TY - JOUR A1 - Ettlinger, Julia A1 - Schenk, Jörg A. A1 - Micheel, Burkhard A1 - Ehrentreich-Förster, Eva A1 - Gajovic-Eichelmann, Nenad T1 - A direct competitive homogeneous immunoassay for progesterone - the Redox Quenching Immunoassay JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - A direct competitive amperometric immunoassay format for the detection of haptens and proteins was developed. The method is based on the quenching of electroactivity of ferrocenium, which is coupled to the antigen and used as the primary reporter, upon binding to a monoclonal anti-ferrocenium antibody, which is coupled to the detection antibody and used as a secondary reporter. A separation-free progesterone immunoassay with a lower detection limit of 1 ng?mL-1 (3.18 nmol?L-1) in 1?:?2 diluted blood serum was realised by combining two bifunctional conjugates, a ferrocenium-PEG-progesterone tracer and a bioconjugate of one anti-progesterone and one anti-ferrocenium antibody. The immune complex is formed within 30 s upon addition of progesterone, resulting in a total analysis time of 1.5 min. KW - Immunoassay KW - Amperometry KW - Ferrocene KW - Progesterone Y1 - 2012 U6 - https://doi.org/10.1002/elan.201200107 SN - 1040-0397 VL - 24 IS - 7 SP - 1567 EP - 1575 PB - Wiley-VCH CY - Weinheim ER -