Investigations of Strain Fields in 3D Hydrogels Under Dynamic Confined Loading

Hydrogels are common scaffolds used to maintain chondrocyte phenotype in culture for mechanobiology and tissue engineering studies. However, the internal strain field and the zone-specific deformation patterns of chondrocytes within hydrogels under dynamic compressive strain have not been well characterized. In this study, we characterized the strain fields within the surface, middle and bottom zones of 3-dimensional collagen and agarose hydrogel constructs, in response to 5 and 15% applied compressive strain. Hydrogel microstructure and chondrocyte deformation were also analysed and compared to uncompressed conditions using scanning electron microscopy. We observed that there are inhomogeneous strain distributions in both collagen and agarose hydrogel constructs. In collagen gels, we observed that the microstructure varied greatly between uncompressed gels to gels with 5% applied compression. The percentage porosity in the surface zone of the gel decreased significantly upon initial application of 5% compression, but remained unchanged when compressed further to 15%. In agarose gels, only the cells in the middle zone of the gel deformed significantly under compression while cells in the other zones underwent deformation that was not statistically significant. These findings indicate that deformation of chondrocytes seeded hydrogels under compression is both inhomogeneous and location-dependent. Therefore, it is important to consider these inhomogeneities in order to accurately understand how mechanical stimuli may affect chondrocyte behaviour.