The main components of the cell-free DNA blood collection tube usually include the following categories:

EDTA (Ethylenediaminetetraacetic Acid): This is one of the most commonly used anticoagulants, which can form stable chelates with calcium ions in the blood, preventing blood coagulation and facilitating subsequent extraction and analysis of cell-free DNA.
Heparin: It is also an effective anticoagulant that inhibits the formation of thrombin by enhancing the activity of antithrombin III, thereby preventing blood coagulation. However, heparin may have some interference with some downstream molecular biology experiments, and caution should be exercised when using it.

Guanidine salts: Such as guanidine hydrochloride and guanidine isothiocyanate, have strong denaturing effects, can destroy the cell structure, and inactivate intracellular nucleases, thereby protecting cell-free DNA from nuclease degradation and ensuring the integrity of the DNA.
Protease inhibitors: Can inhibit the activity of various proteases in the blood, preventing the degradation of cell-free DNA by proteases. Common protease inhibitors include PMSF (Phenylmethylsulfonyl fluoride) and AEBSF (4-(2-Aminoethyl)benzenesulfonyl fluoride hydrochloride).

Surfactants: Such as sodium dodecyl sulfate (SDS) and Triton X-100, can disrupt the lipid bilayer of the cell membrane, causing cell lysis and releasing cell-free DNA. At the same time, they can also help remove protein and other impurities in the blood, improving the purity of cell-free DNA.

Buffer: Such as Tris-HCl buffer, can maintain the stability of the pH value in the blood collection tube, provide a relatively stable environment for cell-free DNA, and ensure its stability during storage and transportation.
Nucleic acid co-precipitant: Some blood collection tubes may add nucleic acid co-precipitants, such as glycogen and linear polyacrylamide, which can help DNA better precipitate during the extraction process of cell-free DNA and improve the recovery rate of DNA.