Biomedical Engineering: Bridging Medicine and Technology 1st Edition by Veronique Tran,Mark Saltzman

Exercise 9

PC12 cells produce dopamine and so they may be useful in treating Parkin- son's disease (when dopamine is missing). One approach would be to encap- sulate PC12 cells inside a spherical capsule (400 µm in outer diameter [OD]; 25-µm wall thickness) and then implant these capsules inside the brain. Figure 5.24 Diagram of a hemocytometer for use in Problem 10. The capsules serve to protect the cells from the brain of the recipient. Under one set of circumstances, the cell density in the capsules is initially 1 × 106 cells/mL, and the capsules are incubated in vitro until enough cells grow up to fill up the entire capsule. Calculate the necessary incubation time for 50 cap- sules to produce enough dopamine for a mouse. The doubling time of a PC12 cell is 8 hours. Data: mass of the mouse: 250 g; ratio of mouse head mass to overall mass: 1/10; ratio of mouse brain mass to head mass: 1/5; dopamine secretion in vitro: 1 g/107 cells/day; initial encapsulation cell density: 1 × 106 PC12 cells/mL; dopamine requirement: 0.1 g/kg brain mass/day