Preparation Of High-Content Chitin Nanowhisker/Polycitrate Nanocomposite And Its Direct Ink Writing 3D Printed Scaffold

Chitin whiskers(CWs)are obtained by chitin through acid hydrolysis,TEMPO oxidation and other methods,and have the characteristics of high elastic modulus,high mechanical strength,biocompatibility and biodegradability.It can be compounded with polymers to improve the mechanical properties,biocompatibility and biodegradation of polymers,and thus CWs are widely applied in the fields of wound dressings,antibacterial materials and bone tissue engineering.Polycitrate is a thermosetting elastomer with excellent biodegradability and rubber-like elasticity,and can be used in the field of biomedicine.This article used polycitrate with excellent biocompatibility and elasticity to modify CW-based materials,and aims to improve the stability of CW-based materials in water and the mechanical properties.The high-content chitin whisker/polycitrate composite scaffolds with excellent biocompatibility and mechanical properties were prepared by freeze-drying method and direct-ink-writing 3D printing method in order to be applied to tissue engineering.The main contents are as follows:(1)Preparation of chitin whiskers by acid hydrolysis method,preparation of POFC prepolymer by melt polycondensation method,and exploration of the effects of CW/POFC compound ratios on various properties of CW/POFC composites.Using TEM,SEM,DSC,BET,and mechanical property testing to characterize the structure and performance of the CW/POFC composites.The conclusions can be drawn as following: when the POFC content is low,the internal structure of the composites is loose,and when the POFC content is high,the internal structure of the composites is relatively dense;when the POFC content increases,the tensile strength and Young's modulus of the CW/POFC composites decrease,but the elongation at break increases significantly,indicating that the introduction of POFC can improve the toughness of the CW-based composites;when the POFC content varies,the pore size distribution,cross-linking degree,swelling degree and in vitro degradation performance of CW/POFC composites differ;when the ratio of CW and POFC is 7:3,6:4 and 5:5,CW/POFC composites exhibit the best overall performance.(2)CW/POFC composite porous scaffolds can be prepared by freeze drying,and the pore structure has a certain degree of orientation.When the pre-freezing temperature is low,the pore size is small;when the POFC content is high,the orientation regularity of the pore structure is reduced.This shows that the useage of CW/POFC as a material for the preparation of composite stents is feasible.(3)The CW/POFC composites with a composite ratio of 7:3,6:4 and 5:5 are configured as inks with different solid contents,and the printability of the CW/POFC inks is preliminarily analyzed by rheological tests,and then 3D printing is performed using direct ink writing(DIW).The conclusions are drawn as follows: CW/POFC ink is a pseudoplastic fluid,which not only has excellent viscoelasticity and thixotropy,but also exhibits a strong shear thinning behavior,which is suitable for DIW printing requirements;by measuring the dimensions of the extruded filaments printed by DIW and morphological observation of the stent structure,it is found that when the solid content is 30 wt%,CW/POFC-64 and CW/POFC-55 inks have excellent printability;as the CW content decreases,the self-supporting property of the CW/POFC structure weakens.