| Abstract
| - Encapsulation of dsDNA fragments (contour length 54 nm) by the cationic diblock copolymer poly(butadiene-b-N-methyl-4-vinyl pyridinium) [PBd-b-P4VPQ] has been studied with phase contrast, polarizedlight, and fluorescence microscopies, as well as scanning electron microscopy. Encapsulation was achievedwith a single emulsion technique. For this purpose, an aqueous DNA solution is emulsified in an organicsolvent (toluene) and stabilized by the amphiphilic diblock copolymer. The PBd block forms an interfacialbrush, whereas the cationic P4VPQ block complexes with DNA. A subsequent change of the quality of theorganic solvent results in a collapse of the PBd brush and the formation of a capsule. Inside the capsules,the DNA is compacted as shown by the appearance of birefringent textures under crossed polarizers andthe increase in fluorescence intensity of labeled DNA. The capsules can also be dispersed in an aqueousmedium to form vesicles, provided they are stabilized with an osmotic agent [poly(ethylene glycol)] in theexternal phase. It is shown that the DNA is released from the vesicles once the osmotic pressure dropsbelow 105 N/m2 or if the ionic strength of the supporting medium exceeds 0.1 M. The method has alsoproven to be efficient to encapsulate pUC18 plasmid in submicrometer-sized vesicles, and the generalapplicability of the method has been demonstrated by the preparation of the charge inverse system: cationicpoly(ethylene imine) encapsulated by the anionic diblock poly(styrene-b-acrylic acid).
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