A sensitive manual enzyme immunoassay for thyroxine.

Abstract

We describe an immunoassay for thyroxine in serum. In the assay specific antibody covalently bonded to latex particles is used, along with horseradish peroxidase as the label, and o-phenylenediamine as the chromogen. The flexible protocol is designed for manual execution. Performance is similar to that of the highest-sensitivity thyroxine radioimmunoassays. Results correlate well with radioimmunoassay (r = 0.99, slope = 0.93, y-intercept = 2.4 microgram/liter for 201 samples) and an automated enzyme immunoassay (r = 0.97, slope = 0.99, y-intercept = 4.7 coefficients of variation are less than 7.2% over the entire useful range of the assay (20--240 microgram/liter). The limit of detection is less than 94 pg/tube at 20 microgram/liter. Only D-thyroxine is known to interfere with serum assays. This assay has no discernible protein effect from 40 to 80 g of protein per liter, unlike many thyroxine radioimmunoassays. Serum preservatives known to be peroxidase inhibitors do not adversely affect assay performance because of the 56-fold dilution in the final assay mixture. Hemolyzed serum and EDTA-treated plasmas are unsuitable for this assay.

Novel and sensitive noncompetitive (two‐site) enzyme immunoassay for haptens with amino groups

“…13 (SD) pg/L (range, 78-114). These results were consistent with the previous reports of competitive immunoassays (7,14).…”

Immobilization of Peroxidase on SiO2 Surfaces with the Help of a Dendronized Polymer and the Avidin‐Biotin System

“…The non‐covalent denpol‐mediated enzyme immobilization on SiO 2 was investigated by using horseradish peroxidase (HRP) as model enzyme because of its good stability over a wide pH range and in different buffer solutions,26 and due to it's easy quantifiability via spectrophotometry down to the p M range 27–30. The immobilization studies were carried out with the polycationic second generation denpol de‐ PG2 which on average had about 1000 repeating units ( P n = 1000) (Scheme ).…”

Variation in Enzyme‐linked lmmunosorbent Assay (ELISA) Components to Lower Sulfathiazole Detection Limits

“…For these reasons, we chose to compare TMB with OPD in ELISAs. ABTS approved to be as effective as OPD in our study, but the toxicity of ABTS is uncertain (Sigma ImmuNotes, 1991;Hosoda et al, 1986;Schall et al, 1978).…”