Subtle changes in surface-tethered groups on PEGylated DNA nanoparticles significantly influence gene transfection and cellular uptake

PEGylation strategy has been widely used to enhance colloidal stability of polycation/DNA nanoparticles (NPs) for gene delivery. To investigate the effect of polyethylene glycol (PEG) terminal groups on the transfection properties of these NPs, we synthesized DNA NPs using PEG-g-linear polyethyleneimine (lPEI) with PEG terminal groups containing alkyl chains of various lengths with or without a hydroxyl terminal group. For both alkyl- and hydroxyalkyl-decorated NPs with PEG grafting densities of 1.5, 3, or 5% on lPEI, the highest levels of transfection and uptake were consistently achieved at intermediate alkyl chain lengths of 3 to 6 carbons, where the transfection efficiency is significantly higher than that of nonfunctionalized lPEI/DNA NPs. Molecular dynamics simulations revealed that both alkyl- and hydroxyalkyl-decorated NPs with intermediate alkyl chain length exhibited more rapid engulfment than NPs with shorter or longer alkyl chains. This study identifies a new parameter for the engineering design of PEGylated DNA NPs. The effect of PEG terminal groups in the interactions of PEGylated DNA nanoparticles with cells is investigated through an integrated experimental and computational approach. For nanoparticles with alkyl/hydroxyalkyl PEG terminal group, the highest transfection efficiency and cellular uptake levels occur at intermediate alkyl chain length. Subtle changes in PEG terminal groups significantly affect gene expression and cellular uptake levels. [Display omitted]