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Biomedical subjects

S J Updike

Publications and source records attributed to S J Updike.

At least 55 records · Page 3Linked to original sources
PubMed1967

Reagentless substrate analysis with immobilized enzymes.

By coupling an immobilized enzyme system with an electrochemical sensor, the reagent requirement for this glucose method is eliminated. Miniaturization and a further simplification of the instrumentation for the continuous analysis of glucose is achieved.

Biochemistry↗
PubMedDate not supplied

Laboratory evaluation of new reusable blood glucose sensor.

An enzyme-electrode sensor designed specifically for pocket-portable self-monitoring of blood glucose is described. The sensing device in this instrument is unique because it is reusable for at least 30 days, at which time it is easily replaced by placing a new enzyme-membrane cartridge over the electrode. As little as 7 microliters of undiluted whole blood, plasma, or serum is applied directly to the sensor, and glucose is automatically determined in 30 s. No manual timing or wiping step is required after sample application. On eight production instruments, plasma glucose concentration was determined (n = 20) at 57, 125, 246, and 347 mg/dl. The average coefficient of variation for the 80 determinations for each instrument ranged from 2 to 5%, averaging 3.7%. The instrument is inherently linear, independent of hematocrit, and without oxygen limitation when dissolved oxygen concentration is greater than 35 mmHg. No interferences were found from plasma constituents, heparin, or acetaminophen.

Biosensing Techniques↗
PubMedDate not supplied

Implanting the glucose enzyme electrode: problems, progress, and alternative solutions.

An implantable glucose sensor is needed before a reliable artificial pancreas can be realized. The principles and current status of one such device, the glucose enzyme electrode, is presented and discussed. While monitoring glucose this enzyme sensor consumes enough oxygen to become oxygen-limited. This problem has been solved by developing hydrophobic membranes that are more permeable to oxygen than to glucose. Two types of membranes with this property made from (1) cross-linked albumin and (2) sebacyl chloride (nylon) are described. Placing these membranes over the glucose enzyme electrode solves the problem of oxygen limitation. Furthermore, the addition of this type of membrane increases the linear response range of the electrode to glucose to include the entire clinical range of interest (0-400 mg/dl). Other problems in developing an implantable glucose sensor are discussed. Competing strategies to achieve an implantable artificial pancreas without using electronic or mechanical components are presented and evaluated.

Blood Glucose↗
PubMedDate not supplied

Development and evaluation of a wearable blood glucose monitor.

Complex operation, prolonged set-up time, reliability problems, high cost, and excessive size limits the use of currently available extracorporeal continuous blood glucose analyzers. A self-calibrating, wearable blood glucose monitor has been developed to overcome these impediments. The wearable blood glucose monitor is a 410 g forearm-mounted instrument with three miniature pumps for blood sampling, calibration, and insulin infusion, and a flow cell containing an enzyme-electrode sensor capable of determining plasma glucose levels accurately and precisely in undiluted whole blood. The unit is connected to a computer controller with graphics display. Venous blood is drawn from a 21 gauge single lumen cannula through the sensor flow cell. A rate determination of glucose is completed in 20 sec and the blood is returned to the arm vein. Heparinized saline wash solution follows. No blood loss or significant systemic heparinization occurs. Cycle time is set from 2 to 5 min. The method is linear to at least 300 mg/dl glucose, independent of hematocrit, and free of interferences from blood constituents at normal venous pO2 with a coefficient of variation of 1-3% between calibrations. The sensor has a service life of at least 3 weeks. This wearable blood glucose monitor, with its high performance sensor, reduced size, and ease of operation, shows promise for evaluating and treating diabetes.

Animals↗