Development of a hyaluronic acid-based hybrid bioink for stereolithography 3D bioprinting

Abstract In the near future, tissue engineering and 3D bioprinting techniques will be essential to alleviatethe dire need for organs for transplantation. It promises a very automated, rapidly scalable, andpatient-specific process that eradicates existing concerns. Therefore, there is an immediate need todevelop biomaterials with intrinsic biological functionalities that can be used to mimic In vivoconditions. Hyaluronic acid (HA), being an extra-cellular matrix derivative, promises uniqueprospects in tissue-specific applications by virtue of its bioactive properties. The work presentedin this thesis describes a tunable protocol for the synthesis of a dual-crosslinkable methacrylatedhyaluronic acid (MeHA) with a high degree of substitution to be used as a bioink for Digital LightProcessing Stereolithography (DLP-SLA) 3D bioprinting. Furthermore, to overcome the non-celladhesive nature of MeHA, a hybrid bioink in combination with gelatin methacryloyl (GelMA) isdeveloped that can be used to produce 3D cell-laden hydrogel scaffolds. Upon development of thehybrid bioink, the mechanical properties, including microarchitecture, swelling ratio, andcompressive modulus, were assessed along with its biocompatibility. The results show a 55%enhancement in mechanical strength compared to its sole constituents and enable cell-attachmentin the presence of MeHA while maintaining high cell viability. Preliminary investigations alsoreveal that the hybrid bioink is a more suitable candidate for DLP-SLA 3D bioprinting comparedto MeHA because of its printability and cell-adhesive properties. Although, further optimizationof the printing process with the hybrid bioink and the specific influences of MeHA on specializedcell types is required to be understood. This thesis lays out a firm foundation for the developmentof a stable MeHA bioink for DLA-SLA 3D bioprinting. It offers solutions to overcome its majorlimitations, without complex chemical modifications, by developing a hybrid hydrogel bioink.

Compressive Modulus The probe used for the mechanical tests is custom made into a flat-ended rigid cylinder withan elastic half-space. Afterward, a vertical axis micromechanical testing machine (Mach-1 v500c,Biomomentum Inc., Montreal, QC, Canada) along with a flat-cylindrical probe was used tomeasure and record the force vs displacement plots. Approximately, 10% strain was put on thehydrogel surface to obtain the plots and the linear region was selected to calculate the slope.