Polymer-metal complex micelles

Nishiyama, N., Yokoyama, M., Aoyagi, T., Okano, T., Sakurai, Y. and Kataoka, K. (1999) Preparation and characterization of self-assembled polymer-metal complex micelle from cis-dichlorodiammineplatinum(II) and poly(ethylene glycol)-poly(, -aspartic acid) block copolymer in an aqueous medium. Langmuir, 15, 377-383. 

Nishiyama, N. Kato, Y. Sugiyama, Y. Kataoka, K. Cisplatin-loaded polymer-metal complex micelle with time-modulated decaying property as a novel drug delivery system. Pharm. Res. 2001, 18, 1035-1041. 

Figure 4.1. Conventional PM (a) drug-conjugated PM (b) and PICM with the polyionic block consisting of cationic polymer (c) or polynu-cleic acid (antisense oligonucleotides (AON) or small interfering RNA (siRNA)) (d and e). In d and e, the core forming agent is either linear or branched cationic polymer, respectively. Polymer-metal complex micelles formed via the ligand substitution reaction where M and Y are the metal and the ligand, respectively (f).

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. 

Increasing the concentration of surfactants in water to a level above the CMC leads to the formation of rod-like micelles and, subsequently, liquid crystals [251]. Both liquid crystals and liquid-crystalline polymers [252] have been used as media for small particle generation [253, 254] and have also acted as piezoelectric devices [255]. Of particular interest are metallomesogens, the metal complexes of organic ligands which exhibit liquid crystalline behavior [255],... 

In this chapter we will review the recent advances of supramolecular photon chirogenesis in various confined media, excluding micelles, chiral solvents, liquid crystals, metal complexes, polymer matrices, clays, and crystals. Micelles are typical supramolecular assembly with an internal hydrophobic core which shows a unique boundary effect, e.g., enhanced radical recombination of geminate radi-cal pairs produced by ketone photolysis [26], but essentially no asymmetric photon-... 

The coordination of metals to various other pendant sites present in block co-polymers has also been explored. For example, metal coordination to the olefinic groups present in the polybutadiene (PB) blocks of polystyrene-/ -polybutadiene (PS-/ -PB) diblock and PS- -PB-3-PS triblock copolymers has been reported.This was achieved by the reaction of PS-/ -PB with various metal complexes such as Fe3(CO)i2, [Rh(/r-Cl)(CO)2]2, PdCl2(NCMe)2, and PtCl2(NCMe)2 to afford materials with Fe-, Rh-, Pd-, and Pt-containing blocks. Intermolecular cross-linking was possible but solubility in organic solvents was maintained and micellization was observed in most cases. However, on solvent removal and drying, many of the polymers became insoluble. 

We saw that the matching molecular structures of drugs and polymers are important, and the design of the micelles slightly changes if the drugs are metal complexes. This is... 

The attachment of metal complexes to the polymer most often occurs via coordinating functional groups (ligands) boimd to the polymer in a covalent fashion as outlined in the earlier chapters of this book, but various types of noncovalent attachment are also well documented. The latter can be achieved, for instance, by means of electrostatic interactions, physisorption by amphiphilic polymer micelles (either as common association micelles or as unimolecular micelles), by hydrogen bonding, or by specific interactions of proteins with a molecule (Figure 14). 

Micelle Formation via Complexation. Micellization of molecu-larly soluble block copolymers due to interaction with metal compounds was observed in both organic media and water, if one of the two blocks (for a diblock copolymer) is inert while the other is able to form complexes with metal compounds. Micellization of Pd-, Pt-, and Rh-containing polymers derived from PS-fc-PB with a short PB block was first reported in 1998 [48], The crosslinks formed due to complexes between metal atoms and PB blocks of different macromolecules were shown to cause micellization. By contrast, Fe carbonyl... 

Various oxidations with [bis(acyloxy)iodo]arenes are also effectively catalyzed by transition metal salts and complexes [726]. (Diacetoxyiodo)benzene is occasionally used instead of iodosylbenzene as the terminal oxidant in biomimetic oxygenations catalyzed by metalloporphyrins and other transition metal complexes [727-729]. Primary and secondary alcohols can be selectively oxidized to the corresponding carbonyl compounds by PhI(OAc)2 in the presence of transition metal catalysts, such as RuCls [730-732], Ru(Pybox)(Pydic) complex [733], polymer-micelle incarcerated ruthenium catalysts [734], chiral-Mn(salen)-complexes [735,736], Mn(TPP)CN/Im catalytic system [737] and (salen)Cr(III) complexes [738]. The epox-idation of alkenes, such as stilbenes, indene and 1-methylcyclohexene, using (diacetoxyiodo)benzene in the presence of chiral binaphthyl ruthenium(III) catalysts (5 mol%) has also been reported however, the enantioselectivity of this reaction was low (4% ee) [739]. 

---