Cartilage matrix has shown promise as a potentially bioactive and chondroinductive material for promoting hyaline-like cartilage regeneration after acute cartilage damage or osteoarthritis (Kiyotake et al., 2022a). The main challenges for cartilage-based scaffolds have been to fabricate a scaffold that 1) has high mechanical performance akin to native cartilage, (∼ 1.8 MPa compressive elastic modulus (Beck et al., 2016b)), and 2) is easy to surgically deliver/has good retention in the injury.

The methods to fabricate cartilage-based scaffolds have evolved over the past few decades (Kiyotake et al., 2016). Guilak’s group and others commonly fabricated scaffolds via lyophilization of cartilage particle slurries (Cheng et al., 2009, Diekman et al., 2010). To improve the mechanical performance, there was a transition to further crosslink the lyophilized scaffolds (Almeida et al., 2017, Browe et al., 2019, Cheng et al., 2013, Rowland et al., 2013) or mix with existing polymers to improve the mechanical performance (Chen et al., 2019, Lu et al., 2021). While different methods have been used to evaluate the compressive moduli of cartilage-based hydrogels (e.g., aggregate moduli, equilibrium moduli), the majority of studies report the elastic moduli measured via the slope of the stress-strain curve. Regardless of the method, most of the cartilage-matrix scaffolds, even with polymer reinforcements, had compressive moduli less than 0.3 MPa. Only one study fabricated a polymer-reinforced scaffold that possessed a compressive elastic modulus of 1.0 ± 0.1 MPa (Zheng et al., 2011).

Photocrosslinking bioinks have two features that may enhance surgical delivery: 1) the paste-like and injectable rheology may enable easy surgical implantation/retainment, and 2) the controllable photocrosslinking enables in situ crosslinking of the precursor into irregularly-shaped defects. A few innovative studies developed methacryloylated solubilized cartilage to form photocrosslinked cartilage-matrix based hydrogels (Behan et al., 2022, Visscher et al., 2021, Visser et al., 2015). However, all of them required additional polymers (i.e., gelatin and/or hyaluronic acid) to increase the viscosity/printability of the solubilized cartilage and had compressive moduli under 0.1 MPa. In previous studies, we developed methacryloylated solubilized devitalized cartilage (MeSDVC) hydrogels without added polymers and achieved high compressive moduli of 0.675–1.58 MPa (Beck et al., 2016b, Beck et al., 2016c, Kiyotake et al., 2022a). Furthermore, our MeSDVC precursor had a paste-like rheology/printability. However, one disadvantage of the MeSDVC hydrogels was that they had slow crosslinking times (i.e., 5–6 min).

We have previously applied a pentenoate-modification to hyaluronic acid (PHA) to form faster crosslinking HA hydrogels via thiol-ene click chemistry (Townsend et al., 2022). Given that only methacryl-modifications have been investigated for SDVC, in the current study, we applied a pentenoate modification to the SDVC to achieve faster crosslinking times. Therefore, the purpose of the current study was to form a pentenoate-functionalized, solubilized, devitalized cartilage (PSDVC) hydrogel with fast crosslinking, high compressive moduli, and a paste-like rheology/printability for enhanced surgical translation.