Determination method of steroid anabolic hormone drug residue analysis technology (5)

(6) Immunoassay (IA)

Immunoassay is actually a special analysis method that uses antibodies or antigens as analytical reagents
.

Immunoassay methods include enzyme-linked immunoassay (ELISA), radioimmunoassay (RIA) and colloidal gold immunochromatographic analysis (GICA).

1) Radioimmunoassay (radioimmunoassay, RIA)

RIA is an in vitro microanalysis method of radioisotopes that utilizes the competitive binding between the antigenic substance to be measured and its label (labeled antigen) and the specific antibody.
It is seldom used because of its radioactive hazard to the human body
.

Xu Meiyi and others used the RIA method to detect the residual amounts of growth hormone, estradiol , progesterone, and testosterone in the muscles of farmed and wild cobia

2) Enzyme-linked immunosorbent assay (ELISA)

ELISA uses the characteristic of specific chimerism between antigen and antibody to detect specimens
.

Because the antigen or antibody bound to a solid carrier (usually a plastic well plate) can still have immunological activity, after designing its chimeric mechanism, with the color reaction of enzymes, it can show whether the specific antigen or antibody is present, and Quantitative analysis using the shade of color

A.
Indirect competitive ELISA method

Peng et al.
established an indirect competitive ELISA method for detecting medroxyprogesterone acetate in pork
.

Use carbodiimide and mixed acid anhydride method to immunize the drug with bovine serum albumin (BSA) to obtain antibodies

B.
Direct competition ELISA method

Jiang et al.
also established a direct competitive enzyme-linked immunosorbent assay (dcELISA) method for detecting 19-nortestosterone in bovine edible tissues
.

Highly specific monoclonal antibodies (mAbs) are produced through the cell fusion process, and a heterologous direct competition ELISA method based on mAbs has been established

3) Colloidal gold immunochromatographic assay (GICA)

GICA is a new type of immunolabeling technology that uses colloidal gold as a tracer to apply to antigen and antibody
.

Colloidal gold is made of chloroauric acid (HAuCl ₄ ) under the action of reducing agents such as white phosphorus, ascorbic acid, sodium citrate , tannic acid, etc.

Liu Liqiang developed a competitive colloidal gold immunochromatographic test strip for the detection of 19-nortestosterone residues
.

The detection line and the quality control line were sprayed with 0.

Figure 8-7 Synthesis of 19-nortestosterone artificial antigen using EDC method

Wei et al.
established a colloidal gold detection method for norethindrone
.

Hollow silica particles with amino functional groups are used to immobilize gold particles, and horseradish peroxidase (HRP)-labeled secondary antibodies are used to detect norethindrone antigen.

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