Small and ultra small angle neutron scattering on pure and supramolecular composite GelMA hydrogels

Development of highly sophisticated tissue-engineered models capable of eliciting specific health and disease states could revolutionise disease treatment. To accomplish this it requires the generation of highly sophisticated hydrogel/biomaterial systems, including materials with tuneable properties and multiscale architecture composed of structures with different sizes ranges. In developing such systems, it is crucial to quantify any structures and interactions in the nano- and micron-scale range, to determine how these systems may affect cell phenotype. Small and ultra-small angle neutron scattering were used to quantify the structure of two biomaterials previously used in tissue engineering techniques. Gelatin methacryloyl (GelMA) is a commonly used hydrogel for tissue engineering and it has already been established that its Young's modulus can be tuned by controlling the crosslinking density. In this work, neutron scattering showed that there is little difference between the mesh size/fibre spacing (4.7 nm-4.5 nm) in 9.1 % w/v, soft (7.3 kPa ± 2.2 kPa), low crosslinked GelMA hydrogels and stiff (30.5 kPa ± 3.5 kPa), highly crosslinked GelMA hydrogels. However, stiff GelMA hydrogels showed the formation of dense highly crosslinked aggregates with a size of 8.0 nm that were not seen in the soft GelMA hydrogels. Neutron scattering was also performed on newly developed composite hydrogels consisting of GelMA (polymer chain radius 0.7 nm) embedded with significantly larger supramolecular fibres made from stacked bilayers of N-heptyl-galactonamides. Previously characterised pure galactonamide fibres were confirmed to have a thickness of 128 nm with a repeatable stacking/bilayer thickness of 3.7 nm. Incorporation of such large galactonamide fibres within the GelMA led to no disruption of the GelMA network.