Carboxyl-terminated PAMAM dendrimer interaction with 1-palmitoyl-2-oleoyl phosphocholine bilayers

Polyanionic polymers and liposomes have a great potential use as individual drug delivery systems and greater potential as a combined drug delivery system. Thus, it is important to better understand the interactions of polymers with phospholipid bilayers. A mechanistic study of the interaction between carboxyl-terminated poly(amidoamine) (PAMAM) dendrimers with 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) bilayer using fluorescence leakage and quartz crystal microbalance with dissipation monitoring (QCMD) was conducted. Fluorescence leakage experiments demonstrated that carboxyl-terminated generation 2 (G2-COOH) dendrimers caused increased liposome leakage with increasing dendrimer concentration over a 0 to 20μM range. Generation 5 (G5-COOH), on the other hand, reduced leakage over the same concentration range, presumably by increasing lipid packing. QCMD and atomic force microscopy (AFM) measurements demonstrated that G2-COOH interacting with supported bilayers resulted in small defects with some mass loss and no adsorption. In contrast, G5-COOH interaction with a bilayer resulted in adsorption and local bilayer swelling.