Biomedical Engineering Reference
In-Depth Information
characteristics of the surface in the definition of the equilibrium dissociation rate coefficient
whereas the present fractal analysis does. Thus, one may not be able to actually compare the
equilibrium dissociation rate coefficient affinities in these two types of systems. This is a
significant difference in the kinetic analysis of binding and dissociation reactions on bio-
sensor surfaces from what is available in the literature.
It is perhaps appropriate to, at least, briefly present some of the other approaches that have
recently appeared in the literature and to help model the binding and the dissociation kinetics
of the different analytes (present in the liquid phase) on biosensor surfaces. The following
kinetic modeling approaches will be presented and analyzed briefly:
(a) Application of the synthetic jet concept to low Reynolds number biosensor microfluidic
flows for enhanced mixing (
Mautner, 2004
)
(b) Kinetics of analyte capture on nanoscale sensors (
Solomon and Paul, 2006
)
(c) Probing the functional heterogeneity of surface binding sites along with the effect of
mass transport limitation and its influence on binding and dissociation of analytes on
biosensor surfaces (
Svitel et al., 2007
)
2.2.6 The Mautner Model
Mautner (2004)
points out that microfluidic components used in biosensors may be effec-
tively used for the analysis of chemicals and biologicals. He emphasizes that themicrofluidic
systems used in biosensors will operate at low Reynolds numbers. Reynolds number is a
dimensionless number and is used to characterize flows in different types of systems.
Reynolds number (
Re
) is equal to (
Dv
(
r
)/
m
).
r
represents the density of the fluid,
D
is the
diameter of the pipe or a characteristic dimension of the system,
v
is the velocity of the fluid
in the system, and
m
is the viscosity of the fluid. Low Reynolds number regime is
characterized by
Re
less than 10. Furthermore,
Mautner (2004)
points out that these devices
will have characteristic dimensions less than 100
m. He also emphasizes that we are dealing
here with small volumes of fluids (pico to microliters). This type of slow
Re
laminar flow is
characterized by diffusion-only mixing. However,
Mautner (2004)
emphasizes that rapid
mixing is essential in immunoassays. Thus, enhanced mixing is essential to overcome the
slow fluid mixing in low
Re
number flow.
m
Mautner (2004)
points out that the following techniques have been used to enhance mixing in
microfluidic networks:
(i) Use of slanted wells to increase lateral flow transport (
Johnson et al., 2002
)
(ii) Flows over shallow grooves (
Stroock et al., 2002
)
(iii) Utilization of passive mixing in three-dimensional serpentine microchannels (
Liu et al.,
2000
)
