Key Engineering Materials Vols. 361-363

Abstract: The osteoconductive property of calcium phosphate (CaP) biomaterials allow attachment, proliferation, migration, and phenotypic expression of bone cells leading to formation of new bone. The purpose of research is to develop new method of mineralizing commercial GBR membranes with calcium phosphate (CaP) and determine cell response. Resolut Adapt LT (Gore-tex) composed of co-polymer PGA/TMC and Biomend Extend (Zimmer) composed of bovine collagen were used. Membranes were mineralized with CaP using precipitation and new microwave methods. The mineralized and non-mineralized membranes were characterized using SEM, EDS, XRD, FT-IR, and TGA. Cell response to mineralized and non-mineralized membranes was determined using human osteoblastlike cells (MG-63). Microwave method was more efficient in terms of amount of minerals incorporated with membranes and time required. SEM, EDS, and FT-IR identified carbonate apatite in the mineralized membranes. No significant difference in cell proliferation was observed between mineralized and non-mineralized membranes. Greater production of type 1 collagen was observed with CaP mineralized membranes.

Abstract: This study aims at evaluating bone growth in critical-sized femoral defects of rats filled with macro micro porous biphasic calcium phosphate ceramic (MBCP) cylinders surrounded or not by a resorbable collagen membrane. Femoral defects left empty (control) exhibited partial bone ingrowths after 3 and 6 weeks and were completely healed at 12 weeks. The defects filled with the collagen membranes appeared partially healed suggesting that the membranes constraint bone ingrowth. Bone formation occurred around the collagen membrane which partially degraded over time. In the MBCP/membrane group, bone has grown inside the macro pores of the MBCP cylinders. Bone ingrowth was more rapid and abundant in the defects filled with MBCP alone. The combination MBCP/collagen membrane may be beneficial for the reconstruction of large bone defects without using repetitive surgeries and autologous bone grafting.

Abstract: The preparation and characterization of an inorganic/organic composite scaffold is proposed in this paper. The substrate was realized by the polymerization of an electroconductive polymer, namely polypyrrole PPy, into an hydroxyapatite HAp porous support. The PPy/HAp composite was characterized by XRD, Hg porosimetry measurements, SEM-EDS and electrochemical test. The results pointed out that the PPy polymer entered into the HAp whole pores moving through the interconnected paths of the hydroxyapatite matrix. The PPy thin film doped with heparin maintained its electrochemical characteristics even in the ceramic support.

Abstract: Novel hybrid gels in the system gelatin-GPTMS-TEOS were prepared via a sol-gel route, and their ability to release Si(IV) was examined using MG63 osteoblast-like cell culture. The amount of Si released and the release rate were controllable by changing the mixing ratio of GPTMS and TEOS. In addition, the hybrids had biocompatible surfaces. It is expected that the hybrids will be utilized for the investigation of the effect of Si on cell differentiation and tissue regeneration.

Abstract: Biodegradable polymers (e.g. poly-ε-caprolactone, PCL) have been studied largely for tissue engineering applications. The aim of this study was to evaluate the composite fabrication technique on PCL modified with the phosphate salts (i.e. NaH2PO4, Na2HPO4, KH2PO4, or K2HPO4) as well as to determine the compression strengths thereof. The chemical structure and morphology of composites were analyzed using FTIR and SEM/EDX. The influence of a plain phosphate salt in different quantities on the hydrophilic properties of PCL was evaluated by measuring the water contact angle. The results of this study indicated that the addition of phosphate salts led to an improvement in compression strength of PCL composites. According to the results of preliminary biomimetic mineralization, Na2HPO4 seems to increase the bioactivity of PCL.

Abstract: A composite layer of fibroblast growth factor-2 (FGF-2) and low-crystalline apatite was formed on an ethylene-vinyl alcohol copolymer specimen using two types of aqueous calcium phosphate solutions supplemented with 10 !g·mL-1 FGF-2; one is a CP solution that is prepared by dissolving chemical reagents into ultrapure water and the other is an RKB solution that can be prepared by mixing clinically approved infusion fluids. In both solutions, a sufficient amount of FGF-2 for new skin tissue formation (1 !g·cm-2) was immobilized on the specimen surface.

Abstract: In this study, a biocomposite comprising nanostructured α-tricalcium phosphate (α-TCP) in a poly(D,L-lactic-co-glycolic acid) (PLGA) matrix was fabricated by a modified solution evaporation method. As a potential temporary bone fixation and substitution material, its bioactivity was evaluated by its ability to form bone-like apatite layer in simulated body fluid (SBF). Owing to the increased surface area covered by the osteoconductive bioceramic of α-TCP, rapid apatite formation was observed. After 7 days of immersion, enhanced nucleation of apatite was observed on the nanocomposite. At day 14, dense lamellar-like apatite was formed on the nanocomposite whilst apatite nucleation had only just started to develop on the surface of pure PLGA. At the same time, a preliminary in-vitro cell culture study was conducted using human osteoblast-like (HOB) cells. A significant increase in cell number with culturing time was observed for the nanocomposite. After 9 days incubation, a confluent lamellar-like apatite layer was formed on the composite surface. This apatite layer was also shown beneath the proliferating HOB cells at Day 16.

Abstract: The composite scaffolds with nine different ratios of nano-HA and ß-TCP content were fabricated by using lyophilization method. Their microscopy, physical and chemical properties were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and fourier transformed infrared (FTIR) spectroscopy. MTT test was applied to quantitatively assess the number of viable cells attached and grown on the scaffolds. And the result showed that the amount of cells on the scaffold containing 30% by mass of nano-HA was significantly higher than the other samples.

Abstract: Micrometric sphere beads of HA-alginate composite were produced to remove Pb2+ and Cd2+ from contaminated gastric fluid. It was shown that the composite was effective in Pb2+ and Cd2+ immobilization from high-contaminated simulated gastric fluid. X-ray diffraction and scanning electron microscope analyses performed on HA-alginate beads after the Pb2+ uptake showed that lead phosphate, (Pb10-x Cax (PO4)6Cl2), was precipitated on beads surface. X-ray diffraction patterns of HA powder after Cd2+ sorption experiments showed no evidence of other phases, however, dispersive energy spectrometer analyses of the HA-alginate confirmed the presence of Cd2+ on the composite surface. Desorption experiments in simulated enteric fluid showed that composite beads containing Pb2+ and Cd2+ remained stables for one hour in simulated gastrointestinal fluid. The results reinforce the hypothesis that HA-alginate composite can be a very efficient system for Pb2+ and Cd2+ uptake from contaminated gastrointestinal fluid preventing systemic contamination by bloody stream uptake.

Abstract: In these studies, E-glass-fibre-reinforced composite (FRC) implants with photopolymerisable resin systems and bioactive glass granules (BAG) were evaluated as a reconstructive material in the critical size bone defects made to rabbits’ calvarial bones. In the first study, a new experimental resin system, DD1/MMA/BDDMA, was used to impregnate the doubleveil FRC-implants, while in the second study, a commercial resin system composed of BisGMA/MMA/PMMA was used in impregnation. These double-veil FRC-implants were coated with bioactive glass granules (BAG, 315-500 0m). In the second study, an experimental FRC consisting of two laminates of woven fibres, was also tested as an implant material. These implants were filled with BAG-granules and pure fused quartz fibers (Quartzel wool). In the first study, implantation time was 4 or 12 weeks, while in the second study, it was 12 weeks for both the implant types. Results: In the first study, the healing of the defects had started in the form of new bone growth from the defect margins, as well as small islands of woven bone in the middle of the defect, at 4 weeks postoperatively. Ingrowth of dense connective tissue into the pores of the implant was widely seen. At 12 weeks postoperatively, more bony islands were seen as compared to the animals studied at 4 weeks. Part of the newly formed bone had an appearance of lamellar structure. The porous structures of the implant were deeply filled with fibroconnective tissue. Ingrowth of maturing bone to the implant structures was occasionally seen. The inflammatory reaction was moderate, and was mostly found inside the upper part of the implant. In the second study, inflammatory reactions caused by both types of the FRC implants were very slight. Small amount of new bone had started to grow from the defect margins in doulble-veil implanted defects. No ingrowth of connective tissues or new bone formation was seen inside these implants. Instead, both the connective tissues and newly formed, mineralizing bone were seen inside the experimental double-laminate implants. SiO2-fibres seemed to cause moderate inflammatory reaction inside the implants, while BAG granules did not. In both the study groups, the brain tissue was oedemic, but no obvious serious damage was found. Conclusions: The structural properties of the FRC-implants had an influence on the healing process of the bone defect. BAG, as a constituent of the FRCimplants, enhanced the bone formation process. After some modifications to the properties of the FRC, this type of implant has possibilities to become one material alternative in clinical bone defect reconstruction at the craniofacial area in the future.