Mechanical evaluation of poly(vinyl alcohol)-based fibrous composites as biomaterials for meniscal tissue replacement

In this study, poly(vinyl alcohol) (PVA) hydrogels were reinforced with ultrahigh molecular weight polyethylene (UHMWPE) and PP fibers and evaluated as potential nondegradable meniscal replacements. An investigation of hydrogel and composite mechanical properties indicates that fiber-reinforced PVA hydrogels could replicate the unique anisotropic modulus distribution present in the native meniscus; the most commonly damaged orthopedic tissue. More specifically, fibrous reinforcement successfully increased the tensile modulus of the biomaterial from 0.23 ± 0.02 MPa without any reinforcement to 258.1 ± 40.1 MPa at 29 vol.% UHMWPE. Additionally, the molecular weight between cross-links, bound water and the microstructure of the PVA hydrogels were evaluated as a function of freeze–thaw cycles and polymer concentration to lend insight into the processes occurring during synthesis. These results suggest the presence of multiple mechanisms as causes for increasing hydrogel modulus with freeze–thaw cycling, including hydrogen bonding between amorphous and/or crystalline regions, and the formation of highly concentrated regions of mostly amorphous PVA chains. It is possible that the formation of regions with highly concentrated amounts of PVA increases the load-bearing ability of the hydrogels.