Abstract:
This thesis aims to contribute to and deepen the arsenal of synthetic extracellular matrix (ECM)
mimetic substrates for in vitro cell research. Particularly, this thesis focuses on creating substrates
capable of investigating mechanotransduction and biochemical signalling in tandem. Two
bioengineered systems were explored for this: polystyrene-block-polyethylene oxide (PS-b-PEO) and
poly(N-isopropylacrylamide)/polypyrrole (pNIPAM/PPy) platforms.
The PS-b-PEO block copolymer system aims to achieve a local cell-mediated release of biomolecules
near integrin binding sites. This system incorporated lysozyme and FITC-TAT as model biomolecules,
and qualitative and quantitative release studies confirmed the biomolecule release. The final stage
before the system could fully realise its potential in cell studies was controlling the rapid release.
Layer-by-layer (LbL) films were chosen and constructed atop the block copolymer films so cells could
degrade this layer and locally release cargo. Altering polyelectrolyte and PS-b-PEO surface parameters
improved LbL buildup. It was ultimately shown through protein release studies that LbL films could
not be formed on PS-b-PEO without losing or deactivating the cargo.
The pNIPAM/PPy conducting polymer hydrogel system was selected due to its ability to control the
substrate's mechanical properties and capacity for controlled cargo release. This system has been
previously mechanically and electrochemically characterised, and the primary focus of this thesis was
to electrically incorporate and release biomolecules from this hydrogel-based system. Fluorescein was
incorporated into the conducting polymer phase as a model drug, and a comprehensive quantitative
release study was conducted. This investigated release via oxidation and reduction, fluorescein
reloading, release around the pNIPAM phase transition temperature, release with PPy thickness, and
release stability over time. Finally, the corticosteroid drug dexamethasone was electrically
incorporated and released from PPy films with a biphasic pulsed potential. Release of dexamethasone
from pNIPAM/PPy was also demonstrated, but repeatability was an issue.
The results presented provide advancements in two different synthetic systems regarding their
abilities to mimic the biochemical and biophysical properties of the ECM. Creating such systems to
study mechanotransduction and biochemical signalling in vitro enhances our understanding of cell
behaviour in vivo. Through deepening our understanding of these processes, cell therapies and
regenerative medicine become safer and more accessible globally.