Development of nanoparticle / hydrogel based composite structures for cartilage tissue engineering

Bioactive structures with unique biophysical and chemical properties of nanoparticles give great hope for the future development of tissue engineering applications. The purpose of this study to develop gelatin methacrylate (GelMA) hydrogel scaffold, functionalized with alginate-chitosan core-shell nanoparticles to enhance chondrogenic differentiation. Firstly, core-shell nanoparticles were synthesized with chitosan and alginate biopolymers. Different preparation conditions were applied to achieve monodisperse alginate- chitosan core-shell nanoparticles at nanoscale. Monodisperse alginate-chitosan core-shell nanoparticles which were prepared by modified protocol were measured to be 60 ± 3 nm. Different preparation conditions were applied to obtain optimum loading efficiencies and release profiles of growth factors (transforming growth factor beta-1 (TGF β-1) and insulin like growth factor-1 (IGF-1)) in the formation of the dual nanoparticular release system. According to the chosen preparation condition, the loading efficiency of TGF β-1 and IGF-1 was 93.34 ± 0.51 and 91.92 ± 0.22%, respectively. When the 21 days release profile results were evaluated, the amounts of TGF β-1 and IGF-1 were measured as 15.86 ± 0.30 and 28.71 ± 2.27 ng/mL, respectively. Then, GelMA hydrogels were synthesized by photopolymerization method. The prepared nanoparticles and adipose tissue derived mesenchymal stem cells were encapsulated into GelMA hydrogels and incubated in vitro for 3 weeks. The effects of hydrogel, loaded and unloaded core-shell nanoparticles encapsulated hydrogels were evaluated by biochemical and histological analysis on chondrogenesis of adipose tissue derived mesenchymal stem cells. In the presence of chemical cues (chondrogenic medium), the content of DNA in the group containing TGF β-1 and IGF-1 loaded nanoparticles in hydrogel increased by 1.71 and 5.98 times, respectively, compared to the groups with and without nanoparticles on day 21. On the other hand, it was determined that glycosaminoglycan (GAG) production (573.60 ± 1.60 µg/sample) was significantly induced in the group containing both chemical cues and nanoparticles. In addition to biochemical assays, histological analyzes such as GAG and Type-II collagen staining also showed that the application of chemical and biophysical cues were increased GAG and Type-II collagen depositions. In summary, hydrogel scaffold functionalized with nanoparticles successfully occurred suitable environment for cartilage formation and thus it is a promising construct for cartilage tissue engineering applications.