An Investigation on the Influence of Pore Size and Porosity of Sponge on Maximum Cell Concentration

This study investigates the effect of pore size and porosity on the maximum cell concentration in sponge through their influence on nutrient diffusion and surface area. Brownian dynamics simulation is employed to analyze the effect of pore size and porosity exerted on effective diffusivity of sponge. Only porosity is found to have prominent impact on effective diffusivity of nutrient. Simple geometrical relation is used to estimate the impact of pore size and porosity on surface area per unit volume of sponge. Pore size shows an inverse relationship with surface area while porosity is positively related to surface area. Since both nutrient diffusion and surface area are positively related to maximum cell density, a sponge with smaller pore size and larger porosity may probably acquires the capacity of sustaining a higher maximum cell concentration. Introduction Tissue engineering has revealed innumerous potential in finding an alternative for tissue regeneration for medical purpose (Davis and Vacanti, 1996; Mooney and Mikos, 1999). For this purpose, a scaffold with desired feature is thought to have great significance in accommodating cell, guiding their growth and tissue regeneration in three dimensions (Yang et al., 2001; Zhu et al., 2008). Porous sponge is often employed as scaffold in tissue engineering for growing cells (Kose et al., 2003). Also, for the success of transplantation of regenerated tissue, a large number of living cells is sometimes desired to be maintained in scaffold to provide the biological function of tissue when implanted (Davis and Vacanti, 1996). In other words, the maximum living cell concentration in sponge is of great interest. The cell concentration is influenced by many factors, such as the nature of cell, the culturing condition, the culturing medium, the nutrient and waste metabolite diffusion rate and available space (Butler, 2004). Among these factors, the nutrient and waste particle diffusion rate and available space are considerably influenced by the microstructure of sponge, specifically pore size and porosity. Firstly, the effective diffusivity of nutrient and waste particle is significantly affected by the microstructure of sponge (Yang et al., 2001). Secondly, the available space for cell growth is usually dictated by surface area of sponge, which in turn controlled by the microstructure of sponge. Normal animal cells are anchorage-dependent, which means the cell needs to adhere to a solid substratum before proliferation and the substratum is provided by the surface of pore wall (Butler, 2004). Surface area per unit volume of sponge is controlled by pore size and porosity. Since pore size and porosity of sponge exert large influence on nutrient diffusion and available space, they may have certain relation with the maximum living cell concentration. The objective of this work is to analyze qualitatively how pore size and porosity affect the maximum living cell concentration in sponge through their influence on nutrient diffusion