Fig. (1) Schematic illustration of the principle of isolation of podocytes coated with cationic colloidal   silica-coated ferromagnetic nanoparticles (NPs). A: Glomeruli are isolated after perfusion with spherical superparamagnetic beads. B: Simplified schematic illustration of isolated glomeruli. Podocytes residing on the  outer glomerular surface are indicated by arrows. C: Incubation of isolated glomeruli with NPs, binding to the  exposed negatively charged podocyte cell surfaces. D: Excess NPs are removed from the sample by sieving.  Podocyte-bound NPs are cross-linked by addition of poly-acrylic acid, simultaneously neutralizing the exposed  surfaces of NPs to avoid binding to other cell types after cell separation. E: Glomerular cells are dissociated by  enzymatic digestion, gentle mechanic squeezing in a Dounce tissue grinder, and subsequent sieving. F: Isolation  and repeated washing of NP-coated podocytes in a magnetic field.