Determination of biological binding reactions by field-induced birefringence measurements

The measurement of the magnetic field-induced transient birefringence was investigated as a novel technique for the monitoring of biological binding reactions. First, a measurement system was set up and tested towards the detection of magnetic nanoparticles (MNP) with different hydrodynamic diameters. Then, the applicability of magnetic field-induced transient birefringence measurements for the detection of biological binding reactions was investigated. MNP conjugated with an antibody against human IgM (hIgM) were used as model probes. The magnetically marked antibodies were incubated with different amounts of IgM. It was found that the mean relaxation time and hence the size of the magnetic probes increase with increasing amounts of added IgM. (C) 2002 Elsevier Science B.V. All rights reserved.