Preparation Of Zwitterionic Polyelectrolyte Nanogels Based On Electrostatic Assembly Directed Polymerization And Their Applications

Polyelectrolyte nanogels are polymeric hydrogel nanoparticles with three-dimensional crosslinked network structures,which have the advantages of both nanogels and polyelectrolyte,such as high charge density,strong hydrophilicity,excellent thermal stability and chemical stability.Zwitterionic Polyelectrolyte nanogels are special polyelectrolyte nanogels,which has both positive and negative charges.Compared with polyelectrolyte nanogels with single charge,zwitterionic polyelectrolyte nanogels have excellent biocompatibility and anti-protein contamination,which have attracted significant attention in the field of biological therapy.In this thesis,a new strategy namely Electrostatic Assembly Directed Polymerization(EADP),was developed for preparing zwitterionic polyelectrolyte nanogels.The effects of polymerization parameters on the structure and size of nanogel were systematically investigated and optimized.Finally,the property and loading ability of zwitterionic polyelectrolyte nanogels were studied.The main research contents are provided as follows:1.Poly(2-carboxy-N,N-dimethyl-N-(2'-(methacryloyloxy)ethyl)ethanaminium)(PCBMA)zwitterionic polyelectrolyte nanogels were prepared by Electrostatic Assembly Directed Polymerization.pH was adjusted to shield the negative charge(with positive charge only)of PCBMA monomers.And with a polyanion-neutral block polymer as template,polyelectrolyte micelles with uniform particle size were obtained by polymerizing zwitterionic monomers in the presence of cross-linker.Removing the template at high salt concentration creates well-defined PCBMA polyelectrolyte nanogels.It is found that the presence of template constructs a 'confined' assembly and control the particle size,while introduction of cross-linker obtains the stable nanogel particles with crosslinked network.These results confirm the feasibility of Electrostatic Assembly Directed Polymerization for preparing zwitterionic polyelectrolyte nanogels.2.The structure and size of PCBMA zwitterionic polyelectrolyte nanogels were tuned by Electrostatic Assembly Directed Polymerization.It is found that the particle size of the PCBMA zwitterionic nanogel increases with the increasing salt concentration when the salt concentration is below 100 mM.The particle size of nanogel increases with the increasing cross-linker fractions when the cross-linker fraction is less than 20%.Nanogels with different sizes obtained by tuning either salt concentration or cross-linker fractions are all spherical particles with narrow size distribution,These results indicate that the size of PCBMA nanogels can be manipulated tuning the salt concentration or cross-linker fractions during the polymerization.3.The loading properties of PCBMA zwitterionic polyelectrolyte nanogels for dye molecules and cytochrome c were investigated.It is found that the particle size and charge of PCBMA nanogels could be adjusted by changing pH,so the dye molecules with different charges could be selectively loaded.At the same time,cytochrome c could be loaded into PCBMA zwitterionic polyelectrolyte nanogels and remains 70%of its biocatalysis activity.These results show that PCBMA zwitterionic polyelectrolyte nanogels can be used as nano-carrier for loading different functional molecules by tuning their charges,demonstrating great potential for variety of applications.