Biomedical Engineering Reference
In-Depth Information
with the experiment, i.e., it is smaller than that for the biconcave-shape simulation.
For the near-spherical cell the membrane is subject to stronger local stretching for
the same uniaxial deformation compared to the biconcave shape. For the deflated
biconcave shape, the inner fluid volume can be deformed in response to stretching,
while in the near-spherical shape the fluid volume applies additional resistance onto
the stretched membrane. Hence, the cell geometry plays an important role, and it
has to be closely modelled for accurate extraction of parameters from the optical
tweezers experiments.
10.5.1.2 Microfluidics
The microfluidic device with triangular obstacles described in Sect. 10.4.1 is used
also here to perform experiments for the late ring-stage
P.falciparum
-infected RBCs
that are infected with a gene encoding green fluorescent protein (GFP). For both the
converging and diverging geometries infected RBCs exhibit lower average veloci-
ties that healthy RBCs (see Fig. 10.19(a)). In the DPD simulations, the infected cells
are modelled with increased shear modulus and membrane viscosity values obtained
from optical tweezers as explained in the previous section. We model the parasite as a
rigid sphere of two microns in diameter [82] placed inside the cell (see Fig. 10.1(b)).
Snapshots from simulations showing passage of an infected RBC through channels
with converging and diverging pore geometries are shown in Fig. 10.19(b). The DPD
model is able to capture the effect of changes of RBC properties arising from para-
sitization quite accurately. A quantitative comparison of the simulation results with
experimental data for the average velocity of Pf-RBCs as a function of applied pres-
sure gradient is shown in Fig. 10.20.
(a)
(b)
Fig. 10.19.
(a) Experimental images of ring-stage P. falciparum-infected (red arrows) and unin-
fected (blue arrows) RBCs in the channels at a pressure gradient of 0.24 Pa/
μ
m. The small flu-
orescent dot inside the infected cell is the GFP-transfected parasite. At 8
3
s
, it is clear that the
uninfected cell moved about twice as far as each infected cell. (b) DPD simulation images of P.
falciparum-infected RBCs traveling in channels of converging (left) and diverging (right) opening
geometry at 0.48 Pa/μm (from [67])
.
