Biomedical Engineering Reference
In-Depth Information
7.19
A group of engineers is trying to evaluate a new material for a biomedical
application. They seeded 10,000 mammalian cells in a 24-well tissue culture
plate and onto their new material inserted inside a 24-well plate. Assume that
the areas are the same. To understand the growth rate, they added 5-bromo2'-
deoxy-uridine (BrdU), which incorporates into the DNA in place of thymi-
dine. To detect the amount of BrdU incorporated in the DNA, they detected
using a fluorescently conjugated monoclonal antibody against BrdU after de-
naturation of the DNA (usually obtained by exposing the cells to acid, or
heat). After 24 hours, the intensity reading was 1.5, which correlates to the
amount of DNA synthesized. They also counted the cells after 24 hours and
found that the total cell number was 20,000 per culture plate.
(a) If the count on the new material is 1.8 intensity units after 48 hours, is the
growth rate higher or lower to the tissue culture?
(b) What are the assumptions?
7.20
Describe the impact of substrate concentration on growth and substrate uti-
lization. Given a Monod curve, be able to determine the maximum specific
growth rate an
d half saturation constant.
ABC
Specific growth rate constant,
(hr
−
1
)
0.014 0.02 0.001
Extent adhesion (% of initial seeding)
70
μ
40
10
Cell spreading (
μ
m
2
)
40
50
25
7.21
There are three biodegradable materials (
A
,
B
, and
C
) to be tested for a tis-
sue engineering application. The primary requirement is to form a monolayer
of endothelial cells on the surface. Using an initial seeding of 10
4
cells, the
following parameters have been reported for these biomaterials. Using these
values,
(a) Calculate the time required to generate a 1 cm
2
surface of the monolayer.
(b) Which material will you select for further analysis?
(c) If you wish to accelerate the process and reduce the time required for
monolayer development, what parameters will you focus upon?
(d) What interactions will you consider if you were to test the scaffold in vivo?
How would you evaluate these interactions?
7.22
By reading the published literature extensively, you have generated the follow-
ing summary of the differences between the two major types of endothelial
cells used for in vitro investigations:
Umbilical
Vein
Bovine
Aortic
Growth rate
Slow
Fast
Number of population doublings before senescence
20
35
Strength of adhesion to the substrate
High
Low
