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Rod‐to‐Globule Transition of pDNA/PEG–Poly( l ‐Lysine) Polyplex Micelles Induced by a Collapsed Balance Between DNA Rigidity and PEG Crowdedness
Author(s) -
Tockary Theofilus A.,
Osada Kensuke,
Motoda Yusuke,
Hiki Shigehiro,
Chen Qixian,
Takeda Kaori M.,
Dirisala Anjaneyulu,
Osawa Shigehito,
Kataoka Kazunori
Publication year - 2016
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201501815
Subject(s) - peg ratio , ethylene glycol , micelle , biophysics , dna , chemistry , crystallography , conformational change , materials science , chemical engineering , stereochemistry , biochemistry , organic chemistry , aqueous solution , biology , finance , engineering , economics
The role of poly(ethylene‐glycol) (PEG) in rod‐shaped polyplex micelle structures, having a characteristic core of folded plasmid DNA (pDNA) and a shell of tethered PEG chains, is investigated using PEG‐detachable polyplex micelles. Rod shapes undergo change to compacted globule shapes by removal of PEG from polyplex micelles prepared from block copolymer with acid‐labile linkage between PEG and poly( l ‐lysine) (PLys) through exposure to acidic milieu. This structural change supports the previous investigation on the rod shapes that PEG shell prevents the DNA structure from being globule shaped as the most favored structure in minimizing surface area. Noteworthy, despite the PEG is continuously depleted, the structural change does not occur in gradual shortening manner but the rod shapes keep their length unchanged and abruptly transform into globule shapes. Analysis of PEG density reveals the transition occurred when tethered PEG of rod shapes has decreased to a critical crowdedness, i.e., discontacted with neighboring PEG, which eventually illuminates another contribution, rigidity of DNA packaged as bundle in the rod shapes, in addition to the steric repulsion of PEG, in sustaining rod shapes. This investigation affirms significant role of PEG and also DNA rigidity as bundle in the formation of rod‐shaped structures enduring the quest of compaction of charge‐neutralized DNA in the polyplex micelles.