Nitrocellulose filter membrane (NC membrane for short) is used as the carrier of C / T line in colloidal gold test paper. It is also the place where the immunoassay reaction occurs. It is mostly used for the assay definition of residue analysis. NC membrane is one of the most important consumables in biological experiments.

The purchased raw material nitrocellulose particles are a very common organic chemical, dissolved to form a mixed slurry, in the slurry, by adding a certain proportion of reagents to adjust the properties of the final formed film, generally mainly contains A buffer system in which high molecular polymers / salt ions / molding agents are dissolved. The solution formulations added by different manufacturers are not the same, resulting in differences in
products.

The prepared homogenate passes through the roller to form a thin film, which is spread on a very smooth flat carrier. The process is very similar to papermaking.

When the forming agent in the homogenate begins to volatilize, the film is gradually dried and formed. At the same time, due to the relatively high temperature in this process, some manufacturers took the form of forming in a closed cavity in the process, and at the same time supplementing the formula solution to avoid the evaporation of some active ingredients.

The film produced by the above steps is a very wide product. The width is directly related to the size of the drum. The larger the drum, the more convenient the production, but the higher the cost of the equipment. The wide film must be cut to become our purchase. The film is 25mm or 18mm (or 20mm) wide, and the length of the finished roll film and the wide film are the same. In theory, the manufacturer can be cut to any width you need, but this will cause waste of raw materials and The increase in labor costs, and later in the process of coordination with test strip manufacturers, the overall material cost and production convenience basically determined the width mentioned above, based on this standard.

The binding principle of protein and membrane, known binding force includes hydrophobic force H bond electrostatic force, etc. The exact binding principle is not clear, mainly supported by hypothesis. There are two main hypotheses:
1) First, the two are combined by electrostatic force, and then by H bond and hydrophobic interaction to maintain long-term bonding.
2) First, the two are combined by hydrophobic action, and then by electrostatic action to maintain long-term bonding.
Both hypotheses indicate that the combination process is divided into two steps, the first combination and the later combination. Due to the unclear combination principle, the work in this area is very dependent on practical experience.

Membrane pore size:
Some technicians tend to use membrane pore size to distinguish different membranes, but please note that this is only limited to products of the same manufacturer. If they are products of different manufacturers, this comparison is meaningless. The relationship between membrane pore size and chromatography velocity has been described above. As the pore size of the membrane decreases, the actual available surface area of the membrane increases, and the amount of membrane-bound protein also increases. The parameter to estimate the surface area is the surface area ratio (the ratio of the actual available surface area to the flat area of the membrane used).

In addition, the smaller the pore size of the membrane and the lower the chromatographic velocity, the longer the time for the gold standard compound to pass through the T line and the more sufficient the reaction.

Based on the above two points, the conclusion is that the smaller the membrane pore size, the higher the sensitivity. But at the same time, it also slows down the running speed and increases the chance of non-specific binding, that is, the higher the false positive. Therefore, according to the test results, select a suitable membrane for the actual project and find a suitable balance.

Immunoassay; IA is also called immunoassay. Refers to the method of determining trace substances in a sample by immunological methods. It is more sensitive than the chemical ultra-micro method history, and can detect trace substances containing Pg in the sample. For enzymes, hormones, proteins, and other substances or elements. 

There are many methods of immunoassay, such as indirect agglutination reaction, complement binding test, radioimmunoassay, pregnancy test, radial diffusion, immunoelectrophoresis, Ramon flocculent reaction, Prausnitz-reaction, passive skin allergic reaction, toxin neutralization reaction, Rocket immunoelectrophoresis.

PALL (United States)
MILLIPORE (USA), M135 (both with and without backing) M180 (both with and without backing)
WHATMAN and SS, Puraband impuraband
SARTORIUS (Germany), CN140
Yineng (domestic), 8um 6um
Tide (domestic) 8um 6um
MDI (India), 8um 6um
Ealon (China)
TEST (China)
BALLYA (China)

The main features of domestic membrane are low cost and performance close to some imported membranes. After some targeted optimization, they can be used in the production of target pregnancy test products. But not all factories can easily purchase this optimization work. The localization of membrane is a trend, but import manufacturers still face great problems to achieve localization, among which the relocation of plant equipment is a very big problem.

Ballya is committed to the research of biological sciences and has his own profound experience and experience in the use of NC membranes. Using NC membranes, Ballya has successfully developed a variety of rapid test kits for dairy products, honey, aquatic products, pesticides, adulteration, pet diseases and livestock diseases. In the future, Ballya will continue to conduct more in-depth research on more aspects of testing.