A disposable tear glucose biosensor--part 3: assessment of enzymatic specificity.
BACKGROUND
A concept for a tear glucose sensor based on amperometric measurement of enzymatic oxidation of glucose was previously presented, using glucose dehydrogenase flavin adenine dinucleotide (GDH-FAD) as the enzyme. Glucose dehydrogenase flavin adenine dinucleotide is further characterized in this article and evaluated for suitability in glucose-sensing applications in purified tear-like saline, with specific attention to the effect of interfering substances only. These interferents are specifically saccharides that could interact with the enzymatic activity seen in the sensor's performance.


METHODS
Bench top amperometric glucose assays were performed using an assay solution of GDH-FAD and ferricyanide redox mediator with samples of glucose, mannose, lactose, maltose, galactose, fructose, sucrose, and xylose at varying concentrations to evaluate specificity, linear dynamic range, signal size, and signal-to-noise ratio. A comparison study was done by substituting an equivalent activity unit concentration of glucose oxidase (GOx) for GDH-FAD.


RESULTS
Glucose dehydrogenase flavin adenine dinucleotide was found to be more sensitive than GOx, producing larger oxidation currents than GOx on an identical glucose concentration gradient, and GDH-FAD exhibited larger slope response (-5.65 × 10(-7) versus -3.11 × 10(-7) A/mM), signal-to-noise ratio (18.04 versus 2.62), and linear dynamic range (0-30 versus 0-10 mM), and lower background signal (-7.12 versus -261.63 nA) than GOx under the same assay conditions. GDH-FAD responds equally to glucose and xylose but is otherwise specific for glucose.


CONCLUSIONS
Glucose dehydrogenase flavin adenine dinucleotide compares favorably with GOx in many sensor-relevant attributes and may enable measurement of glucose concentrations both higher and lower than those measurable by GOx. GDH-FAD is a viable enzyme to use in the proposed amperometric tear glucose sensor system and perhaps also in detecting extreme hypoglycemia or hyperglycemia in blood.
Biodesign Institute, Arizona State University, Tempe, Arizona 85287-9709, USA.
Kenneth
K
Lan
Kenyon
K
McAferty
Pankti
P
Shah
Erica
E
Lieberman
Dharmendra R
DR
Patel
Curtiss B
CB
Cook
Jeffrey T
JT
La Belle
D015374:Biosensing Techniques; D004563:Electrochemistry; D005947:Glucose / Q000032:analysis*; D042843:Glucose 1-Dehydrogenase / Q000032:analysis*; D005949:Glucose Oxidase / Q000032:analysis*; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio
D042843:Glucose 1-Dehydrogenase; D005949:Glucose Oxidase; D005947:Glucose