Problem 1. Suppose that four students in Tissue Engineering class are always sitting together at the front row. This could be because (i) they really like each other or (ii) nobody else wants to sit next to them. Considering the formation about lipid bilayer, which reasoning will hold true? Explain in detail.
Problem 2. Cell-seeded scaffold implantation is one strategy in tissue engineering. Consider a scaffold that is plasticized (for ease of shaping during the surgery) with glycerol. The scaffold has 75% porosity and contained 25 wt% glycerol. The density of the scaffold is 1.05 g/cm3. When cells are seeded to the scaffold, one approach is to first hydrate the scaffold using saline before seeding cells. The other approach being considered is seeding cells to the scaffold and let it sit for a while for cells to settle.
However one of the concerns in this later strategy is osmotic shock (rapture of cells due to osmotic pressure). Please do some calculations and evaluate if the concern is substantiated.
Problem 3. Dr. Mequanint is interested to design optimum device geometry to encapsulate cells for therapeutic reasons. His main concern is for the cells inside this device to receive enough oxygen to survive. When the oxygen concentration in the device reaches half of the bulk oxygen concentration, cells would start to die. Three choices of geometries (sphere, cylinder and slab) are available for him.
The slab is assumed to be thin compared with its length and width (infinite slab) and the radius of the cylinder is small compared to its length (infinite length). The oxygen uptake kinetics is assumed to be zero order. You may also write your own assumptions.
(a) Express the maximum radius (Rmax) and maximum thickness (Tmax) in terms of bulk oxygen concentration, Cb (mol/mL), diffusivity of oxygen through the device D (cm2/s) and maximum oxygen consumption rate, Vmax (mol/mL/s).
(b) Which geometry allows the largest size construct while keeping cells alive? Which geometry is the least efficient?