Measurement of the susceptibility of paramagnetically labeled cells with paramagnetic solutions

A method of measuring the volumetric magnetic susceptibility, in which magnetically labeled cells or other particles are suspended in a paramagnetic solution of known susceptibility over the poles of a magnet, is presented. If the cells are more magnetic than the solution, they are attracted toward the poles; if they are less magnetic, they are repelled. If they have the same susceptibility as the solution, they do not move. Under this condition, the cells are said to be "isomagnetic" with the surrounding solution. Since the volumetric susceptibility of this solution is known, the susceptibility of the cells is obtained. Using the "isomagnetic" method, the volumetric susceptibilities of test metal powders were determined within +/- 8 X 10(-6) SI units. Yeast, colonic carcinoma, and liver cells, rendered magnetic with erbium chloride, had susceptibilities ranging from 13 to 20 X 10(-6). Particles of articular cartilage treated with erbium chloride were heterogeneous, with susceptibilities ranging between 50 and 125 X 10(-6), while particles of bone had a susceptibility of 560 to 580 X 10(-6). Eukaryotic cells labeled with ferritin attained susceptibilities of less than 1 X 10(-6).