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In recent years, glucose biosensors play an important role in diabetes detection. This paper describes a potentiometric non-enzymatic glucose biosensor. The sensor is modified by silver nanowires (Ag NWs) which are fabricated by the polyol method. Using the voltage-time (V-T) system and electrochemical impedance spectroscopy (EIS), the sensing characteristics of the sensor are analyzed and the impact of silver nanowires (Ag NWs) on the performance of the sensor are investigated.

Prevalence of diabetes mellitus is a growing area of concern worldwide. An accurate and timely detection can lead to a normal life of a patient. The existing enzyme-based method for blood glucose detection suffers from poor sensitivity and interference with other blood constituents. Hence, the nano-material synthesis for sensitive and stable non-enzyme based sensors for blood glucose measurement is a worldwide frontline emerging area of research. In this study, the significance of transition metal nano-particle decorated graphene film as a non-enzymatic sensor is discussed. A scheme for synthesizing this sensor materials with detection mechanism is also proposed. The Biomedical and Bioprocess Engineering will be immensely benefitted by the outcome of such research on non-enzymatic glucose sensor material.

Physical activity and physical fitness may lead to extended health benefits. The human body loses lots of electrolytes during physical activity through perspiration and there is a need to replace them with special drinks, thus we introduce a smart wearable sensor that allows sweat monitoring using biosensors providing realtime feedback through a smartphone application informing the user when there is need to replace electrolytes. The system is based on a potentiostat with wireless communication capabilities that performs electrochemical analysis using biosensors. The preliminary results were obtained using commercial glucose sensors and compared with a glucose meter. A glucose solution was prepared with different concentrations tested using chronoamperometry. The system proved to be efficient in the measurement of high and low concentration of glucose in sweat.

The emergence of real-time glucose sensors has prompted the development of closed-loop insulin delivery systems for type 1 diabetes patients, termed the artificial pancreas. The existing closed-loop systems rely on the user's input to provide meal insulin boluses. However, patients, particularly adolescents, sometimes forget to announce consumed meals to the system. The performance of closed-loop systems after an unannounced meal may be improved with the addition of a meal detection module to the closed-loop system. We have developed a novel meal detection algorithm that detects unannounced meals using glucose measurements and insulin data. The model-based detection algorithm continually estimates an internal patient state using a linear Kalman filter. A generalized likelihood ratio test (GLRT) statistic is computed to evaluate the consistency of the Kalman filter under the null hypothesis that all consumed meals have been announced. A threshold criterion is applied on the GLRT to distinguish if the observed glucose increase is due to an unannounced meal. Simulation results, based on nonlinear time-varying virtual patients and noisy glucose measurements, show a sensitivity of 93.23% and a false positive rate of 4.17%. Moreover, 108 hours (4 patients x 3 visits x 9 hours) of clinical data is used to demonstrate the safety and feasibility of the meal detection module. Four patients underwent a nine-hour three-way inpatient experiment where the lunch meal was not announced to the system. The algorithm successfully detected all unannounced meals within 35 [30]-[40] minutes, without any false positives.

This paper presents a comparative study of several non-invasive RF glucose sensors emphasizing the factors and challenges affecting measurement accuracy and highlighting important sensor design parameters. Non-invasive measurement of blood glucose is a challenging task and appropriate sensor design is vital for achieving acceptable measurement accuracy, which depends on the accurate tracking of the change in the blood's complex permittivity due to the variation in glucose concentration. Since this variation is very limited in quantity, several parameters affecting the accuracy need to be carefully considered. These have been identified and reported previously and are elaborated on in this paper providing new comparative results across several sensors reported in the open literature.

A novel pressure sensing circuit for non-invasive RF/microwave blood glucose sensors is presented in this paper. RF sensors are of interest to researchers for measuring blood glucose levels non-invasively. For the measurements, the finger is a popular site that has a good amount of blood supply. When a finger is placed on top of the RF sensor, the electromagnetic fields radiating from the sensor interact with the blood in the finger and the resulting sensor response depends on the permittivity of the blood. The varying glucose level in the blood results in a permittivity change causing a shift in the sensor's response. Therefore, by observing the sensor's frequency response it may be possible to predict the blood glucose level. However, there are two crucial points in taking and subsequently predicting the blood glucose level. These points are; the position of the finger on the sensor and the pressure applied onto the sensor. A variation in the glucose level causes a very small frequency shift. However, finger positioning and applying inconsistent pressure have more pronounced effect on the sensor response. For this reason, it may not be possible to take a correct reading if these effects are not considered carefully. Two novel pressure sensing circuits are proposed and presented in this paper to accurately monitor the pressure applied.

This paper presents a low power current-mirror based potentiostat for implantable glucose sensor tags. With a potential-control loop and an error-reduction loop, the potentiostat can accurately capture the weak current from glucose sensors. The design has been implemented using SMIC 0.13 μm 1P8M CMOS process. According to the test results, the liner correlation coefficient of the potentiostat is 0.999936 with the current range of 0∼40nA, and the power consumption of the potentiostat is 3.6 μW.

Affinity glucose sensors based on equilibrium binding can offer improved stability and accuracy for continuous glucose monitoring in diabetes care. This paper presents a graphene-based affinity nanosensor for glucose measurements. The nanosensor exploits the affinity binding of a novel, surface-immobilized synthetic polymer with glucose. The binding induces changes in the bulk electrical properties of graphene, which are measured for sensitive glucose detection in a highly miniaturized device without the use of physical barriers commonly employed by existing affinity glucose sensors.

This paper reports on development of a micro glucose sensor integrated-device for cell-based assays. Glucose is the energy source of living cells. Therefore, measuring the glucose consumption on cells is very important in cell biology. In μTAS research field, an enzyme-fixed micro glucose sensor integrated to microfluidic devices has been proposed for measurement of cell kinetics continuously. There are various methods on how to fix the enzyme to the sensor. In this paper, we examined the performance of the micro glucose sensor fabricated by the different enzyme immobilization methods. We measured the sensitivity and the lifetime of the glucose sensors made by different enzyme immobilization methods. As the result, the sensor sensitivity of the crosslinking method was higher than it of the physisorption method. We conclude that the performance of the micro glucose sensor could be modified by optimization of the enzyme immobilization methods.

We have examined changes in the responses of holographic sensors with phenylboronic acid while pH of solution were increasing in water HCl solution and in solutions of NaCl (0,1-0,4 M). Effect ionic strength results in a significant change in sensors response, that is the result of compression of the matrix sensors.

An artificial pancreas has a profound impact on changing the life of patients with Type 1 diabetes (T1D). In spite of the obvious improvements in continuous glucose sensor field, there are still limitations presented such as short life time, existence of lag time, and biocompatibility issues. This paper presents a novel idea of Intravascular Multilayered Glucose Sensor (IMLGS), which is used in the closed loop system of artificial pancreas for T1D patients. This work demonstrates glucose detection directly from the blood using glucose layers made from polyaniline carbon paste (PANI-CPE) crosslinking with a glucose enzyme. The layers of glucose sensors are controlled, and switched from layer to another layer using an algorithm strategy based on calculation of calibration factor. We utilized patient glucose data and criteria of sensor replacement to simulate our proposed idea of IMLGS. Simulation results showed that the total duration time of the glucose sensor occupied approximately 134 days for a five-layer sensor. The simulations also showed that the glucose layer sensor is replaced when the calibration factor exceeds threshold value of 10.8-12.68mg/dlnA-1.

Although non-enzymatic glucose sensors have demonstrated better stability and reproducibility with respect to enzymatic ones, so far they have been inappropriate for most applications, since they require alkaline conditions to achieve the necessary sensitivity. In this work, we propose a gold nanogap-based non-enzymatic sensor to localize the generation of alkaline conditions inside the gap, thus preserving the overall pH in the media during glucose detection. The working principle is based on an electrochemical bi-potentiostatic measurement, where an alkaline aqueous condition is locally generated at one side of nanogap, while glucose detection is performed at the counterpart. To this purpose, a nanogap array platform was fabricated by means of standard lithography and controlled electromigration. Mono-potentiostatic electrochemical detection of ascorbic acid was successfully performed to preliminary test the platform prior to measuring glucose in bi-potentiostatic mode. Cyclic voltammetries reveal that two oxidation peaks are sensitive to glucose concentration, making nanogap glucose detection possible in principle. This promising proof of concept could be innovative in bio-applications with implantable devices or direct monitoring of cell culture, where neutral pH in contact with living tissue is required. Further geometrical improvements of the system to increase the durability of the sensor are currently still in progress, and are briefly discussed in the final part of the paper.

This paper presents the hardware implementation and optimisation of the Biostator II algorithm for control of blood glucose in the hospital. Elevated blood glucose levels occur frequently in hospitalised patients suffering from acute illness and needs to be controlled to minimise secondary complications. Unlike previous efforts, we use subcutaneous glucose sensing, minimising risks and discomfort associated with the intravenous route. Implemented in VHDL, the algorithm is geared towards integration in a CMOS ASIC, combining sensor instrumentation as well as serving as the core for a portable, reliable and affordable system for safe and effective control of blood glucose in hospitalised patient using commercially available subcutaneous continuous glucose sensors and intravenous insulin pumps. The algorithm has been successfully tested in hardware using a commercially available simulator of type 1 diabetes mellitus subjects. It achieves good control with the adults subjects being 98.7% in target with a mean blood glucose of 134.67 mg/dl and the adolescent subjects being 93.56% in target with a mean blood glucose of 126.01 mg/dl.

Due of the clinical significance of measuring blood glucose levels of diabetic patients substantial research and development efforts have been devoted to the realization of reliable glucose sensors for in vitro or in vivo applications [1]. Wang et al introduced a mediator-free and membrane-free biosensor which provided a novel direction for biosensor development [2]. On the other hand the presence of defect sites in vertically aligned carbon nanofiber (VACNF) results in better mechanical stability, sensitivity and response compared to carbon nanotubes (CNT) for sensor applications [3–4]. Based on these scientific observations a mediator-free, bienzyme, glucose sensor incorporating VACNF is proposed in this paper.

The medical applications of MEMS (Micro-Electro-Mechanical-Systems) microsensors have been introduced. MEMS based sensors such as pressure sensors, accelerometers, Glucose sensors, chemical gas sensors and etc. and its advantages with respect to the other sensors in medical applications are explained. Small size, low price, high functionality, high precision, fast response time and so on are some of MEMS sensors benefits. Also, some special applications of these sensors such as blood pressure measurement, pacemaker acceleration measurement, blood glucose measurement and etc. are evaluated.

This paper demonstrates a novel fluorescence resonance energy transfer (RET) sensor system, wherein a competitive binding (CB) assay is encapsulated into microcapsules. For CB approaches intended as smart tattoos, microcapsules are superior to hydrogel microparticle systems, as they provide space in the capsule interior for the free movement of the sensing elements while maintaining constant sensing assay concentration. Previously-developed CB glucose sensors suffer from toxicity, nonspecificity, lack of efficient encapsulation technology, and poor reversibility. To overcome some of these limitations, apo-glucose-oxidase (AG) was used as a glucose binding protein and was entrapped in polyelectrolyte microcapsules. The glucose-sensitive change in RET of the fluorescein isothiocyanate (FITC)-dextran and tetramethylrhodamine isothio-cyanate (TRITC)-AG entrapped in microcapsules showed 5times more specificity towards glucose over other sugars, with a sensitivity of 0.035units/mM in the range of 0-40mM. These response characteristics appear to be suitable for glucose monitoring in diabetic patients

We present a method for fabricating electroenzymatic glucose sensors. The general approach i s to utilize thin- and thick-film deposition techniques similar to those used in the semiconductor processing industry. The sensors are fabricated in lots of 130, with the goal of a cheiving r eproducible s ensor performance and economical fabrication costs, using processes that can be readily up-scaled for manufacturing large numbers of sensors. The sensors are formed on a flexible substrate to provide less irritation and longer, more reliable operation when placed in vivo. Sensor operation has been characterized in vitro, and sensor performance has been found to meet

The present study investigated the temporal modulation in performance of printed thick film electrochemical sensors without immobilized glucose oxidase by comparing the ex vivo performance of such devices with that of in vitro phosphate buffer saline (PBS) maintained sensors, at similar time points. In addition, a preliminary study was conducted to investigate the dependency of the sensor functionality on the method of sterilization. The oxidation and reduction current involving a ferrous-ferric coupling reaction was used to assess the performance of the electrode elements under in vitro and ex vivo conditions. Imaging analysis was employed to investigate the cellular morphology on the surface of the explanted devices. It was concluded that while the devices were affected by the presence of the surrounding biological environment (cellular adhesion, fibrous capsule formation), the ex vivo performance of the printed thick film sensors was comparable to that of the in vitro prototypes, at similar time points.

Although the first implantable glucose sensors were developed a few decades ago, there is still no glucose sensor that can work reliably and for a long period of time after implantation. This loss of function in vivo is caused by events that affect the sensor itself (e.g. degradation, fouling...), as well as by changes in the tissue surrounding the sensor, caused by the implantation. Therefore, in order to develop a reliable implantable glucose sensor that will remain functional for a long time in vivo, it is critical to study and control the effects of the biological environment on the sensor itself, as well as to control the tissue reactions to the sensor. Examples of such studies are described in this paper.

A major obstacle to the widespread application of implantable glucose sensors is that they progressively lose function after a relatively short period of time in vivo. The aim of the study was thus to identify, and possibly prevent, causes for failure of implantable glucose sensors.

Although the first implantable glucose sensors were developed a few decades ago, there is still no glucose sensor that can work reliably and for a long period of time after implantation. This loss of function in vivo is caused by events that affect the sensor itself (e.g. degradation, fouling...), as well as by changes in the tissue surrounding the sensor, caused by the implantation. Therefore, in order to develop a reliable implantable glucose sensor that will remain functional for a long time in vivo, it is critical to study and control the effects of the biological environment on the sensor itself, as well as to control the tissue reactions to the sensor. Examples of such studies are described.