Do you know how does rapid test kit works?

Immunology is a complex subject that contains a lot of professional knowledge. This article aims to introduce you to our products use shortest intelligible language.

In the field of rapid detection, home use usually use colloidal gold method.

Gold nanoparticles are readily conjugated to antibodies, peptides, synthetic oligonucleotides, and other proteins due to the affinity of sulfhydryl (-SH) groups for the gold surface3-5. Gold-biomolecule conjugates have been widely incorporated into diagnostic applications, where their bright red color is used in home and point-of-care test such as the home pregnancy tests

Because the operation is simple, the result is easy to understand, convenient, fast, accurate and other reasons. Colloidal gold method is the main rapid detection method on the market.


Competitive and sandwich assays are the 2 main models in colloidal gold method, They have attracted interest due to their friendly user formats, short assay times, little interferences, low costs, and being easy by operated by non-specialized personnel. This technique is based on biochemical interaction of antigen-antibody hybridization. Our products is composed of four parts: a sample pad, which is the area on which sample is dropped; conjugate pad, on which labeled tags combined with biorecognition elements; reaction membrane containing test line and control line for antigen-antibody interaction; and absorbent pad, which reserves waste. 



1.Assay Principle

Two antibodies binding distinct epitopes present on the virus molecule are used. One (coating antibody) labeled with a colloidal gold nanoparticles and the other (capture antibody) fixed onto surfaces of NC membrane. The coating antibody is in a dehydrated state within the conjugate pad. When standard solution or sample were added onto the sample pad of the test strip, the binder can be instantaneously dissolved upon contact with an aqueous medium containing virus. Then the antibody formed a complex with the virus in the liquid phase and moved forward continuously until it was captured by the antibody fixed on the surfaces of NC membrane, which generated a signal in proportion about the virus concentration. Furthermore, an additional antibody specific to the coating antibody can be used to produce a control signal. The absorbent pad is located at the top to induce by capillarity that enables the immune complex to be pulled to the fixed antibody. A visible color appeared in less than 10 min, and the intensity determines the amount of the virus. In other word, the more virus that was present in the sample, the more noticeable the red band appeared.


Let me briefly explain how these two methods work :

1.Double anti sandwich method

  Double anti sandwich method principle, mainly used for the detection of large molecular weight protein (anti).Two anti are required to target different sites of an antigen.


2. Competition method

 The method of competition refers to the detection method of the antigen coated by the detection line and the antibody of the gold mark of the antigen to be tested.The results of this method are read as opposed to the results of the sandwich method, with one line in the positive and two lines in the negative.


Post time: Dec-03-2019

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