Xingjiang Li

Synthesis and bioactivity of gelatin/multiwalled carbon nanotubes/hydroxyapatite nanofibrous scaffolds towards bone tissue engineering

The objective of this study was to develop a novel three-dimensional biomimetic gelatin/multiwalled carbon nanotubes/hydroxyapatite (gelatin/MWNTs/HA) nanofibrous scaffold via electrospinning technique for bone tissue engineering. The mechanical properties, structure, morphology and the bioactivity of nanofibrous scaffolds in vitro were investigated. Attentions were focused on the adhesion, mineralization, viability and proliferation of human fetal osteoblastic cells (hFOBs) on scaffold. Resulting scaffolds provided relative good mechanical support (7.9 ± 0.32 MPa) and high porosity (91.2%) to mimic a favorable environment for hFOBs. The hydrogen bonds between gelatin molecules and MWNTs/HA units were confirmed, and the incorporation of HA or MWNTs/HA nanoparticles caused an increase in porosity and strength of scaffolds, meanwhile the surface of nanofibers tended to be rough. HA nanoparticles showed a chelating effect to promote osteogenesis and mineralization of bone, and MWNTs had a synergetic effect with HA to induce the apatite formation. As compared to gelatin and gelatin/HA scaffolds, gelatin/MWNTs/HA scaffold exhibited the best viability hFOB cells cultured in vitro, most excellent morphology of hFOB cells seeded into scaffold and a significantly increasing in proliferation. The nanofibrous scaffold will have great potential as an excellent scaffold for in bone tissue engineering.

Synthesis, antimicrobial and release of chloroamphenicol loaded poly(l-lactic acid)/ZrO2 nanofibrous membranes

Electrospinning technique was used to fabricate chloroamphenicol loaded poly (L-lactic acid)/ZrO2 (CP-PLLA/ZrO2) nanofibrous membranes. The average diameter of drug carrier PLLA/ZrO2 nanofibers increased with ZrO2 concentration increasing and ribbon-shape fibers were present when ZrO2 content reached 3% and above. The existence of hydrogen and ZrOC bonds between PLLA and ZrO2 units improved the thermal stability of PLLA. The model drug CP loading showed no significant changes on the size and shape of nanofibers when CP content was below 8%, but the fibers were uneven and interspersed with ball-shape beads when CP content rose up to 10%. From the antimicrobial activity and release experimental result, the CP-PLLA/ZrO2 nanofibrous membranes revealed well controlled release and better antimicrobial activity against Staphylococcus aureus, which may have potential as a new nanofibrous membrane in drug delivery and wound dressing.

Montmorillonite@chitosan-poly (ethylene oxide) nanofibrous membrane enhancing poly (vinyl alcohol-co-ethylene) composite film

A montmorillonite@chitosan-poly (ethylene oxide) nanofibrous membrane (MMT@CPF) enhancing poly (vinyl alcohol-co-ethylene) (EVOH-MMT@CPF) composite film was developed by using a space-filling embedding method. The structure of EVOH-MMT@CPF was characterized, and the thermal stability, mechanical and barrier properties of the films were investigated. The CPF was fabricated via electrospinning technique and the self-assembly of MMT nano-platelets on CPF was achieved by the driving of electrostatic interactions between MMT nano-platelet and CPF. The experimental results indicated that the well-kept MMT@CPF after embedding in the EVOH matrix significantly improved the thermal stability and mechanical properties of the film, and also endowed the film with outstanding oxygen barrier (0.2×10-16cm3cmcm-2s-1Pa-1) and good moisture barrier (4.6×10-6gmm-2s-1atm-1 under a relative humidity of 90%) by prolonging the tortuous paths for molecule penetration. The composite film may have a great potential application in food packaging.

Improvement of the activity and thermostability of microbial transglutaminase by multiple-site mutagenesis

Abstract Microbial transglutaminase (MTG) is an enzyme widely used in the food industry. Mutiple-site mutagenesis of Streptomyces mobaraensis transglutaminase was performed in Escherichia coli. According to enzymatic assay and thermostability study, among three penta-site MTG mutants (DM01-03), DM01 exhibited the highest enzymatic activity of 55.7 ± 1.4 U/mg and longest half-life at 50 °C (418.2 min) and 60 °C (24.8 min).

Research on CCD video signal processing based on correlated double sampling

In CCD detection to micro signals, it is a key technique that the output noise signals of CCD must be restrained or attenuated, so that SNR (Signal-to-Noise Ratio) can be enhanced. This paper initially presents a brief description on the characteristics of CCD output signals and usual processing schemes. And then, CCD output noise characteristics being concerned, CDS (Correlated Double Sampling) is carefully analyzed. Lastly, on the basis of establishing CDS transfer function and noise analysis model, the most proper CDS scheme is employed to test the performance of restraining KTC noise and other low-frequency noises existed in CCD signals. And the results show that if only proper sample time is chosen, 2δ -CDS circuit can not only remove KTC noise, but also restrain low-frequency noises and other white noises in different degrees.

Antibacterial [2-(methacryloyloxy) ethyl] trimethylammonium chloride functionalized reduced graphene oxide/poly (ethylene-co-vinyl alcohol) multilayer barrier film towards food packaging

The objective of present work was to construct antibacterial [2-(methacryloyloxy) ethyl] trimethylammonium chloride functionalized reduced graphene oxide/poly(ethylene-co-vinyl alcohol) (MTAC-rGO/EVOH) multilayer barrier films by using layer-by-layer assembly under a parallel electric field. Besides barrier and mechanical properties, the antibacterial activities of the film and cytotoxicity of MTAC-rGO nanosheets were extensively investigated. The functionalization of rGO was achieved by grafting MTAC onto a graphene framework through C (sp3)-C bonds. The assembly of MTAC-rGO on the EVOH matrix not only significantly improved film mechanical strength, but also endowed the targeting film with outstanding moisture barrier even under a relative humidity of 99% (e.g., 0.019 g m-2 s-1 atm-1 for (MTAC-rGO/EVOH)20) besides good oxygen barrier (e.g., 0.07 cm3 m-2 d-1 atm-1 for (MTAC-rGO/EVOH)20). Among the testing films, MTAC-rGO/EVOH film had the best antibacterial activity, and the activity against S. aureus was better than E. coli. Meanwhile, the cytotoxicity of MTAC-rGO nanosheets was very low. Results suggest that MTAC-rGO/EVOH film may have great potential in food active packaging.

Mesoporous hydroxylapatite/activated carbon bead-on-string nanofibers and their sorption towards Co(II)

The present work aims to prepare mesoporous hydroxylapatite/activated carbon (meso-HA/AC) bead-on-string nanofibers and evaluate their sorption towards Co(II) via sorption kinetics and isotherms. Using polyvinyl alcohol/hydroxylapatite/glucose electrospun nanofibers as the precursor, meso-HA/AC nanofibers are prepared by a hydrothermal process. The nanofibers show bead-on-string structures with mesoporous characteristics, main pores around 29 nm in size, and a specific surface area of 30.014 m2 g−1. Moreover, the rod-like HA crystals assemble into bundles and insert into the two neighboring activated carbon beads. The sorption of Co(II) onto meso-HA/AC nanofibers is strongly dependent on pH and ionic strength. The pseudo-second-order model is valid to describe the sorption of Co(II) onto meso-HA/AC nanofibers, and the intraparticle diffusion is not the sole rate-controlling step. Both Langmuir and Freundlich models can well describe the sorption isotherms, and the Langmuir model is slightly better than the Freundlich model. Moreover, the thermodynamic parameters imply that the sorption process is spontaneous and endothermic. The meso-HA/AC bead-on-string nanofibers may have potential as a highly effective material for the removal of heavy metal ions from aqueous solution.

Butylated hydroxyanisole encapsulated in gelatin fiber mats: Volatile release kinetics, functional effectiveness and application to strawberry preservation

Butylated hydroxyanisole (BHA) encapsulated in gelatin (GA) (GA-BHA) fiber mats were fabricated via electrospinning technique and applied to strawberry preservation. The volatile release kinetics and functional effectiveness of the mats were investigated. BHA was high efficiently encapsulated in GA fibers and the antioxidant activity of BHA could be well protected. The encapsulation of BHA enhanced the stability of GA and favored structure transition of GA from random coil and β-turns to α-helix and β-sheet. The GA-BHA mats showed good antibacterial activity against Staphylococcus aureus, and the predominant volatile release mechanism of BHA from mats was Fickian diffusion. Furthermore, the mats also showed broad-spectrum antifungal activity against four mould genera (Rhizopus sp., Mucor sp., Aspergillus sp. and Penicillium sp.). The shelf-life of strawberry can be prolonged effectively in the presence of GA-BHA mats during storage. Results suggested that the GA-BHA mats may have a great potential in active food packaging.