Shaojin Gu

Electrospinning of carboxyethyl chitosan/poly(vinyl alcohol)/silk fibroin nanoparticles for wound dressings

Composite nanofibrous membranes of water-soluble N-carboxyethyl chitosan/poly(vinyl alcohol)/silk fibroin nanoparticles were successfully fabricated by electrospinning. The composite nanofibers were subjected to detailed analysis by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). SEM results investigated that the morphology and diameter of the nanofibers were affected by silk fibroin nanoparticles content. XRD and DSC demonstrated that there was intermolecular hydrogen bonding among the molecules of carboxyethyl chitosan, silk fibroin and PVA. The crystalline microstructure of the electrospun fibers was not well developed. The indirect cytotoxicity assessments of the nanofibers were studied. The result showed the nanofibers had good biocompatibility. This novel electrospun matrix would be used as potential wound dressing for skin regeneration.

Potential of quaternization-functionalized chitosan fiber for wound dressing.

Quaternization-functionalized chitosan fibers were successfully prepared by using 2,3-epoxypropyl trimethyl ammonium chloride as a quaternized reagent reacted with chitosan fiber. FTIR and (1)H NMR were used to characterize the structure of quaternized chitosan fibers (QCFs). The swelling behavior and mechanical property of QCFs were studied. The results showed that, QCFs had higher liquid absorption capacity than chitosan fiber, while the tensile strength and elongation at break of QCFs were lower than those of chitosan fiber. The antibacterial activity of the QCF had been evaluated by Gram-positive bacteria Staphylococcus aureus (S. aureus). The results indicated that, the antibacterial activity of QCF against S. aureus was stronger than that of chitosan fiber. Indirect cytotoxicity assessment of the fibers indicated that QCF was nontoxic to the L929 cell with relatively low extraction concentration. This novel fiber would be used as potential wound dressing for skin regeneration.

N-carboxyethyl chitosan fibers prepared as potential use in tissue engineering

To improve the hydrophilicity of chitosan fiber, N-carboxyethyl chitosan fiber was prepared through Michael addition between chitosan fiber with acrylic acid. The structure was studied by (1)H NMR. The degree of N-substitution, measured via (1)H NMR, was easily varied from 0.10 to 0.51 by varying the molar ratio of acrylic acid to chitosan. Series of properties of N-carboxyethyl chitosan fiber including mechanical property, crystallinity, thermal property and in vitro degradation were investigated by Instron machine, X-ray diffraction and differential scanning calorimetry and thermogravimetric analysis, respectively. The results showed that, introducing the carboxyethyl group into the backbone chain of chitosan fiber destroyed the intra/intermolecular hydrogen bonding, leading to loss of the intra/intermolecular hydrogen bonding and improvement of hydrophilicity. Indirect cytotoxicity assessment of carboxyethyl chitosan fibers was investigated using a L929 cell line. And the obtained results clearly suggested that N-carboxyethyl chitosan fiber was nontoxic to L929 cells. The N-carboxyethyl chitosan fibers are potential as tissue engineering scaffolds.

A study on the influence of a surface-contacting spinning strand on yarn appearance during sirofil spinning

Ring spun yarn hairiness can be reduced by such methods as spinning with a contact surface and Z-twisting the staple strand in a “left diagonal” yarn path (denoted as LDP). Actually, the LDP method already exists in sirofil spinning technology. In this study, mechanism analysis of controlling and trapping staple fibers is conducted theoretically for sirofil spinning with a contact surface. Analysis reveals that contacting with a rubber surface leads to deformation of the straight sirofil spinning strand; this can better the tension and twist distribution on the right-hand component of the sirofil spinning triangle to improve LDP sirofil yarn appearance. Related experiments are also carried out to validate the theoretical analysis. Online pictorial investigation confirms the deformation of the straight sirofil composite yarn once it contacts with a rubber surface. Experimental results show that the lower weight loss and smoother appearance are bestowed upon LDP sirofil yarn spun with a rubber contact surface, which agrees well with corresponding theoretical analysis.

Synthesis, spectroscopic, and thermal properties of polyurethanes containing zwitterionic sulfobetaine groups

A series of novel polyurethanes (PUs) containing zwitterionic sulfobetaine groups were synthesized from polycarbonatediol with alkyne groups and 3-((2-azidoethyl)dimethylammonio)propane-1-sulfonate using the copper-catalyzed 1,3-dipolar cycloaddition (click) reaction. All the polyurethanes were fully characterized by 1H NMR, Fourier transform infrared spectrometer, gel permeation chromatography, and elemental analysis; the thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. It has been proved that the thermal stability of zwitterionic sulfobetaine functionalized polyurethanes were greater than the starting alkyne-containing polyurethane. Protein adsorption was measured and it was indicated that PUs with zwitterionic sulfobetain structure are a kind of biocompatible materials with a better anti-protein fouling property compared to the corresponding alkyne-containing polyurethanes.

Regenerated egg white/silk fibroin composite films for biomedical applications

Protein-based composites have always been desirable biomaterials as they can be fabricated into a wide range of biomaterials with tunable properties, including modulation of mechanical properties and control of cell responses. Both egg white protein (EW) and silk fibroin (SF) are biocompatible, biodegradable, non-toxic and naturally abundant biopolymers. In order to obtain biocompatible composite films with tunable performance, EW and SF were blended at various ratios. Raising the SF ratio in the composite films significantly increased breaking strength, but impaired flexibility. Conversely, increasing the EW ratio remarkably enhanced elasticity of the composite films. Furthermore, the biological assays based on endothelial cells showed that the incorporation of EW promoted cell viability. These make them potential materials with controllable mechanical property and enhanced bioactivity, providing useful options for the fabrication of tissue engineering scaffolds.

Selective aminolysis of acetylated lignin: Toward simultaneously improving thermal-oxidative stability and maintaining mechanical properties of polypropylene

Even with outstanding radical capturing ability, the utilization of lignin as a natural antioxidant in polypropylene (PP) still has been pended. Usually, the compatibility of its blends is improved based on the reaction of hydroxyl content, thus leading to the decreasing content of phenolic hydroxyl (Ph-OH) group and inferior thermal-oxidative stability of lignin blends. Here, the selective aminolysis of acetylated Kraft lignin (pyr-KL) was investigated, which structures were characterized using FTIR, 31P-NMR and GPC. The Ph-OH group of acetylated KL could be released by the addition of pyrrolidine; however the aliphatic hydroxyl group is still blocked. With the control of reaction conditions, the highest oxidation induction time of pyr-KL/PP (0.5wt% loading) reaches up to 22.6min, almost 2.6 times than that of pure PP. More importantly, the mechanical properties of PP were also maintained under the loading of pyr-KL, which is much better than that of curde KL/PP.

The effect of natural silk fibroin microparticles on the physical properties and drug release behavior of biomedical polyurethane filament

Abstract In this study, filaments comprising natural silk fibroin microparticles (NSFP) and biomedical polyurethane (BPU) were prepared via wet-spinning as a reusable-controlled drug-delivery system. The rheological properties of the spinning solution were studied to examine the effect of NSFP on the BPU/NSFP filament formation. The influences of NSFP content and spinning conditions on the morphology, molecular interactions, mechanical properties, and swelling performance of BPU/NSFP filaments were also investigated. The morphology and mechanical property studies showed that NSPF and BPU exhibit good compatibility. The capacity of the BPU/NSFP filaments as drug loading carriers and drug release behavior were studied by spectroscopy. The presence of NSFP in the drug controlled system increase the drug loading amount and enhance the drug release time. This paper presents a well-designed manufacturing method for preparing BPU/NSFP filaments with good controlled drug delivery.

Thermal-oxidative effect of Kraft lignin antioxidant in polypropylene: Uncovering the key factor using correlation analysis model

Which factors are crucial to improving lignin antioxidant ability in polymers has been debated over years. Here, the structural effect of natural antioxidant from technical Kraft lignin (KL) on the oxidation induction time (OIT) of KL/polypropylene (PP) was quantitatively investigated using correlation analysis model instead of traditional linear fitting model. The correlation coefficient and significance value of their relationship clearly demonstrated the dominating role of non-condensed Phenolic OH (Ph-OH) in improving KL/PP thermal-oxidation stability, subsequently followed by M¯n, aliphatic OH/total Ph-OH, condensed Ph-OH and polydispersity. OIT is positive with non-condensed and total Ph-OH, while it declines with increase of the above other factors. Remarkably, the longest OIT (∼90min) was obtained even at extreme loading (0.5wt%), almost ∼911% and ∼201% huge increase in contrast to that of pure PP and crude KL/PP composite, respectively. Meanwhile, the mechanical properties of KL fractions/PP blends can be maintained at the same or better level than that of pure PP, due to strong interfacial adhesion strength.

Non-isothermal crystallization kinetics of eucalyptus lignosulfonate/polyvinyl alcohol composite

The nonisothermal crystallinization kinetic was performed on Polyvinyl alcohol (PVA) mixed with eucalyptus lignosulfonate calcuim (HLS) as the biobased thermal stabilizer, which was systematically analyzed based on Jeziorny model, Ozawa equation and the Mo method. The results indicated that the entire crystallization process took place through two main stages involving the primary and secondary crystallization processes. The Mo method described nonisothermal crystallization behavior well. Based on the results of the half time for completing crystallization, kc value in Jeziorny model, F(T) value in Mo method and crystallization activation energy, it was concluded that low loading of HLS accelerated PVA crystallization process, however, the growth rate of PVA crystallization was impeded at high content of HLS.