Thiolated Chitosan/Silk Fibroin/Bioactive Glass Hydrogels And Their Applications In Repairing Bone Defects Associated With Tumor Resection

In comparison to the cases correlated to the repair of non-tumor-related bone defects,the repair of bone defects caused by tumor-related bone resections needs overcoming more difficulties.Thus,it is important to develop an effective and safe method for the postoperative bone repair of bone defects that are resulted from tumor-related bone resection.In this study,a new type of double-network composite hydrogel was developed by using thiolated chitosan,silk fibroin and gallium-doped bioactive glass nanoparticles.The results demonstrated that the optimally achieved composite hydrogels have enhanced mechanical properties,significantly improved biodegradability resistance,and abilities to synchronously promote bone repair and inhibit the growth of osteosarcoma cells.The major investigations and results were briefly summarized as follows.(1)Preparation and characterization of CNS dual-network hydrogelsCS-NAC with a high substitution degree of thiol groups and good water solubility was synthesized by coupling N-acetylcysteine(NAC)onto chitosan chains.SF was prepared using a high concentrated Li Br solution as a solvent.The CNS dual-network hydrogel was built by using CS-NAC and SF together.The hydrogel was able to be rapidly gelation at physiological temperature and p H.The rheological results revealed that CNS dual-network hydrogels were injectable,and they exhibited higher strength and good elasticity than the single-network hydrogels constructed by either CS-NAC or SF alone.The optimized CNS dual-network hydrogels have high porosity with a large average pore size.In vitro assessments on gel-cell constructs show that CNS dual-network hydrogel can support the growth of seeded cells and the synthesis of extracellular matrix.(2)Preparation and characterization of GaBG/CNS composite hydrogelsThe BG and GaBG nanoparticles were synthesized using a sol-gel method.The obtained nanoparticles were spherical with well-defined dispersity and high specific surface area.Their particle size was estimated to be about 350 nm.BG/CNS composite hydrogel and GaBG/CNS composite hydrogel were prepared by incorporating two kinds of nanoparticles into CNS gels,respectively.The results based on rheological measurements show that both BG/CNS and GaBG/CNS composite hydrogels have shear-thinning properties.Compared with CNS dual-network hydrogels,BG/CNS and GaBG/CNS composite hydrogels have higher mechanical strength.SEM images for BG/CNS and GaBG/CNS composite gels showed that these hydrogels had well-interconnected porous structures,and BG or GaBG nanoparticles were distributed on the wall of pores in the gel without obvious agglomeration.Compared with CNS dual-network hydrogels,the addition of nanoparticles did not significantly affect the pore morphology of BG/CNS and GaBG/CNS composite hydrogels.In vitro ion release tests indicated that GaBG/CNS composite hydrogel can sustainably release Si,Ca and Ga ions for around 4 weeks.After mineralizing BG/CNS and GaBG/CNS composite hydrogels in the simulated body fluid for a period of up to 28 days,hydroxyapatite layers were detected on the surface of the hydrogels.In vitro cell experiments showed that the optimized GaBG/CNS composite hydrogel had no side effects on mouse osteoblast MC3T3-E1,but showed obvious cytotoxicity on UMR-106 or MG-63 osteosarcoma cells.(3)Effects of GaBG/CNS composite hydrogel on calvarial bone defect repair and osteosarcoma suppressionA critical-size rat calvarial bone defect model was established and it was repaired by filling with the optimally achieved GaBG/CNS composite hydrogel.The results based on micro-CT examination,volume fraction,trabecular thickness and trabecular number in new bone tissue demonstrate that GaBG/CNS composite hydrogel had no significant side effects on the formation of new bone tissue in the defect area.The osteosarcoma model was established by using nude mice and the optimized GaBG/CNS composite hydrogel was injected into the residual osteosarcoma region to inhibit the growth of osteosarcoma.The results obtained from tumour volume,body weight,tumour weight and histological analysis revealed that GaBG/CNS composite hydrogel can significantly suppress the growth of tumors without side effects on major organs of nude mice.These results demonstrate that the newly developed GaBG/CNS composite gels have a high potential in promoting bone regeneration while suppressing osteosarcoma growth.