Biomedical Engineering Reference
In-Depth Information
(3D image)
Phagocytosis
Actin fiber
Endocytosis
Clathrin- or caveolin-
mediated
Clathrin- or caveolin-
independent
FIGURE 8.1
Schematic presentation of phagocytosis and endocytosis. (Adapted from Conner, S.D. and
Schmid, S.L.,
Nature
, 422, 37, 2003.)
The suspended particles in the culture medium reach the cell monolayer
by either diffusional movement or gravitational settling. The time for a par-
ticle to travel to the target cell by diffusion is calculated using the following
equation:
2
r
RT
Nd
(8.1)
t
=
,
D
=
2
D
6
µ
where
t
= average time to reach to the target
r
= distance to the target
D
= diffusion coefficient (m
2
s
-1
)
R
= gas constant (8.31 J K-mol
-1
)
N
= Avogadoro number (6.02 × 10
23
mol
-1
)
μ = viscosity (kg m
-1
s
-1
)
d
= diameter of a particle (m)
On the other hand, gravitational settling is determined by Stoke's law and
the time for the particle to settle onto the target cell is expressed by the fol-
lowing equation:
2
g
(
ρρ
µ
−
)
d
2
r
v
p
m
t
=
,
v
=
(8.2)
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