The Preparation And Characterization Of Gelatin-Gellan Gum Hydrogel

Cartilage tissue is an important part of the human body,which could dissipate the weight-bearing stresses to protect the bones from being damaged directly.However,because of the lack of neural lymphatic networks,cartilage defect caused by trauma,disease,and aging has limited the self-repairing capacity.Hydrogels,a three dimensional network material,is similar to soft tissues in terms of water content,biological structure,and physical properties,which has been widely used as cartilage substitute materials.In this thesis,gelatin?Gel?and low acyl gellan gum?GG?with good biocompatibility were chosen as raw materials to construct the hydrogel networks based on different crosslinking methods.The structures and properties of hydrogels were characterized systematically,and their possibility as cartilage substitute materials was also evaluated.?1?The oxidized gellan gum?OG?with aldehyde groups?-CHO?was obtained by oxidizing GG using Na IO₄.Fourier transform-infrared spectroscopy?FTIR?revealed that aldehyde groups exist in OG.Based on the results of determination of aldehyde groups,the optimized oxidization condition was as 40°C,8 h,and the mass ratio of GG/Na IO₄?1:0.9?.The results of particle size by dynamic light scattering?DLS?suggested that the particle size of GG is decresed from 518.4 to 269.0 nm after oxidization.OG exhibits a narrower particle size distribution than GG,which favored the crosslinking between OG and Gel.Both single-network and double-network hydrogels were prepared by OG,Gel,and Ca²⁺.The results of FTIR revealed that the aldehyde groups were consumed by the reaction between Gel and OG,leading to a red-shift of C-O.At the OG concentration of 2 wt%and Ca²⁺content of 0.10 wt%,the network structure of obtained hydrogel is tighter than those of other hydrogels,with the highest compressive strength at 90%strain,and the lowest equilibrium swelling ratio.Besides,the properties of double-network hydrogel were improved,compared to that of single-network hydrogel,which might meet the demand for application as a compression composite in vivo.?2?Different degrees of methacrylation?DM?of methacrylate gelatin?Gel MA?were synthesized by Gel and methacrylic anhydride?MA?.The DM increases with the increase amount of MA.Gel MA10 has the highest DM?81%?,which corresponds to the highest brittleness and hardness.Herein,Gel MA10 and Gel-OG were chosen as rigid network and flexible network,respectively.The Gel-OG/Gel MA10 composite hydrogel was prepared via UV crosslinking and Schiff's base reaction.FTIR indicated that Gel MA was synthesized successfully.FESEM suggested the double network structure of composite hydrogel,Gel-OG network,and Gel MA network,which was tighter than that of Gel-OG hydrogel.Besides,compared to the Gel-OG hydrogel,the compressive strength of composite hydrogel at 75%strain is improved from 0.12 to1.10 MPa,and the equilibrium swelling ratio is decreased from 1330%to 900%.This work might provide an approach by a two-step crosslinking process to construct the hydrogel with double network structure for cartilage application.?3?The hydroxyapatite?Hap?was modified by tetraethyl orthosilicate?TEOS?and3-aminopropyl-triethoxysilane?APTES?to obtain the amino hydroxyapatite?m Hap?.The Gel-OG/m Hap hybrid hydrogel was prepared by incorporating different amounts of m Hap into Gel-OG hydrogel.FTIR showed that amino groups?-NH₂?were successfully introduced in Hap,and the good interactions between m Hap and Gel-OG network.XRD suggested that the crystal shape of Hap is not changed by the modification.Both DLS and FESEM indicated that the particle size of Hap is decreased from 750.2 to 187.8 nm after modification.The m Hap exhibited an even distribution in the solution.Notably,the composite with 1 wt%m Hap has the tightest network,highest compressive stress?2.03 MPa?,lowest swelling ratio?769%?and degradation rate than other hydrogels.The MTT test showed that the Gel-OG/m Hap hydrogels have good biocompatibility.This work might provide an approach using silane coupling agents to construct the organic composite/inorganic hydrogel,as well as to improve its properies.