| dc.description.abstract | Microdialysis is a technique for both recovering and administering substances at
a target site (which may be tissues, organs, etc.), using a small equipment termed as
probe. There are many types of microdialysis probes such as the linear probe, the shunt
probe and the concentric probe, and the probe choices are depended on the site of
implantation, whether it is for the tissue (different type of tissue for different probe
design) or in the quiescent medium. Although the probe needs to be physically inserted
into the site, the microdialysis probe is relatively small and is minimally-invasive (i.e., causing minimal changes or injuries to the target site). This along with many other features of microdialysis (e.g., can be performed on almost every organ and tissue, can be used on living, awake and even moving patients, etc.) make this technique very
popular. Nonetheless, poor recovery, doubts related to temporal resolution, and tedious
preparations plus the need of pre-runs for calibration, limits the application of this
technique. These constraints are generally attributed to mass transfer limitations. In this
thesis, a mathematical framework incorporating convection and diffusion equations
have been proposed to represent transport phenomena in microdialysis probes. This
mathematical framework is then used to analyse the possible influence of various
relevant parameters on glucose (i.e., analyte) recovery. In this work, it is defined that
within the probe’s membrane and probe surrounding area (PSA), the transport process is
solely driven by diffusion. The model parameters and operating conditions have been
obtained from literature. In the first part, a mathematical framework was constructed to
represent mass transport in two primitive microdialysis probes, namely the linear and
shunt probes. Using the respective mathematical frameworks, glucose recoveries under
various operating conditions were compared between the two probes, which were
defined to operate under similar conditions. As there is no mathematical work that has
been done to evaluate these both probes, it would be interesting to see how these two
microdialysis probes may perform under similar operating conditions. It is clearly seen
that the frameworks were sensitive enough to show concentration changes when
parameters were varied. These results were comparable to what was discussed in
literature. Comparing the two probe’s performance under similar conditions, the shunt
probe displayed higher glucose recoveries, which reflect better performance. The
mathematical approach from the more primitive linear and shunt microdialysis probe
frameworks was expanded to represent mass transport in the more complex concentric
microdialysis probe. This probe is arguably the more popular and is the most commonly
referred to in microdialysis literature. The framework is then used to evaluate mass
transport within the probe and its surrounding area. Results on percentage recovery and
overall mass transfer coefficient under various operating conditions have been
discussed. Comparisons were made with the Bungay’s microdialysis framework (BMF)
on mass transport performance under different design and operating parameters. The
results suggested that the concentric probe framework is sensitive to parameter changes,
and the concentration profiles obtained are comparable to the widely accepted BMF.
This is one indication that the proposed concentric probe framework can be used to
represent mass transport phenomena in such probes. The results from the numerical
efforts were then compared to experimental work. It was shown that the simulated data
fits well with experimental data using a 5 mm concentric probe, for membrane
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hindrance factor, α, of 10. The comparison was done again using a similar probe, with a
different length (10 mm) and fitting was also found best with α of approximately 10. It
is justified that the concentric mathematical framework can be used to represent mass
transport phenomena in those probes, and in one way, justifies the validity of the
mathematical frameworks for the more primitive probes, beforehand. | en_US |
