Tuning the charge density and crosslinking of precise amphiphilic oligo(ethanamino)amides for efficient and biocompatible gene delivery

Abstract

Cationic polymers are a class of promising carriers for nucleic acid delivery. However, the balance between biosafety and transfection efficiency is still a major obstacle for nucleic acid delivery. Accurate structural design can effectively evaluate the relationship between structural factors and nucleic acid delivery. Previously designed series of vectors optimized based on artificial amino acid Stp have been shown to effectively improve gene transfection. Here, a series of sequenced-defined oligomers containing hydrophobic oleic acid with different topologies, different charge densities and with or without crosslinking cystine domains were designed and synthesized for a better understanding of the structure–activity relationship. The oligomers were further mixed with either pDNA or siRNA to form polyplexes. The particle size, zeta potential, formation properties, in vitro stability and reductive responsiveness of the polyplexes were investigated. In addition, studies regarding the transfection efficiency, cellular uptake, cellular trafficking, cytotoxicity and hemolysis were performed. The resulting oligomers display general good complexation ability with pDNA and siRNA with enhanced stability and redox sensitivity. Some of the oligomers showed adequate or surpassed transfection efficiency compared with PEI. The polyplexes formed with oligomer #1 have good cellular uptake and endo-lysosome escape properties. In addition, all the oligomers and the polyplexes showed low cytotoxicity and hemolysis, and demonstrated high biocompatibility. In summary, the results evidenced that tuning the charge density combined with hydrophobic oleic acid and thiol crosslinking cystine improves the overall performance in delivering pDNA and siRNA.