Dual composition Chondroitin Sulfate and gelatin biomimetic hydrogel based on tyramine crosslinking for tissue regenerative medicine

Abstract

Hydrogels with bone biomimetic microenvironment are of great importance for the development of bone-graft materials. Herein, a biomimetic hydrogel, which was based on biopolymer as an extracellular matrix (ECM) mimicking components with the incorporation of biphasic calcium phosphate (BCP) nanoparticles, was prepared via the enzymatic crosslinking. Chondroitin sulfate and gelatin were first modified to form tyramine (TA) moieties on the natural polymers, which were ultilized as precursors for in-situ forming hydrogel (CDTA-GTA) under physiological conditions. The amount of CDTA to GTA was optimized for gelation time as well as degraded ability with in collagenase medium. Increasing the CDTA amount delayed the time for crosslinking process, but the water holding capacity was increased. The subjection of BCP into CDTA-GTA hydrogel produced an injectable system with suitable biomineralizated property. This hydrogel formed more rapidly in 90–100 s under 3 mM H2O2 and 0.125 mg/mL HRP enzyme. BCP/CDTA-GTA hydrogel exhibited the porous structure (100–300 µm in diameter) with the homogenous distribution of BCP nanoparticles on the wall of the interconnected networks, suggesting the good environment for bone growth. Further, the degradation process of the obtained hydrogel followed pseudo-first-order kinetics in the collagenase condition. After soaking in SBF for 28 days, SEM following EDS technique confirmed the aggregation of the calcium and phosphorus on the surface of CDTA-GTA hydrogel (Ca/P ratio ∼ 1.34) which improved in case of BCP/ CDTA-GTA hydrogel (Ca/P ratios ∼ 1.77). Through X-ray diffraction, the formation of calcite crystals was only detected with BCP hydrogel. In vitro cytotoxicity assays with hMSC cells exhibited non-toxicity of the biomimetic hydrogel. Interestingly, the remarkably enhancement of the level intracellular calcium deposit as well as the activity of ALP-osteogenic related marker were observed in MSC cells treated with biomimetic hydrogel, showing superior scaffold osteogenic potential. These results indicate that enzymatic cross-linked CDTA-GTA gel with BCP nanoparticles would be a favorable option to accelerate bone repair and thus should potentially be useful for osteochondral tissue engineering.