The principle of the early blood glucose strip is photochemical method, which uses the change of color of blood glucose and enzyme reaction to calculate blood glucose value. However, due to too many interference factors, the current commercially available blood glucose strips are all changed to electrochemical methods. The principle of electrochemical method is that blood glucose and enzymes react to generate electric current, and the number of electrons is read to calculate glucose concentration. The advantage of the electrochemical method is that a little blood is enough and the accuracy is high. So the past photochemical methods have been replaced by electrochemical methods.
Electrochemical detection of blood glucose requires electrodes. Currently, two types of electrodes are used to make blood glucose test strips on the market,
- Carbon electrode: The raw material is graphite. Due to the graphite electrode is easily corroded by sweat and cosmetics on the hands, the accuracy will be affected.
- Metal electrode: The raw materials are palladium and gold, which are extremely corrosion-resistant, and their conductivity is 1400 times that of graphite electrodes. It is more accurate than traditional carbon electrodes. However, the cost of metal electrodes is extremely high. At present, only a small number of blood glucose strip on the market are metal electrodes. Because graphite is cheap, it still occupies a large amount in the market.
The principle of blood glucose strip detection of blood glucose is that blood glucose reacts with enzymes, and the source of these enzymes is secreted by genetically recombined microorganisms.
The most common enzymes are as follows,
- GOD: The earliest type of enzyme developed, it is highly specific to glucose and will not react with other carbohydrate. However, the disadvantage of GOD enzyme blood glucose strip is that it is easily interfered by oxygen. Some diseases related to blood oxygen concentration include asthma, smoking, chronic obstructive pulmonary disease and other diseases, which can cause changes in blood oxygen concentration and affect blood glucose test results. In addition, because the GOD enzyme will react with oxygen, the blood glucose strip must be sealed and stored after opening, otherwise the accuracy will be affected.
- GDH: The advantage of GDH enzymes is that they will not be disturbed by oxygen, so the accuracy will not be affected by oxygen. However, the disadvantage of GDH enzyme blood glucose strip is that it easily reacts with other carbohydrate. Some patients include injectable maltose or immunoglobulin, or patients with galactosemia cannot use GDH blood glucose strips.
Due to price factors, the main blood glucose strips on the market are still GOD enzyme blood glucose strips.