1 research outputs found
Effect of Thiol Pendant Conjugates on Plasmid DNA Binding, Release, and Stability of Polymeric Delivery Vectors
Polymers have attracted much attention as potential gene
delivery
vectors due to their chemical and structural versatility. However,
several challenges associated with polymeric carriers, including low
transfection efficiencies, insufficient cargo release, and high cytotoxicity
levels have prevented clinical implementation. Strong electrostatic
interactions between polymeric carriers and DNA cargo can prohibit
complete cargo release within the cell. As a result, cargo DNA never
reaches the cell’s nucleus where gene expression takes place.
In addition, highly charged cationic polymers have been correlated
with high cytotoxicity levels, making them unsuitable carriers in
vivo. Using polyÂ(allylamine) (PAA) as a model, we investigated how
pH-sensitive disulfide cross-linked polymer networks can improve the
delivery potential of cationic polymer carriers. To accomplish this,
we conjugated thiol-terminated pendant chains onto the primary amines
of PAA using 2-iminothiolane, developing three new polymer vectors
with 5, 13, or 20% thiol modification. Unmodified PAA and thiol-conjugated
polymers were tested for their ability to bind and release plasmid
DNA, their capacity to protect genetic cargo from enzymatic degradation,
and their potential for endolysosomal escape. Our results demonstrate
that polymer–plasmid complexes (polyplexes) formed by the 13%
thiolated polymer demonstrate the greatest delivery potential. At
high N/P ratios, all thiolated polymers (but not unmodified counterparts)
were able to resist decomplexation in the presence of heparin, a negatively
charged polysaccharide used to mimic in vivo polyplex–protein
interactions. Further, all thiolated polymers exhibited higher buffering
capacities than unmodified PAA and, therefore, have a greater potential
for endolysosomal escape. However, 5 and 20% thiolated polymers exhibited
poor DNA binding-release kinetics, making them unsuitable carriers
for gene delivery. The 13% thiolated polymers, on the other hand,
displayed high DNA binding efficiency and pH-sensitive release