Nanofiber Polyplex Formation Based on the Morphology Elongation by the Intrapolyplex PEG Crowding Effect

We prepared a multiarm poly(ethylene glycol)-poly(l-lysine) block copolymer (maPEG-PLL) with a size-controllable maPEG head and a cationic PLL tail for the evaluation of the effect of maPEG crowding to the polyplex formation with plasmid DNA. maPEG-PLLs of various compositions were synthesized and the formation of a polyplex was confirmed by gel retardation assay. The maPEG-PLL exhibited noncooperative polyplex formation behavior, suggesting the effective hydration of the polyplex. Also, an increase in the size of the maPEG head induces the elongation of polyplex morphology from spherical aggregates to nanorods and nanofibers because of the intrapolyplex PEG crowding effect. Furthermore, an increase in the size of the maPEG head also improves the effective inhibition of the decrease in cell-free gene expression, indicating the importance of the control of pDNA packaging in the polyplex.