title: Direct observation of lipid bilayer disruption by poly(amidoamine) dendrimers.
abstract: Atomic force microscopy (AFM) is employed to observe the effect of poly(amidoamine) (PAMAM) dendrimers on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayers. Aqueous solutions of generation 7 PAMAM dendrimers cause the formation of holes 15-40 nm in diameter in previously intact bilayers. This effect is observed for two different branch end-groups--amine and carboxyl. In contrast, carboxyl-terminated core-shell tectodendrimer clusters do not create holes in the lipid membrane but instead show a strong affinity to adsorb to the edges of existing bilayer defects. A possible mechanism for the formation of holes in the lipid bilayer is proposed. The dendrimers remove lipid molecules from the substrate and form aggregates consisting of a dendrimer surrounded by lipid molecules. Dynamic light scattering (DLS) measurements as well as 31P NMR data support this explanation. The fact that tectodendrimers behave differently suggests that their cluster-like architecture plays an important role in their interaction with the lipid bilayer.
authors.affiliation: Department of Physics, University of Michigan, 500 E. University Avenue, Ann Arbor, MI 48109, USA.
authors.forename: Almut
authors.initials: A
authors.lastname: Mecke
authors.forename: Srinivas
authors.initials: S
authors.lastname: Uppuluri
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Sassanella
authors.forename: Dong-Kuk
authors.initials: DK
authors.lastname: Lee
authors.forename: A
authors.initials: A
authors.lastname: Ramamoorthy
authors.forename: James R
authors.initials: JR
authors.lastname: Baker
authors.forename: Bradford G
authors.initials: BG
authors.lastname: Orr
authors.forename: Mark M
authors.initials: MM
authors.lastname: Banaszak Holl
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008560:Membrane Fluidity; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force; D010316:Particle Size; D011073:Polyamines / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D046911:Macromolecular Substances; D008567:Membranes, Artificial; D011073:Polyamines; D004134:Dimyristoylphosphatidylcholine