Delivery of membrane-impermeant fluorescent probes into living neural cell populations by lipotransfer

Use of fluorescent probes to monitor f-actin in living cells typically relies on difficult microinjection procedures. The current work has developed cationic lipotransfer of membrane-impermeant probes as an alternative to microinjection. BODIPY(R) FL-phallacidin, a fluorescent f-actin probe, was packaged into 40-50 nm cationic liposomes. Packaging, verified by gel filtration, enabled delivery of the probe into living nerve cells and provided an image of f-actin that was identical to that seen in fixed, permeabilized cells. Phallacidin alone did not enter living cells, nor was its uptake stimulated by the presence of empty liposomes. All predicted f-actin structures were fluorescent in living cells, indicating a high efficacy of delivery. Cationic lipotransfer of fluorescent probes was rapid, not disruptive to cells, and delivered a probe en masse to a large sample population. Lipotransfer appears to be a promising alternative to microinjection for introducing membrane-impermeant probes and reagents into living cells.