Simple dip strip ELISA for airborne estrogenic steroids

An ELISA for the potent estrogenic steroids, ethinyl estradiol (ETED), 17-beta-estradiol (ED) and estrone (ES) has been developed and used to determine the recovery of ED and ETED following spiking from seven filters commonly used in samplers for ascertaining personal exposure of workers to airborne biochemicals. Best results were obtained with cellulose nitrate (CN) and polytetrafluoroethylene (PTFE) filters. The assay reagents have also been used to develop a simple dip strip assay that can be used to determine the presence of steroids on the filters. Steroids captured from the air on the surface of filters within a conventional personal exposure sampler are extracted with specific antiserum. A spot of hapten-protein conjugate is immobilised on a small square of CN filter attached to a plastic strip. This is immersed in the sampler solution where unbound antibodies bind to the hapten on the spot. The strips are then transferred to a 96 well filter plate located within a filter manifold. Following washing, strips are incubated with alkaline phosphatase-labelled second antibody and the spots were developed by addition of substrate. The intensity of the developed blue spot is inversely proportional to the amount of steroid originally captured on the filter. A batch of over 50 samplers can be screened within 1h. Spots on strips from filters on which 10ng of ED, ES or ETED are present can be visually discerned from strips from filters where no steroid is present.