Quality determination of magnetic labeling reagents by cell magnetophoresis measurement

Abstract

Access to high affinity, high magnetic susceptibility antibody-nanoparticle combinations specific to target cell populations is important for isolation of low frequency cells or cells expressing low level of antigenic markers. A specialized instrument (Cell Tracking Velocimeter, CTV) to measure single cell magnetophoretic mobility (MM) on large cell sample sizes (in thousands) was developed in our laboratories to determine effects of magnetic cell labeling. First, using a hematopoietic progenitor cell line, KG-1a (ATCC, Manassas, VA) seven different CD34 monoclonal antibody and nanoparticles combinations were tested for highest MM: Progenitor KitTM (Miltenyi Biotec, CA) showed the highest MM (2.14±0.31 mm3/T-A-s with 95% confidence). Second, the specificity of the Kit for labeling of progenitor cells in clinical leukapheresis samples was determined by comparing CTV-measured frequency of cells moving in the magnetic field with the flow cytometry (FCM) measured frequency of cells expressing CD34 marker (n=6, r2=0.87). Third, clinical leukapheresis samples labeled with the Kit were enriched for CD34+ cells by continuous magnetophoresis and assayed by CTV and FCM. The results show that the cell MM and the performance of the magnetic separation protocol depend on selection of the magnetic labeling reagent.