Induced dye leakage by PAMAM G6 does not imply dendrimer entry into vesicle lumen

TY - JOUR

T1 - Induced dye leakage by PAMAM G6 does not imply dendrimer entry into vesicle lumen

AU - Åkesson, Anna Karin Louise

AU - Lundgaard, Christian Veje

AU - Ehrlich, Nicky

AU - Günther-Pomorski, Thomas

AU - Stamou, Dimitrios

AU - Cardenas Gomez, Marite

PY - 2012/9/14

Y1 - 2012/9/14

N2 - Dendrimers are polymers with unique properties that make them promising in a variety of applications such as potential drug and gene delivery systems. Polyamidoamine (PAMAM) dendrimers, in particular, have been widely investigated since they enter rapidly into cells. The entry mechanism, however, is still not yet fully clarified as both passive and active uptake have been proposed. In this work we focus on understanding passive uptake, for which simple cell model systems are used in order to ensure that only dendrimer-lipid interactions are probed. We developed protocols for investigating independently the effect of the dendrimer on lipid bilayer integrity, in terms of permeability of small dyes and effective dendrimer translocation. This was achieved by the use of membrane labeled giant unilamellar vesicles (GUVs) either containing Alexa 488 hydrazide in the vesicle lumen or FITC-labeled PAMAM G6 dendrimers. Vesicle integrity and dendrimer-membrane binding were then assessed by fluorescence microscopy. The importance of membrane fluidity and charge was investigated using GUVs composed of various lipid compositions. A quartz crystal microbalance with dissipation was used to probe the effect of dendrimers on the rigidity of vesicle layers. The results indicate that PAMAM dendrimers can locally alter the membrane properties. An increased bilayer permeability towards soluble small dyes but no effective translocation, where PAMAM dendrimers could dissociate from the lipid membrane into the vesicle lumen, was observed. To our knowledge this is the first time it is shown that PAMAM G6 dendrimer does not effectively translocate the lipid bilayer although it readily interacts with the model membrane, regardless of lipid membrane properties. However, bilayer charge and fluidity modulate the dendrimer interaction in agreement with previous reports. The results clearly highlight the importance of the choice of the model system when investigating nanoparticles interaction with lipid membranes.

AB - Dendrimers are polymers with unique properties that make them promising in a variety of applications such as potential drug and gene delivery systems. Polyamidoamine (PAMAM) dendrimers, in particular, have been widely investigated since they enter rapidly into cells. The entry mechanism, however, is still not yet fully clarified as both passive and active uptake have been proposed. In this work we focus on understanding passive uptake, for which simple cell model systems are used in order to ensure that only dendrimer-lipid interactions are probed. We developed protocols for investigating independently the effect of the dendrimer on lipid bilayer integrity, in terms of permeability of small dyes and effective dendrimer translocation. This was achieved by the use of membrane labeled giant unilamellar vesicles (GUVs) either containing Alexa 488 hydrazide in the vesicle lumen or FITC-labeled PAMAM G6 dendrimers. Vesicle integrity and dendrimer-membrane binding were then assessed by fluorescence microscopy. The importance of membrane fluidity and charge was investigated using GUVs composed of various lipid compositions. A quartz crystal microbalance with dissipation was used to probe the effect of dendrimers on the rigidity of vesicle layers. The results indicate that PAMAM dendrimers can locally alter the membrane properties. An increased bilayer permeability towards soluble small dyes but no effective translocation, where PAMAM dendrimers could dissociate from the lipid membrane into the vesicle lumen, was observed. To our knowledge this is the first time it is shown that PAMAM G6 dendrimer does not effectively translocate the lipid bilayer although it readily interacts with the model membrane, regardless of lipid membrane properties. However, bilayer charge and fluidity modulate the dendrimer interaction in agreement with previous reports. The results clearly highlight the importance of the choice of the model system when investigating nanoparticles interaction with lipid membranes.

U2 - 10.1039/c2sm25864a

DO - 10.1039/c2sm25864a

M3 - Journal article

SN - 1744-683X

VL - 8

SP - 8972

EP - 8980

JO - Soft Matter

JF - Soft Matter

IS - 34

ER -