Preparation And Properties Of High Strength Natural Protein Hydrogels

Hydrogels prepared with natural proteins as the basic unit of the network have excellent properties,such as good biocompatibility and biodegradability,and low cytotoxicity and immunogenicity,endowed natural protein hydrogels with broad application prospects in biomedicine and other fields.However,there are few studies on high-strength hydrogels of globulin at present,and many artificial polymers such as polyacrylamide had been introduced into the hydrogel system,which affected the properties of natural protein hydrogels.Studies have found that tyrosine chemical bonds play an important role in the mechanical properties of natural materials,thus the tyrosine bonds can be used as the basic structure of the new protein gels.Bovine serum albumin（BSA）contains a large amount of tyrosine,which provides the basis for the formation of dityrosine bonds.Therefore,BSA was used as model proteins to prepare BSA-Ru（II）hydrogels with Ru（II）as an initiator in this thesis.And three kind of BSA-based high strength hydrogels were prepared through chemical,ionic and physical crosslinking methods respectively:1.Based on the chemical cross-linking structure composed of dityrosine bonds,EDC/NHS was used to couple the carboxyl and amino groups of the BSA molecule to form amide bonds,forming a second chemical cross-linking network,and finally prepared bi-chemically cross-linked BSA SN hydrogel with excellent compression properties（Ec=300 k Pa,εc=89%,σc=38 MPa）and good elasticity（dissipated energy of5.96 k J/m³ atεc=50%）.2.Based on the chemical cross-linking structure composed of dityrosine bonds,La³⁺ions were introduced into the hydrogels to form the ionic crosslinking points through ionic interaction,preparing chemical/ion hybrid cross-linked BSA SN hydrogels with good energy dissipation capabilities and excellent compressive properties（Ec=2121 k Pa,εc=88.74%,σc=94.44 MPa）.3.Based on the chemical cross-linking structure composed of dityrosine bonds,chemical/physical hybrid cross-linked BSA DC hydrogels was prepared through heating process without introducing other monomers.The BSA DC gel showed high strength,large hysteresis performance,fast self-recovery and excellent fatigue resistance at room temperature.The compressive strength of BSA DC gel was 37.81MPa,which was equivalent to articular cartilage.Moreover,the gel also exhibited high transparency and non-swelling at pH=3.0 and pH=10.0,thereby maintaining high mechanical performance.Combining the properties of simple preparation,high strength and non-swelling,BSA DC gel had shown great potential in the field of biomedicine.