A Delicate Balance When Substituting a Small Hydrophobe onto Low Molecular Weight Polyethylenimine to Improve Its Nucleic Acid Delivery Efficiency.
High molecular weight (HMW) polyethylenimine (PEI) is one of the most versatile nonviral gene vectors that was extensively investigated over the past two decades. The cytotoxic profile of HMW PEI, however, encouraged a search for safer alternatives. Because of lack of cytotoxicity of low molecular weight (LMW) PEI, enhancing its performance via hydrophobic modifications has been pursued to this end. Since the performance of modified PEIs depends on the nature and extent of substituents, we systematically investigated the effect of hydrophobic modification of LMW (1.2 kDa) PEI with a short propionic acid (PrA). Moderate enhancements in PEI hydrophobicity resulted in enhanced cellular uptake of polyplexes and siRNA-induced silencing efficacy, whereas further increase in PrA substitution abolished the uptake as well as the silencing. We performed all-atom molecular dynamics simulations to elucidate the mechanistic details behind these observations. A new assembly mechanism was observed by the presence of hydrophobic PrA moieties, where PrA migrated to core of the polyplex. This phenomenon caused higher surface hydrophobicity and surface charge density at low substitutions, and it caused deleterious effects on surface hydrophobicity and cationic charge at higher substitutions. It is evident that an optimal balance of hydrophobicity/hydrophilicity is needed to achieve the desired polyplex properties for an efficient siRNA delivery, and our mechanistic findings should provide valuable insights for the design of improved substituents on nonviral carriers.
Department of Biomedical Engineering, Faculties of Medicine & Dentistry and Engineering, ‡Department of Chemical & Materials Engineering, Faculty of Engineering, §Department of Mechanical Engineering, Faculty of Engineering, and ∥Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta , Alberta, Canada.
Deniz
D
Meneksedag-Erol
Department of Biomedical Engineering, Faculties of Medicine & Dentistry and Engineering, ‡Department of Chemical & Materials Engineering, Faculty of Engineering, §Department of Mechanical Engineering, Faculty of Engineering, and ∥Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta , Alberta, Canada.
Remant Bahadur
RB
KC
Department of Biomedical Engineering, Faculties of Medicine & Dentistry and Engineering, ‡Department of Chemical & Materials Engineering, Faculty of Engineering, §Department of Mechanical Engineering, Faculty of Engineering, and ∥Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta , Alberta, Canada.
Tian
T
Tang
Department of Biomedical Engineering, Faculties of Medicine & Dentistry and Engineering, ‡Department of Chemical & Materials Engineering, Faculty of Engineering, §Department of Mechanical Engineering, Faculty of Engineering, and ∥Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta , Alberta, Canada.
Hasan
H
Uludağ
D002244:Carbon / Q000737:chemistry; D003198:Computer Simulation; D020868:Gene Silencing; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006801:Humans; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D020014:K562 Cells; D056004:Molecular Dynamics Simulation; D008970:Molecular Weight; D009696:Nucleic Acids / Q000737:chemistry*; D011094:Polyethyleneimine / Q000737:chemistry*; D011422:Propionates / Q000737:chemistry; D015202:Protein Engineering / Q000379:methods; D034741:RNA, Small Interfering / Q000378:metabolism; D013499:Surface Properties
D009696:Nucleic Acids; D011422:Propionates; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins; D002244:Carbon; D011094:Polyethyleneimine; C029658:propionic acid
gene delivery; hydrophobic modification; molecular dynamics; polyethylenimine; siRNA