Fabrication Of Self-Assembled Micro-Nano Structures And Their Mechanisms For Regulating Cell Adhesion

Self-assembled micro-nano structures are ubiquitous in nature and constitute highly ordered hierarchical structures in living organisms.As an environment for cell survival,the extracellular matrix is able to fabricate hierarchical micro-nano structures through the self-assembly process of glycoproteins,laminin and collagen components,which regulate physiological processes such as signaling transmission,cell adhesion,migration,proliferation and differentiation.Good cell adhesion plays an important role in many biological processes such as embryo development,tissue regeneration and wound healing.Therefore,it is of great significance to study the effects of self-assembled micro-nano structures on cell adhesion and related mechanisms.In this thesis,the self-assembled micro-nano structures of cholesteric cellulose nanocrystals and photo-responsive liquid crystalline block copolymers were fabricated respectively,and the effects of the above self-assembled micro-nano structures on cell adhesion and their mechanisms of action were investigated.In Chapter 2,cellulose nanocrystals(CNC)were successfully prepared by sulfuric acid hydrolysis and characterized for their morphology and physicochemical properties.Cholesteric and amorphous cellulose nanocrystal films(L-CNC and A-CNC)were prepared by evaporation-induced self-assembly of CNC suspension and addition of strong electrolytes in the CNC suspension,respectively,and the characterization revealed that the L-CNC have a left handed cholesteric orientation,while the A-CNC was randomly arranged.Mouse fibroblasts(L929)were cultured on the surface of the two different micro-nano structures,and experimental characterization such as fluorescence staining and single-cell force spectroscopy showed that the cell adhesion on the L-CNC surface was superior to that on the A-CNC surface.Immunofluorescence staining and Western blot showed that micro-nano structures of L-CNC surface enhanced integrin-mediated cell adhesion and promoted intracellular Talin expression and F-actin assembly,which in turn affected the cell adhesion.In Chapter 3,in order to further explore the dynamic regulation of surface micro-nano structures on cell adhesion,liquid crystalline block copolymers with dynamically switchable morphology of surface in response to light were synthesized based on azobenzene.The polymer coatings with oriented morphology were successfully prepared and could rapidly respond to UV light(365 nm)to realize the transformation of micro-nano structures of surface.Mouse fibroblasts(L929)were cultured on the surface of the material,and the effect of the photo-responsive micro-nano structures of surface on the cell adhesion behavior was initially explored.In this thesis,the effects of micro-nano structures of surface formed by self-assembly of cholesteric cellulose nanocrystals and photo-responsive liquid crystalline block copolymers on cell adhesion and the related adhesion mechanisms are explored respectively,which is helpful to better understand the interaction between materials and cells.It provides a new starting point for the design of biomedical materials,especially self-assembled bionanomaterials,implant-related materials such as tissue repair materials.