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Linearity Glucose biosensors should be evaluated for linearity across the reportable range. Therefore, data collection requires two to four replicates from 5 to 11 samples with varying concentrations that are known relative to one another by the dilution ratio or by the formulation.
The correlation coefficient and linear regression equations are calculated from the obtained results versus glucose concentration values.
User performance If the glucose biosensors are evaluated by highly trained health care professionals only, they could miss the complications that are likely to occur by patients using the devices [ ]. The purpose of user performance evaluation is to demonstrate that users are able to operate the glucose biosensors, given only the instructions and training materials routinely provided with the system and obtain valid glucose results.
Results obtained by the lay user are compared to the results obtained by a validated glucose measurement procedure as well as to the results obtained by a healthcare professional from the same sample, using the same devices. At least 50 subjects, with varying demographics age, gender, and education levelshould be included for each lot.
User studies are conducted using at least three different reagent lots at multiple sites. After reviewing the routinely provided training materials, the users perform Biosensors or enzyme electrodes own finger sticks and test themselves using the devices.
The second blood sample should be collected within five minutes. The results are fitted to regression equations with confidence intervals and plots showing all data points. The results should include a comparison of the user results, professional results, and reference results.
Interferences A number of variables can influence the reliability of the test results, including hematocrit, hypoxemia, hypotension, altitude, temperature, and humidity. Electrochemical interferents in the blood cause a false high glucose reading by donating non-glucose-derived electrons.
An interfering molecule is a species that is electroactive at the operating potential of the amperometric sensor. Suggested standard interferents developed by the FDA include: Hematocrit values have a marked effect on the strip-based glucose assay . Oxygen from red blood cells can compete with the redox mediator for glucose-derived electrons in strips when the enzyme used is GOx.
Further, the viscosity of blood increases with increasing hematocrit values, and this increase slows the diffusion of all components and reduces the current in the amperometric sensors [ ].
Low hematocrit values may be the result of anemia and are associated with overestimated results. Hematocrit causes the most significant error in POC glucose biosensors, especially in the intensive care unit. Ascorbic acid is one of the most common interfering substances that affect the accuracy of glucose biosensors .
For glucose biosensors based on electrochemical analysis, ascorbic acid is oxidized at the electrode surface, resulting in the production of more electrons and the generation of a greater current. Increased levels of ascorbic acid lead to increased glucose levels due to the varying degrees of interference caused by ascorbic acid on the glucose biosensors; this may be due to the differences in the enzymes used, technical methodology, or construction of the test strips.
GDH-PQQ catalyzes not only the oxidation of glucose, but also of other sugars, such as maltose, maltriose, maltotetraose, and icodextrin Extraneal; Baxter, Brussels, Belgium [ — ]. Most GDH-based POC devices have significant overestimations of glucose in patients undergoing peritoneal dialysis using icodextrin as an osmotic agent .
Icodextrin is metabolized in the systemic circulation into different glucose polymers, but mainly maltose, which interferes with the GDH-PQQ-based method. The maltose effect on glucose measurement has been demonstrated by Janssen et al.
These authors found that icodextrin metabolites can cause positive interference that may lead to a missed diagnosis of hypoglycemia. Clinicians should be aware of this analytical interference. The glucose biosensors based on the GDH-PQQ method should preferably not be used in this high-risk population, and POC glucose results inconsistent with clinical suspicion of hypoglycemic coma should be retested with another testing system.
Various drugs have been shown to interfere with glucose [ ]. Acetaminophen is one of the most common drugs associated with both accidental and intentional poisoning. A high dose of acetaminophen can generate analytical interference on electrochemical biosensors [ ].
This drug is directly oxidized after diffusing across a porous membrane to the electrode surface, producing an interfering current that increases the glucose reading. Conclusions The measurement of blood glucose levels is carried out using various glucose biosensors for the screening, diagnosis, and long-term management of patients with diabetes.
Since the prevalence of diabetes is increasing, novel glucose biosensor technologies, including POC devices, CGMS, and noninvasive glucose monitoring systems, have been developed during the last few decades. Rapid and effective corrections of blood glucose levels are based on regular glucose measurements using glucose biosensors.
Glucose biosensors have evolved to be more reliable, rapid, and accurate and are also more compact and easy to use. Research for advanced technologies, including electrodes, membrane, immobilization strategies, and nanomaterials, continue to be performed.
Despite the impressive advances in glucose biosensor technology, there are still several challenges related to the achievement of reliable glucose monitoring.Electrochemical Glucose Biosensors Joseph Wang* Biodesign Institute, Center for Bioelectronics and Biosensors, Departments of Chemical Engineering and Chemistry and Biochemistry, enzyme electrode relied on a thin layer of GOx entrapped over an oxygen electrode via a semipermeable dialysis membrane.
Measurements were .
A biosensor for 3-hydroxybutyrate (3-HB) involving immobilization of the enzyme 3-hydroxybutyrate dehydrogenase onto a screen-printed carbon electrode modified with reduced graphene oxide (GO) and thionine (THI) is reported here. Such biosensors are often made by screen printing the electrode patterns on a plastic substrate, coated with a conducting polymer and then some protein (enzyme or antibody) is attached.
They have only two electrodes and are extremely sensitive and robust. Biosensors or enzyme electrodes invariably refer to such devices that sence and analyze biological informations. A biosensor is a device that detects, records, and transmits information regarding a physiological change or the presence of various chemical or biological materials in the environment.
The enzyme electrode is a combination of any electrochemical probe (amperometric, potentiometric or conductimetric) with a thin layer (10 - mm) of immobilised enzyme. History Enzyme electrodes are a type of biosensor that have enzyme as a biological component/5(3).
The peroxidase electrode linked to the peroxidase enzyme works at a low voltage, which prevents interference of other electroactive species in this catalytic reaction. Glucose Biosensors The glucose biosensor (based on probes manufactured by YSI Inc.) is a great example of an electrochemical biosensor.