DNA encapsulation via nanotemplates from cationic block copolymer micelles

We report on a method for the encapsulation of DNA into polymeric nanocapsules. The encapsulation procedure involves three steps: formation of polyplexes between DNA and cationic polymeric micelles; coating of polyplexes with a cross-linked shell; dissociation of polyplexes. In the first step copolymer micelles were obtained by self-assembly of an amphiphilic polystyrene-b-poly(quaternized 2-vinylpyridine) (PS-b-PQ2VP) block copolymer in aqueous solution. Nanosized polyplexes (D-h = 190 nm and zeta = -21 mV) were formed upon the addition of DNA to the micellar solution at a phosphate/amine group ratio of 3 : 1. In the second step the complexes were coated with a crosslinked shell formed by seeded radical polymerization of N-isopropylacrylamide which resulted in a slight shift of zeta potential of the particles to a less negative value. The dissociation of polyplexes and removal of PS-b-PQ2VP were achieved by addition of salt and solvent exchange. Following rehydration via dialysis against water, polymeric nanocapsules with entrapped DNA were obtained. The nanocapsules were visualized by transmission electron microscopy; they exhibited smaller dimensions compared to the initial polyplexes and zeta potential very close to that of the pristine DNA.