Preparation And Characterization Of Photocrosslinked Hydrogel Based On Galactomannan

Articular cartilage injury caused by physical trauma or disease is the cause for millions of people suffering with joint pain and disability around the world.However,cartilage tissue’s structure is unique,which makes the existing treatment methods unable to cure cartilage defects easily.With the development of cartilage tissue engineering,it is possible to completely repair cartilage damage.Scaffold is the key factor for cartilage tissue engineering,and good repair results can be obtained by using excellent scaffold materials.Hydrogel has similar composition and structure to natural cartilage,and is an ideal scaffold for cartilage repair undoubtedly.Therefore,it is of great significance to develop new hydrogels with excellent properties for cartilage tissue engineering.Injectable hydrogels and 3D printed hydrogels have been widely studied for their own advantages.In this study,galactomannan was used as raw material to prepare injectable photocrosslinkable hydrogel and bioink which can be used as 3D printing hydrogel,and they were investigated both materials science and biology.In the first chapter,based on the properties of galactomannan,methylacrylated galactomannans（GM-MA）with three increasing modification degrees were prepared by grafting methacrylate anhydride chemically,which were named GM-MA-1,GM-MA-2 and GM-MA-3.The success of modification was confirmed by FTIR.Further,the photocrosslinked GM-MA hydrogel was prepared,and the basic properties of GM-MA hydrogel were comprehensively evaluated by material characterization such as swelling,rheology and mechanical properties.The test results show that GM-MA hydrogel can maintain a good shape and has a high swelling rate in d H₂O.In addition,GM-MA-1,GM-MA-2 and GM-MA-3 hydrogels all show elastic properties,but GM-MA-1 hydrogels are closer to viscous materials.GM-MA-1,GM-MA-2 and GM-MA-3 hydrogels all behave as elastic materials under pressure,and the compressive strength of GM-MA-2 hydrogel is the best,which is 86.1±8.7k Pa.GM-MA hydrogels with chondrocytes were photocrosslinked in situ,and they were cultured for a period of time.The results showed that chondrocytes were viable,indicating that GM-MA hydrogel had no obvious toxic effect on chondrocytes.The results of HE and SO staining showed that the hydrogel/cell complex formed a classical lacuna structure of cartilage tissue after long-term culture in vitro,which proved that GM-MA is expected to be used as injectable hydrogel for cartilage tissue engineering.In the second chapter,oxidized and methylacrylated galactomannan（Ox GM-MA）was obtained by two-step modification of GM.The modification was also successfully confirmed by FTIR.Solubility and viscosity tests showed that two-step modification process greatly improved the solubility and viscosity of GM.Furthermore,Ox GM-MA solutions with increasing concentrations were prepared into hydrogels by photocrosslinking,namely Ox GM-MA-2,Ox GM-MA-4 and Ox GM-MA-6.Their SEM and porosity data showed that the porosity of hydrogel was above 70%,and the pore size was between 100-200μm.Further swelling,rheological and mechanical tests showed that hydrogels had sufficient stability and high swelling rate in aqueous solution.Hydrogels show viscoelastic behavior and have good elasticity.The compressive strengths of hydrogels are 12.8±1.4 k Pa,52.3±6.7 k Pa and85.2±12.4 k Pa,respectively,which have good mechanical properties.FDA staining results of in-situ cultured hydrogels showed that chondrocytes have good viability on the 1st,3rd and 7th day,which indicated that hydrogel had no obvious cytotoxicity and good biocompatibility.With comprehensive consideration,Ox GM-MA precursor solution with mass concentration of 4%was selected as bioink.Firstly,the printing parameters of 4%Ox GM-MA ink were explored,and printed structures with good outline were successfully prepared through optimized adjustment.On this basis,Ox GM-MA bioink encapsulated chondrocytes at chondrocyte density of 1.2×10⁷ cells per m L containing 0.03%（w/v）tartrazine was printed successfully.And the printed structure containing chondrocytes presented good outline.Then the printed structures were cultured for 3 and 5 days in vitro,results of FDA staining showed that chondrocytes in printed structures still keep alive and have good viability,indicating that Ox GM-MA bioink could be used in cartilage tissue engineering.To sum up,the injectable photocrosslinkable GM-MA hydrogel and Ox GM-MA bioink prepared in this study can both be prepared into hydrogel scaffolds with excellent performance,which expands the research of new 3D printing bioink for cartilage tissue engineering and are expected to play a role in cartilage tissue engineering.