The roles of surface configurations of biomaterials in the regeneration of surrounding tissues should be considered for the application of biomaterials to regenerative medicine. Many reports have been published on the relationship between the surface configurations of oral implants and osseointegration.To obtain basic data on the effects of the surface configurations of biomaterials, we examined the effects of the linear structures of nylon fiber bundles with a diameter of about 10 μm on cell differentiation and those of two types of monomer and metal ion exposure on cytotoxicity levels.Cell differentiation was examined using alkaline phosphatase activities, demonstrating that absorbance was slightly decreased on dish bottoms, compared with linear structures, with MC3T3-E1 and C2C12 cells, but remained unchanged with ES-D3 cells. Cytotoxicity levels were examined based on cell viability using the MTT method. The linear structures tended to decrease the viability of MC-3T3-E1 and C2C12 cells, as compared with the dish bottoms. On the other hand, no difference was noted in the viability of ES-D3 cells. Microscopically, elongated fibrous structures were observed along the striatum structures in MC-3T3-E1 and C2C12 cells, while no marked morphological difference was noted in ES-D3 cells.In the present study, linear structures showed different differentiation and cytotoxicity levels between MC3T3-E1 and C2C12 cells. Unlike cells on dish bottoms, most cells surrounding biomaterials in vivo cannot extend without limitation in multiple directions. Thus, in vitro cell differentiation and cytotoxicity levels may vary with the surface configurations of biomaterials.

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Titanium (Ti) is frequently used as a biomaterial in dental and orthopedic implants and in bone fixation devices. Effective modification of the Ti surface plays a crucial role in improving biocompatibility. Carbon nanotubes (CNTs) are among the most interesting nanomaterials due to their unique properties. In this study, we fabricated CNT-Ti composite surfaces by annealing Ti plates covered by different sized CNTs (Nanocyl NC 7000, 9.5 nm diameter and VGCF-H, 150 nm diameter). The properties of these surfaces were examined by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, raman spectroscopy, contact angle measurement and osteoblast-like cell seeding. In addition, samples were implanted into the subcutaneous tissue of rats. The three-dimensional nanostructures of CNTs and creation of titanium carbide were evident on the Ti surfaces, suggesting that the CNTs were well-anchored onto the Ti plates. CNT modification promoted desirable cell behavior, including cell spreading and proliferation, especially on the Nanocyl-modified surface. Inflammatory response was rarely observed on the Nanocyl surface, but macrophage-like giant cells were frequently observed on the VGCF-H surface. Therefore, the nanomorphology of narrow diameter CNTs provides a CNT-Ti composite surface with good biocompatibility.

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The scaffold material for the bone formation in the defect must be bioabsorptive. The calcium mineral of the scaffold is used for newly formed bone. In this study, we clarified the tissue affinity and bioabsorption to three kinds of novel fine calcium carbonate particles, LUMINUS, CUBE-18BH and WHISCAL. These particles were added into cell culture, and the mitochondrial activity of culture cell was calculated. These particles were then implanted under the dorsal skin of the rats, and were histopathologically observed.Five days after addition of the particles, there was no decrease in the mitochondrial activity. The implanted particles had completely disappeared with macrophages, without neutrophils. These kinds of fine calcium carbonate particles were bioabsorbable materials with few inflammatory reactions and were thought to be a useful scaffold for bone formation.

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Embryonic stem cells have the potential to differentiate to all fetal and adult cell types and might represent a useful cell source for tissue regeneration. Moreover, the applicable of an embryonic stem cell can be used not only to the tissue regenerative field but also to in vitro embryotoxicity field. The influences of biomaterials on human reproduction and development are still unclear. Their influences on the next or future generations are also unknown. Although many biomaterials have already been used, many people have concerns over them. Regarding long-term embryotoxicity associated with biomaterial exposure, even the presence or absence of risks is unclear. Spielmann et al. suggested that embryotoxicity could be estimated based on influences on ES cell differentiation. In 1997. Spielmann et al. developed the embryonic stem cell test (EST), which is an in vitro embryotoxicity test method that can be used to estimate the risk of embryotoxicity of chemical substances relatively quickly compared to the conventional methods that involve animal experiments. The EST has been evaluated in a formal validation study funded by the European Centre for the Validation of Alternative Methods: ECVAM in which two other in vitro embryotoxicity tests (micromass test, whole embryo culture test) were validated against a set of test chemicals characterized by high levels of in vivo embryotoxicity data in laboratory animals and humans. In a validation study in Europe, the EST was found to be reproducible, demonstrating an overall accuracy of 80% and 100% correct prediction of strong embryotoxicity for chemicals studied under blind conditions. However, use of EST is impossible for the Biomaterials, which is not dissolved in a culture medium. Therefore, some improvement of EST protocol is proposed.

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