Preparation And Application Of Chiral Nanozymes

One of the main features of the living world is its chirality.The chiral nature of living systems has evident implications on biologically active compounds interacting with them.Most of the molecules of importance to living systems are chiral,e.g.amino acids,sugars,proteins and nucleic acids.Under physiological conditions,different enantiomers often have significantly different effects with chiral targets（e.g.receptors,enzymes,and ion channels）through differential interactions.Enantioselectivity is often a characteristic feature of enzymatic reactions.Therefore,the mimic of the enantioselectivity of natural enzymes is of great significance in chiral catalysis.In this paper,enantioselective nanozymes were constructed and the enantioselective recognition and catalysis of chiral substrate were investigated,which provided new ideas and methods for the design of novel nanozymes.Nanozymes refers to a class of mimic enzymes that have both unique properties and catalytic functions,including inorganic nanoparticulate enzyme mimics,polymeric enzyme mimics,supramolecular enzyme mimics,protein and antibody enzyme mimics.Compared to natural enzymes,nanozymes has a lot of excellent performance,which usually has higher physicochemical stability,lower preparation cost,simpler and more controllable preparation method,and excellent catalytic activity.However,it lacks the enantioselectivity to the substrate,and it is very important to better mimic the catalytic function of the natural enzyme by conferring the nanozyme enantioselectivity.There is a little study about enantioselective nanozymes.In this paper,two kinds of enantioselective nanozymes,chiral molecular imprinting nanozymes and enantioselective single-chain polymeric nanozymes,were constructed.We not only studied the enantioselective recognition and catalysis of chiral molecularly imprinted nanozymes,but also constructed enantioselective single-chain polymeric nanozymes.The main contents of this paper are as follows:（1）In chapter 2,Fe₃O₄ NPs,which was a model of nanozyme,was synthesized by hydrothermal method.L/D-Tyrosinol（Tyr）were chosen as templates,which can be catalyzed by the peroxidase mimicking Fe₃O₄ in the presence of H₂O₂.To incorporate the Fe₃O₄ into MIP,we added acrylamide and NIPAAm as monomers.In the presence of APS and TEMED as initiators,this system underwent precipitation polymerization to yield chiral imprinted nanoparticles.It was proved by transmission electron microscopy（TEM）,Fourier transform infrared spectroscopy（FT-IR）and thermogravimetric analysis（TGA）that the surface of Fe₃O₄ was successfully coated with chiral imprinted polymer.The enzyme kinetics experiment and QCM technique were used to study the differences in the catalysis and adsorption behaviors of chiral substrates.The results showed that molecular imprinting polymers（MIP）can be used as the achiral capping ligands to endow Fe₃O₄ with the chiral binding pockets,resulting in enantioselective recognition and catalysis.（2）In chapter 3,Rhodamine B labeled L/D-Tyr were chosen as chiral fluorescent template molecule.On basis of the research in chapter 2,another chiral molecularly imprinting nanozymes RB-L-and D-MIP were prepared.The enzyme kinetics experiment and QCM technique were used to study the differences in the catalysis and adsorption behaviors of chiral substrates.In this chapter,the enantioselectivity-fluorescence intensities link was established for fluorescence analysis.Fluorescence microscopy and flow cytometry was used to verify the interaction between the RB-L/D-MIP and chiral substrates at the cellular level.（3）In chapter 4,chiral single-chain polymer nanozymes（SCPNs）was prepared,in which four different metalloporphyrin complexes were chosen as catalytic active centers.The products were named Fe-、Cu-、Zn-and Co-SCPNs.The SCPNs was composed of four parts,including water-soluble side chains to ensure water solubility,benzene-1,3,5-tricarboxamide supramolecular moieties in order to trigger hydrogen-bonding-induced polymer folding,catalytically active sites and chiral ligands L-Phenylalanine.The spherical shape of SCPNs was observed by transmission electron microscopy（TEM）and atomic force microscopy（AFM）.The chiral characteristics of SCPNs were characterized by circular dichroism（CD）.The results showed that chiral SCPNs were successfully prepared.