Preparation And Property Study Of Porous Poly (Vinyl Alcohol) Hydrogels

Since articular cartilage diseases incurred by high-speed impact-induced trauma or natural aging continue to increase,the repair of articular cartilage injury has been one of the main challenges in orthopedic surgeries.Traditional repairing procedures for treating articular cartilage injury is time-consuming and often have side effects such as the degraded surface of the restored tissue,the weak combination between the tissue and surrounding cartilage,and the weak strength of the restored tissue.The development of the artificial articular cartilage replacement technology has resulted in many new ideas for the treatment of joint injury.As a result,the patients can be treated with surgery to restore mobility function within a relatively short time period.Polyvinyl alcohol(PVA)hydrogel is widely used in artificial articular cartilage substitute materials because of its good biocompatibility,excellent mechanical properties and superior water absorption ability.However,the PVA hydrogel is not bioactive,and cannot combine the merits of high mechanical strength and porous structures,which allow cells to grow into repairing materials and to combine well with peripheral cartilage tissue,limiting its use on bionic cartilage.In this thesis,the PVA/AG hydrogel with both high strength and porous structure is made by the freeze-thawing method,in which the non-toxic and good biocompatible agarose(AG)is added as pore-forming agents.The effects of the preparation process on the mechanical properties of PVA/AG hydrogel are studied.The structure and composition of PVA/AG hydrogel are analyzed.The tensile and compressive mechanical properties of PVA/AG hydrogel are investigated with in-lab experiments.The pore formation mechanism of the PVA/AG hydrogel is explored.The AG removal method and the effects of AG removal on the structure and compressibility of the PVA hydrogel are investigated.With a PVA mass fraction of 15% and an AG mass fraction of 4% under three freeze-thaw cycles(frozen for 16 h in one cycle at the temperature of-20 °C,and thawed for 8h in another cycle at the temperature of 18 °C),we can obtain the PVA/AG hydrogel with the compressive strength of 5.12 MPa and compression modulus of 0.82-17.15 MPa.The size of most of pores is over 100 ?m and these pores are highly 3D interconnecting.The porosity is 72.98%,and the water content is 75.67%.The PVA/AG hydrogel is frozen with liquid nitrogen,and then freeze-dried using a freeze drier.The AG is removed by immersing in deionized water at 45 °C.FT-IR indicates the removal of AG and the connectivity.With the use of liquid nitrogen freezing to make the crystallization of PVA hydrogel more thoroughly,the compressive strength of porous PVA hydrogel(without AG)after liquid nitrogen frozen is 6.05 MPa and the compressive modulus is 0.64-19.8 MPa,which satisfies the strength requirement of artificial cartilage replacement materials.The PVA porous hydrogel as prepared in this work has good biocompatibility,excellent mechanical properties and suitable pore size for the proliferation of cells.The future work is required to confirm that the PVA porous hydrogel could be well combined with surrounding tissue in order for them to be applied in the field of artificial articular cartilage replacement.