Polymer-amphiphile complexes

Uchegbu and coworkers have studied the complexation and delivery of DNA using a unique poly(amino acid)-based polymer vesicle. A polymer of either poly (L-lysine) or poly(L-omithine) was functionalized with methoxy-poly(ethylene glycol) (mPEG) and hydrophobic palmitic acid chains to synthesize an amphiphilic triblock of either mPEG-6-poly(L-lysine)-6-palmitoyl or mPEG-Z>-poly(L-omithine)-6-palmitoyl. Vesicles formed from these polymers were complexed with DNA and showed improved transfection in vitro over poly(amino acid) complexed with DNA or DNA alone [82]. 

In the second approach, metal-ion/complex was first attached to one of the polymer blocks. A thin film of the resulting polymer metal complex was then obtained by spin coating/solution casting. Alternatively, the polymer metal complex may also be dissolved in a suitable solvent system that selectively dissolves one of the blocks. Micelles or nanosized aggregates formed in this case. The micellization of amphiphilic block copolymers and their use in the formation of metal nanoparticles has been discussed previously.44 A monolayer of micelles was introduced on a substrate surface by dipping or electrostatic attraction. The substrate was then subjected to further chemical or physical treatments as mentioned earlier. The third approach involves the formation of micelles from the metal-free block copolymer in a suitable solvent system. The micelle solution was then added with metal ion, which was selectively coordinated to one of the blocks. These micelle-metal complexes can also be processed by a procedures similar to the second approach. 

LPEI was used for DNA complexation. Novel two triblock copolymers, LPEI-b-PEG-b-LPEI (M 2100-3400-2100 and 4000-3400-4000) (Scheme 60(a)), were shown to condense plasmid DNA effectively to give polymer/DNA complexes (poly-plexes) of small sizes (<100nm) and moderate -potentials ( + 10mV) at polymer/plasmid weight ratios >1.5/1. These polyplexes efficiently transfected COS-7 cells and primary bovine endothelial cells in vitro and are a novel class of nonviral gene delivery systems.Lipopolymers were prepared as a potential candidate for constmcting tailored model cell membranes. A lipid triflate was used as initiator for CROP of hydrophilic monomers, MeOZO and EtOZO, to produce an amphiphilic polymer as the model (Scheme 60(b)). 

N-heterocyclic carbene (NHC) palladium complexes supported by three amphiphilic water-soluble block copolymers were synthesized by Nuyken and coworkers [66]. The polymer-bound complexes formed emulsions in water. The resulting macroligand was applied in tlie hydroformylation of 1-octene under aqueous two-phase conditions in four consecutive cycles and showed high activity... 

Proteins, like other macromolecules, can be made into monolayers at the air-water interface either by spreading, adsorption, or specific binding. Proteins, while complex polymers, are interesting because of their inherent surface activity and amphiphilicity. There is an increasing body of literature on proteins at liquid interfaces, and here we only briefly discuss a few highlights. 

The polymers described so far have relatively flexible main chains which can result in complex confonnations. In some cases, tliey can double back and cross over tliemselves. There are also investigations on polymers which are constrained to remain in a confonnation corresponding, at least approximately, to a straight line, but which have amphiphilic properties tliat ensure tliat tliis line is parallel to tire water surface. Chiral molecules are one example and many polypeptides fall into tliis class [107]. Another example is cofacial phtlialocyanine polymers (figure C2.4.9). 

Oheme and co-workers investigated335 in an aqueous micellar system the asymmetric hydrogenation of a-amino acid precursors using optically active rhodium-phosphine complexes. Surfactants of different types significantly enhance both activity and enantioselectivity provided that the concentration of the surfactants is above the critical micelle concentration. The application of amphiphilized polymers and polymerized micelles as surfactants facilitates the phase separation after the reaction. Table 2 shows selected hydrogenation results with and without amphiphiles and with amphiphilized polymers for the reaction in Scheme 61.335... 

Tb clarify the effect of addition of a cationic HC surfactant on phase separation behavior in the mixed monolayers of anionic HC and FC surfactants polyion complexed with cationic polymers, the mixed monolayers containing three amphiphilic components complexed with PVA were transferred on various substrate plates and studied by AFM, FFM, SSPM, and SIMS. As a cationic surfactant, ODTMAC was examined. 

Shimomura and Kunitake have reported that stable monolayers and LB films were obtained by electrostatic interaction of water soluble anionic polymers with cationic amphiphiles [58]. This polyion-complexation was also a useful method for stabilization of monolayers of unstable [59] or water soluble anionic surfactants [60]. Mixtures of water soluble cationic and anionic surfactants (1 1) also formed stable Langmuir monolayers at the air/ water interface [60]. 

As a cationic polymer and a cationic amphiphile, poly(allyl amine hydrochloride) (PAA) and octadecylamine (ODA) shown in Fig. 6 were used, respectively. The stability of the monolayers of the anionic amphiphiles was increased by polyion-complexation with PAA added in the aqueous subphase in comparison with Ca2+ salt formation. Ion complexation (1 1) of each anionic amphiphile with ODA was also performed at the air-water interface by spreading a chloroform solution of a 1 1 surfactant mixture. 

The sizes of the phase separated HC islands in the mixed monolayers of HC and FC anionic amphiphiles polyion complexed with cationic polymers were increased by addition of a HC cationic amphiphile. The HC islands sat on the FC sea in a structure of on-top in a two story monolayer in the same way as two-component amphiphile systems. By SSPM and conventional and SNOAM fluorescence microscopies, the cationic HC amphiphile was found to dissolve preferentially into the HC islands, although it also dissolved partially in the FC sea phase. 

Figure 21 shows three possible routes to obtain oriented PAV films by the LB technique. In these route, it is anticipated that orientational orderliness of precursor polymers is introduced in the precursor LB films through the formation of two-dimensionally oriented monolayer of a polyelectrolyte precursor-anionic amphiphile polyion complex at the air/subphase interface and orientation of the precursor monolayers along the dipping direction dining the deposition process. As a result, it is expected to obtain oriented PAV LB films with well-developed jt-coryugation system. In this study, we successfully prepared oriented PAV films using two routes of them, b-1 and b-2 route [35-37]. The chemical structures of PAVs, their polyelectrolyte precursors and an anionic amphiphile used in this study are shown in Fig.22. 

Using the b-1 route, PPV LB films were successfully fabricated [35], The precursor polymer of PPV was prepared according to ref.27. Anionic amphiphile 2C12SUC was purchased from Sogo Pharmaceutical Co. and used without further purification. An aqueous solution of the precursor polymer was added dropwise to an aqueous 2C12SUC solution. Then, the precursor-anionic amphiphile polyion complex was precipitated. The precipitates were filtered and washed with deionized... 

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