| dc.description.abstract | Nanoparticles (NPs) can be used in clinical applications (e.g. for drug delivery or
bioimaging) in order to better treat and diagnose disease. Many nanomedicines are made
from polymers, and improvements in polymer NP synthesis methods have made it easier
to design and synthesise complex and diverse polymer NPs (PNPs) for clinical use.
However, investigation into PNP safety has lagged behind their development, resulting
in uncertainties regarding the safety of these PNPs. In vitro studies conducted to date have
focused on assessment of cytotoxicity and cytokine production to screen the toxicity of
nanomedicines.
Micelles are one of the most attractive PNPs for medical use as they have a hydrophobic
core that can carry cargo and a hydrophilic shell that interacts with the exterior
environment. A panel of micellar PNPs of varying complexity were selected for
investigation in this study. In the first instance, a novel polymer was used to generate poly
(decamethylene succinate-co-pheylsuccinate) (PDP) NPs to investigate the influence of
an adsorbed pluronic acid (PF68) coating on the toxicity of NPs. Next, the impact of polylactic-co-glycolic acid (PLGA) chain length (4K, 15K and 55K) on PNP toxicity was
investigated. Finally, the toxicity of redox-reactive (RR)-NPs, composed from PLGA,
was compared to NPs which lacked this element (nRR-NP). All NPs tested had a
polyethylene glycol (PEG) element in the shell.
PNP safety was investigated via assessment of cytotoxicity, cytokine production, cellular
uptake, genotoxicity, reactive oxygen species (ROS) production, urea and albumin
production and intracellular calcium concentration ([Ca2+]i). The toxicity of the PNP
panel to the C3A hepatocyte cell line was assessed in vitro as it is established that NPs
administered via various routes (e.g. inhalation, ingestion, intravenous injection)
accumulate in the liver.
There was little to no cytotoxicity observed for all PNPs. Uptake of the PDP NPs by C3A
cells was greatest, but low for 4K, 15K, 55K, RR and nRR NPs. PDP-PF68 PNPs and
nRR-NPs induced genotoxicity via an oxidative mechanism, whereas the other NPs did
not. Production of the anti-inflammatory cytokine interleukin (IL)-1ra, was elevated. No
change in the production of the other cytokines (e.g. IL-8. Tumour necrosis factor (TNF)α, IL-1β) was observed. ROS production was elevated by all PNPs investigated.
Liver-specific markers of toxicity (urea and albumin production) were decreased for all
PNPs investigated, with the greatest effect observed for nRR-NPs. A slight increase in
[Ca2+]i was observed for cells exposed to RR-NPs.
The findings obtained allowed the physicochemical properties of the PNPs which
conferred toxicity to be identified; this can inform the design of PNPs in the future. More
specifically, the addition of a PF-68 shell or a redox-responsive linker increased the safety
of the PNPs. However, increasing chain length enhanced PNP toxicity. This study could
also aid in developing evidence-based in vitro approaches to screen PNP safety, and
therefore contribute to the development of a tiered testing strategy to facilitate assessing
the toxicity of future generations of PNPs. By using a battery of tests to screen the toxicity
of the PNP panel in this study a comprehensive assessment of PNP safety was performed,
and the findings provided insight into their mechanism of action. | en |
