| Budget Amount *help |
¥16,670,000 (Direct Cost: ¥14,600,000、Indirect Cost: ¥2,070,000)
Fiscal Year 2007: ¥8,970,000 (Direct Cost: ¥6,900,000、Indirect Cost: ¥2,070,000)
Fiscal Year 2006: ¥7,700,000 (Direct Cost: ¥7,700,000)
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| Research Abstract |
Living creatures are fundamentally composed of cells, which may adapt to their environment; they get together finding the same kind of cells, exclude inconvenient stimulus to them, and keep the best condition for life conservation. Though the cells have been treated in biology, medical science, or bio-chemistry, they may be paid attention by mechanical engineers when they are regarded as a prototype of micro-machine. But, almost nothing has been studied as for the mechanical properties of cells. This project is concentrated to reveal mechanical properties of living cells and they are applied to construct more intelligent structures. As living cells, a bone related cell are used in this study.
Bone cells have adaptability to the surrounding mechanical condition. Osteoblasts, which are responsible for bone formation, were reported that they responded to mechanical vibration and changed the cell proliferation and the amount of generated bone mass. In order to find the effective stimulation
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on osteogenesis, it is necessary to understand the mechanical properties such as elasticity or viscosity of the cells in the view of mechanical engineering. In the case of bone cells, it is important to understand the mechanical properties under adhesive condition because they attach on surfaces of bone matrices. In this study, I measured dynamic viscoelasticity of a cultured osteoblast, MC3T3-E1, under adhesive condition by applying sinusoidal deformation. Using these experimental results, we derived Voigt model for viscoelasticity and identified the value of each parameter.
Next, the effect of mechanical stimulation was evaluated. Mechanical stimulation to bones affects osteogenesis such as decrease of bone mass of astronauts under zero gravity and fracture repair with ultrasound devices. Bone cells have been reported to sense and response to mechanical stimulation at cellular level morphologically and metabolically. In the view of mechanical vibrations, bone cells are deformed according to mechanical stimulation and their mechanical characteristics. It was reported that viscoelasticity of cells was measured using tensile and creep tests and that there was likely natural frequency and nonlinearity of cells in the sense of structural dynamics. It suggests that there is effective frequency and amplitude of mechanical stimulation on osteogenesis by bone cells. In this study, sinusoidal inertia force was applied to cultured osteoblasts, MC3T3-E1, and effects of frequency and acceleration amplitude of mechanical vibration on the cells were investigated in respect of the cell proliferation, bone matrix generation and alkaline phosphatase (ALP) gene expression. Less
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