Controlled preparation of cholesterol-bearing polycations with pendent l-lysine for efficient gene delivery

Abstract

A new series of cholesterol-bearing poly(methacrylate)s with pendant cationic (l-)-lysine (Chol-PHML) was synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization, followed by Boc-deprotection. Their structures were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). Then, the average particle sizes and zeta potentials of the Chol-PHML/pDNA polyplexes were examined using dynamic light scattering (DLS), and their plasmid DNA (pDNA)-binding ability was analyzed using agarose gel retardation assay. In vitro cytotoxicity of the polycations was determined using a cell counting kit-8 (CCK-8) assay and lactate dehydrogenase (LDH) kits in HeLa cells. The polyplex’s gene transfection effectiveness was investigated using a luciferase assay. The results revealed that the Chol-PHML series could efficiently bind/load pDNA with a high binding affinity (N/P < 3.0) and subsequently form nanoparticles with the sizes of 90–200 nm and zeta potentials of ∼+40 mV in an aqueous solution. The in vitro cytotoxicity and gene transfection efficiency considerably depended on the Chol-PHML vector’s molecular weight. The optimal Chol-PHML27 exhibited a substantially higher gene transfection efficiency and lower cytotoxicity than those of the linear structural PLL (15 K–30K) and PHML26 control. This study presents a simple method for synthesizing biocompatible and controllable cationic gene vectors by introducing hydrophobic cholesterol moieties, which will function as a promising foundation for gene delivery.