Key Engineering Materials Vols. 396-398

Abstract: We have developed a new injectable bone substitute combining specific granules of BCP with or without radiopaque elements with a reversible thermo sensitive resorbable carrier such as Pluronic F-127. The composite is liquid at ambient temperature and set as hydrogel at 37°C. Rabbit experiment demonstrates high biocompatibility and bone ingrowth at the expense of the injectable bioceramic composite.

Abstract: The aim of this work was to investigate the behaviour of rat calvarial osteoblastics cells on porous PLGA/HA composite scaffolds. Cells were submitted to cytotoxicity and cell adhesion assay. In addition, the cells morphology were observed by SEM, and the collagen synthesis measured by Sirius Red colorimetric method. The results showed that the material was not cytotoxic and hydroxyapatite improved cell adhesion. Osteoblastic cells could adhere and spread on the scaffolds as observed. After 14 days the presence of hydroxyapatite increased the synthesis of collagen. This study demonstrates that composite scaffolds presented better cellular responses compared to polymer scaffolds.

Abstract: Magnetic nanocomposite films of the Fe3O4/pHEMA were prepared by dispersing the Fe3O4 nanoparticles into the HEMA monomer before they were polymerized. The resultant nanocomposite films were characterized by Fourier transform infrared (FT-IR) and the vibrating sample magnetometer (VSM). The swelling behavies and the hemolytic ratios of the filmes were also investigated in this work.The equilibrium swelling ratio decreased with the increase of the amount of nanoparticles. The nanocomposite films had a clear superparamagnetic behavior because of the addition of nanoparticles. The hemolytic ratios were all lower than 5%, which indicated that the nanocomposites films had the good blood compatibility and can be used in the biomedical field

Abstract: This study describes the preparation of a composite material [1] from synthetic nano-scaled hydroxyapatite (nHA) and a gelatin matrix (80% nHA, 20% gelatin). This composite material is intended to extend the range of biological hydroxyapatite-based defect-filling materials for bone replacement. Ostim® (aqueous suspension of nHA having a crystallite size of about 20nm) was used as the inorganic component whereas porcine gelatin (type A, 180 Bloom) composed the organic part. Both components were homogenized during a spray-drying process. Cylindrical samples of the spray-dried granulate (HG 80/20) produced by pressing had adequate mechanical stability for storage, transport and handling in the surgery. The flexural strengths for the samples were determined on dry samples as well as after storing in media (distilled water, SBF solution) for 60 minutes. After staying 30 minutes in a SBF solution or in water, flexural strength dropped off about 30% while the shape of the sample was retained. Temperature treatments of both granulate and pressed samples resulted in reduction of the sample swelling from 70vol-% to 50vol-%. The sample produced by pressing can be machined (turned, drilled, milled).

Abstract: Current resorbable membranes are generally from animal origin, like collagen, and are largely used in dentistry or orthopaedic for TGR (Tissue Guided Regeneration), in neurosurgery for Dura matter healing and others. Calcium alginates are generally used for wound dressing (external uses). The purpose of this study was to evaluate the osteogenic property of meshes realized with calcium alginate fibers. Membrane meshes were implanted in critical size defect of rabbit femoral epiphysis during 3 and 6 weeks. Micro CT and histological analysis demonstrated biocompatibility of calcium alginate meshes in bony area. Calcium alginate meshes have no osteogenic and osteoconductive properties, however calcium alginate meshes could be a good candidate for replacement of dacron balloon used in vertebroplasty.

Abstract: Though hydroxyapatite has the ability to promote bone growing, devices based on OHAp are mechanically weak and need to be reinforced for load bearing applications or in the manufacturing of scaffolds for bone regeneration. Graphite (Gr) could provide appropriate reinforcement properties to OHAp without being deleterious for the biocompatibility of the system. This paper describes an accelerated synthesis of the OHAp with ultrasonic agitation in the presence of functionalized graphite (GO). The toxicity of the Graphite and the GO-OHAp system is evaluated. GO-OHAp was produced by a wet chemical reaction involving CaCl2 and Na2HPO4. The calcium salt solution was added first and the solution sonicated for 1 hour, before repeating the operation with the phosphate solution. Biocompatibility was tested by using a primary cell culture of HOB (ECCAC). The disappearance of the maximum at 2q = 26.32º corresponding to the d002 plane of graphite and the appearance of the maximum at 2q = 13.2º in the XRD patterns is related with an expansion of the grapheme sheets from 0.34 nm to 0.59 nm and it has been used to assess the graphite oxidation. The OHAP on GO growing has been confirmed by the appearance of a broad peak centred at 2q = 31.5º and a sharpened peak at 2q = 26.0º characteristic of low crystalline apatites. Although the employed graphite can be considered biocompatible, cellular viability is significantly improved by the presence of apatite.

Abstract: This paper focuses on the preparation of siloxane-polyurethane hybrid materials using a sol-gel method. The global aim of the project is to tailor mechanical properties, degradability rate, bioactivity and biocompatibility to design scaffolds for musculoskeletal applications. A series of seven hybrid materials were synthesized with varying the proportion of polydimethylsiloxane (PDMS), and Polyurethane (PU). The organic part ratios (by weight) employed were (% PDMS:% PU) 30:0, 35:5, 20:10, 15:15, 10:20, 5:25, and 0:30. The organic part was reacted with constant 70 % TEOS to obtain the hybrid materials. A sol-gel process was selected for the synthesis of the hybrids. The characterization of materials was carried out by the fourier-infrared spectroscopy (FT-IR), x-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electronic microscopy (SEM) and proton nuclear magnetic resonance (1H-NMR) techniques in order to analyze the structure, microstructure and chemical composition of the hybrid materials. Gelification time depends on the proportion of PU used. When no PU is employed, the gel time is 8 hours but it rises up to 18 days for 30 % of polyurethane. Materials range from opaque to translucent but with a greater fragility for greater amounts of polyurethane. No differences in the bonding of materials could be appreciated.

Abstract: he aim of this study was to evaluate the effect of HA on the demineralization resistance and bonding strength of light-curing glass ionomer dental cement. Tests were conducted using (1) pure Fuji II LC GIC, (2) 15% micro HA-Fuji II LC GIC. Physical properties, demineralization resistance and bonding strength to dentin of teeth were determined. The curing depth in all groups were satisfied the requirement of curing depth of ISO 9917-2:2004(minimum curing depth = 1mm). The depth of cure was reduced with addition of HA, presumably due to the light scattering effect of HA particles. Regarding sensitivity to ambient light, there were no detectable changes of the homogeneity in any groups. Also all groups were satisfied the requirement of the flexural strength of ISO 9917-2:2004(minimum flexural strength = 20MPa). 15% HA-Fuji II LC GIC group was found to present a greater flexural strength than pure Fuji II LC GIC, as the addition of HA promotes a chemical reaction between the HA, the glass powder, and the polyacid. Observing under the CLSM after 4 days of demineralization, there were significant differences in the CLSM and SEM images. Pure Fuji II LC GIC group showed greater enamel demineralization layer than in 15% HA-Fuji II LC GIC group. In SEM analysis, there was greater enamel demineralization in the pure Fuji II LC GIC group, and less demineralized under the influence of HA particles, 15% HA-Fuji II LC GIC group had more even surface particles. 15% HA-Fuji II LC GIC group was found to present a greater bonding strength than pure Fuji II LC GIC group. Observing the fractured surfaces under SEM after the bonding strength test, the cohesive failure rate was found to be in increasing order of pure Fuji II LC GIC, 15% HA-Fuji II LC GIC group. There were bone-like apatite particles observed to be formed in 15% HA-Fuji II LC GIC group.

Abstract: In recent years, considerable attention has been focused on the development of new composite materials for application as drug delivery systems. In this field, calcium phosphate cements (CPCs) are often employed as support to delivery of drugs, but their behavior has some drawback related to the so-called burst effect. The aim of this work was to develop new CPCs formulations from synthesized tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous TTCP and drug-containing hybrid microparticles (DCHM). The main function of these DCHM is providing nuclei of high concentration of drugs into the CPCs. The DCHM were synthesized via the sol-gel method from a bridged precursor of the type (H3CO)3 – Bridge – (OCH3)3 and aspirin (AS) as model drug. The inorganic polycondensation reached 89.5 % as calculated by 29Si NMR. The analysis by small angle X-ray scattering (SAXS) reveled a short range structural ordering in the DCHM at molecular level. Effective incorporation of AS inside the microspheres was detected by FTIR spectroscopy. In vitro tests of DCHM according to ISO 10993-5 revealed non-cytotoxic behavior. Four CPCs formulations containing 0, 1, 5 and 10 wt % of DCHM, were evaluated. The presence of DCHM did not modify neither the degree of conversion to low-crystallinity HA nor the measured setting times of the CPCs, however, the amount of incorporated microparticles considerably affected the degree of porosity (macropores of 200 µm) and interconnectivity of the cement matrix.

Abstract: The purpose of this study is the obtaining of different orthopedic materials and chemical and mechanical characterization. The chemical tests used were setting time, water absorption and from the point of view of mechanical properties the Young modulus, compressive strength, and maximum strength. Also, the surface of orthopedic bioceramics materials was characterized by porosity test.