(84f) Anisotropic Chitosan-Based Hydrogels for Cartilage Regeneration

Cartilage is a tough, semi-transparent, elastic tissue that assists in reducing friction facilitating bone movement. Cartilage could be ravaged by various diseases and regular physical activities; osteoarthritis is the most common joint disorder requiring significant medical aid.  Tissue engineering or regeneration techniques offer alternative strategies, but require seeding immuno-compatible cells to colonize biodegradable scaffolds to circumvent immune rejection.  Before cells can be seeded to promote the regeneration of the tissue, scaffolds made of biomaterials with biomimetic properties must be formulated.  Both synthetic and natural biomaterials have been explored and processed differently to regenerate tissues both in vivo and in vitro.  Further, different processing strategies have led to the development of novel surgical procedures.  More recently, hydrogels have been desired for cartilage scaffolding because the hydrogel offers an environment similar to physiological conditions.  Also, injectable hydrogels have been extensively explored because they offer a minimally invasive alternative to arthroscopic surgeries and ease of incorporation of cells and biologically active agent.  The objectives of this study are to investigate the bio-mimicry of an anisotropic chitosan-based hydrogel that represents the multilayered architecture and properties of native cartilage.

Hydrogels have been formulated isotropically to match three of the four layers of articular cartilage.  The hydrogels are chitosan based and each combined with a component that is found in native cartilage.  The additional components for the layers are gelatin, hyaluronic acid (HA), and beta tri-calcium phosphate (β-TCP) superficial, radial, and calcified cartilage zones. The transitional zone is formed by the anisotropy of the superficial and radial zones.  Mechanical, rheological, and physical characteristics were assessed on the chitosan-gelatin/ HA/ β-TCP hydrogels of different concentrations at the physiological conditions.  After isotropic analysis of the hydrogels, anisotropy of the hydrogels was tested to establish a hydrogel morphology that is consistent with cartilage. 

The compressive modulus was significantly improved by increasing the chitosan concentration.  Further, increasing the chitosan concentration of the hydrogels increased the rate of gelation as well as the structural integrity at physiological diameters.  Cyclical tests demonstrated repeatable strength and durability with no sign of failure in the cycle range.  Anisotropic gels were formed with different gradations of chitosan-based gels.