Magnetic transfection complexes are effectively immobilized within an LS cell separation column and are associated with cells after the magselectofection procedure. The magnetic transfection complex PEI-Mag2/DF-Gold/¹²⁵I-pBLuc containing 20 μg of plasmid labeled with the ¹²⁵I isotope was loaded onto the column. The column was placed into the MidiMACS^TM Separator. Jurkat T cells that had been magnetically labeled with CD45 MicroBeads were loaded onto the column in 4 portions of 0.5 mL RPMI media each, and free elution fractions were collected. After 30 minutes of incubation, the column was removed from the separator, and the cells that had been retained were flushed out by firmly applying the plunger supplied with the column using 8 portions of 0.5 mL RPMI media each (Pressure enforced elution fractions). The fractions were centrifuged, and the radioactivity was measured in the supernatants and pellets (Cells) to recalculate the DNA fraction associated with the cells, unbound DNA in supernatant and the total DNA recovered from the column (Supernatant&Cells).