Two virus detection technologies, both of which are electronic technologies

    Previously, the common method for detecting viruses was to culture and separate organisms and their cells, and then observe them under a microscope. This usually takes 1 to 2 weeks, and this method cannot be used for POCT (point-of-care testing).

    Currently, there are two main detection principles used in virus detection methods for POCT (Figure 1). One is the antigen-antibody reaction, and the other is a method that utilizes the complementarity of DNA and RNA.

Figure 1: There are two main methods for detecting viruses. There
are two main methods for detecting influenza viruses. One is to screen and fix a protein on the surface of the virus through antigen-antibody reaction, and then test it through fluorescent labeling. The other is to amplify RNA for detection. Currently, the most commonly used method is the immunochromatography method that uses antigen-antibody reaction, but this method has low sensitivity, and methods that can achieve high sensitivity are being developed.

    Antigen-antibody reaction refers to the reaction in which specific proteins (antibodies) of organisms and specific proteins (antigens) of bacteria and viruses from the outside selectively bind to each other like a key and a lock. Using this principle, only specific viruses can be separated from solutions mixed with various substances and cells such as blood. By adding fluorescent dyes or other markers to antibodies and then irradiating them with ultraviolet light, the presence and amount of viruses can be inferred from the intensity of fluorescence.

    The most common method of this type is immunochromatography. However, since this method does not involve culture and amplification, it has the problem of low sensitivity and inability to detect viruses when there are few viruses in the sample. Detection technology based on electronic technology is one of the promising candidates for significantly improving sensitivity.

    Another detection method that uses DNA complementarity is a method that directly uses cell division or the reproduction of viruses in cells. DNA is composed of two single strands, each of which is a "template" for the next new strand. The template of the DNA or RNA to be tested is added with a specific synthase and a DNA fragment as a sample, and the DNA or RNA can be replicated in large quantities based on the template. The representative method is the PCR method. The recent development of POCT using DNA analysis technology mainly depends on the development of the PCR method.

    However, this method has a disadvantage, that is, DNA will have more or less errors when it is replicated, that is, gene mutations will occur. The more DNA and RNA are amplified, the more such errors there will be. Therefore, when you want to know the exact DNA base sequence, you need to use technology that can detect DNA without amplification. In this way, electronic technology has its place.