Construction And Functionalization Of Artificial Cell Wall Based On Single Cell Surface

In nature,the behavior of most biological cells is closely related to the surface of the cell membrane and cell wall,and all cellular behavior is directly or indirectly controlled or regulated by the interface between the cell surface and the external environment.The cell surface engineering technology is introduced into the cell surface by using chemical methods to design an"artificial nano cell wall"with good compatibility,which is considered to be the most promising biotechnology.Then,the artificial cell wall becomes the outer surface of the cell in the coated cells,which significantly improves the viability and stability of the cell in the harsh environment,and expands the application of this nuclear shell structure in cell catalysis,cell sensors,cell therapy,tissue engineering,etc.Meanwhile,the change of the cell surface will inevitably lead to change in cell function.Therefore,this thesis has carried on the different design synthesis to the artificial shell according to the demand of different cell template.By regulating the synergistic effect of the artificial cell wall with the internal and external environment of the cell,the potential function of cell in shell structure can be excavated.The specific research contents are as follows:Proteinosomes were used as coating templates.Metal chelate complexes(TA-Fe³⁺)were coated on the surface of simulated cells?protein capsules?by layer-by-layer self-assembly technology.Under vacuum drying conditions,the successful coating of the TA-Fe³⁺shell allowed the simulated cells to maintain their original shape,and the Young's modulus of cell surface increased from 0.95 GPa to 1.84 GPa before and after coating,which effectively enhanced the mechanical strength of proteinosomes and resisted protease and TCEP.By adding EDTA,the formation and degradation of artificial shell could be regulated,and then the loaded DNA was effectively released.At the same time,the electrostatic gated artificial shell could regulate the permeability of proteinosomes by electrostatic interaction with the substrate,thereby regulating the activity of loading alkaline phosphatase?ALP?.Due to the introduction of tannic acid?TA?in the artificial shell,the TA-Fe³⁺shell had antioxidant capacity,which can eliminate free radicals,such as ABTS⁺.By constructing a protective layer on the surface of inactive proteinosomes,it lays a foundation for the subsequent coating of living cells,and has more knowledge and understanding in the construction methods,protection and functional regulation of artificial shells.Thus,creating an intelligent artificial cell wall to endow the fabricated cells with more advanced functionalities is highly desirable.An efficient and cytocompatible approach was proposed to generate a type of viable artificial cell wall based on direct self-assembly of coacervate microdroplets?BSA-NH₂ and Dextran-COOH?on individual cellular surface,which could protect the fabricated cell against various external stresses,and then could prolong the storage of the fabricated cells over two months.Moreover,as a type of viable artificial cell wall,it could not only help the fabricated cell sequester nutrients or functionalized substances like catalase,or iron oxide nanoparticles actively from the solution which then made the fabricated cell more versatile,but also allow the fabricated cell proliferate.Significantly,the artificial cell wall also showed heritable behavior which could reserve its protection to as far as the third generation daughter cell.Undoubtedly,such illustrated artificial cell wall provides a conceptually new and promising technique towards the cell-based research as well as application of next-generation.Through the comprehensive study of the multi-functionality of cells in the coating of living cells,we systematically studied the transformation of cell function through the synergy between artificial cell wall and cells.A universal way was developed to create an enzyme modulated oxygen-consuming sandwich-like layer by using polydopamine,laccase and tannic acid as building blocks,which then could generate an independent anaerobic microenvironment around the cell.The created layer could not only take a physical protection role against external stresses,but also enable the encapsulated Chlorella pyrenoidosa cell to switch its functionality from normal photosynthetic O₂towards photobiological H₂ production,where the switching cycle could be easily modulated by the laccase-based catalyzing reaction.Significantly,the fabricated layer showed less effect on the activity of PSII of the encapsulated cell which contributed the significant enhancement on both the rate(0.32?mol H₂ h^-1?mg chlorophyll?^-1)and the duration?7 days?of H₂ production.This strategy is expected to provide a viable pathway for modulating functionality of the engineering cells as well as for the new breakthrough in the photobiological hydrogen production towards developing green energy alternatives.