The objective of this study was to generate PVA hydrogels that mimic cartilage and meniscus anisotropy. We hypothesize that bending and circumferential forces will induce cartilage- and meniscus-like anisotropy, respectively, through a combination of tensile and compressive loads.
PVA solutions (20% w/v) were created as previously described in [1]. PVA was cast into custom-built 3D-printed molds; dogbones (25x5x5 mm) were cast for bending and “wedge shapes” (43x5x9 mm) were cast for circumferential loads. Cast PVA was partially crosslinked through three freeze/thaw cycles [1] and then samples were loaded. Bending was achieved through custom clamps built to fix samples in a U-Shape (Figure 1A) while circumferential loads were achieved by stretching wedges (250%) around a post (Figure 1B). All samples underwent an additional three freeze-thaw cycles while in the loaded configuration before characterization in which samples were visualized under a circular polarizer to determine zonal organization.
Samples undergoing bending exhibited a “neutral axis” along the mid-line of the sample with differing alignment above and below the axis (Mean difference: 29.43° ± 11.37°, Figure 2A). Circumferentially-loaded samples exhibited a less obvious neutral axis and instead a primarily tension-like phenotype oriented along a curve (Average range: -19.16° to 17.01°, average center ROI: 0.86°, Figure 2B).
In this study, we were able to generate hydrogels with alignment that looks like cartilage and meniscus through the application of bending and circumferential loads. Previously studies have generated uniaxially aligned structures that mimic muscle and tendon [2,3], this work extends this concept to generate multidirectional anisotropy. The ability to generate biomimetic tissue replacements from a single material provides improved fracture toughness and longevity of the structures under cyclic fatigue loads [3]. Current work is underway to more completely characterize PVA hydrogel structures obtained through bending and circumferential loads.