Showing papers on "Glucose Measurement published in 1993"

Reverse iontophoresis : development of a noninvasive approach for glucose monitoring

Abstract: Solvent flow generated during iontophoresis can be used to convect neutral molecules through the skin, thereby greatly enhancing their flux. This concept was exploited to realize noninvasive glucose measurement by its iontophoretic extraction from the subcutaneous tissue. The hypothesis was tested in vitro using hairless mouse skin. The dermal surface was bathed with a glucose solution; chambers on the epidermal surface housed the current delivery electrodes. Iontophoresis (at 0.36 mA/cm2) was performed for 2 hr, at the end of which the solutions in contact with the electrodes were analyzed. The amount extracted was proportional to the glucose solution concentration bathing the dermis. Higher radioactivity levels were found at the anode than at the cathode, possibly because of glucose metabolism during its outward transport across the skin. Glucose biotransformation results in negatively charged metabolites which migrate to the anode. Two sensitive glucose sensors were developed; one was selective for glucose, the other for glucose and related compounds. Both sensors indicated the presence of glucose at the cathode but an abnormally high value was also recorded at the anode. This signal, however, was not due to glucose but rather to electroactive ascorbate withdrawn from the skin. Finally, a system has been developed with which glucose can be extracted noninvasively from the subcutaneous tissue and unambiguously measured. Whether iontophoretic glucose sampling in vivo will be equally successful remains to be answered.

On line continuous monitoring of subcutaneous tissue glucose is feasible by combining portable glucosensor with microdialysis.

Abstract: A new method for continuous measurement of subcutaneous tissue glucose content is introduced: by combining the microdialysis technique with a wearable amperometric glucose sensor, a device for continuous glucose measurement in the subcutaneous tissue was obtained. This device was applied to healthy volunteers (n = 10) over the period of an oral glucose load and to type I diabetic patients (n = 10) under the conditions of daily life. Glucose profiles in both healthy and diabetic persons were followed in the subcutaneous tissue up to 27 hours. This technique will certainly open new perspectives of monitoring and treating diabetic patients.

Noninvasive measurement of blood glucose concentrations by analysing Fourier transform infra-red absorbance spectra through oral mucosa

Abstract: Whether Fourier transform infra-red spectroscopy with an attenuated total reflection prism could be applied for noninvasive glucose measurement through oral mucosa was evaluated. As a result, the same absorbance peak at 1033 cm−1 as in glucose aqueous solution was found in the absorbance spectra through mucous membrane. However, these glucose specific peaks were interfered with by the baseline drifts owing to prism attachment and the background spectra from body constituents other than glucose. Therefore, to eliminate these interferences, the calibration curve between the second derivatives of the absorbance peak at 1033 cm−1 and those at 2920 cm−1 was calculated (r=0·910). By using this calibration curve, the spectral changes due to prism attachment were first eliminated. Secondly, by obtaining the second derivative of the difference between the postprandial absorbance peak and the fasting sample as a characteristic of an individual, high correlations between the corrected second derivatives of absorbance spectra through the mucous membrane of the lip at 1033 cm−1 and the increases in blood glucose concentrations above fasting levels were observed (r=0·910). In conclusion, it was suggested that Fourier transform infra-red spectroscopy could be useful for noninvasive monitoring of glucose through oral mucosa.

Highly Selective and Sensitive Amperometric Biosensing of Glucose at Ruthenium-Dispersed Carbon Paste Enzyme Electrodes

Abstract: The selectivity and sensitivity of glucose measurements at carbon-paste based amperometric biosensors are greatly enhanced through the use of ruthenium-dispersed graphite particles. The improved performance is attributed to the substantial lowering of the overvoltage for the reduction of the hydrogen peroxide product. Hence, cathodic measurements of glucose can be caried out at an optimal potential range (-0.15 to +0.20 V). Contributions from easily oxidizable substances (e.g. acetaminophen, ascorbic and uric acids) are eliminated, without the need for mediators or membrane barriers. The electrocatalytic action of the ruthenium sites results also in a substantially improved sensitivity. A fast flow injection operation is illustrated.

Ferrocene-mediated thermal biosensor

Abstract: A biosensor that combines electrochemistry and calorimetry was investigated. Using this sensor, glucose measurements were performed by employing glucose oxidase together with ferrocene as electron-transfer mediator. The electrochemical reaction was accomplished by applying a voltage between a platinum column (working electrode), in contact with a crushed reticulated vitreous carbon (RVC) matrix onto which glucose oxidase was immobilized, and platinum wires (counter electrodes) located at the inlet and outlet of the column. For detection, the thermal signal generated by the redox reaction was measured as opposed to measuring the electrochemical signal. By using this method, a linear range of glucose concentration up to 20 mmol l–1 was achieved.

Use of the microdialysis technique in the monitoring of subcutaneous tissue glucose concentration.

Abstract: For some time the subcutaneous (s.c.) tissue has been the target for continuous glucose measurement. The microdialysis technique permits an extracellular region approach, which has been used for about two decades for measuring various metabolites in dialysates obtained from different body regions. By connecting a s.c. implanted microdialysis probe to a flow chamber of an amperometric glucose sensor, the procedure of glucose sensing was transferred to ex vivo. Using this device it was possible to obtain, for up to 24 hours, s.c. tissue glucose profiles of healthy and diabetic people. The microdialysis theory, the calibration process and other microdialysis technique applications are discussed in this paper. Although the combination of the microdialysis technique and amperometric glucose sensing requires certain technical equipment, the combination of microdialysis and glucose sensor seems to be a promising approach to a continuously functioning glucose sensing system.

Capillary blood glucose measurements in hospital inpatients using portable glucose meters.

Abstract: Background: The use of portable glucose meters by nursing staff to perform bedside capillary blood glucose measurements is standard practice in the management of diabetic hospital inpatients. Few studies, however, have examined the practical limitations or the cost of this technology. Aim: To investigate the performance and cost of capillary blood glucose measurements using portable glucose meters in a hospital inpatient population being managed for diabetes mellitus. Methods: The setting was a 500 bed metropolitan University Teaching hospital, with 22 meters (Glucometer-M) in routine use by about 450 accredited nursing staff. The Glucometer-M was also compared with an operator-independent meter (Hemocue) to assess the effect of operator bias on the overall efficacy and cost of the programme. Results: Retrospective analysis of Glucometer-M reagent strips and comparison of measurements (n = 72) with the Hemocue revealed a marked operator bias which diminished accuracy and increased costs. The significant proportion of low haematocrits (< 30%) in the hospital population limited the applicability of the Glucometer-M which only operates reliably over the haematocrit range 35–50%. The excess of blood glucose measurements was highlighted by both a hospital ward audit and the frequency which exceeded that of routine electrolyte assays. Conclusions: Reliable bedside estimation of capillary blood glucose levels in hospitals requires a meter which is accurate, has negligible operator bias, is largely unaffected by haematocrit, and has insignificant risk of cross-contamination. At present only the Hemocue fulfils these specifications. Irrespective of meter choice, it is necessary to develop criteria for glucose measurements and monitor adherence. (Aust NZ J Med 1993; 23: 667–671.)

Microdialysis implemented in the design of a system for continuous glucose monitoring

Abstract: A system for continuous glucose measurements has been developed. The monitoring system is based on glucose withdrawal from the sample site via microdialysis fibre. By perfusing the microdialysis fibre with a saline solution, the glucose variations around the fibre can also be observed in the perfusion liquid exiting the fibre. The perfusion liquid is passed on to a glucose sensor where the readout of the glucose concentration is performed. A brief description of the design of the microdialysis probe and the glucose sensor is presented. The system is calibrated in vitro for two different flow rates and displays a linear calibration plot within 0–3.5 mmol at 12 μl/ min and 0–7 mmol at 25 μl/min. by inserting the microdialysis probe subcutaneously, a continuous in vivo monitoring sequence has been performed and compared with the actual blood glucose values of the patient.

Measurement of the glucosinolate content in rapeseed using the TRUBLUGLU meter

Abstract: A simple and inexpensive method for the estimation of total glucosinolate (GSL) content in rapeseed is described. It employs a newly developed portable reflectance instrument, the TRUBLUGLU meter. The assay is based on the selective hydrolysis of GSLs by endogenous myrosinase at pH 9, followed by measurement of the released glucose using Clinistix strips. The meter, which is calibrated prior to use with a standard glucose solution, can display a digital readout in units of either mM glucose or μmol GSL/g seed

A Continuous Monitoring system for Blood Glucose Measurements in conscious Animals without Surgery

Abstract: The hypoglycemic activity of insulin delivered via the various routes is commonly determined by measuring glucose levels in the whole blood samples taken intermittently at frequent intervals. This procedure is usually performed in the anaesthetized animals, however, the glucose levels determined could be higher than those in the conscious animals. Furthermore, the animals are usually excited by direct contact with the investigator during the frequent blood sampling in conscious state, which could cause the glucose level to be higher than at undisturbed state. To overcome these problems, a continuous blood glucose monitoring system was developed by connecting the sensor chamber of a glucose analyzer (YSI Industrial Analyzer model 27), which utilizes glucose oxidase for glucose measurement, to a peristaltic pump with a specially designed mixing chamber and a data acquisition station. By using this system, the hyper-/hypoglycemic activity of glucagon/insulin formulations in the conscious animals, aft...