Rethinking the impact of the protonable amine density on cationic polymers for gene delivery : a comparative study of partially hydrolyzed poly(2-ethyl-2-oxazoline)s and linear poly(ethylene imine)s

To gain a more profound insight into the impact of the number and the density of protonable amines on the performance of polycations as non-viral vectors, a series of linear poly(ethylene imine)s (LPEIs) with different numbers of ethylene imine (EI) units was compared to partially hydrolyzed (21 to 86%, 20 kDa) poly(2-ethyl-2-oxazoline)s (PHPEtOxs) with a corresponding number of El units but with varying densities. PHPEtOx polyplexes demonstrated lower transfection efficiencies than the corresponding LPEIs although having the same number of EI units as LPEI, exhibiting smaller or comparable polyplex diameters, similar zeta potentials, and similar or even preferred cyto- and hemocompatibility profiles. The lower efficiency was found to be related to a lower DNA binding capacity and less efficient protection of plasmid DNA against enzymatic degradation. The direct comparison of both types of polymers revealed that the density of charges within the polymer backbone seems to be more important than the total number of EI units. In conclusion, the reduction of the El density to produce more biocompatible polyplexes must be critically examined, since the presence of high numbers of EI next to each other seems to have a dramatically higher impact on the transfection efficiency than on the in vitro toxicity

Multiple Micellar Morphologies from Tri- and Tetrablock Copoly(2-oxazoline)s in Binary Water-Ethanol Mixtures

We report on the micellization behavior of tri- and tetrablock copoly(2-oxazoline)s in water-ethanol mixtures. The copolymers are based on different combinations of 2-methyl-, 2-ethyl-, 2-phenyl-, and 2-nonyl-2-oxazoline. The solvophilic/solvophobic balance of these copolymers can be tuned thanks to the solubility dependence of the poly(2-phenyl-2-oxazoline) block on the solvent composition. Characterization of the obtained micelles by dynamic light scattering and transmission electron microscopy revealed that their size and morphology depend on the solvophobic content of the copolymers and on the block order. Spherical micelles are always obtained when poly(2-nonyl-2-oxazoline) is the only solvophobic block. When the solvophobic fraction consists of both the poly(2-phenyl-2oxazoline) and poly(2-nonyl-2-oxazoline) blocks, spherical and cylindrical micelles as well as vesicles have been observed. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3095-3102, 201

Thermal properties of oligo(2-ethyl-2-oxazoline) containing comb and graft copolymers and their aqueous solutions

Summary: The cationic ring opening polymerization of 2-ethyl-2-oxazoline (EtOx) was applied for the synthesis of methacrylate end-functionalized well-defined macromonomers that could be polymerized in a controlled manner using reversible addition-fragmentation chain transfer polymerization. The obtained comb polymers revealed lower critical solution temperature behavior in aqueous solution. The cloud points of these solutions could be tuned in a range from 35 8C to 85 8C by the incorporation of hydrophobic methyl methacrylate comonomer in varying amounts into the graft copolymers whereas copolymerization with methacrylic acid rendered temperature and pH sensitive copolymers. Thermo-gravimetric analysis showed a two-step decomposition of the graft copolymers and differential scanning calorimetry revealed glass transition temperatures that are significantly lowered in comparison to linear PEtOx

Solubility Behavior of Amphiphilic Block and Random Copolymers Based on 2-Ethyl-2-oxazoline and 2-Nonyl-2-oxazoline in Binary Water-Ethanol Mixtures

The solution properties of random and block copolymers based on 2-ethyl-2-oxazoline (EtOx) and 2-nonyl-2-oxazoline (NonOx) were investigated in binary solvent mixtures ranging from pure water to pure ethanol. The solubility phase diagrams for the random and block copolymers revealed solubility (after beating), insolubility, dispersions, micellization as well as lower critical solution temperature (LCST) and upper critical solution temperature behavior. The random and block copolymers containing over 60 mol % pNonOx were found to be solubilized in ethanol upon heating, whereas the dissolution temperature of the block copolymers was found to be much higher than for the random copolymers due to the higher extent of crystallinity. Furthermore, the block copolymer containing 10 mol % pNonOx exhibited a LCST in aqueous solution at 68.7 degrees C, whereas the LCST for the random copolymer was found to be only 20.8 degrees C based on the formation of hydrophobic micro-domains in the block copolymer. The random copolymer displayed a small increase in LCST up to a solvent mixture of 9 wt % EtOH, whereas further increase of ethanol led to a decrease in LCST, which is probably due to the "water-breaking" effect causing an increased attraction between ethanol and the hydrophobic part of the copolymer. In addition, the EtOx-NonOx block copolymers revealed the formation of micelles and dynamic light scattering demonstrated that the micellar size is increasing with increasing the ethanol content due to the enhanced solubility of EtOx. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 515-522, 200

Linear poly(alkyl ethylene imine) with varying side chain length: synthesis and physical properties

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A schizophrenic gradient copolymer: switching and reversing poly(2-oxazoline) micelles based on UCST and subtle solvent changes

The self-assembly of hydrophobic gradient copolymers of 2-nonyl-2-oxazoline and 2-phenyl-2-oxazoline in ethanol-water solvent mixtures is demonstrated to result in structures that respond to changes in temperature as well as subtle changes in the solvent composition leading to both switching and reversing of the formed micelles