Fabrication and characterization of collagen, hyaluronic acid and chondroitin sulfate scaffolds for cartilage tissue engineering applications
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Native cartilage has very little capacity for self-healing and even the current clinical methods have limited ability to regenerate functional cartilage. In the recent decade research related to cartilage repair has been increasingly focused on tissue engineering solutions that offer scaffold-based strategies for new cartilage formation. The combination of collagen (COL) with two glycosaminoglycans, chondroitin sulfate (CS) and hyaluronic acid (HA) has received widespread interest because all three are naturally abundant in the native cartilage tissue. The objective of this thesis was to fabricate and characterize COL, HA and/or CS containing scaffolds applicable for cartilage tissue engineering. Porous 3D scaffolds were fabricated by freeze-drying and cross-linked with either 1-ethyl-3-(3-dimethylaminopro-pyl)-carbodiimide hydrochloride / N-hydroxysuccinimide (EDC/NHS) or genipin (GP). Fabricated COL+CS/HA and COL+CS+HA scaffolds were characterized by compression and water uptake testing, Fourier transform infrared (FTIR) spectroscopy and micro-computed tomography (micro-CT) imaging. In general, the 80 wt.% COL containing composite scaffolds endured fabrication and both cross-linking procedures better than the 60 wt.% COL containing composite scaffolds. Water uptake ability was higher in GP cross-linked versus EDC/NHS cross-linked scaffolds, in the 80 wt.% COL containing versus 60 wt.% COL containing scaffolds and in COL+HA versus COL+CS composite scaffolds. The swelling/shrinkage upon water uptake of all of the scaffolds was below 20%; in most cases around 10%. FTIR spectra confirmed successful cross-linking with both GP and EDC/NHS and micro-CT images revealed highly porous microstructure (88-94%) with interconnected pores (pore sizes 26-57 μm) in all the scaffolds. The dry scaffolds had significantly higher compressive modulus than the corresponding wet scaffolds; the difference being bigger with GP cross-linked scaffolds. In case of both dry and wet scaffolds the three highest compressive modulus values were measured from CS containing scaffolds. Two scaffold groups with the lowest compressive modulus contained COL and HA. Both wet and dry scaffolds recovered well from compression. This thesis demonstrated successful incorporation of CS and/or HA to COL in order to fabricate a highly porous freeze-dried 3D scaffold applicable for cartilage TE. In addition, the novel crosslinker GP proved to be a promising alternative to the conventional EDC/NHS crosslinker.