Showing papers on "Glucose Measurement published in 2015"

The Performance and Usability of a Factory-Calibrated Flash Glucose Monitoring System.

Abstract: Introduction: The purpose of the study was to evaluate the performance and usability of the FreeStyle® Libre™ Flash glucose monitoring system (Abbott Diabetes Care, Alameda, CA) for interstitial glucose results compared with capillary blood glucose results. Materials and Methods: Seventy-two study participants with type 1 or type 2 diabetes were enrolled by four U.S. clinical sites. A sensor was inserted on the back of each upper arm for up to 14 days. Three factory-only calibrated sensor lots were used in the study. Sensor glucose measurements were compared with capillary blood glucose (BG) results (approximately eight per day) obtained using the BG meter built into the reader (BG reference) and with the YSI analyzer (Yellow Springs Instrument, Yellow Springs, OH) reference tests at three clinic visits (32 samples per visit). Sensor readings were masked to the participants. Results: The accuracy of the results was demonstrated against capillary BG reference values, with 86.7% of sensor results w...

Recent advances in nanotechnology for diabetes treatment.

Abstract: Nanotechnology in diabetes research has facilitated the development of novel glucose measurement and insulin delivery modalities which hold the potential to dramatically improve quality of life for diabetics. Recent progress in the field of diabetes research at its interface with nanotechnology is our focus. In particular, we examine glucose sensors with nanoscale components including metal nanoparticles and carbon nanostructures. The addition of nanoscale components commonly increases glucose sensor sensitivity, temporal response, and can lead to sensors which facilitate continuous in vivo glucose monitoring. Additionally, we survey nanoscale approaches to 'closed-loop' insulin delivery strategies which automatically release insulin in response to fluctuating blood glucose levels (BGLs). 'Closing the loop' between BGL measurements and insulin administration by removing the requirement of patient action holds the potential to dramatically improve the health and quality of life of diabetics. Advantages and limitations of current strategies, as well as future opportunities and challenges are also discussed.

Analysis of Continuous Glucose Monitoring in Pregnant Women With Diabetes:Distinct Temporal Patterns of Glucose Associated With Large-for-Gestational-Age Infants

Abstract: OBJECTIVE Continuous glucose monitoring (CGM) is increasingly used to assess glucose control in diabetes. The objective was to examine how analysis of glucose data might improve our understanding of the role temporal glucose variation has on large-for-gestational-age (LGA) infants born to women with diabetes. RESEARCH DESIGN AND METHODS Functional data analysis (FDA) was applied to 1.68 million glucose measurements from 759 measurement episodes, obtained from two previously published randomized controlled trials of CGM in pregnant women with diabetes. A total of 117 women with type 1 diabetes ( n = 89) and type 2 diabetes ( n = 28) who used repeated CGM during pregnancy were recruited from secondary care multidisciplinary obstetric clinics for diabetes in the U.K. and Denmark. LGA was defined as birth weight ≥90th percentile adjusted for sex and gestational age. RESULTS A total of 54 of 117 (46%) women developed LGA. LGA was associated with lower mean glucose (7.0 vs. 7.1 mmol/L; P P P CONCLUSIONS FDA of CGM data identified specific times of day that maternal glucose excursions were associated with LGA. It highlights trimester-specific differences, allowing treatment to be targeted to gestational glucose patterns.

Utility of different glycemic control metrics for optimizing management of diabetes

Abstract: The benchmark for assessing quality of long-term glycemic control and adjustment of therapy is currently glycated hemoglobin (HbA1c). Despite its importance as an indicator for the development of diabetic complications, recent studies have revealed that this metric has some limitations; it conveys a rather complex message, which has to be taken into consideration for diabetes screening and treatment. On the basis of recent clinical trials, the relationship between HbA1c and cardiovascular outcomes in long-standing diabetes has been called into question. It becomes obvious that other surrogate and biomarkers are needed to better predict cardiovascular diabetes complications and assess efficiency of therapy. Glycated albumin, fructosamin, and 1,5-anhydroglucitol have received growing interest as alternative markers of glycemic control. In addition to measures of hyperglycemia, advanced glucose monitoring methods became available. An indispensible adjunct to HbA1c in routine diabetes care is self-monitoring of blood glucose. This monitoring method is now widely used, as it provides immediate feedback to patients on short-term changes, involving fasting, preprandial, and postprandial glucose levels. Beyond the traditional metrics, glycemic variability has been identified as a predictor of hypoglycemia, and it might also be implicated in the pathogenesis of vascular diabetes complications. Assessment of glycemic variability is thus important, but exact quantification requires frequently sampled glucose measurements. In order to optimize diabetes treatment, there is a need for both key metrics of glycemic control on a day-to-day basis and for more advanced, user-friendly monitoring methods. In addition to traditional discontinuous glucose testing, continuous glucose sensing has become a useful tool to reveal insufficient glycemic management. This new technology is particularly effective in patients with complicated diabetes and provides the opportunity to characterize glucose dynamics. Several continuous glucose monitoring (CGM) systems, which have shown usefulness in clinical practice, are presently on the market. They can broadly be divided into systems providing retrospective or real-time information on glucose patterns. The widespread clinical application of CGM is still hampered by the lack of generally accepted measures for assessment of glucose profiles and standardized reporting of glucose data. In this article, we will discuss advantages and limitations of various metrics for glycemic control as well as possibilities for evaluation of glucose data with the special focus on glycemic variability and application of CGM to improve individual diabetes management.

Affinity based glucose measurement using fiber optic surface plasmon resonance sensor with surface modification by borate polymer

Abstract: An affinity based method of glucose measurement using a fiber optic surface plasmon resonance (FO-SPR) sensor with surface modification by a borate polymer was proposed. In this method, the sensor is able to obtain the glucose concentration by detecting the surface refractive index of the sensor, which could avoid the impact of bioelectricity from viable tissues when applied for implantable measurement. A biocompatible borate polymer, PAA-ran-PAAPBA, which is capable of associating and dissociating with glucose molecules dynamically, performed non-consumption measurement of glucose, thereby enabling the possibility of glucose detection in hypoglycemic situations. Numerical simulation was performed based on the FO-SPR theory, and an online-transmission FO-SPR sensor with optimized structural parameters was fabricated. PAA-ran-PAAPBA was synthesized and immobilized onto the surface of the FO-SPR sensor using layer-by-layer self-assembly technique. An experimental system was built, and contrast-measurement experiment for 1–10 and 10–300 mg/dL glucose solutions was performed; the FO-SPR sensor bonded with the borate polymer exhibited higher accuracy, especially for low-concentration detection. This study laid a technical foundation for further exploration of implantable measurement systems for blood glucose.

The effects of intravenous vitamin C on point-of-care glucose monitoring.

Abstract: Ascorbic acid (vitamin C) decreases systemic inflammation and lowers fluid requirements after thermal injury; therefore it has been adopted in many burn centers as an adjunct to resuscitation. However, recent concerns have been expressed over clinically significant hypoglycemic events caused by vitamin C interference with the point-of-care (POC) glucose measurements. This case series presents a direct comparison of POC and laboratory reference glucose values in the patients receiving vitamin C infusion. Vitamin C was administered at 66 mg/kg/hour in seven patients with burns >30% TBSA. The baseline characteristics and burn characteristics were recorded. POC glucose measurements were made with a commonly used hand-held device, and the laboratory values were obtained using standard spectrophotometric methods. POC and laboratory glucose values drawn within the same hour were compared. Hemoglobin, which is known to cause interference in POC testing, was also recorded. All the patients demonstrated falsely elevated POC glucose values during and/or immediately after the infusion period, with discrepancies ranging from 10 to 200 mg/dl. These findings were irregular, unpredictable and unrelated to hemoglobin levels. The findings suggest an idiosyncratic reaction that cannot be easily corrected at the bedside using mathematical equations. POC glucose monitoring should be avoided during and after vitamin C therapy.

Comparative Performance Assessment of Point-of-Care Testing Devices for Measuring Glucose and Ketones at the Patient Bedside:

Abstract: Point-of-care (POC) testing devices for monitoring glucose and ketones can play a key role in the management of dysglycemia in hospitalized diabetes patients. The accuracy of glucose devices can be influenced by biochemical changes that commonly occur in critically ill hospital patients and by the medication prescribed. Little is known about the influence of these factors on ketone POC measurements. The aim of this study was to assess the analytical performance of POC hospital wholeblood glucose and ketone meters and the extent of glucose interference factors on the design and accuracy of ketone results. StatStrip glucose/ketone, Optium FreeStyle glucose/ketone, and Accu-Chek Performa glucose were also assessed and results compared to a central laboratory reference method. The analytical evaluation was performed according to Clinical and Laboratory Standards Institute (CLSI) protocols for precision, linearity, method comparison, and interference. The interferences assessed included acetoacetate, acetaminophen, ascorbic acid, galactose, maltose, uric acid, and sodium. The accuracies of both Optium ketone and glucose measurements were significantly influenced by varying levels of hematocrit and ascorbic acid. StatStrip ketone and glucose measurements were unaffected by the interferences tested with exception of ascorbic acid, which reduced the higher level ketone value. The accuracy of Accu-Chek glucose measurements was affected by hematocrit, by ascorbic acid, and significantly by galactose. The method correlation assessment indicated differences between the meters in compliance to ISO 15197 and CLSI 12-A3 performance criteria. Combined POC glucose/ketone methods are now available. The use of these devices in a hospital setting requires careful consideration with regard to the selection of instruments not sensitive to hematocrit variation and presence of interfering substances.

Accuracy of Continuous Glucose Monitoring Measurements in Normo-Glycemic Individuals.

Abstract: Background The validity of continuous glucose monitoring (CGM) is well established in diabetic patients. CGM is also increasingly used for research purposes in normo-glycemic individuals, but the CGM validity in such individuals is unknown. We studied the accuracy of CGM measurements in normo-glycemic individuals by comparing CGM-derived versus venous blood-derived glucose levels and measures of glycemia and glycemic variability. Methods In 34 healthy participants (mean age 65.7 years), glucose was simultaneously measured every 10 minutes, via both an Enlite® CGM sensor, and in venous blood sampled over a 24-hour period. Validity of CGM-derived individual glucose measurements, calculated measures of glycemia over daytime (09:00h-23:00h) and nighttime (23:00h-09:00h), and calculated measures of glycemic variability (e.g. 24h standard deviation [SD]) were assessed by Pearson correlation coefficients, mean absolute relative difference (MARD) and paired t-tests. Results The median correlation coefficient between CGM and venous glucose measurements per participant was 0.68 (interquartile range: 0.40–0.78), and the MARD was 17.6% (SD = 17%). Compared with venous sampling, the calculated measure of glycemia during daytime was 0.22 mmol/L higher when derived from CGM, but no difference was observed during nighttime. Most measures of glycemic variability were lower with CGM than with venous blood sampling (e.g., 24h SD: 1.07 with CGM and 1.26 with venous blood; p-value = 0.004). Conclusion In normo-glycemic individuals, CGM-derived glucose measurements had good agreement with venous glucose levels. However, the measure of glycemia was higher during the day and most measures of glycemic variability were lower when derived from CGM.

NIR photoacoustic spectroscopy for non-invasive glucose measurement

Abstract: The use of near infra red (NIR) photoacoustic spectroscopy (PAS) for continuous non-invasive glucose measurement is outlined in the paper. A photoacoustic (PA) measurement apparatus was constructed and PA measurements were made on glucose solutions at multiple NIR excitation wavelengths. A variety of time and frequency domain features, including amplitude and area based features, were extracted from the PA measurements. These features were observed to be proportional to the glucose concentration of the sample. PA measurements from samples of whole blood at different glucose concentrations showed similar results. Subsequently, in vivo PA measurements made on a cohort of 30 volunteers were calibrated using a quadratic fit, and the results were compared to reference glucose concentrations made using a regular blood glucose meter. A comparison of 196 measurement pairs of predicted and reference glucose concentrations using a Clarke Error Grid gave a point distribution of 87.24% and 12.76% over zones A and B of the grid, with no measurement pairs falling in unacceptable zones C-E of the error grid. The predicted measurements had a mean absolute difference (MAD) of 12.57 ± 13.90 mg/dl and a mean absolute relative difference (MARD) of 9.61% ± 10.55%. This is an improvement over previous results obtained using PAS and other non-invasive techniques, validating the potential of PAS for continuous noninvasive glucose monitoring.

Dynamic and Wireless Sensing Measurements of Potentiometric Glucose Biosensor Based on Graphene and Magnetic Beads

Abstract: In this paper, the arrayed flexible pH sensor and glucose biosensor modified by magnetic beads and graphene were proposed. The ruthenium dioxide (RuO2) sensing films were deposited by radio frequency sputtering system and the screen-printed technique was used to construct the silver conducting wires and insulation layer of the RuO2 electrodes. In order to enhance performance of the pH sensor and glucose biosensor, the microfluidic device had been utilized and developed. In the measurement processes, the different pH and glucose solutions were investigated in various flow rates. According to the experimental results, the average sensitivity of the pH sensor was enhanced from 52.280 to 57.981 mV/pH and the average sensitivity of the RuO2/graphene/magnetic bead-GO x -Nafion glucose biosensor was enhanced from 10.628 to 13.541 mV/mM. With regard to the wireless sensing measurements, the wireless sensing system which complied the ZigBee standard was employed to transmit the signals of the pH or glucose measurements in this investigation, and the system consisted of the Xbee device, Arduino Mega 2560, readout circuit, pH or glucose biosensor and computer. According to the experimental results, the average sensitivity and linearity of the pH sensor were 51.063 mV/pH and 0.988, respectively, and the average sensitivity and linearity of the RuO2/graphene/magnetic bead-GO x -Nafion glucose biosensor were 11.005 mV/mM and 0.995, respectively.

Non-invasive tracking and monitoring glucose content using near infrared spectroscopy

Abstract: Diabetes is deliberate as one of the major contributors of crystallize infirmity and death in non-infectious diseases. Common method for determination of blood glucose concentration is using a self-monitoring glucose meter. This process requires pricking the finger and pry out the blood from the forearm and doing the chemical analysis with the help of disposable test strips. The pain and difficulty caused by this method have lead to the evolution of a noninvasive method. This method makes use of a near infrared sensor for transmission and reception of rays from fingertip. Near-infrared (NIR) is passing through the fingertip, before and after obstructing the flow of blood. By explicate the variation in received signal intensity achieved after reflection in both the cases, glucose present in blood can be predicted and wirelessly transmitted to a remote PC. The results show the potential of glucose measurement using Near-infrared.

Design and development of infrared LED based non invasive blood glucometer

Abstract: Diabetes affects more than 285 million people globally according to estimates by the International Diabetes Federation (IDF). It is a metabolic pathological condition of concern, which affects vital organs of body if not diagnosed and treated on time. Regular monitoring of blood glucose is important to avoid further complication. Commonly used glucose measurement methods are invasive which generally involve finger puncturing. These methods are painful and frequent pricking cause calluses on the skin. It also has a risk of spreading infectious diseases if the needle is contaminated or used more than once. Therefore there is a need to develop a non-invasive monitoring system which can measure blood glucose continuously without posing much problem and easy to use for the diabetic population. In this paper, near infrared optical measurement is applied to overcome the invasive method drawbacks like frequent puncturing, high recurring consumable cost and danger of spreading infectious diseases. The designed device consists of an infrared LED having a wavelength of 900 to 1100 nm as emitter which placed over the fingertip for measurement of blood glucose optically. The intensity of received light depends on the glucose concentration present in blood. The signal is then amplified and fed as input to microcontroller Arduino uno for displaying glucose signal on a computer after carrying out Regression analysis. By analyzing the variation in voltages received after reflection of incident light in the cases the approximate glucose level of the individual is going to be predicted. A compact framework for non-invasive blood glucose measurement has been designed and tested successfully. The results obtained were validated by using various statistical techniques like standard deviation, standard error, percentage linearity etc. It is found that statistical analysis gives correlation coefficient of 0.93. The result obtained shows that voltage intensity level due to pulsatile nature of blood flow and blood glucose level has correlation.

Inaccuracy of Venous Point-of-Care Glucose Measurements in Critically Ill Patients: A Cross-Sectional Study.

Abstract: Introduction Current guidelines and consensus recommend arterial and venous samples as equally acceptable for blood glucose assessment in point-of-care devices, but there is limited evidence to support this recommendation. We evaluated the accuracy of two devices for bedside point-of-care blood glucose measurements using arterial, fingerstick and catheter venous blood samples in ICU patients, and assessed which factors could impair their accuracy.

A novel insulin resistance index to monitor changes in insulin sensitivity and glucose tolerance: the ACT NOW study.

Abstract: Objective: The objective was to test the clinical utility of Quantose MQ to monitor changes in insulin sensitivity after pioglitazone therapy in prediabetic subjects. Quantose MQ is derived from fasting measurements of insulin, α-hydroxybutyrate, linoleoyl-glycerophosphocholine, and oleate, three nonglucose metabolites shown to correlate with insulin-stimulated glucose disposal. Research Design and Methods: Participants were 428 of the total of 602 ACT NOW impaired glucose tolerance (IGT) subjects randomized to pioglitazone (45 mg/d) or placebo and followed for 2.4 years. At baseline and study end, fasting plasma metabolites required for determination of Quantose, glycated hemoglobin, and oral glucose tolerance test with frequent plasma insulin and glucose measurements to calculate the Matsuda index of insulin sensitivity were obtained. Results: Pioglitazone treatment lowered IGT conversion to diabetes (hazard ratio = 0.25; 95% confidence interval = 0.13–0.50; P < .0001). Although glycated hemoglobin did ...

The incidence of hyperglycaemia in very low birth weight preterm newborns. results of a continuous glucose monitoring study--preliminary report.

Abstract: AIM To determine the incidence of hyperglycaemia in very low birth weight preterm newborns. To assess risk factors in hyperglycemia and outcome in groups of children with and without clinically significant hyperglycaemia. MATERIAL AND METHODS The prospective study included newborns with very low birth weight in whom the continuous glucose monitoring system was used for glucose measurements. A standardized hyperglycaemia treatment schedule was implemented and a uniform nutrition strategy introduced. The patients were divided into groups: group A--patients with under 5% of the readings over 150 mg/dL of glucose (control group), group B--patients with more than 5% of the readings over 150 mg/dL of glucose and under 5% of the readings over 180 mg/dL of glucose (mild hyperglycaemia), and group C--patients with over 5% of the readings > 180 mg/dL or on insulin treatment (moderate or severe hyperglycaemia). RESULTS 63 patients were included in the study. Their mean gestational age was 27.7 weeks (SD:2.4), the mean birth weight was 1059g (SD: 262 g). Hyperglycaemia was detected in 27 (42.9%), including mild hyperglycaemia in 19 (30.2%), and moderate or severe hyperglycaemia in 8 (12.7%) neonates. Lower gestational age (p = 0.02) and higher CRIB IIscore (p < 0.01) were positively associated with hyperglycaemia. Early-onset sepsis (p < 0.01) was associated with higher glucose levels as well. A significantly higher mortality rate on the 28th day of life (p = 0.02), depending on the severity of hyperglycemia, was noted. No adverse effects related to the continuous glucose monitoring system were observed. CONCLUSIONS The study confirmed the usefulness and safety of the continuous glucose monitoring system in VLBW neonates. A continuous glucose monitoring system should be used in neonatal intensive care units as a standard method.

A single-loop fiber attenuated total reflection sensor enhanced by silver nanoparticles for continuous glucose monitoring

Abstract: Currently, the implantable enzyme electrode sensor is the only method for continuous glucose monitoring in clinical applications, but the significant drift caused by bioelectricity in body and the effect of electrochemical reactions under hypoxia reduce the accuracy of the glucose measurements. Therefore, finger-prick blood corrections are often required to calibrate enzyme-based glucose sensors several times each day. In this paper, we proposed an implantable miniaturized fiber Attenuated Total Reflection (ATR) sensor based on mid-infrared spectroscopy to overcome the two drawbacks. A single-loop structure of fiber ATR sensor was used to increase the effective optical length to enhance the sensitivity. By growing silver nanoparticles (AgNPs) on the cylindrical surface of the fiber ATR sensor with a chemical silver mirror method, the sensitivity of the infrared absorption signal was further enhanced. In the experiment, the fiber ATR sensor enhanced by AgNPs combined with a CO 2 laser showed an intense absorption signal from glucose, with enhancement factors of two to six folds at different absorption wavenumbers compared with the bare fiber ATR sensors. The prediction of glucose concentration with high accuracy was achieved by using the five-variable partial least-squares model yielding a root-mean-square error of prediction as small as 4.45 mg/dL.

A photoacoustics based continuous non-invasive blood glucose monitoring system

Abstract: The paper examines the use of photoacoustic spectroscopy (PAS) for making continuous non-invasive blood glucose measurements. An apparatus for performing photoacoustic (PA) measurements is constructed and the technique is verified in vitro and in vivo through measurements on glucose solutions and live tissue. The signal amplitude is observed to increase with the glucose concentration in both cases. A linear calibration method is applied on each individual to obtain a glucose concentration value from each PA measurement. The glucose values obtained are compared with reference glucose concentrations measured using a standard glucose meter, giving a mean absolute difference (MAD) of 23.75 mg/dl and a mean absolute relative difference (MARD) of 18.03%. A plot of 196 measurement pairs taken over 30 normal subjects on a Clarke Error Grid gives a point distribution of 67.86%, 31.12%, 0.0%, 1.02% and 0.0% over zones A to E of the grid. This performance is an improvement over those obtained previously using PAS and point to the potential of the technique for non-invasive glucose measurements. An FPGA based reconfigurable embedded architecture is proposed for high speed data acquisition, noise reduction and display of PA measurements. The architecture operates at 274.823 MHz on a Xilinx Virtex-II Pro FPGA providing an SNR improvement of 30 dB and enabling a portable blood glucose monitoring system.

Challenges of inpatient blood glucose monitoring: standards, methods, and devices to measure blood glucose.

Abstract: Glucose control in the hospital setting is very important. There is a high incidence of hyperglycemia, hypoglycemia, and glycemic variability in hospitalized patients. Safe insulin delivery and glucose control is dependent on reliable glucose meters and monitoring systems in the hospital. Different glucose monitoring systems use arterial, venous, central venous, and capillary blood samples. It is important for clinicians to be aware that there are limitations of specific point-of-care (POC) glucose meters and that situations exist whereby POC glucose meters as the sole measurement device should be avoided. POC meter devices are not approved by the Food and Drug Administration for use in critical care, although POC meter devices are commonly used in critical care settings and elsewhere. This review focuses on glucose assay principles, instrument technology, influences on glucose measurement, standards for glucose measurement, and an evaluation of different methods to measure blood glucose in the hospital setting.

Accuracy of a Simplified Glucose Measurement Device—The HemoCue Glucose 201RT

Abstract: Background: Easily available, accurate glucose recordings are important when screening for and managing people with diabetes. The photometric HemoCue® (Angelholm, Sweden) Glucose 201+ system, which delivers lab-comparable glucose recordings, has the drawback that its microcuvettes must be delivered and stored at 4–8°C. A newly developed system, HemoCue Glucose 201RT, has microcuvettes that can be stored at room temperature. Subjects and Methods: Participants (n=444; 18–80 years old) in the EUROASPIRE IV survey, all with coronary artery disease, some with known diabetes, were investigated. Plasma glucose recordings, fasting in all participants and postprandial in the majority, were simultaneously recorded with both pieces of equipment. Congruence was expressed as median absolute difference and median absolute relative difference between the two sets of equipment and also compared according to the International Organization for Standardization (ISO) 15197:2013 criteria. Clinical accuracy was calcul...

Origin of Low Detection Limit and High Selectivity of Roche Accu‐Chek Test Strips that Enables Measurement of Tear Glucose Levels

Abstract: Tear glucose measurements have been suggested as a potential alternative to blood glucose monitoring for diabetic patients. While previous work has reported a correlation between blood and tear glucose levels in humans, this link has not been thoroughly established and additional clinical studies are needed. We recently reported that Roche’s electrochemical Accu-Chek blood glucose test strips exhibit far superior analytical performance over other commercial brands, with the low detection limit and high selectivity required for quantitating tear glucose levels. Herein, we evaluate the origin of the high sensitivity and selectivity of the Roche test strips and show that the use of pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase (GDH) as an active enzyme reagent in combination with a nitrosoaniline derivative as an electron transfer mediator are primarily responsible for the low limit of quantification (LOQ) (ca. 9 µM) and enhanced selectivity achieved with these strips.

Vascular Glucose Sensor Symposium Continuous Glucose Monitoring Systems (CGMS) for Hospitalized and Ambulatory Patients at Risk for Hyperglycemia, Hypoglycemia, and Glycemic Variability

Abstract: Hyperglycemia, hypoglycemia, and glycemic variability have been associated with increased morbidity, mortality, length of stay, and cost in a variety of critical care and non–critical care patient populations in the hospital. The results from prospective randomized clinical trials designed to determine the risks and benefits of intensive insulin therapy and tight glycemic control have been confusing; and at times conflicting. The limitations of point-of-care blood glucose (BG) monitoring in the hospital highlight the great clinical need for an automated real-time continuous glucose monitoring system (CGMS) that can accurately measure the concentration of glucose every few minutes. Automation and standardization of the glucose measurement process have the potential to significantly improve BG control, clinical outcome, safety and cost.

Enzyme Sensor With Polydimethylsiloxane Membrane and CMOS Potentiostat for Wide-Range Glucose Measurements

Abstract: We report on an electrochemical measurement setup comprising a glucose sensor and a CMOS potentiostat with a two-layer membrane as the first steps toward the development of an integrated in-situ sensor system for bioreactors. The potentiostat has a chip size of 2.1 mm × 2.5 mm and a linear current range from -220 nA to 240 nA with a linearity of R 2 = 0.9995. For wide range measurements of glucose concentrations in cell culture media, electrodes functionalized with the enzyme glucose oxidase were spin-coated with membranes made from polydimethylsiloxane (PDMS). A two-stage curing scheme of the PDMS was applied, and different membrane thicknesses and curing times were evaluated. With these membranes, glucose concentrations up to 500 mM were measured with a linear measurement range up to 200 mM. The sensors were successfully employed in the glucose monitoring of a culture of Saccharomyces cerevisiae to monitor the glucose consumption of the cells. For interference elimination, the cellulose acetate membranes were employed.