Simple dip strip ELISA for airborne estrogenic steroids

An ELISA for the potent estrogenic steroids, ethinyl estradiol (ETED), 17-b eta -estradiol (ED) and estrone (ES) has been developed and used to determi ne the recovery of ED and ETED following spiking from seven filters commonl y used in samplers for ascertaining personal exposure of workers to airborn e biochemicals. Best results were obtained with cellulose nitrate (CN) and polytetrafluoroethylene (PTFE) filters. The assay reagents have also been u sed to develop a simple dip strip assay that can be used to determine the p resence of steroids on the filters. Steroids captured from the air on the s urface of filters within a conventional personal exposure sampler are extra cted with specific antiserum. A spot of hapten-protein conjugate is immobil ised on a small square of CN filter attached to a plastic strip. This is im mersed 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 loca ted 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 inver sely proportional to the amount of steroid originally captured on the filte r. A batch of over 50 samplers can be screened within I h. Spots on strips from filters on which 10 ng of ED, ES or ETED are present can be visually d iscerned from strips from filters where no steroid is present. (C) 2001 Els evier Science B.V. All rights reserved.