In 1857, British physicist and chemist Michael Faraday used reduction method to prepare colloidal gold from aqueous solution of chloroauric acid. In 1962, Feldherr et al. first proposed the idea of using colloidal gold as a tracer marker for electron microscope. In 1971, Faulk et al. combined rabbit anti-salmonella anti-serum with colloidal gold particles to form gold labeled antibody, which was used to detect the antigen distribution of bacterial surface, indicating that colloidal gold was used as a new colored marker in the field of immunology.
Lateral flow immunochromatography is a new immunocolloid gold labeling technique which is used as a tracer for antigen-antibody reactions. Between colloidal gold particles, by electrostatic action to form a stable colloidal state, also known as gold sol. Colloidal gold labeling is a coating process in which proteins and other polymers are adsorbed to the surface of colloidal gold particles. The adsorption mechanism is that the negative charge on the surface of the colloidal gold particles and the positive charge groups of the protein are adsorbed and firmly bound by electrostatic. Colloidal gold particles with different particle sizes and colors can be easily prepared by reduction method. This spherical particle has a strong adsorption capacity for proteins, and can bind noncovalently with staphylococcus a protein, immunoglobulin, toxin, glycoprotein, enzyme, antibiotic, hormone, bovine serum albumin peptide, etc., thus it becomes a very useful tool in basic research, inspection and quarantine.
The components of LFIA
Sample pad: used for receiving sample
PVC baseplate: the solid phase carrier of test kit
Colloidal gold pad: colloidal gold labeled antibody
Test line: specific antibody or antigen or antigenic analogue
Control line: anti-gold labeled antibody secondary antibody
NC membrane: the carrier of binding protein
Absorption pad: collect the sample flowed from sample pad
Lateral flow immunochromatography technology is one of the four immunomarker technologies, which is widely used in biomedical research fields, especially in diagnostics. This technique has the following characteristics compared with other three labeling techniques, namely luciferin, radioisotope and enzyme. 1) colloidal gold is easy to prepare with low price and low cost; 2) the size of colloidal gold particles can be controlled, the particles can be uniform, double and multiple labeling, and multiple substances can be detected at the same time; 3) the non-specific adsorption of immunocolloidal gold on tissue cells is small, with high specificity and sensitivity; 4) it can be used not only for optical microscope, but also for transmission electron microscope and scanning electron microscope; 5) the colloidal gold itself has a bright wine red color, and the detection results are directly displayed by color. It is easy to judge by naked eyes, without instruments and equipment, and intuitive and reliable. It is especially suitable for the application of the majority of grass-roots units, hospitals, field workers and remote areas. 6) simplify the tedious operation process, greatly shorten the detection time, and reduce the operating error.
Principle of LFIA
Double antibody sandwich method. The colloidal gold was coupled with the specific antibody (Ab1) of the antigen to be tested and deposited on the binding zone. When the sample is added to the sample area, due to capillary action, the sample quickly permeates the binding area, Ab1 with marker is dissolved, and the sample solution moves forward along the membrane strip under the pull of the absorbent tension of the upper material. If the antigen in question is present in the sample, it binds to labeled Ab1 to form ag-ab1. Subsequently, the ag-ab1 complex is captured to form the ab1-ag-ab2 complex when the sample has the detection line region of the capture antibody (generally another epitope specific antibody Ab2 of the antigen to be tested) by solid phase. Some of the samples not bound to Ab1 continue to move forward, and the ab3-ab1 complex is formed when the quality control line area with anti-ab1 resistance (Ab3) is solidified. This method is usually used to detect the analysis of multiple antigen sites, and is often used for the detection of pathogenic bacteria, large molecular proteins, etc.
The colloidal gold was coupled with the specific antibody (Ab1) of the antigen to be tested and deposited in the binding region. The solid phase at the detection area is the antigen to be tested or an analogue of the antigen to be tested. If the sample contains the antigen to be tested, the antigen in the sample and Ab1 with the marker form ag-ab1 complex. Subsequently, when the test area of the antigen to be tested or its analogues is solid phase, the reaction no longer occurs due to competition inhibition, and the color does not show at the detection line. As the sample continued to move forward, ag-ab1 complex was solid phase bound by anti-ab1 antibody (Ab2) at the quality control line to form ab1-ag-ab2 complex, making the quality control line color. This method is suitable for detection of small molecular antigen with single epitope, and is often used for detection of pesticide and veterinary drug residues and illegal drugs.
Introduction of our products
You can find all our products based on the LFIA in link below.