Biomedical Engineering Reference
In-Depth Information
Both single- and dual-fractal analysis are used to adequately model the binding and dissociation
kinetics. The dual-fractal analysis was used only when the single-fractal analysis did not provide
an adequate fit (sum of least squares less than 0.97). This was done by the regression analysis
provided by Corel Quattro Pro 8.0 (1997). The fractal analysis permits a link between the binding
rate coefficient,
k
, and the degree of heterogeneity,
D
f
that exists on the biosensor surface. This
provides a more complete picture of the reaction kinetics occurring on the sensor chip surface.
It is suggested that the fractal surface (roughness) leads to turbulence, which enhances mixing,
decreases diffusional limitations, and leads to an increase in the binding rate coefficient
(
Martin et al., 1991
). For this to occur, the characteristic length of the turbulent boundary layer
may have to extend a few monolayers above the sensor chip surface to affect bulk diffusion to
and from the surface. However, given the extremely laminar flow regimes in most biosensors
this may not actually take place. The sensor chip (arrays/microarrays/DNA chips) surface is
characterized by grooves and ridges, and this surface morphology may lead to eddy diffusion.
This eddy diffusion can then help to enhance the mixing and extend the characteristic length of
the boundary layer to affect the bulk diffusion to and from the surface.
The analysis of the different examples of the detection of analytes on arrays/microarrays/
DNA chips should encourage experimentalists to pay more attention to the nature of the sur-
face, and how it may be manipulated in desired directions. Detection of analytes on arrays/
microarrays/DNA chips is bound to increase in the future as these “tools” find increasing
applications in a wide variety of areas. This is of particular value primarily in the biomedical
area, and also in other areas of application. For example, the identification of DNA sequences
is of particular value in clinical pathology. A clinical pathologist is a medical doctor respon-
sible for the diagnosis of diseases based on the analysis of body fluids, for example, blood
and urine. The earlier one may detect and diagnose the probable onset of diseases the earlier
one can begin the medical protocols necessary to help prevent, alleviate, or correct the onset
of, especially, debilitating and intractable diseases. It is hoped that fractal analysis should be
particularly helpful in providing a better understanding of the onset of diseases, particularly
those that are insidious and debilitating. Any insight that is made available by such an
analysis that helps in the management of intractable diseases should prove invaluable.
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