WEB Hyaluronic Acid-based Bioink Composition Enabling 3D Bioprinting and Improving Quality of Deposited Cartilaginous Extracellular Matrix
In 3D bioprinting, bioinks with high concentrations of polymeric materials are commonly employed to facilitate the fabrication of 3D constructs with sufficient shape fidelity and stability. However, this is often associated with restricted cell bioactivity and an inhomogeneous or pericellular distribution of newly produced extracellular matrix (ECM). Therefore, this study investigated hyaluronic acid (HA)-based bioink formulations, an attractive material for cartilage engineering, that allowed for reduction of polymer content and simultaneously improved quality of deposited cartilaginous ECM.
Thiol-modified HA (HA-SH) was UV-crosslinked with allyl-modified poly(glycidol) employing different concentrations of both components (3 wt.% to 15 wt.%). Bioink viscosity was increased by further supplementation with 1 wt.% unmodified high molecular weight HA (hmHA) to enable PCL-supported 3D bioprinting. Chondrogenic differentiation of incorporated human mesenchymal stromal cells was assessed by imaging of deposited ECM, quantification of glycosaminoglycan and collagen content, and gene expression analysis.
Strikingly, addition of hmHA to gels with a low polymer content (3 wt.%) resulted in distinct increase of construct quality with a homogeneous ECM distribution throughout the constructs, irrespective of the printing process. This was demonstrated histologically, immunohistochemically, and by histomorphometric quantification of key ECM components. This homogeneous ECM distribution was associated with a 175-fold increase in Young’s modulus of the constructs after chondrogenic differentiation, while higher concentrated constructs (10 wt.%) only showed pericellular matrix deposition and just 2.5-fold increased Young’s modulus over time. Further characterization such as GPC analysis of the supernatants, cryo-SEM imaging of the constructs and diffusion analysis with FITC-labeled dextrans, suggested the release of hmHA as mechanism for the generation of porous constructs facilitating ECM distribution throughout the hydrogels. In conclusion, this study contributes to effective bioink development, demonstrating the dual function of a supplement enabling PCL-supported bioprinting and at the same time improving biological properties of the resulting constructs.