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On the ability of PAMAM dendrimers and dendrimer/DNA aggregates to penetrate POPC model biomembranes

On the ability of PAMAM dendrimers and dendrimer/DNA aggregates to penetrate POPC model biomembranes
On the ability of PAMAM dendrimers and dendrimer/DNA aggregates to penetrate POPC model biomembranes

Poly(amido amine) (PAMAM) dendrimers have previously been shown, as cationic condensing agents of DNA, to have high potential for nonviral gene delivery. This study addresses two key issues for gene delivery: the interaction of the biomembrane with (i) the condensing agent (the cationic PAMAM dendrimer) and (ii) the corresponding dendrimer/DNA aggregate. Using in situ null ellipsometry and neutron reflection, parallel experiments were carried out involving dendrimers of generations 2 (G2), 4 (G4), and 6 (G6). The study demonstrates that free dendrimers of all three generations were able to traverse supported palmitoyloleoylphosphatidylcholine (POPC) bilayers deposited on silica surfaces. The model biomembranes were elevated from the solid surfaces upon dendrimer penetration, which offers a promising new way to generate more realistic model biomembranes where the contact with the supporting surface is reduced and where aqueous cavities are present beneath the bilayer. The largest dendrimer (G6) induced partial bilayer destruction directly upon penetration, whereas the smaller dendrimers (G2 and G4) leave the bilayer intact, so we propose that lower generation dendrimers have greater potential as transfection mediators. In addition to the experimental observations, coarse-grained simulations on the interaction between generation 3 (G3) dendrimers and POPC bilayers were performed in the absence and presence of a bilayer-supporting negatively charged surface that emulates the support. The simulations demonstrate that G3 is transported across free-standing POPC bilayers by direct penetration and not by endocytosis. The penetrability was, however, reduced in the presence of a surface, indicating that the membrane transport observed experimentally was not driven solely by the surface. The experimental reflection techniques were also applied to dendrimer/DNA aggregates of charge ratio = 0.5, and while G2/DNA and G4/DNA aggregates interact with POPC bilayers, G6/DNA displays no such interaction. These results indicate that, in contrast to free dendrimer molecules, dendrimer/DNA aggregates of low charge ratios are not able to traverse a membrane by direct penetration.

1520-6106
7229-7244
Ainalem, Marie Louise
c4bb25ad-5de6-49b8-978c-1f02f7e6d1b4
Campbell, Richard A.
c1f06f05-53d3-4b4f-a450-53e1c24e6763
Khalid, Syma
90fbd954-7248-4f47-9525-4d6af9636394
Gillams, Richard J.
89341fe4-db94-4d27-a5be-c092e2e8de5b
Rennie, Adrian R.
28f474c8-9bce-49e7-b395-757461650255
Nylander, Tommy
18d94ea0-6456-4eaf-b552-844261a37283
Ainalem, Marie Louise
c4bb25ad-5de6-49b8-978c-1f02f7e6d1b4
Campbell, Richard A.
c1f06f05-53d3-4b4f-a450-53e1c24e6763
Khalid, Syma
90fbd954-7248-4f47-9525-4d6af9636394
Gillams, Richard J.
89341fe4-db94-4d27-a5be-c092e2e8de5b
Rennie, Adrian R.
28f474c8-9bce-49e7-b395-757461650255
Nylander, Tommy
18d94ea0-6456-4eaf-b552-844261a37283

Ainalem, Marie Louise, Campbell, Richard A., Khalid, Syma, Gillams, Richard J., Rennie, Adrian R. and Nylander, Tommy (2010) On the ability of PAMAM dendrimers and dendrimer/DNA aggregates to penetrate POPC model biomembranes. The Journal of Physical Chemistry B, 114 (21), 7229-7244. (doi:10.1021/jp9119809).

Record type: Article

Abstract

Poly(amido amine) (PAMAM) dendrimers have previously been shown, as cationic condensing agents of DNA, to have high potential for nonviral gene delivery. This study addresses two key issues for gene delivery: the interaction of the biomembrane with (i) the condensing agent (the cationic PAMAM dendrimer) and (ii) the corresponding dendrimer/DNA aggregate. Using in situ null ellipsometry and neutron reflection, parallel experiments were carried out involving dendrimers of generations 2 (G2), 4 (G4), and 6 (G6). The study demonstrates that free dendrimers of all three generations were able to traverse supported palmitoyloleoylphosphatidylcholine (POPC) bilayers deposited on silica surfaces. The model biomembranes were elevated from the solid surfaces upon dendrimer penetration, which offers a promising new way to generate more realistic model biomembranes where the contact with the supporting surface is reduced and where aqueous cavities are present beneath the bilayer. The largest dendrimer (G6) induced partial bilayer destruction directly upon penetration, whereas the smaller dendrimers (G2 and G4) leave the bilayer intact, so we propose that lower generation dendrimers have greater potential as transfection mediators. In addition to the experimental observations, coarse-grained simulations on the interaction between generation 3 (G3) dendrimers and POPC bilayers were performed in the absence and presence of a bilayer-supporting negatively charged surface that emulates the support. The simulations demonstrate that G3 is transported across free-standing POPC bilayers by direct penetration and not by endocytosis. The penetrability was, however, reduced in the presence of a surface, indicating that the membrane transport observed experimentally was not driven solely by the surface. The experimental reflection techniques were also applied to dendrimer/DNA aggregates of charge ratio = 0.5, and while G2/DNA and G4/DNA aggregates interact with POPC bilayers, G6/DNA displays no such interaction. These results indicate that, in contrast to free dendrimer molecules, dendrimer/DNA aggregates of low charge ratios are not able to traverse a membrane by direct penetration.

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More information

Published date: 11 May 2010

Identifiers

Local EPrints ID: 434257
URI: http://eprints.soton.ac.uk/id/eprint/434257
ISSN: 1520-6106
PURE UUID: 2c1f363b-3490-496a-a2c6-69f434d918eb
ORCID for Syma Khalid: ORCID iD orcid.org/0000-0002-3694-5044
ORCID for Richard J. Gillams: ORCID iD orcid.org/0000-0002-8597-8723

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Date deposited: 18 Sep 2019 16:30
Last modified: 26 Nov 2019 01:43

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