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light as stimulus and detection of fluorescence at
violet or blue have shown a very good correlation
with the glucose concentrations in DMEM solution.
Light stimulation with blue light and the detection of
fluorescence by green region shows also a high
correlation with the glucose concentrations. The
detected glucose signals will be then subjected to
perturbations from the surroundings and from the
background of the measured locations due to tissue
alteration and physiological parameter variations.
All perturbations such as temperature, humidity and
applied pressure variations have to be included by
the calculations, as illustrated by Figure 6.
The drift of the characteristics of the electronic
and optical components may cause high disturbances
to the measurements. The integration of further
parameters may enhance the reproducibility but
decrease the accuracy due to the measurement
errors. The system complexity and the number of the
measured parameters have to be minimized.
There are few fluorescence-based glucose
detection methods that have reached the stage of
testing in vivo, but none have entered clinical
practice for diabetes management. This will be an
area of active investigation in a future work. We will
need to explore different interferences and the
stability as well as accuracy under normal life
conditions.
There is no doubt that fluorescence technologies
have considerable promise for glucose sensing.
As a future work, all developed sensors will be
integrated in one system that enables the
simultenous processing of the detected signals
(Caduff, 2009). Other blood components like total
hemoglobin concentrations and fractional oxygen
saturation measured non-invasively have to be taken
as parameters by the glucose calculations. The
suitable locations for measurements may be earlobe
for transmission measurements or forehead as well
as abdomen for reflection measurements has to be
chosen. Applying the Twersky theory or diffusion
theory by the calculations are our next perspectives.
After that a clinical study for non-invasive
measurements and applying the neural fuzzy
techniques the results and the system will be
optimized.
Using a daily, disposable contact lens embedded
with newly developed boronic acid containing
fluorophores may also be suitable for the continuous
monitoring of tear glucose levels.
ACKNOWLEDGEMENTS
This work is a part of the project „System for Non-
invasive Detection of Glucose “supported by the
Foundation Baden-Württemberg Stiftung by
Research Program: Microsystem technology for the
life sciences. We thank also Dr. Michaela Mueller
and Svenja Hinderer from Fraunhofer Institute
Institute IGB, University of Stuttgart for the
measurements.
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