Wash-free immunomagnetic detection for serum through magnetic susceptibility reduction

In this study, a platform for wash-free immunomagnetic detections is discussed. The reagent is a magnetic fluid composed of biofunctionalized magnetic particles dispersed in water. The assay instrument is a mixed-frequency magnetosusceptometer. The mixed-frequency ac magnetic susceptibility χac of the magnetic reagent is reduced, as a result of the formation of magnetic clusters via the association among magnetic nanoparticles and a specific biotarget. The immunoassay detection of proteins in water, such as aqueous c-reactive protein, is characterized and is compared to that in serum. These observations demonstrate the advantages of high convenience, high sensitivity, and high specificity for χac-reduction immunomagnetic detection.