What is Colloidal Silver?

The colloidal gold method is made of chloroauric acid (HAuCl4) under the action of reducing agents such as white phosphorus, ascorbic acid, sodium citrate, tannic acid, etc., and can be polymerized into gold particles of a certain size, and becomes a stable colloidal state due to static electricity. Forms a negatively charged hydrophobic gum solution, which becomes a stable colloidal state due to electrostatic action, so it is called colloidal gold. Colloidal gold is also an ideal immunomarker in immunoelectron microscopy. ^[1]

Colloidal gold

Colloidal gold technology has the advantages of convenience, speed, specific sensitivity, strong stability, no need for special equipment and reagents, intuitive results judgment, etc., so it is particularly suitable for the majority of grass-roots inspectors as well as large-scale inspections and large-scale censuses. And broad application prospects. ^[2]

Measure 200ml of ultrapure water with a volumetric flask and add it to a 500ml Erlenmeyer flask. Place the Erlenmeyer flask on the heating plate of a magnetic heating stirrer, put a magnetic stirrer, and open the stirring knob to an appropriate speed. Pipette 2ml of 1% chloroauric acid solution into the above 200ml ultrapure water, stir for 1min, turn off the stirring knob, turn on the heating knob, and heat to boiling. Turn on the stirring knob to an appropriate speed, and quickly add it through a microporous membrane filter. 0.8% 1% trisodium citrate solution, the solution changed from gray to black and finally red within 2 minutes, and continued heating and stirring for 10 minutes. Turn off the heating knob, stir to room temperature at an appropriate speed, make up to 200ml, and store at 4 ~ C. ^[3]

Common immunocolloidal gold detection techniques: (1) Cellular smears or tissue sections of immunocolloidal gold microscopy staining can be stained with colloidal gold-labeled antibodies, or can be enhanced with silver developer on the basis of colloidal gold labels. Labeling, so that reduced silver atoms are deposited on the surface of the labeled gold particles, can significantly enhance the sensitivity of colloidal gold labeling. (2) The immunocolloidal gold electron microscope staining method can use colloidal gold-labeled antibodies or anti-antibodies to bind negatively stained virus samples or tissue ultrathin sections, and then perform negative staining. Can be used for observation of virus morphology and virus detection. Dot immunogold diafiltration method (3) Apply a microporous filter (such as a membrane) as a carrier, first spot the antigen or antibody on the membrane, add the sample to be tested after blocking, and wash the corresponding antigen with colloidal gold-labeled antibody after washing. Or antibodies. (4) Colloidal gold immunochromatography fixes specific antigens or antibodies on the membrane in a strip, and colloidal gold labeling reagent (antibody or monoclonal antibody) is adsorbed on the binding pad. When the sample to be tested is added to the test strip After the sample pad at one end is moved forward by capillary action, the colloidal gold-labeled reagent on the binding pad is dissolved and reacts with each other. When it moves to the area of the fixed antigen or antibody, the conjugate of the test substance and the gold standard reagent reacts with it. Specific binding occurs and is trapped, aggregates on the detection band, and the color development result can be observed by the naked eye. The method has been developed into a diagnostic test strip, which is very convenient to use.