Co-assembly of block copolymer thin films and signalling molecules for stimuli-responsive biointerface

Abstract

The ability of stem cells to either self-renew or differentiate towards other cell types is tightly regulated in space and time by the cell microenvironment and interactions between the cell and biomolecules. Two fundamental processes through which cells perceive their surroundings are mechanotransduction and growth factor (GF) receptor signalling, which have been demonstrated to function synergistically. Much of the work directed to study the crosstalk between these two systems often present biomolecules in solution or tethered to the substrate in typical cell culture techniques. However, these procedures do not allow internalization of the biomolecule and co-localization of mechanotransduction and GF receptors simultaneously, restricting a broader understanding of the synergies between these signalling pathways. There is currently a lack of experimental methods that allow the local release of biomolecules close to cell adhesion regions. To address these limitations, this thesis has focused on the development of a model system capable of releasing signalling molecules in a stimuli-responsive manner. In the developed platform, self-assembling block copolymers (BCPs) are used to create a thin nanopatterned layer in which active biomolecules are incorporated. Cargo release from the polymer film is regulated by enzymatic degradation of a coating layer. The ultimate goal of this procedure is to ensure cargo delivery close to cell adhesions, when and where they are needed. Polystyrene-blockpoly( ethylene oxide) thin films were demonstrated to be cytocompatible and successfully co-assembled with cell-penetrating peptides, the chosen model biomolecule. Spin-coating concentrated collagen type I solutions onto the polymer film resulted in interconnected monolayers of collagen molecules, which were shown to significantly reduce natural cargo release in aqueous environment. It was also demonstrated that the release could be partially restored via degradation of the collagen layer with collagenase. The methods presented here are envisaged to contribute towards the development of a biointerface for cell-mediated release of GFs. The presented approach is generic and can be applied to a range of cell types and signalling molecules. By mimicking vital parts of the in vivo environment, synergies between mechanotransduction and GF signalling can be further explored in vitro for better understanding and control of stem cell behaviour.