1 research outputs found
Cell Penetrating Polymers Containing Guanidinium Trigger Apoptosis in Human Hepatocellular Carcinoma Cells unless Conjugated to a Targeting <i>N</i>‑Acetyl-Galactosamine Block
A series
of 3-guanidinopropyl methacrylamide (GPMA)-based polymeric
gene delivery vehicles were developed via aqueous reversible addition–fragmentation
chain transfer (RAFT) polymerization. The polymers have been evaluated
for their cellular internalization ability, transfection efficiency,
and cytotoxicity. Two homopolymers: PÂ(GPMA<sub>20</sub>), PÂ(GPMA<sub>34</sub>), were synthesized to study the effect of guanidium polymer
length on delivery efficiency and toxicity. In addition, an <i>N</i>-acetyl-d-galactosamine (GalNAc)-based hydrophilic
block was incorporated to produce diblock polymers, which provides
a neutral hydrophilic block that sterically protects plasmid–polymer
complexes (polyplexes) from colloidal aggregation and aids polyplex
targeting to hepatocytes via binding to asialoglycoprotein receptors
(ASGPRs). Polyplexes formed with PÂ(GPMA<sub><i>x</i></sub>) (<i>x</i> = 20, 34) homopolymers were shown to be internalized
via both energy-dependent and independent pathways, whereas polyplexes
formed with block polymers were internalized through endocytosis.
Notably, PÂ(GPMA<sub><i>x</i></sub>) polyplexes enter cells
very efficiently but are also very toxic to human hepatocellular carcinoma
(HepG2) cells and triggered cell apoptosis. In comparison, the presence
of a carbohydrate block in the polymer structures reduced the cytotoxicity
of the polyplex formulations and increased gene delivery efficiency
with HepG2 cells. Transfection efficiency and toxicity studies were
also carried out with HEK 293T (human embryonic kidney) cells for
comparison. Results showed that polyplexes formed with the PÂ(GPMA<sub><i>x</i></sub>) homopolymers exhibit much higher transfection
efficiency and lower toxicity with HEK 293T cells. The presence of
the carbohydrate block did not further increase transfection efficiency
in comparison to the homopolymers with HEK 293T cells, likely due
to the lack of ASGPRs on the HEK 293T cell line. This study revealed
that although guanidinium-based polymers have high membrane permeability,
their application as plasmid delivery vehicles may be limited by their
high cytotoxicity to certain cell types. Thus, the use of cell penetrating
structures in polyplex formulations should be used with caution and
carefully tailored toward individual cell/tissue types