Magnetophoretic mobilities correlate to antibody binding capacities

Abstract

Methods A methodology and a mathematical theory have been developed, which allow quantitation of the expression levels of cellular surface antigens using immunomagnetic labels and cell tracking velocimetry (CTV) technology. Results Quantum Simply Cellular (QSC) microbeads were immunomagnetically labeled with anti‐CD2 fluorescein isothiocyanate (FITC) antibodies and anti‐FITC MACS paramagnetic nanoparticles. Magnetophoretic mobility has been defined as the magnetically induced velocity of the labeled cell or microbead divided by the magnetophoretic driving force, proportional to the magnetic energy density gradient. Discussion Using computer imaging and processing technology, the mobility measurements were accomplished by microscopically recording and calculating the velocity of immunomagnetically labeled QSC microbeads in a nearly constant magnetic energy gradient. A calibration curve correlating the measured magnetophoretic mobility of the immunomagnetically labeled microbeads to their antibody binding capacities (ABC) has been obtained. Conclusion The results, in agreement with theory, indicate a linear relationship between magnetophoretic mobility and ABC for microbeads with less than 30,000 ABC. The mathematical relationships and QSC standardization curve obtained allow determination of the number of surface antigens on similarly immunomagnetically labeled cells. Cytometry 40:307–315, 2000