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Gold-Conjugated Antibodies

Antibodies, also called immunoglobulins, are Y-shaped proteins produced by an immune system to identify specific antigens. Often these antigens are pathogens such as viruses or bacteria which, when recognized by and bound to a corresponding antibody, will trigger white blood cells to destroy the targeted antigen. To prevent destruction of healthy cells or non-harmful agents, antibodies are extremely specific and only bind to an exactly-matched antigen. This specificity has allowed scientists to develop antibodies for many different types of molecules to detect the presence of a wide variety of antigens, such as pathogens in blood or drugs in urine. Although antibodies are extremely small, they can be made visible when conjugated with certain molecules such as gold. 

Gold is biologically inert, yet antibodies attach to it readily. Because of its optical characteristics, gold is an ideal molecule to visualize the complex formed when the antibodies interact with their specific antigens. This ability to visualize the antibody-antigen complex is frequently used in lateral flow assays to detect the presence or absence of certain compounds of interest, such as in drug tests. 

In a competitive lateral flow assay, a biological fluid sample (e.g. blood, saliva, urine) is placed on one end of a strip of nitrocellulose membrane, which conducts the sample along the membrane in a unidirectional flow. As the sample flows towards the opposite end of the membrane, it passes over a field of gold-conjugated antibodies targeting the compound of interest (methamphetamine, for example). If there is no methamphetamine present, the sample will flow across the field of conjugated antibodies, carrying them to the test line, which contains a sequestered version of the compound of interest. The antibodies will be free to bind with the sequestered antigen, aggregating enough gold particles as to become visible in a red line. This indicates a negative test. On the other hand, if there is methamphetamine present in the sample, the antibodies will attach to it and be unable to bind to the antigen conjugates sequestered on the test line. Thus they will not aggregate into a visible line. This absence of color in the test line reveals the presence of methamphetamine. The test is positive.

Pyxis Laboratories has for many years been a leader in providing high-quality protein conjugates to known drugs of abuse, as well as other compounds of interest. Pyxis is now offering gold-conjugated antibodies for the following drug of abuse:
















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