| As a kind of artificial cell technology,single-cells encapsulation can increase the stability of cells and improve their tolerance to the environment.The armored cells with functional shells are widely used in fileds including cell storage,cell therapy,cell delivery,cell sensor and biocatalysis.Current single-cell modification techniques usually introduce the shell layers that directly contact with the cells surface,which is prone to produce additional physical/chemical pressure on the cell.In order to solve this problem,a method to prepare hollow polymeric shells for encapsulation of single yeast cells based on the biomimetic mineralization and visible light induced graft crosslinking polymerization was developed.The main results were listed here:1.By means of biomimetic mineralization technology,aninorganic mineralization shell was successfully prepared on the surface of yeast cells.Firstly,PD ADM AC and PA A were used as polyelectrolyte for layer-by-layer assembly to modify the surface of yeast cells.Then calcium carbonate and calcium phosphate were deposited onto the modified yeast cells and the characteristics and rules of depostition process were explored.A complete calcium phosphate deposit layer was successfully fabricated on the surface of yeast cells.And its zeta potential was-19.54 mV at pH=7.4,which provided a basis for the adsorption of polyethylenimine(PEI)which acts as a photoinduced hydrogen donor in the next step.2.Based on visible light induced graft polymerization,a novel strategy that coating single yeast cells with hollow polymeric shells was developed.PEI was first introduced to the surface of the yeast cell that encapsulated within calcium phosphate shell by electrostatic adsorption.Then,surface initated graft polymerization of PEGDA on calcium phosphate shell was carried out under visible light irradiation and using TX-Ct/PEI as initiation system.After removing the calcium phosphate by EDTA,hollow shells coated single yeast cells are prepared.The success of grafting polymerization and the existence of hollow polymer shell were confirmed by SEM,TEM,FTIR,CLSM,Zeta potential analysis and other methods.The results of flow cytometry test indicated that the modified yeast cells could still maintain high viability(above 99%)at all stages,indicating that the visible light induced graft polymerization technology was very suitable for the modification of living cells.The results of the yeast cells proliferation experiments showed that the hollow polymeric shell coated yeast cells showed a retarded stagnation phase of about 20-24 h,indicating that the introduction of the polymer coating could effectively delay the proliferation of yeast cells.3.Based on the above results,a pH-sensitive hollow shell of PAAS was successfully introduced on the surface of yeast cells.The effects of different crosslinking agents and their dosage on the grafting polymerization of sodium acrylate were explored and the optimal grafting reaction conditions were obtained.Through SEM,FTIR,CLSM,XPS and Zeta potential characterization,it was verified that the hollow cross-linking shells of PAAS was successfully introduced on the surface of yeastˇcells.The flow cytometric analysis showed that the cell viability could be kept above 99%at each modification stage,indicating that the visible light induced graft polymerization of sodium acrylate would not significantly change the cell viability.It was found that the PAAS shells had a significant inhibitory effect on the proliferation of yeast cells. |
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