Preparation And Properties Of Multifunctional Hydrogel Based On Sodium Alginate/Gelatin

Biomass materials represented by alginate,gelatin and nanocellulose have gained widespread attention in the fields of biomedicine,energy storage,et al.Hydrogel is a hydrophilic three-dimensional network structure with a microstructure similar to that of extracellular matrix and is considered to be the closest biofunctional material to living tissue.It is of great research significance to design and construct biomass hydrogels using biomass as a substrate to achieve high value use of biomass materials.Meanwhile,with the development of high technology fields such as artificial intelligence,the disadvantages of traditional hydrogels,such as poor mechanical properties and single function,no longer meet the needs of people in production and life.Thus,it is urgent to develop multifunctional biomass-based hydrogels such as injectable,self-healing,conductive and self-adhesive.In this thesis,two multifunctional hydrogels based on alginate/gelatin were designed and prepared via a simple one-step method using the synergistic effect of dynamic imine and hydrogen bonds,and their properties and applications in the fields of bone repair and flexible sensors were investigated,respectively.(1)Oxidized alginate(OSA)was prepared by oxidation reaction via sodium periodate.Followed by the addition of gelatin(Gel)and nanocellulose(CNFs),an injectable,self-healing nanocellulose reinforced sodium alginate/gelatin hydrogel(OSA/Gel/CNF)was successfully prepared through a simple one-step method without chemical cross-linking agents.The introduction of CNFs considerably increased the compressive modulus of the hydrogel up to 361.3 KPa.In addition,under the synergistic effect of dynamic imine bonds and hydrogen bonds,the OSA/Gel/CNF hydrogel showed excellent injectability and the gelation time was up to 200 s,which ensured smooth extrusions and curing.At the same time,the OSA/Gel/CNF hydrogel was self-healing with a self-healing efficiency of 92%at 24 h.Finally,the OSA/Gel/CNF hydrogel exhibited a cell viability of more than 96%with no apparent biotoxicity.In vitro biomineralization,its osteogenic activity(Ca/P～1.69)was similar to that of human bone tissue,which showed a good osteoblast differentiation.(2)TA@CNC was prepared by coating tannic acid(TA)on the surface of cellulose nanocrystals(CNC).As a reinforcer for the hydrogel system,TA@CNC also enhanced the self-adhesive,UV-filter and anti-bacterial properties of the material.Conductive hydrogels(OGTCG)with self-adhesive,self-healing,transparent,anti-UV,anti-freeze,anti-bacterial and non-toxic properties were prepared as flexible sensors by using OSA,Gel and TA@CNC blended under a water/glycerol system with the introduction of borax.Comparing to human skin,the OGTCG hydrogel had strong tensile properties(0-250%),high toughness(218.67 KPa)and elastic modulus(100.32 KPa).The transparency of it could reach 94%,while the TA@CNC had an obvious blocking effect on UV.The OGTCG hydrogel had good self-healing abilities with an efficiency of over 90%at 6h due to the combination of imine,borate,and hydrogen bonds.The addition of glycerol allowed the OGTCG hydrogel to withstand-80℃,greatly broadening the application of the hydrogel in extreme environments.Moreover,the hydrogel is non-toxic.The interaction between the TA@CNC and borax could make the hydrogel antibacterial.Due to the ionic migration,the OGTCG hydrogel had an electrical conductivity of 2.3 mS cm-1 and a sensitivity of 3.97.Finally,its application to monitor human movement under small or large strains had demonstrated its rapid response in practical applications and its potential for real-time monitoring.In conclusion,two multifunctional hydrogels were constructed by a simple one-step method using sodium alginate/gelatin as a substrate and the synergistic effect of dynamic covalent bonds and hydrogen bonds without any chemical cross-linking agent.Their applications in the fields of bone repair and flexible sensors were studied,providing a new research method for the realisation of high value utilisation of biomass materials and multifunctionalisation of hydrogels.