Continuous glucose detection has a great significance for diabetics. On the one hand, it can fully reflect the patient blood glucose change level. On the other hand, it can better guide the insulin dosage, and achieve closed-loop control of insulin pump. A continuous detection method of glucose concentration by borate polymer fluorescent indicator is proposed in the paper. The principle of this method is based on the competing reaction between alizarin, glucose and borate polymer. The borate polymer has high specific reaction with glucose, meanwhile reacts with non fluorescent alizarin. The product of the reaction between borate polymer and alizarin is fluorescent, called as fluorescent indicator. When glucose was introduced, the glucose molecules could react with the borate polymer in fluorescent indicator because of the high specificity. This competing process leads to the decomposition of fluorescent indicator into the non-fluorescent alizarin, and the fluorescent intensity gets loss. Therefore, the change of fluorescent intensity can reflect the glucose concentration level. In this method, the fluorescent indicator can well identify the glucose molecules. According to the experiment, we know that there is a high specific and good linear reaction between glucose and borate polymer. The linear fitting is up to 0.97 and the detection limitation can reach to 10 mg/dL. The fluorescent intensity reaches strongest with the optimal proportion of alizarin: borate polymer as 1:3. The reaction of the fluorescent indicator identifying glucose molecules has a good linear relationship, the linear fitting of which can reach to 0.98. The detection limitation can reach to 30 mg/dL, which fulfills the detection
requirements of glucose concentration in vivo.
In recent years, using the detection of interstitial fluid glucose concentration to realize the real-time continuous
monitoring of blood glucose concentration gets more and more attention, because for one person, the relationship
between blood glucose concentration and interstitial fluid glucose concentration satisfies specific rules. However, the
glucose concentration in interstitial fluid is not entirely equal to the glucose concentration in blood and has a
physiological lag because of the physiological difference of cells in blood and interstitial fluid. Because the clinical
diagnostic criteria of diabetes are still blood glucose concentration, the evaluation model of the physiological lag
parameter between the glucose concentration in blood and the glucose concentration in interstitial fluid should be
established. The physiological difference in glucose molecules uptake, utilization, and elimination by cells in blood and
interstitial fluid and the diffusion velocity of glucose molecule from blood to interstitial fluid will be induced to the mass
transfer model to express the physiological lag parameter. Based on the continuous monitoring of glucose concentration
in interstitial fluid, the project had studied the mass transfer model to establish the evaluation model of the physiological
lag parameter between the glucose concentration in blood and the glucose concentration in interstitial fluid. We have
preliminary achieved to evaluate the physiological lag parameter exactly and predict the glucose concentration in blood
through the glucose concentration in interstitial fluid accurately.
The continuous blood glucose monitoring system using interstitial fluid (ISF) extracted by ultrasound and vacuum is
proposed in this paper. The skin impedance measurement is introduced into the system to monitor the skin permeability
variation. Low-frequency ultrasound is applied on skin surface to enhance the skin permeability by disrupting the lipid
bilayers of the stratum corneum (SC), and then ISF is extracted out of skin continuously by vacuum. The extracted ISF is
diluted and the concentration of glucose in it is detected by a biosensor and used to predict the blood glucose
concentration. The skin permeability is variable during the extraction, and its variation affects the prediction accuracy.
The skin impedance is an excellent indicator of skin permeability in that the lipid bilayers of the SC, which offer
electrical resistance to the skin, retard transdermal transport of molecules. So the skin impedance measured during the
extraction is transformed to skin conductivity to estimate correlation coefficient between skin conductivity and
permeability. Skin conductivity correlates well with skin permeability. The method and experiment system mentioned
above may be significative for improving the prediction accuracy of continuous blood glucose monitoring system.
Proc. SPIE. 5633, Advanced Materials and Devices for Sensing and Imaging II
KEYWORDS: Mirrors, Beam splitters, Interferometers, Control systems, Artificial neural networks, Control systems design, Systems modeling, Device simulation, Beam controllers, Laser systems engineering
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