Colloidal Gold and Paramagnetic Labels in Lateral Flow Assay Detecting Ricin
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Kolloidinen kulta ja paramagneettinen leima risiiniä mittaavassa lateraalivirtaustestissä
Lateral flow assay is an antibody-based, fast, easy to use, affordable and accurate measurement method for the detection of small quantities of substances. The analytes are detected with antibody-label complex and the label can be detected. In this research the relatively new label, a paramagnetic iron oxide particle, is examined and its behaviour in lateral flow assay is compared with a commonly used label, colloidal gold. At the same time, the performance of a magnetic particle reader, MIAU (Magnasense Technologies, Finland), is evaluated. Tests were prepared for ricin, which is a toxic protein concentrated on the seed of Ricinus communis plant. In this study, the lateral flow test strips were prepared and used to measure different concentrations of two types of ricin samples: the ricin preparation extracted from the seeds and a pure ricin A-chain. The detection limits for both label types were almost the same: for the ricin preparation and A-chain the paramagnetic particles showed 56 ng/ml and 600 ng/ml and the colloidal gold 31 ng/ml and 480 ng/ml, respectively. The linear range of magnetic measurement was significantly wider than in colloidal gold measurements. Also, the re-measurements after four weeks with paramagnetic particles resulted in practically the same as immediately after the test run.