Xinyuan Shen

Preparation of Polycaprolactone Tissue Engineering Scaffolds by Improved Solvent Casting/Particulate Leaching Method

The classic solvent casting/particulate leaching method to fabricate PCL scaffolds was improved by using a centrifugal technology, a direct bonding process in preparing salt matrices and a technology of vacuum treatment under heating in the desolvation process. Series operations of preshaping, centrifuging, casting and desolvating were employed during the scaffolds manufacture. The scaffolds properties were characterized including micro‐structures, pore dimensions, porosity and hydrophilicity. The results show that centrifugal technology can improve the pore uniformity of scaffolds. In the bonding process, well‐interconnected porous structures were formed if water content was between 2∼7%. The distribution of pore dimensions was from 10 to 80 μm, and the porosities were about 89%. Generally, the porosities formed by vacuum treatment at high temperature are greater than those formed by vacuum treatment at ambient temperature in the desolvation process. The fabricated porous PCL scaffolds with good elasticity and desired thickness could be a good choice for application in soft tissue engineering.

Solubility of a High Molecular-Weight Bacterial Cellulose in Lithium Chloride/N,N-dimethylacetamide Solution

High molecular-weight bacterial cellulose (BC) was found to be soluble in a lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) solvent system with a maximal concentration of 3 wt% if an activation procedure was performed beforehand. The granular BC was not favored and had to be ground to powders before dissolution. To facilitate subsequent dissolution, an activation procedure consisting of stewing the BC samples at 45°C–50°C in DMAc containing dissolved KMnO4 was adopted. It was found that a swelling temperature of 45°C was preferred, for about 4 h, but continuous, constant temperature heating during dissolving procedure was unfavorable, possibly due to the instability of the intermediate complex formed between the Li+ ion and the carbonyl oxygen of DMAc. However, the BC sample would be gradually dissolved if placed at room temperature for a long enough time.

Synthesis and Characterization of La‐Doped Fe3O4‐Polyaniline Magnetic Response Nanocomposites

Lanathum (La)‐doped Fe3O4 magnetic nanoparticles were prepared in aqueous solution at room temperature, then La‐doped Fe3O4‐polyaniline (PANI) nanocomposites containing a dispersion of La‐doped Fe3O4 nanoparticles were synthesized via in‐situ polymerization of aniline monomer. The structure and properties of the synthesized samples were characterized with X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometry (ICPAES), and a vibrating sample magnetometer (VSM). The resulting particles of La‐doped Fe3O4 and La‐doped Fe3O4‐PANI were almost spherical with diameters ranging from 15 to 25 nm and 25 to 85 nm, respectively. The La‐doped Fe3O4‐PANI composite presented core‐shell structures; polyaniline covered the La‐doped Fe3O4 completely. The specific saturation magnetization of La‐doped Fe3O4‐PANI depended on the starting material of La‐doped Fe3O4. It increased with increasing amounts of La and Fe3O4 content.

Preparation, Characterization, and Rheological Properties of Dibutyrylchitin

Dibutyrylchitin was prepared by an acylating reaction in a heterogeneous system with butyric anhydride as an acylating agent and perchloric acid as a catalyst. The effects of the preparation conditions, including chitin grain size, reaction temperature, and reaction time, on conversion ratio of chitin to dibutyrylchitin are discussed in detail. By adjusting reaction time and reaction temperature, dibutyrylchitin with an adequate intrinsic viscosity could be obtained. Steady-state rheological measurement was also performed and the results revealed that concentration, temperature, and shear rate had a great influence on the rheological properties of dibutyrylchitin/dimethylformamide solutions. Thus, a suitable spinning condition could be determined from the rheological analyses.

Electrospinning and Mechanical Properties of Polystyrene and Styrene―Isoprene―Styrene Block Copolymer Blend Nanofibres

Electrospinning of polystyrene (PS) and styrene–isoprene–styrene block copolymer (SIS) blends with different composition weight ratios was carried out with a mixed solvent, tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) (80/20, v/v). Electrospun PS/SIS blend fibers were characterized using scanning electron microscopy. The results indicated that the presence of DMF resulted in a beneficial effect on fiber formation and greater electrospinnability of as-spun fibers. Furthermore, the morphological structure and diameters of as-spun fibers from PS and SIS blends were affected by the composition weight ratio and the solution properties. The fibers from 10 wt% solution exhibited the best mechanical properties compared to the fibers from other concentrations for the same composition, and increasing the SIS content one observes a vanishing of PS-related properties, while SIS-related properties emerges.