Efficient Condensation of DNA into Environmentally Responsive Polyplexes Produced from Block Catiomers Carrying Amine or Diamine Groups.

The intracellular delivery of nucleic acids requires a vector system as they cannot diffuse across lipid membranes. Although polymeric transfecting agents have been extensively investigated, none of the proposed gene delivery vehicles fulfill all of the requirements needed for an effective therapy, namely, the ability to bind and compact DNA into polyplexes, stability in the serum environment, endosome-disrupting capacity, efficient intracellular DNA release, and low toxicity. The challenges are mainly attributed to conflicting properties such as stability vs efficient DNA release and toxicity vs efficient endosome-disrupting capacity. Accordingly, investigations aimed at safe and efficient therapies are still essential to achieving gene therapy clinical success. Taking into account the mentioned issues, herein we have evaluated the DNA condensation ability of poly(ethylene oxide)113-b-poly[2-(diisopropylamino)ethyl methacrylate]50 (PEO113-b-PDPA50), poly(ethylene oxide)113-b-poly[2-(diethylamino)ethyl methacrylate]50 (PEO113-b-PDEA50), poly[oligo(ethylene glycol)methyl ether methacrylate]70-b-poly[oligo(ethylene glycol)methyl ether methacrylate10-co-2-(diethylamino)ethyl methacrylate47-co-2-(diisopropylamino)ethyl methacrylate47] (POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47), and poly[oligo(ethylene glycol)methyl ether methacrylate]70-b-poly{oligo(ethylene glycol)methyl ether methacrylate10-co-2-methylacrylic acid 2-[(2-(dimethylamino)ethyl)methylamino]ethyl ester44} (POEGMA70-b-P(OEGMA10-co-DAMA44). Block copolymers PEO113-b-PDEA50 and POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47) were evidenced to properly condense DNA into particles with a desirable size for cellular uptake via endocytic pathways (R(H) ≈ 65-85 nm). The structure of the polyplexes was characterized in detail by scattering techniques and atomic force microscopy. The isothermal titration calorimetric data revealed that the polymer/DNA binding is endothermic; therefore, the process in entropically driven. The combination of results supports that POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47) condenses DNA more efficiently and with higher thermodynamic outputs than does PEO113-b-PDEA50. Finally, circular dichroism spectroscopy indicated that the conformation of DNA remained the same after complexation and that the polyplexes are very stable in the serum environment.

Film/contact loading method improves the encapsulated amount of triazene anticancer compounds in polymeric micelles.

The development of organic solvent-free methods for the encapsulation of hydrophobic molecules is necessary for advances in micelle-mediated drug delivery. In this study we investigated the film/contact approach in which the use of organic solvents is limited to the preparation of a dry film before encapsulation. Unloaded micelles of five structurally related block copolymers were placed in contact with thin homogeneous films of two hydrophobic triazene anticancer compounds (1-(4-amidophenyl)-3-(4-acetylphenyl)triazene (1) and corresponding triazenido complex with triphenylphosphanegold(I) fragment (2)). The micelle surface becomes saturated with the drug, which eventually penetrates as a front into the core. Because the drug interacts with both the shell and the core microenvironments of micelle during the process, the maximum loading capacities were very sensitive to block copolymer micelle composition, ranging from 2.2 to 20.4% (wt./wt. of polymer). We conclude that micelles with poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) cores are the best option for the encapsulation of triazene compounds because i) they are prepared in absence of organic phase; ii) the drug concentration in the particles is high enough for a therapeutic effect and iii) the responsiveness properties of PDPA is appropriate for practical applications in pH-triggered drug release systems.