Explain the principles of operation of test strips and biosensors for measuring the concentration of glucose in blood and urine, with reference to glucose oxidase and peroxidase enzymes

Sourav PanNovember 1, 2024

Answered

Test strips and biosensors are widely used for measuring glucose concentrations in blood and urine. Both rely on biochemical reactions involving the enzymes glucose oxidase and peroxidase to detect and quantify glucose levels. Here’s an explanation of how they operate:

1. Principles of Operation of Glucose Test Strips

Glucose test strips are commonly used for quick and convenient glucose testing, especially for individuals with diabetes. They typically work as follows:

• Enzyme Reaction: Test strips contain glucose oxidase, an enzyme that specifically catalyzes the oxidation of glucose in the sample (blood or urine). When glucose oxidase interacts with glucose in the sample, it converts glucose to gluconic acid and produces hydrogen peroxide (H₂O₂) as a byproduct.
• Role of Peroxidase: The strip also contains peroxidase, an enzyme that reacts with the hydrogen peroxide produced. Peroxidase catalyzes a reaction between hydrogen peroxide and a color-changing dye (often incorporated into the strip). As hydrogen peroxide breaks down, it oxidizes the dye, causing a color change that indicates the presence and concentration of glucose.
• Color Change and Interpretation: The intensity of the color change on the strip correlates with the glucose concentration in the sample—the more glucose present, the greater the production of hydrogen peroxide, leading to a more intense color. This color change can be visually matched to a chart on the packaging to estimate glucose levels, or in some cases, read by a digital meter that interprets the color intensity.

2. Principles of Operation of Glucose Biosensors

Glucose biosensors are electronic devices that offer precise glucose measurement, typically using an electrochemical detection method. They also rely on glucose oxidase but employ electrodes to detect the biochemical reaction’s output.

• Enzyme Reaction in Biosensor: Similar to test strips, glucose biosensors contain glucose oxidase. When a blood sample is applied, glucose oxidase catalyzes the oxidation of glucose to gluconic acid, generating hydrogen peroxide.
• Electrochemical Detection: In a biosensor, the hydrogen peroxide produced is not reacted with a color-changing dye but instead detected by an electrode within the device. The electrode measures the current generated by the oxidation of hydrogen peroxide, which is proportional to the concentration of glucose in the sample.
• Digital Display of Glucose Level: The biosensor converts the electrical signal into a digital readout that displays the glucose concentration in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). This precise quantification allows for more accurate monitoring and better diabetes management.

Comparison and Summary

• Glucose Test Strips use glucose oxidase and peroxidase to produce a color change in response to glucose, allowing for a quick, visual estimation of glucose levels.
• Glucose Biosensors use glucose oxidase to generate an electrochemical signal directly proportional to glucose concentration, giving a precise digital reading.

Both methods employ glucose oxidase due to its specificity for glucose, and they differ mainly in how they measure the reaction products, with test strips focusing on a colorimetric approach and biosensors on electrochemical detection.