The Preparation And Properties Of Silk Fibrion/Cellulose Nanocomposite Materials

Silk fibroin has a good biocompatibility,biodegradability and low inflammation in vivo,which makes silk fibrion possess broad applications in the field of biomedical materials,however,the mechanical properties and biological activities of the regenerated silk fibroin materials need to be further improved to meet the demands of different tissue engineering.Cellulose nanofibrils(CNFs)also have an excellent biocompatibility and high strength and the CNFs structure can provide guide for cells.Whereas,the complex separation technology of CNFs and low degradation ratio in vivo limit their applications as biomaterials.Previous studies showed that cellulose could be well dissolved in LiBr aqueous solution.CNFs of cellulose have high crystallinity and strong resistance to solvents,so this paper envisaged to separate CNFs by controlling dissolved degree of microcrystalline cellulose heating in LiBr aqueous solution.Manwhile,LiBr aqueous solution isalso commomly solvent used for dissolving silk fibrion.Then adopting LiBraqueous solution as co-solvent to dissolve silk fibroin and cellulose,we candirectly prepared silk fibroin/cellulose nanocomposites.First of all,this paper studies dissolution conditions influences on microcrystalline cellulose dissolving and regenerated cellulose films properties.The results showed that microcrystalline cellulose can be well dissolved in 9.3M LiBr aqueous solution when the temperature is higher than 110 °C with dissolving more than 1 h.The mechanical properties of regenerated cellulose films will be significantly reduced with the increasing of dissolution time and temperature.Theobtained cellulose solution contains a lot of CNFs with a diameter distribution of 10-50 nm,their sizes are close to natural CNFs.Then,we served LiBr solution as co-solvent to dissolve and prepare different blend ratio silk fibroin/cellulosenanocomposite films which was composed of silk fibrion,cellulose and CNFs.Due to cellulose solutionquickly gelling,CNFs were uniformly distributed in composite films.The FTIR results showed thatnew intermolecular hydrogen bonding formed between silk fibrion and cellulose micromolecular.Because of the existence of cellulose,CNFs and the hydrogen bonding interaction between SF and cellulose,the nanocomposite mechanical propertiesincluding tensile strength,elongation andYoung’s modulussignificantly enhanced with the increasing of cellulose content.Futher,we studied the nanocomposite films biocompatibility by HUVECscultivated in vitro.The results showed that silk fibroin/cellulose nanocomposite filmshavea good biocompatibility and can support the adhesion and proliferation of HUVECs.Moreover,HUVECson pure cellulose film were higher viability,which hinted cellulose and its CNFs promoted cell activity of silk fibrion materials.The in vitro degradation experiments showed that the cellulose was very difficult to be degraded in Protease XIV solution and the degradation rate of nanocomposite films increased gradually with the introduction of silk fibroin content.Finally,on the basis of above methods,we prepared silk fibroin/cellulose nanoporous materials,and preliminary studied the influence of freezing temperature and blending ratio on the structure of porous materials.The results showed that CNFs formed regular pore structure with a diameter distribution of 50-120μmwhen the freezing temperature is-20 °C,the hole wall has many CNFs,when the freezing temperature decreased to-40°C,pore regularity would be deviated.With the increasing of the content of silk fibroin,the holes became smaller and fibril began to exposemore evidently in pore.With silk fibrion content reached to 50%,CNFs wereuniformly distributed in the hole of porous materials.At the same time,water absorption tests showed that the porous materials have good hydrophilicity,water absorption rate is higher than 90% and slightly increased with cellulose content.From this study,we proposed a simple and effective method to prepare silk fibroin/cellulose nanocomposite materials,its mechanical properties were obviously enhanced,biocompatibility is excellent and degradation rate can be adjusted and controlled to a degree.Thus,it provided a new idea and method for expansion of silk fibroin as biomaterials.