Endocytic Uptake, Transport and Macromolecular Interactions of Anionic PAMAM Dendrimers within Lung Tissue
Endocytic Uptake, Transport and Macromolecular Interactions of Anionic PAMAM Dendrimers within Lung Tissue
Christopher J. Morris 0 1 2
Ghaith Aljayyoussi 0 1 2
Omar Mansour 0 1 2
Peter Griffiths 0 1 2
Mark Gumbleton 0 1 2
Christopher J. Morris 0 1 2
0 Department of Pharmaceutical, Chemical and Environmental Science, University of Greenwich , Medway Campus, Kent ME4 4TB , UK
1 Cardiff School of Pharmacy & Pharmaceutical Sciences , Redwood Building, Cardiff CF10 3NB , UK
2 School of Pharmacy, University of East Anglia , Norwich Research Park NR4 7TJ , UK
Purpose Polyamidoamine (PAMAM) dendrimers are a promising class of nanocarrier with applications in both small and large molecule drug delivery. Here we report a comprehensive evaluation of the uptake and transport pathways that contribute to the lung disposition of dendrimers. Methods Anionic PAMAM dendrimers and control dextran probes were applied to an isolated perfused rat lung (IPRL) model and lung epithelial monolayers. Endocytosis pathways were examined in primary alveolar epithelial cultures by confocal microscopy. Molecular interactions of dendrimers with protein and lipid lung fluid components were studied using small angle neutron scattering (SANS). Results Dendrimers were absorbed across the intact lung via a passive, size-dependent transport pathway at rates slower than dextrans of similar molecular sizes. SANS investigations of concentration-dependent PAMAM transport in the IPRL confirmed no aggregation of PAMAMs with either albumin or dipalmitoylphosphatidylcholine lung lining fluid components. Distinct endocytic compartments were identified within primary alveolar epithelial cells and their functionality in the rapid uptake of fluorescent dendrimers and model macromolecular probes was confirmed by co-localisation studies. Conclusions PAMAM dendrimers display favourable lung biocompatibility but modest lung to blood absorption kinetics. These data support the investigation of dendrimer-based carriers for controlled-release drug delivery to the deep lung.
dendrimer; endocytosis; lung; polymer; scattering; transport; uptake
-
* Mark Gumbleton
ABBREVIATIONS
BSA Bovine serum albumin
DPPC 1,2-dipalmitoyl-sn-glycero-3-phosphocholine
IPRL Isolated perfused rat lung
MRI Magnetic resonance imaging
PAMAM Polyamidoamine
INTRODUCTION
Dendrimers represent an important uniform and nanosized
polymer architecture for biomedical and clinical applications
and display a variety of synthetic approaches, chemistries, and
an ability to carry cargo either by encapsulation,
complexation or as pendant groups on the polymer surface. Dendrimers
retain promise as nanosized drug carriers displaying a narrow
polydispersity and an ease of control in the modification of
surface functional groups. The first full family of dendrimer
molecules, spanning a number of growth generations were the
poly(amidoamine) (PAMAM) dendrimers synthesised by the
divergent approach with the iterative addition of methyl
acrylate and ethylenediamine to a polymer core and modified
with hydroxyl (neutral), amine (positive) or carboxyl (negative)
surface functionalities (Scheme 1).
The polyamidoamine (PAMAM) class of dendrimers have
been the most widely studied as carriers for low molecular
Scheme 1 (a) Structure of
exemplar anionic PAMAM
generation 1.5. Iterative branching
of each generation is highlighted by
concentric circles. (b) Molecular
mass (Mw) and the number of
surface functional groups for the
PAMAM generations tested here.
weight drugs, for MRI contrast agents, and as carriers of
biomacromolecules including vaccines, peptides, antibodies
and DNA. A number of groups have used cationic PAMAM
dendrimers to enhance drug delivery across cell membranes,
including avoidance of efflux transporters (1), or for example
enhancing cytoplasmic delivery of nucleic acid therapeutics (2)
or vaccines (3). However, cell membrane disruption and
compromise of tight junction integrity is a significant concern for
the exploitation of cationic dendrimers, although approaches
have been developed to mitigate the biocompatibility issues
associated with the use of these platforms (4).
The dendrimer-enhanced delivery of drugs with low oral
bioavailability has been of particular interest with many studies
(5) reporting dendrimer permeation of cultured intestinal
epithelial cell monolayers, although fewer investigations of
transport in the fully intact ex vivo or in vivo tissue have been
evidenced. Using an everted gut sac model Wiwatanapatapee
et al. (6) reported the effect of dendrimer generation and surface
functionality (anionic and cationic) upon the association of
PAMAM dendrimers with intestinal tissue and upon
dendrimer mucosal to serosal transport. In an in-vivo rat model
Florence and co-workers (7) administered by oral solution
gavage a poly(lysine)15 dendrimer bearing at the surface
covalently linked C12 alkyl chains and studied the subsequent
intestinal and whole body tissue accumulation.
In co (...truncated)