Can BioMag be used for positive and negative selection?

BioMag can be used for both positive and negative selection. However, QIAGEN recommends negative selection for most cell separation applications. During negative selection, BioMag particles are attached to the unwanted component of the mixture and the cells or molecules of interest are left behind after the magnetic separation has been performed. The resulting supernatant is then enriched for the target cells/molecules. QIAGEN recommends this procedure for cell separation to achieve naïve, untouched target cells. When BioMag is used to pull out only the target cells/molecules out of solution and the supernatant is discarded, this is referred to as positive selection. In positive selection, only the target cells/molecules will be attached to the BioMag and all other contaminating cells/molecules are discarded resulting in a pure suspension of the target components. This procedure can be performed using BioMags, however the BioMag particles will remain attached to the target analyte or cell. Although this is not a problem for molecular biology applications (e.g. subsequent RNA or DNA extraction from cells), the presence of BioMag particles may interfere with FACS signal / interpretation if positively selected cells are used in fluorescent flow cytometry.