Nano-Bottlebrush Electrospun Fibres for Investigation of Cell-Substrate Interactions

Cells respond to many environmental signals, including biological signals (such as adhesion proteins, growth factors and small peptide analogs) and physical features such as topography and mechanical properties. Variation of multiple, concurrently presented signals can lead to a change in cell response that is not easily predictable from investigations of individual signals. Investigation of these non-linear responses requires a culture platform where both physical and biochemical signals can be varied independently of each other.

While these systems exist for flat substrates and hydrogels, we have developed a platform that utilises electrospun fibres, whose fibrous morphology can mimic that of the native extracellular matrix (ECM). These are produced from poly(styrene-co-vinylbenzyl chloride), where the VBC monomer subunits allow for the subsequent grafting of polymer brushes onto the fibres via atom transfer radical polymerisation (ATRP) without requiring further chemical activation. This process creates a bottlebrush-like core-shell structure. Polymer brush layers containing poly(ethylene glycol) can provide a low protein fouling background, and can be co-grafted with other functional monomers. This has allowed the creation of low-fouling electrospun fibres that contain reactive groups, such as alkynes. When combined with azide-modified peptides, this allows for oriented, chemically orthogonal covalent attachment of these peptides via click-chemistry. At the same time, the physical properties of the material can be altered easily through optimisation of the electrospinning and grafting conditions, independently of changes in peptide attachment. This type of material can provide a highly controlled 3D nanofibre substrate within which cell-substrate interactions may in the future be investigated and optimised.