Key Engineering Materials Vols. 342-343

Abstract: Mesenchymal stem cells (MSCs) from bone marrow seem to be the one of best candidates to regenerate injured tissue. However, recent advances in application of MSCs toward large tissue regeneration are faced with lack of vascularity. In this study, endothelial cells differentiated from MSCs were applied for constructing tissue-engineered bone and cartilage. It was found that endothelial cells from MSCs play an important role of providing vasculature.

Abstract: In this study, we prepared polystyrene (PS) nanofibers as hepatocytes culture substrates by electrospinning method and subsequently coated with specific ligand (poly(N-
-vinylbenzyl-- β-D-galactopyranosyl-(14)-D-gluconamide)(PVLA) for hepatocytes attachment. Rat hepatocytes’ behavior on the PVLA-coated and non-coated PS nanofibrous matrices have been investigated. Electrospun PS fiber structures revealed randomly aligned fibers with average diameter of 500 nm. Fabricated PS nanofibers had no bonding points like cotton fibers. Analyses by ATR/FTIR and ESCA revealed that PVLA was successfully coated to the surfaces of PS nanofibers. More hepatocytes were attached on the surface of PS nanofibers coated with PVLA than that on noncoated PS nanofibers. PS nanofibrous matrix could incorporate many cells into the interior of the matrix probably due to the suitable pore size. Cell viabilities cultured on PVLA-coated PS nanofibrous mats were maintained for 2 weeks, while it was decreased rapidly on PVLA-coated PS dishes. High hepatic function especially albumin secretion was maintained for 2 weeks on nanofibrous mats but rapidly decreased on flat PS dishes. These results indicate that nanofibrous structure enabled spheroid-like culture results in providing cell-cell communication and subsequent long-term maintenance of specific cell function.

Abstract: Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibrous matrix containing gelatin was fabricated by electrospinning method. The average diameter of electrospun PHBV/Gelatin (1:1) nanofibers was 600 nm determined by FE-SEM. ATR-FTIR and ESCA measurements were used to confirm the presence of gelatin in PHBV/Gelatin nanofibers. Human fibroblasts' behavior on PHBV/Gelatin nanofibrous matrix has been investigated. Fibroblasts were well attached on the surface of control PHBV and PHBV/Gelatin nanofibers. Initial cell attachment on PHBV/Gelatin nanofibers was higher than that of control PHBV nanofibers. Gelatin has many RGD moiety that mediate cell attachment. From this reason, initial cell attachment increased on the surface of PHBV/Gelatin nanofibers. From the results, coelectrospinning of PHBV and gelatin is a promising method for tissue engineering scaffold.

Abstract: The β-tricalcium phosphate (β-TCP)/ poly(lactide-co-glycolide) (PLGA) composites for biodegradable scaffolds in bone tissue engineering were synthesized by in situ polymerization with microwave energy. The degradation behavior of β-TCP/PLGA composite was investigated by soaking in simulated body fluid (SBF) for 4 weeks. The molecular weight of the β-TCP/PLGA composites decreased with soaking time until week 2, whereas the loss rate of molecular weight reduced after week 2. The incubation time was needed for the degradation of the β-TCP, indicating that the β-TCP should be detached from the PLGA matrix and then degraded into SBF solution. The studies of mass loss of the composites with the soaking time revealed that the degradation behavior of PLGA would be processed with the transformation from the polymer to the oligomer followed by the degradation. Morphological changes, whisker-like, due to transformation and degradation of polymer in the composites were observed after week 2. On the basis of the results, it found that the degradation behavior of β-TCP/PLGA composites was influenced by the β-TCP content in the composite and the degradation rate of the composite could be controlled by the initial molecular weight of PLGA in the composite.

Abstract: Previously we have found that the immobilization of Type I collagen on
the poly(vinyl alcohol)(PVA) hydrogel disc was effective in supporting adhesion and growth of the corneal epithelium and stromal cell in vitro. But the durability of the produced corneal epithelium layer in vivo has some problem. We hypothesized the cell construction force is much stronger than the force of the cell adhesion on the flat modified PVA surfaces. Therefore the improvement of mechanical anchoring force between the substrate and formed corneal cell layer maybe become one of the solving methods. In this study, we prepared the PVA nanofiber mat by using the electrospinning method and the surface modification of the PVA nanofiber was studied to improve the durability of the corneal epithelium layer. The collagen-immobilized PVA nanofiber sheets could support the adhesion and proliferation of rabbit corneal epithelial cells. And the stratified corneal epithelium structure was observed on the PVA nanofiber sheets when the epithelium was co-cultured with rabbit corneal stromal cells. It means that the corneal epithelium was well differentiated on the collagen immobilized PVA nanofiber sheet. The stability of the corneal epithelium layer on the PVA was dramatically improved; the stratified epithelium layer was kept for two weeks after the differentiation introduction, totally after one month. A light transmittance of these materials is not yet enough. Further study to improve the transmission of light, is required.

Abstract: The purpose of this study is to find out an effective method to prepare natural hydroxyapatite (HA) from biological source, i.e., pig bones, pig teeth, and extracted human teeth. For the preparation of natural HA a calcining method with different temperatures was used, in combination with the thermal gravimetric analysis (TGA). Three analysis methods, i.e., Fourier transform infrared spectroscope (FTIR), X-ray diffraction (XRD), and inductively coupled plasma (ICP) have been used to investigate the characteristics of the prepared materials. The spectrum of the prepared material, obtained by means of FTIR and XRD, are consistent with the standard FTIR spectrum and JCPDS index of XRD of hydroxyapitite. It confirms that the material prepared is hydroxyapitite indeed. The natural HA obtained by calcining at 850°C shows a desired quality.

Abstract: Porous HAp/chitosan-alginate composite scaffolds were successfully synthesized by insitu co-precipitation method. During the preparation of HAp/chitosan-alginate composite scaffolds, the interaction between chitosan-alginate molecules would be reduced with increasing HAp content, with the resulting that the chitosan-alginate molecules were homogeneously dispersed in the composite scaffolds. The chitosan-alginate content was found to be almost consistent as initially added during the preparation. These results imply that chitosan-alginate was almost perfectly incorporated into the composites. It was found that the pore structure of the composite scaffolds with low HAp content was similar to chitosan-alginate scaffolds, and the morphology of uniform microstructure was unaffected by the presence of HAp. However, the pore diameter decreased with increasing the HAp content up to HAp content of 30 wt%, eventually the pore structure was collapsed and the composites scaffolds appeared to be agglomerated at higher HAp content.

Abstract: In this work, we developed a novel patterned co-culture method with thermo-responsive poly(N-isopropylacrylamide) (PIPAAm) and poly(N-ρ-vinylbenzyl-Ο-β-D-galactopyranosyl-(1→ 4)-D-gluconamide) (PVLA) inducing active hepatocyte attachment. Patterned graft of PIPAAm onto PS dishes was carried out by electron beam irradiation using cover-glass as a photomask. PVLA was only coated onto PIPAAm-ungrafted domain because of hydrated hydrophilic property of PIPAAm at below the LCST. Analysis by attenuated total reflection-Fourier transform infrared and electron spectroscopy for chemical analysis revealed that PIPAAm and PVLA were successfully grafted and coated on surfaces of PS dishes. PIPAAm-grafted surface exhibited decreasing contact angle by changing temperature from 37 to 20°C, while PVLA-coated PS and non-treated PS had negligible contact angle changes with temperature alternation. Atomic force microscopy (AFM) results showed that PIPAAm-grafted and PVLA-coated PS had smoother surfaces than that of ungrafted PS dishes. After culture for 12 hours, hepatocytes were well attached on PVLA-coated domain. Hepatocytes adherent on PIPAAm-grafted domain were detached by decreasing temperature. And then, fibroblasts were seeded onto PIPAAm pattern-grafted domain. Fibroblasts were only attached and spread onto PIPAAm-grafted domain. Co-cultured hepatocytes showed better differentiated function of albumin expression compared to homotypic hepatocyte culture

Abstract: Poly(γ-glutamic acid)(γ-PGA) based nanofiber sheets were prepared by using electrospinning technique to evaluate the ability of the prevention of postoperative tissue adhesion. The anti-adhesion membranes were prepared from poly(γ-glutamic acid) and PLGA with different compositions by electrospinning. Also nonsteroidal anti-inflammatory drug (ibuprofen) was incorporated during fabrication of nanofibers. Various electrospun nanofibers were characterized by the measurements of microstructure (surface morphology and fiber diameter by SEM), ATR-FTIR, water contact angle and in vivo animal study using Sprague Dawley rat model. The average diameter of nanofibers electrospun from trifluoroacetic acid (TFA) solution ranged from 300 nm to 900 nm, approximately. From in vivo animal study, it was observed that ibuprofen-incorporated γ- PGA nanofiber sheet was significantly effective in preventing tissue adhesion and inducing wound healing, probably due to the appropriate hydrophilicity of γ-PGA preventing shrinkage of the sheet and appropriate barrier property, while PLGA nanofibrous mat was dramatically contracted in in vivo due to its high hydrophobicity resulted in insufficient coverage of wound.

Abstract: In order to obtain porous silk fibroin films that suit all kinds of different tissue and organs, to design the configuration of the porous silk fibroin films more rationally, this paper made a modeling of the oxygen diffusing system of the capillary, and also solved the model. Moreover the paper gave a method to estimate the density of the capillaries in the tissue; and hereby brought forward the basic requirements in designing the configuration of the porous silk fibroin film.