The specific introduction is as follows:

The working principle of saliva DNA collection cards mainly involves several aspects such as saliva collection, cell lysis, DNA adsorption and preservation. The specific introduction is as follows:

1. Saliva Collection and Cell Enrichment
   • Saliva contains various types of cells, including oral epithelial cells, white blood cells, etc., which carry an individual’s DNA. When saliva is collected on the collection card, these cells are also retained on the card. The collection card is usually made of a special material that can adsorb and retain saliva and cells effectively.
2. Cell Lysis
   • After the saliva sample is collected and dried on the collection card, when the card is processed in the laboratory, a lysis buffer is added. The lysis buffer contains substances such as detergents and enzymes. Detergents can disrupt the cell membrane and nuclear membrane, while enzymes can break down proteins and other substances in the cell, thereby releasing the DNA in the cell nucleus.
3. DNA Adsorption
   • The collection card is composed of a matrix with specific physical and chemical properties. It usually contains materials such as silica gel or cellulose. These materials have a strong affinity for DNA. Under certain conditions, such as in the presence of specific salts and pH environment, the released DNA molecules in the cell will be adsorbed and bound to the surface of the collection card matrix.
4. DNA Preservation
   • The matrix material of the collection card can protect the adsorbed DNA from degradation. It can isolate DNA from external factors such as nucleases, oxygen and moisture that may cause DNA degradation. In a dry state, the activity of nucleases is significantly reduced, and the stability of DNA is enhanced. Therefore, the DNA on the collection card can be stored for a long time under appropriate conditions.
5. DNA Elution and Detection
   • When it is necessary to extract and detect DNA, an elution buffer is added to the collection card. The elution buffer can change the physical and chemical environment of the DNA adsorbed on the collection card, weaken the binding force between DNA and the matrix, so that DNA can be eluted from the collection card. The eluted DNA solution can then be used for various DNA analysis techniques, such as polymerase chain reaction (PCR), gene sequencing, and genetic fingerprinting, to obtain relevant genetic information.