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Principles of rapid detection of new coronaviruses

Views:3     Author:Site Editor     Publish Time: 2020-03-30      Origin:Site

Recently, several companies and departments have promoted the development of kits that can quickly detect new types of coronavirus infections, and discuss the principles behind them.


One is similar to colloidal gold test strips that are now common in influenza virus detection.



Colloidal gold test strips are actually labeled with a colloidal form of gold macromolecules and fixed on a PVC test strip, leaving sample holes, setting detection lines and quality control lines, so that the sample is added to the sample hole. After that, add a few drops of liquid medium, and let the liquid flow to the absorbent pad on the other end of the test strip, and perform chromatography on the test strip, usually 10-15 minutes. After the immune reaction on the test strip occurs, colloidal gold can be seen. Is there a red band at the location, visible to the naked eye, so you know the test result.



At present, two types of colloidal gold test strips have been advertised on the new coronavirus. One is to detect the antigen of the new coronavirus.


This method uses the double-antibody sandwich method, that is, for the same antigen, there are two kinds of antibodies on the test strip, but at different positions on the test strip. The colloidal gold-labeled antibody is one of the antibodies against the antigen, which is on the binding pad of the test strip.



For example, after a sample of throat swab, nasal swab, or alveolar lavage fluid is added to the sample hole, a few drops of flow medium are added. If there is a specific viral antigen in the clinical sample, then the gold on the pad will be bound. Recognize the target antibody to form an antigen-antibody complex. At this time, the flow continues to the direction of the absorbent pad. On the detection line, there is another antibody against the antigen. The epitope recognized by this antibody is not the same as the gold label antibody, so the same antigen can be used by both antibodies at the same time. Identified. At this time, the gold-labeled antibody will be partially intercepted at the detection line, and the color will be developed on the detection line.



Of course, the amount of gold-labeled antibody is definitely surplus, so it will not only be trapped at the detection line, but will continue to flow in the direction of the absorbent pad. At this time, there is a quality control line. Above the line are antibodies specific to gold-labeled antibodies (that is, anti-antibodies, which are essentially antibodies, but the antigenic objects they recognize are also antibodies). Because the quality control line has a very strong ability to recognize gold-labeled antibodies, this line will definitely develop color. This is also the reason for quality control. If this line does not develop color, then the test result is invalid.



Therefore, the judgement of yin and positivity is very simple. Both lines are colored-positive; only the quality control line is colored-negative; except for these two cases, they are invalid experiments.


The two-antibody sandwich method for antigen detection is introduced above, and the other is the detection of IgM antibodies specific to the new coronavirus in patients' blood. This is the colloidal gold test paper for IgM capture method.

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