The use of coated paramagnetic particles as a physical label in a magneto-immunoassay

An ideal label for use in an immunoassay would require no further chemical or electromagnetic stimulation prior to its detection and would be free fro m interference from the sample matrix. Micron sized paramagnetic particles are able to perturb magnetic fields. This perturbation can be directly dete cted using a suitable electronic device and is independent of the sample ma trix. In this study coated paramagnetic particles were used as a physical l abel in a non-competitive solid phase 'sandwich' assay for the detection of human transferrin. The transferrin acted as a 'biological bridge' allowing a dose dependant immobilization of the paramagnetic particles to a polyeth ylene terephthalate solid phase. Quantitation of the paramagnetic label was achieved using an electronic detection system allowing a linear dose respo nse with a femtomolar detection lin-Lit (260 fmol). (C) 2001 Elsevier Scien ce B.V. All rights reserved.