Health promotion requires novel digital healthcare devices for noninvasive and continuous monitoring of health related parameters and their log in order to reduce explosive growth of national medical expense and to increase Quality of Life (QOL) by introducing home care, preventive medicine and self-medication. Blood glucose sensors may play a major role in the digital healthcare field. This paper describes the overview of the digital healthcare field, adult diseases as a main target of the field and blood glucose sensors suitable to the field.

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Our research team has developed a confocal optical system using a near-infrared laser that is capable of reducing the effects of scattering during a measurement of glucose concentration. We have measured the light reflection of our samples and because our system has the depth resolution offered by a confocal optical system it is able to limit the length of the light path and to detect light absorption at each depth level of the samples; thereby restricting the point of measurement. This report details the use of this system for the basic experiment of measuring blood samples and predicting glucose concentration levels. The results show a high correlation between glucose concentration and near-infrared light absorption. Moreover, we have showed the possibility of calculating glucose concentration in living organisms using our system.

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This review covers our studies about fully implantable sensor using glucose responsive fluorescence hydrogel based on our previous publications. We succeeded to fabricate the fluorescence hydrogel micro-beads and micro-fibers that have capability to be implanted to the ear of a mouse. Implanted fluorescence hydrogel sensors tracked the fluctuation of blood glucose concentration in the in vivo tests, and the glucose traceability has maintained until 140 days from the implantation with micro-fibers. PEG-bonded micro-fibers successfully suppressed the inflammation. The fluorescence measurement system has the great potential to realize the minimally-invasive and long-term implantable continuous glucose monitoring.

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In this paper, we describe about small sized and extremely low power consumption transceiver module for wireless sensor network, especially suitable for bio-signal transmission. Currently, many types of transceiver modules, such as Bluetooth, ZigBee, low power radio modules for 315MHz and so on, are available in the market. However, when we consider extremely small and light system including a battery and transceiver module for wireless sensor network installed on a human body, almost all the transceiver modules in the market consume too large power and too large area for assembling. In this study, we concentrated on realizing an extremely low power consumption and small/lightweight transceiver module for 315MHz radio band. As a result, we successfully designed and fabricated the transceiver module with size of 11×11×1.5 mm³ including a bipolar ASIC for radio circuit and 8bit micro controller. The operation currents of the receiver and transmitter are 2 and 1 mA, respectively for supply voltage of 2.5V. These results are generally sufficient for many cases of wireless sensor network systems not only for bio-signal applications.

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Non-invasive and continuous glucose monitoring is of increasing significance since diabetes mellitus has been a global problem, not only the developed country. Usually, continuous glucose monitors (CGMs) use relationship between blood glucose and other body fluids. Particularly, we focused on the relationship between blood glucose and tear glucose. A soft-contact lens (SCL) biosensor has been developed for assessment of blood glucose by real-time tear sugar monitoring. The SCL biosensor has film electrodes on the rounded surface of polydimethyl siloxane (PDMS) contact-lens and glucose oxidase (GOD) was immobilized on the sensing region of the electrodes. In this paper, the status of SCL biosensor development and the application of the SCL biosensor in real-time monitoring of tear glucose are reviewed.

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Diabetes is not an infectious disease but its increasingly rapid and worldwide prevalence has been recognized as "pandemic". Despite the necessity for continuous and accurate glycemic control in the management of insulin dependent diabetes mellitus, the current palliative treatment relies almost solely on the patient-self injection of insulin, which not only impinges on quality of life of the patients but also fails to precisely control dose of insulin where the overdose must be strictly avoided otherwise causing serious hypoglycemia. Development of self-regulated insulin delivery systems is a long-standing challenge of materials science, for which exploitations of glucose oxidase and sugar-binding lectin are two prevalent strategies to install the function of glucose-sensitivity. These protein-based components, however, intolerant of long-term use and storage with their denaturing and cytotoxic natures, are hardly suitable for any implantable applications thus have not yet been in clinical usage to date. This review intends to provide an overview of the current efforts to develop a thoroughly synthetic alternative making use of a phenylboronic acid derivatized polyacrylamide gel.

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