3D-Printed Hybrid Collagen/GelMA Hydrogels for Tissue Engineering Applications

SIMPLE SUMMARY: Incorporating natural polymers along with semi-synthetic gelatin methacrylate (GelMA) is known to improve the mechanical properties of developed hybrid hydrogels. Here, we provide a novel comparison of bioprinted GelMA hybrid hydrogel meshes with different concentrations of collagen extracted from bovine hide and ovine skin by assessing their physicochemical characterizations. No previous work has reported the incorporation of ovine collagen with GelMA to develop hybrid hydrogels. Furthermore, different parameters of extrusion-based bioprinting of the inks, and their printing fidelity were investigated. The maximum percentage of collagen that could be incorporated into the meshes was identified as 1%, as these meshes showed good shape fidelity with stable degradation rates. The results indicate these hydrogel meshes may be suitable for specific tissue engineering applications depending on the source of collagen used. Hybrid meshes with ovine (water-soluble) were found to possess properties that could make them suitable for bone tissue engineering applications. Similarly, results indicated that hybrid meshes with bovine collagen could be used for corneal, cartilage, and various soft tissue engineering applications. ABSTRACT: Bioprinting is an emerging technology involved in the fabrication of three-dimensional tissue constructs for the repair and regeneration of various tissues and organs. Collagen, a natural protein found abundantly in the extracellular matrix of several tissues, can be extracted from collagen-rich tissues of animals such as sheep, cows, rats, pigs, horses, birds, and marine animals. However, due to the poor printability of collagen bioinks, biocompatible collagen scaffolds that mimic the extracellular matrix (ECM) are difficult to fabricate using bioprinting techniques. Gelatin methacrylate (GelMA), a semi-synthetic polymer with tunable physical and chemical properties, has been found to be a promising biomaterial in various bioprinting applications. The printability of collagen can be improved by combining it with semi-synthetic polymers such as GelMA to develop hybrid hydrogels. Such hybrid hydrogels printed have also been identified to have enhanced mechanical properties. Hybrid GelMA meshes have not previously been prepared with collagen from ovine sources. This study provides a novel comparison between the properties of hybrid meshes with ovine skin and bovine hide collagen. GelMA (8% w/v) was integrated with three different concentrations (0.5%, 1%, and 2%) of bovine and ovine collagen forming hybrid hydrogels inks that were printed into meshes with enhanced properties. The maximum percentage of collagen suitable for integration with GelMA, forming hybrid hydrogels with a stable degradation rate was 1%. The water-soluble nature of ovine collagen promoted faster degradation of the hybrid meshes, although the structural crosslinking was identified to be higher than bovine hybrid meshes. The 1% bovine collagen hybrid meshes stood out in terms of their stable degradation rates.