Schematic representation of the magselectofection procedure. (A) A vector, viral or nonviral, is associated with magnetic nanoparticles. In this manner, one can immobilize the vector on magnetic cell separation devices, such as shown here on a magnetic cell separation column from Miltenyi Biotec. (B) Magnetic particles binding specifically to target cells by virtue of affinity ligands bound to the particle surface are used to magnetically label target cells. The cells are then loaded to the vector-modified cell separation device while it is exposed to a magnetic field and are thus retained. Nontarget cells are not retained and are flushed from the device. During this procedure, the target cells bind the magnetically retained vector. (C) Finally, the cell separation device is removed from the magnetic field, and the selected cells are flushed from the device and (D) cultivated until further use. This general scheme was implemented on MACS cell separation devices (Miltenyi Biotec) and led to rapid, efficient, and target cell-specific gene delivery.