Access Type

Open Access Thesis

Date of Award

January 2013

Degree Type

Thesis

Degree Name

M.S.

Department

Biomedical Engineering

First Advisor

Weiping Ren

Abstract

A good designed bone scaffold is crucial to bone tissue engineering. We have developed and characterized a novel gradient bone scaffold by combination of Calcium Polyphosphate (CPP) with different size of porogen (stearic acids). Compared with homogenous scaffold, the gradient bone scaffold with different pore size and porosity can better mimic natural bone structure. Directly perfusion flow bioreactor was developed. This 3D dynamic cell culture was better mimic the physiological condition for cell growth. It was beneficial to nutrition and oxygen delivery throughout the whole scaffold and was able to form shear stress. We wanted to investigate the effect of the gradient structure on murine MC3T3 cells' behavior after dynamic cell culture. We hypothesize that the adhesion, proliferation and differentiation of osteogenic cells on gradient scaffolds are significantly enhanced, compared to that in homogenous scaffold.

The porosity, degradation rate and mechanical properties of gradient and homogenous scaffolds had been investigated. The total porous volume and degradation rate were similar between two scaffolds. While pore size and porosity on 1st and 2nd layer of the gradient scaffold were higher than the homogenous scaffold, which resulted in the mechanical strength of homogenous scaffolds was higher than gradient one.

The cell proliferation (MTT method), cell distribution (confocal microscopy) and cell differentiation (Alkaline phosphatase activity) were measured. Although the level of cell proliferation on two kinds of scaffolds was similar, cell distribution and the level of cell differentiation were different between two scaffolds. On the gradient scaffold, the level of cell differentiation was two times higher than the homogenous scaffold. In order to investigate the function of each layer on the gradient scaffold, micro-PET technology was applied. The PET image showed that the majority of new forming HA was distributed on the 1st and 2nd layer of gradient scaffold. Also tetracycline labeling study showed the crystal structure of HA from the gradient scaffold. Therefore, the gradient scaffold with four functional layers (1st and 2nd for cell growth, 3rd and 4th for providing mechanical strength) did affect the cells' distribution and enhance the cells' differentiated which was beneficial for new bone forming.

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