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Quantitative measurement of triiodothyronine (T3)

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Competitive Tests

Radioimmunoassay techniques are used in vitro for the quantitative measurement of triiodothyronine (T3). It depends on competition between T3 (red) present in the sample and 125I-labelled T3 (orange) for a limited number of binding sites on a sheep anti-T3 antibody (blue) bound to magnetisable polymer particles (Figure 1).

Competitive Tests
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Figure 1: Radioimmunoassay: quantitative measurement of triiodothyronine (T3).

Separation of the antibody-bound fraction is effected by magnetic separation, followed by decanting of the supernatant.

The amount of tracer (radiolabel or fluorescent) bound is inversely proportional to the concentration of T3 present.

In competitive test, utilisation of large particles (> 1.2 µm) is preferable and allows a better signal or sensitivity.

The Estapor® Magnetic Microspheres are, in fact, super paramagnetic materials. The magnetization of the microspheres increases with the applied magnetic field and falls back to zero when the field is removed.

From this point, the microspheres demagnetize and redisperse easily. This property allows efficient washing steps, low background and good reproducibility.

Our Magnetic Microspheres are perfectly suited for immunoassays applications:

Adrenal/pituitary Cortisol
Anaemia Ferritine, Folate, Vit B12, EPO
Bone metabolism Intact PTH
Diabetes Insulin
Drug of abuse (DOA) Cocaine, morphine, THC
Fertility Beta-HCG, LH, FSH, Estradiol, Progesterone, Testosterone
Thyroid T3, T4 (Free, Total)

Allergy Ig E
Auto-immune ANA, ds, ADN Ab
Blood virus HAV, HBV (HBs,HBe, HBc), HCV, HIV
Cancer PSA (prostate)
Cardiac markers FABP, proBNP, Troponin, Digoxin, CKMB, Myoglobin
Infectious diseases CMV, Rubella, Toxoplasma
Inflammation IL-6

For CLIA development, SuperParamagnetic microspheres with different surfaces (plain, COOH, NH2, CH2Cl, OH, tosyl, or bioactivated), different sizes (0.30-2.60 µm), and different ferrite contents (10 – 70%) are required.