed a near zero-order profile, though its kinetics varied. Compared to the spontaneous IB release from the hydrogel in 0.9% NaCl solution (at 0 V), the application of negative biases to the coated titanium plate had profound effluences on the release behavior. The release was retarded when -1.0 V was applied, but a faster kinetics was observed at -5.0 V. These results imply that a rapid, mild and facile electrical process for covering titanium implants by complex IB-MSNs/chitosan hydrogel films can be used for controlled drug delivery applications.

Poly(vinyl alcohol)/sodium alginate/layered silicate based nanofibrous mats for bacterial inhibition

Poly(vinyl alcohol) (PVA)/sodium alginate (ALG)/organic rectorite (OREC) composite nanofibrous mats are fabricated by electrospinning aqueous solutions with different mixing ratios. Both good fiber shape and three-dimensional structure of nanofibrous mats can be observed by Field Emission Scanning Electron Microscopy. Energy-dispersive X-ray spectroscopy shows the existence of OREC in the as-spun composite mats. In addition, small-angle X-ray diffraction confirms that the interlayer of OREC is intercalated by ALG/PVA chains, and the distance between OREC interlayers is increased from 4.50 to 4.74 nm. Wide angle X-ray diffraction and Fourier transform infrared spectra further verify the intercalation is between polymers and layered silicate. Moreover, the thermal gravimetric analysis shows that the addition of OREC has only a small effect on the thermal stability of composites. Furthermore, the antibacterial experiments illustrate that OREC can enhance the bacterial inhibition ability of nanofibrous mats against Escherichia coli and Staphylococcus aureus.

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.

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.

Highly cost-effective and high-strength hydrogels as dye adsorbents from natural polymers: chitosan and cellulose

Search for cost-effective and high-strength dye adsorbents has become an urgent problem in wastewater treatment. Natural polymers such as chitosan and cellulose are low-cost and can be fabricated as hydrogels for dye adsorption, but these hydrogels usually have weak strength. Here, novel high-strength and highly cost-effective hydrogels with a high capacity of dye adsorption were prepared with chitosan and cellulose. The chitosan/cellulose hydrogels could be knotted and twisted without fracture and could be restore rapidly after compression. These features showed that the hydrogels had good elasticity, high strength and excellent resilience. Also, the incorporation of rectorite into hydrogels could increase the thermal stability and strength of composite hydrogels. Subsequently, the adsorption capacity of hydrogels to Congo Red was investigated: chitosan was the main functional material for adsorption and rectorite participated in dye adsorption as well, but cellulose supported the structure. Furthermore, the adsorption process fitted closely with the Freundlich model, and was best described by a pseudo-second-order kinetic model. The hydrogels were biodegradable and could be easily collected after adsorption. These environmental friendly hydrogels could be promising candidates for dye removal in the future.

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.