Bio-Medical Materials and Engineering - Volume 17, issue 1

Authors: Xu, Shanglong | Li, Dichen | Wang, Chaofeng | Wang, Zhen | Lu, Bingheng

Article Type: Research Article

Abstract: Calcium phosphate cement (CPC) scaffold design should improve nutrient and cell transfer to the scaffold centre. To achieve this goal, a channel network with proper channel diameters should be incorporated into the scaffold. In this study, CPC scaffolds with a single central channel were fabricated indirectly using a stereolithography rapid prototyping (RP) technology. The diameters of the central channels ranged from 402 μm to 1988 μm. These scaffolds were seeded with rabbit marrow stem cells (MSCs) labeling DiI and cultured for 5 days. Cell observation on the wall of the central channels was performed. The data of the experimental point …revealed that cell coverage was from approximately 18% (1988 μm) to approximately 35% (592 μm). There was a significant increase from day 1 to day 5 in cell coverage in the same channel. The cell area coverage increased lineally with the central channel diameter when the channel diameter was less than approximately 789 μm. Afterwards (from 789 to 1988 μm), the relationship between cell area coverage and channel diameter was also linear relationship. But the increase was more slowly than before. Preliminary demonstration from the data that the minimum channel diameter required for cell migration into and adhesion on CPC scaffold was approximately 72 μm. These results are promising for the development of optimal scaffold with a three-dimensional channel network. Show more

Keywords: CPC, scaffold, channel, cell cultures

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 1, pp. 1-8, 2007

Authors: Gagnieu, Christian Henry | Forest, Patricia Odile

Article Type: Research Article

Abstract: Oxidized glycogen is used as a collagen crosslinker to prepare materials with defined crosslinking rates. Thus, films are prepared from native or denatured porcine type I atelocollagen crosslinked with three crosslinking levels defined by the ratios between the aldehyde groups of the glycogen and the amino groups of the collagen. The remaining free aldehyde groups and the imine bonds formed in the reaction are subsequently reduced or not. All the materials are subjected to in vivo biocompatibility and biodegradability evaluations by subcutaneous implantation in mice, while immunogenicity is evaluated by rabbit immunizations. As a result, cellular reactions on the implantation …site are more important with nonreduced materials, and biodegradability is correlated to the structural integrity of the collagen molecule, the crosslinking rate and the reduction state of the material. No immunological reaction or calcification is detected in our in vivo experimental model. This new method for collagen crosslinking using oxidized glycogen as a crosslinking agent enables the obtention of reproducible and biocompatible materials with a large scale of biodegradability, starting from 28 days to more than 7 months. Show more

Keywords: Collagen, crosslinking, oxidized glycogen, biodegradability biocompatibility

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 1, pp. 9-18, 2007

Authors: Sarathi Kopparti, Partha | Lewis, Gladius

Article Type: Research Article

Abstract: A finite element analysis of the stresses in a three-dimensional model of the proximal human tibia containing the tibial components (insert, tray, and stem) of a cemented total knee joint replacement was conducted. 12 cases of this model, covering three variables (composition of applied loading, interface conditions, and assignment of elastic properties to the cortical and cancellous bones) were analyzed. It was found that the stresses in various parts of the model were markedly lower when (a) the applied load comprised a compressive joint reaction force (F), of 2 kN, only (quadriceps inactive) versus F+ a patellar ligament force of …1.46 kN (P), representing the situation when the quadriceps are active; and (b) the interfaces were considered fully bonded compared to when they represented as having surface-to-surface Coulomb frictional contact (coefficient of friction = 0.2). However, the nature of the elastic properties that were assigned to the bones (isotropic versus anisotropic) had only a marginal influence on the stresses. Show more

Keywords: Finite element analysis, total knee joint replacement, Coulomb friction, gap elements

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 1, pp. 19-28, 2007

Authors: Hesaraki, Saeed | Sharifi, Davood

Article Type: Research Article

Abstract: Calcium phosphate cements (CPCs) are biocompatible and osteoconductive materials used in dental, craniofacial and orthopaedic applications. One of the most important advantages of these materials is their replacement with bone followed by resorption. Already several attempts have been made to improve the resorption behaviour of calcium phosphate cements by increasing the porosity of the material. In this investigation a mixture of NaHCO3 and citric acid monohydrate was added to the apatite cement component as an effervescent additive for producing interconnected macropores into the cement matrix. Mercury intrusion porosimetry was employed to determine pore volume and pore size distribution in …the calcium phosphate cement (CPC) samples. Results showed that addition of only 10 wt % of the effervescent additive (based on the cement powder) to the CPC components lead to producing about 20 V % macropores (with the size of 10 to 1000 μm) into the cement structure. The setting time was measured in an incubator at 37°C and decreased from 40 min for additive-free CPC to about 14 min for CPC containing effervescent additive. Other properties of the CPCs such as compressive strength, phase composition, microstructure morphology and dissolution behavior were evaluated after immersing them in a simulated body fluid solution. The results showed that the rate of formation of poor crystalline apatite phase have been improved by production of macroporosity into the cement matrix. Show more

Keywords: Calcium phosphate cement, macroporosity, bone cement, hydroxyapatite

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 1, pp. 29-38, 2007

Authors: Luis, Ana L. | Rodrigues, Jorge M. | Lobato, José V. | Lopes, Maria A. | Amado, Sandra | Veloso, António P. | Armada-da-Silva, Paulo A.S. | Raimondo, Stefania | Geuna, Stefano | Ferreira, António J. | Varejão, Artur S.P. | Santos, José D. | Maurício, Ana C.

Article Type: Research Article

Abstract: The purpose of this study was to test in vivo two different nerve guides, one of PLGA made of a novel proportion (90:10) of the two polymers, Poly(L-lactide):Poly(glycolide), with (DL-lactide-ε-caprolactone) copolyester (Neurolac® ) tube, in promoting nerve regeneration across a 10 mm-gap of the rat sciatic nerve. Finally, end-to-end coaptation was performed. Motor and sensory functional recovery was assessed throughout the healing period of 20 weeks and the repaired nerves were processed for morphological analysis. Both motor and sensory functions improved significantly in all experimental nerve repair groups, although the rate and extent of recovery was significantly higher in the …end-to-end group. No significant differences were detected in the comparison between the two types of tubes. Compatible with results of functional tests, morphological analysis showed that axon regeneration occurred in both PLGA and Neurolac® experimental groups but disclosed a different pattern of degradation of the two types of tubes with larger biodegradation of PLGA material by the end of 20 weeks. These results suggest that both types of biomaterial are a good substrate for preparing tubular nerve guides and the different pattern of degradation does not seem to influence the degree of nerve regeneration. Show more

Keywords: Nerve entubulation, PLGA, caprolactone, sciatic nerve, rat

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 1, pp. 39-52, 2007

Authors: Hsu, Shan-hui | Liu, Bai-Shuan | Lin, Wen-Hung | Chiang, Heng-Chieh | Huang, Shih-Ching | Cheng, Shih-Shyong

Article Type: Research Article

Abstract: The biological properties of commercial pure titanium (cp-Ti) dental implants can be improved by surface treatment. In this study, the cp-Ti surfaces were prepared to enable machined surfaces (TM) to be compared to the machined, sandblasted, laser irradiated and dual-acid etched surfaces (TA). The surface elements and roughness were characterized. The biocompatibility was evaluated by cell and organ culture in vitro. The removal torque was measured in rabbit implantation. Surface characterization revealed that TA surface was more oxidized than TM surface. The TA surface had micrometric, beehive-like coarse concaves. The average roughness (2.28 μm) was larger than that typical of …acid-etched surfaces. Extracts of both materials were not cytotoxic to bone cells. The morphology of cells attached on the TA surface was superior to that on the TM surface. TA promoted cell migration and repaired damaged bones more effectively in organ culture. The formation of bone-like nodules on TA disk exceeded that on TM disk. Rabbit tibia implantation also proved that TA implant had greater removal torque value. These results suggested that TA had good osteoconductivity and was a potential material for dental implantation. Show more

Keywords: Surface treatment, dental implants, cell culture, organ culture, osteoconductivity

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 1, pp. 53-68, 2007