Key Engineering Materials Vols. 342-343

Abstract: PLGA (75:25)/hydroxyapatite (HA) composite films were fabricated by solvent-casting method to investigate the effect of various hydroxyapatite content ratio to the PLGA film for cellular attachment and proliferation. Mechanical property of the composite film was characterized by tensile test. The ultimate tensile strength of 10% HA content film was two folds higher than control group. The surface of the film was characterized by contact angle measurement. The PLGA/HA composite film was more hydrophilic than control film. In vitro chondrocyte responses to the composite films were measured by cellular attachment and proliferation test. The attached and proliferated cells were significantly higher on PLGA/HA (10%) composite film than control group (1.44 times higher in attachment test and 1.31 times higher for 6th-day at culture in proliferation assaying, p<0.05). Base on these finding, the PLGA/HA (10%) composite was effective for the cell attachment for the initial stage of cultivation and cell proliferation.

Abstract: The purpose of this study was to evaluate the effects of collagen membrane coated with PLGA on bone regeneration in rat calvarial defect. Five groups of 10 animals each received either collagen membrane coated with 0.5%, 1%, 3% concentration of PLGA, collagen membrane only or surgical control. Each group of animals was healed into 2 healing periods of 2(5 animals) and 8(5 animals)weeks and histologic and histomorphometric analysis were done. The results of the following study revealed that surgical implantation of collagen membranes coated with PLGA enhanced local bone formation at both 2 and 8 weeks independent of different PLGA concentrations. In conclusion, collagen membrane coated with PLGA shows a significant bone formation behavior irrespective of their concentration.

Abstract: The aim of this study was to evaluate the regenerative effects of chitosan membranes containing tetracycline (TC) applied to surgically created one-wall intrabony defects in beagle dogs. The defects either received chitosan membrane (CH), chitosan membrane containing 0.5%, 1% TC (CH-TC0.5, CH-TC1.0) or flap operation only. The animals were sacrificed 8 weeks after the experimental surgery, and comparative histological and histometric examinations were done. The amount of junctional epithelium migration and connective tissue adhesion did not show any statistically significant differences among the groups. The amount of new cementum regeneration, and new bone regeneration were significantly greater in CH-TC1.0 group than the control (P<0.05). The results suggest that chitosan membrane combined with 1.0% TC may have beneficial effect on the regeneration of bone and cementum in intrabony periodontal defects.

Abstract: The most commonly used sterilization method of human skin allografts is ethylene oxide (EO). EO gas, however, can change the biomechanical properties of the grafts and produce toxic residues which are harmful to the recipient. The heating method cannot be applied for sterilization of soft tissues because of damage due to heat. The purpose of this study was to determine whether it is possible to apply gamma-irradiation for sterilization of soft tissues as well as for hard tissues.

Abstract: This study evaluated the potential of the PCL (poly
-caprolactone)/HA(Hydroxyapatite) composite materials as a scaffold for bone regeneration. For this, we fabricated scaffolds utilizing salt leaching method. The PCL/HA composite scaffolds were prepared with various HA contents (20wt%, 40wt%, 60 wt %). To ensure the potential for the scaffolds, porosity tests were conducted along with SEM observations. The porosity decreased with the increase of the contents of HA particles. The porosity of the composite with the highest contents of HA was still adoptable (~85%). In addition, the PCL/HA composite scaffolds were evaluated for their ability of osteogenic differentiation with human bone marrow stromal cell (hBMSC) in vitro. Alkaline phosphatase (ALP) activity, markers for osteoblastic differentiation, and total protein contents were evaluated in hBMSCs following 14 days of cultivation. The addition of HA particles enhanced proliferation of hBMSC during the test. Also, the differentiation ability of the cells was increased as HA particles were added. In this study, we concluded that PCL/HA composite scaffolds has great potential as a scaffold for bone tissue engineering.

Abstract: PMMA remains the most popular material of bone cement for orthopaedic surgeries. However, conventional PMMA bone cement still has some problems. For this, we suggested new composite material (BBC) consisting of hydroxyapatite (45%), chitosan (10%) and PMMA. The purpose of this study was to evaluate the bonding stress at the interface of PMMA with additives and host bone using a rabbit model. After 6, 12 weeks of operation, the bonding stresses were evaluated by measuring shear stress through push-out test. The results of the tests showed that after 6 weeks the shear stress of the BBC was 2.65±0.29MPa and the PMMA was 1.21±0.31MPa (p<0.05). However, after 12 weeks, there were no significant differences between BBC and conventional PMMA bone cement. In SEM analysis, bone surface of BBC showed higher roughness than that of conventional PMMA bone cement after push-out test. From the study we conducted, addition of HA particles and chitosan to conventional PMMA bone cement showed promising results. The BBC has clinical potential of bone substitutes replacing conventional PMMA.

Abstract: The effect of β-glucan-reinforced PLGA scaffold on cell proliferation was investigated. The PLGA scaffolds were prepared by salt-leaching method. The prepared scaffolds were grafted with (1→3) (1→6)-β-glucan in various ratios after plasma treatment on the surface. The surface of the scaffold was characterized by scanning electron microscope (SEM). The HDFs (Human dermal fibroblasts, 1
105 cells/scaffold) were used to evaluate the cell proliferation on PLGA scaffold before and after plasma/β-glucan treatment. In results, in the β-glucan treated scaffolds, the pores seemed to become narrower and even looked like closed form. The result of cell proliferation showed that the plasma/β-glucan treated scaffolds had narrower pores because the β-glucan was attached in the pores that would not be allowed the cells to penetrate into the inner areas. Consequently, cell proliferation was not effective in the plasma/β-glucan treated scaffolds in this study.

Abstract: Human demineralized bone matrix (DBM) containing bone morphogenetic proteins (BMPs) is naturally biocompatible and can be remodeled by patients’ own bone. The major shortcoming of many of the currently used DBM gel formulations is that they have a tendency to flow, particularly if there is continuous bleeding at the application site. In this study, the physicochemical properties of human DBM were examined to improve the efficiency of DBM formulations. DBM remarkably showed higher water absorption than nondemineralized bone powder after 150 min. Hydroxyl groups in DBM appeared in fourier transform infrared analysis, although hydroxyl band in nondemineralized bone powder was not observed. The results suggested that hydrogels such as CMC, hyaluronic acid, or poloxamer as carriers can be applied for injectable DBM products, such as gel or putty types.

Abstract: In cartilage tissue engineering, as a cell source, adult stem cells are very attractive for clinical applications. Recent studies suggest that human adipose tissue-derived stromal cells (ASCs) have multilineage potential similar to bone marrow-derived stromal cells (BMSCs). ASCs are obtained from adipose tissue easily isolated by suction-assisted lipectomy in various body parts. Also, as one of major factors of cartilage tissue engineering, scaffolds have an important role in cartilage formation. Poly(L-lactide-co-ε-carprolactone) scaffolds have physiological activity, biodegradability, high cell affinity, and mechano-activity. The object of this study is cartilaginous tissue formation using highly elastic PLCL scaffolds and ASCs in vitro and in vivo. Poly(L-lactide-co-ε-carprolactone) copolymers were synthesized from lactide and ε-carprolactone in the presence of stannous octoate as catalyst. The scaffolds with 85% porosity and 300-500μm pore size were fabricated by gel-pressing method. ASCs were seeded on scaffolds and cultured for 21days in vitro. Cell/polymer constructs were characterized by reverse transcriptase-polymerase chain reaction for confirming differentiation to chondrocytes onto PLCL scaffolds. Also, for examining cartilaginous tissue formation in vivo, ASCs seeded scaffolds which were induced chondrogenesis for 2 weeks were implanted in nude mice subcutaneously for up to 8weeks. Histological studies showed that implants partially developed cartilaginous tissue within lacunae. And there was an accumulation of sulfated glycoaminoglycans. Immunohistochemical analysis revealed that implants were positively stained for specific extracellular matrix. These results indicate that ASCs and PLCL scaffols could be used to cartilage tissue engineering.

Abstract: In order to application for the tissue engineered intervertebral disc (IVD), we designed the synthetic/natural hybrid scaffolds with poly(lactide-co-glycolide) (PLGA) and small intestine submucosa (SIS). SIS has been widely used as a biomaterial because SIS consists of various collagens and cytokines. SIS, however, possesses disadvantages such as their weak mechanical properties and uncontrolled degradation. Novel composite scaffolds of PLGA/SIS were manufactured by simple immersion method of PLGA scaffolds in SIS solution under vacuum. Then SIS was crosslinked. Also, PLGA scaffolds and SIS sponges were manufactured by solvent casting/salt leaching and freeze-dried methods, respectively. We evaluated pore structure, porosity, water absorption ability and cell viability of three types of scaffolds for the application of IVD.