Use of solid phase biochemistry for potentiometric enzyme immunoassay of oestradiol-17 beta - preliminary report.

The present report gives preliminary results of a new sensitive method for potentiometric determination of oestradiol-17 beta in solution, as an application of the competitive enzyme-linked immunoassay technique. Anti-oestradiol-17 beta antibodies are immobilized on a pig skin gelatin membrane, which is incubated with peroxidase-labelled steroid and oestradiol. After fixation of the membrane onto the sensor of an iodide sensitive electrode, the enzymatic activity was evaluated in the presence of hydrogen peroxide and iodides, the electrode potential being a function of hapten concentration in the solution. The purpose of this preliminary work was to determine the optimized conditions for specificity and sensitivity of the antibody-coated membrane in the presence of peroxidase-labelled oestradiol and oestradiol, and to eliminate possible interferences due to adsorption or ionic fixation of enzyme-labelled steroid. The first tests carried out with oestradiol standard solutions gave satisfactory results at levels ranging from 57 pmol/l to 9.2 nmol/l, suggesting that this new procedure should find application in the determination of oestradiol-17 beta in biological fluids.