These constructs were evaluated at days 1 and 7 for cell viability and proliferation as well as oxygen concentration as a function of depth within the construct. The bases of the scaffolds were sealed with an impermeable layer of PCL and the scaffolds were surrounded with a tubing of low air permeability to allow diffusion of air into the constructs mainly from the top. Cylindrical polycaprolactone (PCL) scaffolds fabricated using precision extrusion deposition and having the same pore size but different porosities and tortuosities, and hence different permeabilities, were statically seeded with MG63 cells. The current study addresses these issues by evaluating the effect of these architectural parameters on oxygen concentration and cell behavior in the interior of scaffolds with different architectures. These transport issues relate to oxygen and nutrient delivery, waste removal, protein transport and cell migration, which in turn are governed by scaffold porosity and permeability. Since transport within the scaffold is mainly a function of diffusion, careful design of the diffusion characteristics of the scaffold is critical. This could be attributed to the fact that as cells within the pores of the scaffold begin to proliferate and secrete extracellular matrix, they simultaneously begin to occlude the pores and decrease supply of nutrients to the interior. Viable tissue formation is often observed in peripheral regions of tissue engineering scaffolds whereas the interior fails to support viable tissue.
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