Uploaded by Abdulgadir Ahmed

Assignment 1

Faculté de génie
Génie Chimique
Faculty of Engineering
Chemical Engineering
CHG 4160 Assignment 1
50 points
Due Oct 5th
Question 1. (10 points)
The chemical structure of a new degradable polymer, poly (ethylene glycol)-bpolylysine-b-poly (D, L-lactide), is shown below.
a. What will the end-point degradation products of this polymer be if it is degraded
by incubation in vitro in phosphate buffered saline (PBS), pH 7.4 at 37°C?
Question 2. (10 points)
Explain the working mechanism of XPS technique? And explain why advancing and
receding water contact angle measurements shows hydrophobic and hydrophilic
properties of a surface, respectively?
Question 4. (15 points)
Different basal medium is a buffer that requires different CO2 levels in incubators for cell
cultures. For example, Eagle’s MEM (E-MEM) requires CO2 level of 5% while
Dulbecco’s M-EM (DMEM) requires 10% CO2. Try to explain why there is a difference
in CO2 level? (Hint: To maintain a pH 7.4 in the buffer, the NaHCO3 concentrations in EMEM and D-MEM are different).
Question 5. (15 points)
Explain why in cryo-preservation, it is established that the optimal cooling rate to freeze
the cells is ~1c/min? And why are cryo-protectants necessary? What are they and what is
the normal concentration range?