Key Engineering Materials Vols. 342-343

Abstract: A series of porous silk fibroin materials were prepared by freezing fibroin aqueous solution at –18 °C for 10 days. The process required no freeze-drying, chemical cross-linking, or the aid of other polymeric materials. X-ray powder diffraction patterns from the porous silk materials displayed features of crystal of metastable silk I polymorph. By adjusting the preparation conditions, silk I porous materials with average pore diameter of 30-240 μm and porosity of 70 -95 % can be prepared. The silk I porous materials were embedded in hypodermis on the dorsal surface of SD white rats, resulting that all rats survived with good general condition, and silk I porous materials were degraded and absorbed mostly in 6 weeks.

Abstract: The objective of this work was to investigate cell adhesion, Poly Glycolic Acid (PGA) and PGA/ collagen nano-fibers on the silicone membrane. PGA with the weight-mixing ration of 40% was fabricated through the electronspun technique. The behaviors of Human Umbilical Vein Endothelial cells on these scaffolds are evaluated. The highest cell adhesion was observed in the PGA/collagen fibers with the diameter of 500 nm. This study indicates the effect of nano-fibers on the Human Umbilical Vein Endothelial cells for better understanding of interactions of cells with scaffold materials. Such information will have important implications for implantable vascular tissue engineering constructs.

Abstract: Bombyx mori Sericin films were prepared with PEG-DE as cross linking agent. The main physical properties, structure characteristics, cytotoxicity and cell proliferation of sericin films were measured and analyzed. The result showed that sericin films prepared by cast method containing 30-40% of PEG-DE, showed good mechanical properties. PEG-DE caused the changes of the condensed structure of sericin films. The films prepared from sericin extracted both from silk-gland and cocoon shell showed good cytocompatibility. Silk sericin films with PEG-DE had no obvious cytotoxicity to cells.

Abstract: Rapid recovery of cell sheets is considered important to maintain the biological function and viability of recovered cell sheets. To accelerate required culture substrate hydrophilic/ hydrophobic structural changes in response to culture temperature alteration, poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(N-isopropylacrylamide) (PIPAAm) were grafted successively onto tissue culture polystyrene (TCPS) dishes by electron beam irradiation. Analysis by attenuated total reflection-Fourier transform infrared revealed that PHEMA and PIPAAm were successfully grafted to surfaces of TCPS dish. PIPAAm-PHEMA-grafted TCPS (PIPAAm-PHEMA-TCPS) dishes were compared with PIPAAm-grafted TCPS dishes for cell sheet detachment experiments. Approximately 75 min was required to completely detach cell sheets from PIPAAm-TCPS dish, compared to only 13 min to detach cell sheets from PIPAAm-PHEMA-TCPS dish, which is successively grafted with PHEMA and PIPAAm. PHEMA is a well-known as a high hygroscopic polymer. In the case of PIPAAm-PHEMA-TCPS dish, PHEMA layer acted as a water pool to accelerate the hydration of PIPAAm layer due to the effective and simultaneous water supply to PIPAAm layer, resulting in rapid hydration of grafted PIPAAm molecules and detachment of cell sheet compare to PIPAAm-TCPS dish without PHEMA layer.

Abstract: PHBV ultrafine fibers were fabricated by electrospinning process. Electrospun PHBV fiber structures revealed randomly aligned fibers with average diameter of 400 nm. PIPAAm was grafted on the surface of PHBV nanofibrous mat by electron beam irradiation. PIPAAm-grafted PHBV mats were determined by ATR-FTIR and ESCA. Water contact angles were determined by a sessile drop method at 20 and 37
. To examine the tissue compatibility, human fibroblasts were evenly seeded onto PIPAAm-grafted PHBV mat and cast film, ungrafted PHBV mat and film. Attached and spread fibroblasts on nanofibrous mat were proliferated more rapidly than that of flat film surface. Initial cell attachment on PIPAAm-grafted surfaces was higher than ungrafted surfaces. The surface property changed to hydrophilic by PIPAAm graft, which increased initial cell attachment. Detachment of single cells from PIPAAm-grafted PHBV matrixes was measured by low temperature treatment after incubation at 37
. Cultured cells were rapidly detached from PIPAAm-grafted PHBV mat compared with film. With porous mats, the water molecules easily reach to grafted PIPAAm from underneath and peripheral to the attached cells, resulting in rapid hydration of grafted PIPAAm molecules and detachment of the cells.

Abstract: Nonporous PLLA film and porous PLLA scaffolds were prepared and then grafted with acrylic acid (AA) using in situ direct plasma treatment to obtain PLLA-g-PAA. Chondrocytes isolated from rabbit knee articular cartilages were cultivated in Dulbecco’s modified eagle medium- F12 (DMEM-F12) containing 10% fetal bovine serum (FBS) and 1% antibiotics and passaged twice before cell seeding. Once seeded on either PLLA films or scaffolds, they were placed in a bioreactor system and an intermittent hydrodynamic pressure (IHP) was applied in 3 bars, while turned on for 2 min and off for 28 min during 15-day culture. AA grafting to PLLA surface was confirmed from various surface analyses. From WST-1 assay, chondrocyte proliferation was significantly improved with dynamic IHP for PLLA and PLLA-g-PAA scaffolds as compared to static culture. This study indicates that IHP may have significant influence on chondrocytes behavior in 3D culture environment.

Abstract: Emerging studies have showed that silk fibroin might be as a naturally occurring degradable biomaterial for tissue engineering with unique mechanical properties, biocompatib ility and processability. To optimize the formation of the regenerated silk fibroin film, in thi s study, we examined the genotoxic potential of the regenerated silk fibroin films by differe nt cross-linking mode with micronucleus and the single cell gel electrophoresis (comet) assa y. The data showed that MNF in group PC and group SD showed significantly no differenc e with blank group (P>0.05), and no evident comet tails were observed. However, the resul t of EC group was significantly different from the control group(P<0.01). Taken together, R SFFs in group PC and group SD have no evident genotoxicity, which is better than group EC.

Abstract: The purpose of this study is to make use of trans10,cis12 CLA (t-CLA) that has potential for proliferation and differentiation to form adipocyte on the collagen-coated surface. Results provided evidences of good adhesion, growth, viability, and differentiation of adipocyte on collagen-coated surface compared with non-coated surface. Also, the results showed that mouse 3T3-L1 preadipocyte can be successfully and reproducibly cultured on the collagen-coated surface, and the adipocyte precursor cells placed on the collagen-coated surface are able to undergo full maturation into adipocytes in the control cells. Moreover, glycerol-3-phosphate dehydrogenase (GPDH) activity in 3T3-L1 preadipocyte cultured on collagen-coated surface with t-CLA was higher than that on polystyrene (PS) surface due to higher cell adhesion and cell viability. These results suggest that collagen coating may provide a promising approach to develop a new adipocyte replacement strategy using CLA.

Abstract: In this study, novel polycaprolactone/hydroxyapatite (PCL/HA) scaffolds were prepared to increase mechanical properties and degradation of PCL/HA ones for bone tissue engineering. PCL macromers were synthesized through the reaction of PCL diol (Mn: 530, 1250, and 2000) and PCL triol (Mn: 900) with acryloyl chloride and confirmed using nuclear magnetic resonance spectrometer (NMR) and fourier transform infrared (FTIR). The PCL/HA scaffolds were prepared by cross-linking of PCL macromer in the presence of HA by UV treatment and freeze drying methods. Mechanical property and porosity as well as degradability of the PCL/HA scaffolds were also investigated. PCL/HA scaffolds showed faster degradation and higher compressive modulus than those of PCL itself due to their low crystallinity and modification of terminal groups. The pore morphology and pore sizes of the PCL/HA scaffold were checked by scanning electron microscope (SEM). Cell cytotoxicity and proliferation of MG-63 osteoblast cultured onto the PCL/HA scaffold was assessed by lactate dehydrogenase (LDH) assay and Alamar blue assay, respectively. The novel PCL/HA scaffold appears to be suitable for bone substitutes.

Abstract: The ideal dermal matrix should be able to provide the right physical and biological environment to ensure homogenous cell and extracellular matrix (ECM) distribution, as well as the biocompatible interactions with tissue. Chitosan (CS)/poloxamer semi-interpenetrating polymer networks (SIPNs) was prepared by crosslinking of poloxamer macromer in the presence of CS in order to improve its mechanical property required in skin tissue engineering application. Furthermore, we also prepared CS/poloxamer SIPNs with ShebaTM, human acellular dermis, to overcome a low biocompatibility of the CS/poloxamer SIPNs. The CS/poloxamer SIPNs/ShebaTM showed remarkably highly cell attachment and viability in the two-dimensional (2D) culture and similar cell morphology on the CS/poloxamer SIPNs/ShebaTM compared with on tissue culturing polystylene (TCPS) as a positive control. These results suggest that CS/poloxamer SIPNs containing ShebaTM have good possibility for artificial skin system application.