3D Bioprinting of human adipose stem cells (hADSCs) encapsulated hyaluronic acid (HA) based biomimetic double crosslinked hydrogel bioink for cartilage tissue engineering (CTE)
Articular cartilage covers the edges of the bones and provides wear resistant load bearing capacity which ultimately supports the flexible joint movement. Therefore, once these articular cartilages get damaged, they limit the free joint movements in patients and cause severe complication. Also, articular cartilage is avascular in nature, which also restricts its ability to repair itself after any damage. To address these issues associated with articular cartilage damage, cartilage tissue engineering (CTE) has been introduced. CTE helps in repairing or regenerating damaged cartilages by using a combined strategy which involves cell, growth factors, and biomaterial scaffolds. Hydrogel with the ability to absorb a large amount of water viewed as an ideal material for cartilage mimetic scaffold owing to the similarity between the hydrogel and native cartilage. Combining stem cell or chondrocytes with hydrogel scaffold is regarded as a promising approach for CTE. This strategy is capable of supporting highly dense cell population, cell attachment, homogeneous cell distribution, and also offer an ideal microenvironment for cell growth and differentiation. Unfortunately, developing hydrogel scaffold with required structural integrity is a major issue that limits the application of hydrogel in CTE. Therefore, to address the problems associated with existing CTE, this thesis aimed to utilize 3D bioprinting to print cartilage constructs by combining adipose-derived stem cells (ADSCs) and hyaluronic acid (HA) based hydrogels. First, to develop a new cartilage extracellular matrix (ECM) mimetic hydrogel system, we synthesized biotinylated-hyaluronic acid (HA-Biotin) and confirmed the successful grafting of biotin with HA trough Fourier Transform Infrared Spectroscopy (FTIR) analysis. Next, HA-Bio hydrogel was prepared and Streptavidin was mixed with this hydrogel to form partially crosslinked HA-based hydrogel through non-covalent bonding between biotin and streptavidin. Addition of streptavidin also supports higher cell attachment due to the presence of cell adhesion sites in streptavidin. After that, partially crosslinked HA-Bio-Streptavidin (HBS) hydrogel was mixed with sodium alginate and subsequently printed using Rokit INVIVO bioprinter. After printing, 3D scaffolds were submerged into CaCl2 solution achieve ionic crosslinking through ion transfer between sodium alginate and CaCl2. Different parameters such as fiber formation, self-supporting ability, printing resolution, and crosslinker concentration were optimized to get desired 3D printed constructs. In vitro cell proliferation and live/dead staining assay were also performed on 3D cell-laden scaffolds. The result showed that partially crosslinking the biotinylated-HA based hydrogel with streptavidin has a significant effect on printability. Morphological analysis of optimal 3D printed scaffold showed clearly visible pores with desired shape and geometry. Favorable cell proliferation and growth was also observed in 3D HBSA based hydrogel scaffolds. These result further confirmed that double crosslinking HA-based hydrogel could be a good choice for 3D bioprinting based tissue engineering.