Optical immunosensor for fast and sensitive detection of DDT and related compounds in river water samples

9 pages, 5 figures.-- PMID: 16870422 [PubMed].-- Available online Jul 25, 2006.A surface plasmon resonance (SPR) based immunosensor has been developed for the monitoring of environmentally persistent pollutants like DDT, its metabolites and analogues in real water samples. A reusable immunosurface is provided via the covalent attachment of the analyte derivative to a self-assembled alkanethiol monolayer formed onto the SPR gold-thin layer. The regeneration of the sensor surface allowed the performance of 270 assay cycles within an analysis time of 20 min for each assay cycle. Immunoassays based on a binding inhibition format were performed by using two monoclonal antibodies (MAbs) with different selectivity. Low limits of detection (LODs), in the sub-nanogram per litre range, were attained for DDT-selective (15 ng L−1) and DDT group-selective immunoassays (31 ng L−1). Both assays were carried out in spiked river water samples without significant effect of the matrix. SPR measurements were validated using gas-chromatography–mass spectrometry. The comparison between methods was in good agreement showing an excellent correlation coefficient (r^2 = 0.995). The SPR analysis of DDT proved to be three times more sensitive than colorimetric ELISAs without the need of labelling and a much lower time of response. Our SPR biosensor portable platform (β-SPR) is already commercialised by the company SENSIA, S.L. (Spain).This work has been supported by CSIC project, DESREMOL (2004 20FO280).Peer reviewe