Rational Design Of Amphiphilic Polymers For Biomacromolecule Delivery

To delivery biomacromolecules to the cellular cytoplasm,polymer vector must navigate a series of obstacles both extracellular and intracellular.These barriers include complexes formation,polymer-membrane interaction,cellular uptake,endosomal escape and intracellular cargo release etc.Lacking one or more of the components essential to the function of the vector may result in unsatisfactory transfection efficiency.Serveral modification strategies including lipid modification,peptide modification,cationic moleculars modification etc have been used to overcome these barriers.Different modification strategies facilitate the intracellular trafficking in different ways.For instant,Lipid modification enhances the cellular uptake and endosome escape of dendrimer though membrane fusion effect;Peptide or protein modification can improve the cellular uptake of dendrimer through ligand-recepter interaction;Phenylalanine and arginine modification enhance endosome escape and nucleic acid binding affinity through synergistic effect.From strategies are mentioned above we find that hydrophobility plays a vital role in improving transfecion efficiency.Therefore,a systematic study of hydrophobic functional groups and other conjugated chemistry will be benefit to the design of highly efficient polymer vector.In this dissertation,we studied the influence of hydrophobic groups and other functional groups on transfection efficiency.And through the combination of different functional groups,we design a series of highly efficient,low toxic and promising biomacromolecule delivery systems.Detailed methods and results are summarized as follows:(1)G5 dendrimers are modified with alkyl chains with different length(from C2 to C18).With the increasing of the chain length,transfection efficiency of G5 dendrimer gradully improved.G5 dendrimer modified with lauric acid(C12)shows the highest transfection efficacy.The improved gene silencing efficacy can be explained by increased cellular uptake efficacy through membrane fusion mechanism of the lipids and proton sponge effect of the dendrimers.Conjugation of aliphatic acids with longer chains such as myristic acid(C14),palmitic acid(C16)and fatty acid(C18)fails to knockdown the luciferase gene probably due to steric hindrance on the dendrimer surface.Steric hindrance result in poor nucleic acid binding and membrane association.(2)The effects of the dendrimer generation and the lipid conjugation ratio on the gene silencing efficacy were investigated.Among dodecylated G2,G3 and G4 dendrimer,G4-23C12 shows the highest gene knockdown efficacy.(3)We also study the position effect of the hydrophobic groups.The diaminododecane cored(C12)dendrimer have better transfection efficiency compared with an EDA(C2)cored dendrimer.The diaminododecane cored(C12)of dendrimer enhances the DNA condensation ability and endosomal escape capacity of dendrimers with minimal toxicity.Besides,there is no steric hindrance on the surface of C12G4 dendrimer.Thus,gene transfection efficiency of diaminododecane cored dendrimer can be further improved by surface-modification.(4)After a view of the hydrophobic effect,we found that the combination of phenyl and guanidyl groups on dendrimer can enable highly efficient RNA and DNA delivery with minimal toxicity.This strategy integrates different functional structure within one groups(GBA).And The combination of guanidyl and phenyl shows a synergistic effect in nucleic acid binding,endocytosis and endosome escape.Besides,guanidyl can form salt brigde(hydrogen bond and ionic bonding)with protein/peptide,which make GBA modified dendrimer also a highly efficient protein/peptide delivery vector.In summary,hydrophobic groups play a vital role in the process of biomacromolecule delivery.High efficient gene vecors can be synthesized through hydrophobic group modification.According to the interaction between hydrophobic groups and cell membrane,combination of phenyl and guanidyl group enables efficient gene and protein delivery.This combination strategy provides a facile and promising approach for the rational design of polymeric vehicles for intracellular protein and peptide delivery.