Preparation And Properties Of Micro-nano Corn Stalk Cellulose Reinforced Tissue Engineering Hydrogel

Hydrogel is widely used in tissue engineering since it has similar structure and properties to extracellular matrix(ECM).Freeze dried scaffold of hydrogel can achieve temporary replacement and mechanical support for the defect site,but there will be a second swelling process in the body environment after implantation.The "freeze drying and swelling" process has effects on properties of hydrogel,especially mechanical properties.Here,micro-nano corn stalk cellulose reinforced gelatin composite hydrogels(CF/GEL)were designed and prepared.The effects of cellulose fiber content and hydrogel matrix on structure and properties of composite hydrogels and freeze dried scaffolds composition were discussed and the mechanism was analyzed.On the basis of this,the influence of “freeze drying and swelling” process on the mechanical properties of composite hydrogel was discussed,which provide further evidence for applicarion of tissue engineering hydrogel.Firstly,cellulose microfibers(CMF)were extracted from corn stalk by steam explosion,alkali treatment and bleaching,and then CMF were modified into TEMPO oxidized cellulose nanofibers(TOCNF).The effects of extraction and modification processes on cellulose fiber size,crystallinity and chemical structure were investigated.TOCNF was obtained with a diameter of 17.40±4.00 nm,a length of 700-1500 nm,an aspect ratio of 53-88 and a crystallinity of 74.98%.The carboxyl group was successfully introduced into the cellulose in TEMPO oxidation treatment process.The strength,modulus and failure strain of the composite hydrogel were improved by adding cellulose.In the micro-nano cellulose reinforced composite hydrogel,the interface interaction between TOCNF and gelatin matrix was higher than intereaction between of CMF and gelatin matrix.By adding 3% TOCNF in the composite hydrogel,the compressive strength was increased by 219.78% and the failure strain was increased by 29.10%.The addition of sodium alginate(ALG)and oxidized sodium alginate(OA)forms an interpenetrating network(IPN)structure between gelatin and ALG/OA,which further adjusted the mechanical properties and significantly slows down the degradation rate.Compared with the initial hydrogel,the compressive strength and modulus of the freeze dried scaffold were significantly improved while the compressive strength and modulus of the swollen hydrogel were decreased,but the failure strain of swollen hydrogel increased significantly.The addition of cellulose fibers,ALG and OA effectively alleviated the loss of mechanical properties of the composite hydrogel caused by the freeze drying and swelling process.