Abstract:

Over the past several decades, for tissue engineering application, tremendous efforts have been made to customize biomimetic hydrogels mimicking specific mechanical behaviours of extracellular microenvironment of tissues [1]. However, natural loading tissues like tendon possess complex mechanical behaviours and ultra-high “linear-region” Young’s modulus higher than 1 GPa originating from its highly orientated hierarchical structure of collagen fibres. Thus far, it is still a challenge to fabricate such tendon-mimetic hydrogels. In the present project, via a feasible uniaxial-tension-drying method, we have fabricated tendon mimetic aramid (ANF)-poly (vinyl alcohol) (PVA) composite hydrogels that afford a very similar structural and mechanical properties to natural tendon, including (1) extremely high orientation of hierarchical ANF and PVA nanofibers that are interlaced by hydrogen bonding, which enables an extraordinary ultimate stress of 50-80 MPa, “linear-region” Young’s modulus of 500-1100 MPa. (2) similar shape of the stress–strain curve with an initial concave region at strain lower than ~3% similar to the “toe region” of the tendon, a similar “linear region” at 3-8% strain range and ultimate strain of ~10%. (3) viscoelastic properties originating from the reconfiguration of ANF-PVA chains. (4) water content of 58-70%.

This ANF-PVA hydrogel substrate with tendon-mimetic mechanical properties can be employed for fibroblast culture to explore the influence of substrate stiffness and stiffness anisotropy on cellular morphology, orientation and spreading. The fibroblasts on anisotropic and stiff ANF-PVA substrate show high orientation along the stiffer direction compared with those cultured on stiff but isotropic polystyrene substrate. Furthermore, in comparison with soft polydimethylsiloxane substrate, higher cell aspect ratio and larger cell spread area are observed on the ANF-PVA substrate. These results indicate that this tendon-mimetic ANF-PVA hydrogel may find applications in functional biomaterials and tissue engineering.