Preparation of magnetic particle antibodies for radioimmunoassay and immunoradiometric assay of thyroid related hormones

Silanized magnetic particles have been developed by means of a number of different methods for coupling antibodies for use in radioimmunoassay (RIA) and immunoradiometric assay (IRMA) of thyroid related hormones. Carbodiimide, glutaraldehyde, glutaric anhydride and spacer-arms coupling methods were studied for immobilization of triiodothyronine (T3), thyroxine (T4) and thyroid stimultating hormone (TSH) antibodies on magnetic particles, respectively. The effect of the magnetic particle preparation on the couplings was discussed. The influence of coupling conditions on the preparation of magnetic particle antibodies and the assay performance was also investigated. The storage stability and reproducibility of the magnetic particla T3, T4 and TSH antibodies were good enough for use in total T3, total T4 RIA and TSH IRMA. A comparison of five types of magnetic particles from different sources for coupling TSH antibody for TSH IRMA application was made. Silanized magnetic particles and other types of particles showed comparable sesults. Five TSH antibodies, inluding two polyclonal and three monoclona; antibodies coupled to silanized magnetic particles respectively, were used in TSH IRMA. It was found that each of them and a commercial monoclonal TSH antibody as label formed good sandwich partners and gave a high signal to low levels of TSH. (author). 13, refs., 6 tabs