Preparation of an enzyme catalyzed in situ forming hydrogel based on chemically modified tragacanth for cartilage tissue engineering

In the present study, an enzyme catalyzed in situ forming hydrogel based on chemically modified tragacanth was prepared and then evaluated for use in cartilage tissue engineering. For this purpose, firstly tyramine was conjugated on the galacturonic acid methyl ester units of gum tragacanth (GT) via ammonolysis of methyl ester groups in heterogeneous media. Then, the hydrogel was prepared by mixing of functionalized polymer, horseradish peroxidase (HRP) and hydrogen peroxide using a double syringe equipped with a mixing chamber. Then, cell viability of the encapsulated human mesenchymal stem cells (hMSCs) and in vitro chondrocyte differentiation of them, incubated in the presence of differentiation medium, were investigated. After mixing of the gel promoters, hydrogel formation was obtained due to enzyme catalyzed oxidative coupling reaction between phenolic groups of tyramine functional groups. The tunable gelation time of hydrogels was less than 2 minute. Viability of the encapsulated cells was more than 95% and 75% after 2 h and 21 days of incubation. The expression of chondrocytic genes and sulphated glycosaminoglycan indicated that the encapsulated hMSCs differentiated to chondrocyte cells during in vitro differentiation time.