Dendrimers dendrimer-porphyrins

Scheme 3 Schematic representations of electrostatic assemblies of dendrimer porphyrins 6a, 7a with MV2+...

For some examples, see e.g. (a) Hogan CF, Harris AR, Bond AM et al (2006) Electrochemical studies of porphyrin-appended dendrimers. PhysChemChemPhys 8 2058-2065 (b) Jang W-D, Nishiyama N, Zhang G-D et al (2005) Supramolecular nanocarrier of anionic dendrimer porphyrins with cationic block copolymers modified with polyethylene glycol to enhance intracellular photodynamic efficacy. Angew Chem Int Ed 44 419 -23 (c) Loiseau F, Campagna S, Hameurlaine A et al (2005) Dendrimers made of porphyrin cores and carbazole chromophores as peripheral units. Absorption spectra, luminescence properties, and oxidation... 

Specific functional units can be immobiUzed at the center of a dendrimer. In the example depicted in Fig. 3.12, a porphyrin imit is immobihzed in a dendrimer (which is called a dendrimer porphyrin). Because the porphyrin unit is buried deep in the dendrimer structure, the dendrimer porphyrin is a good model of a heme protein. The environment of the dendrimer can be evaluated via the spectral characteristics of the central porphyrin. If the size of the dendrimer is large enough, the adsorption spectrum of the porphyrin shows that it is basically independent of surrounding solvent molecules the central porphyrin is shielded by the dendrimer cage. The structural mobility of the inner part of the dendrimer porphyrin has been evaluated via NMR... 

These structural characteristics mean that the dendrimer porphyrin can be used to mimic the function of the heme protein - its ability to bind to oxygen. A dendrimer porphyrin with an Fe(II) ion can stably trap oxygen via coordination with imidazole ligands. The oxygen was reversibly trapped within the dendrimer, and it can be released when the oxygen in the surrounding solvent was removed. The dendrimer sphere shields the porphyrin part from the outer environment. Therefore, side effects such as irreversible oxidation of the porphyrin by water and dimerization of the oxygen-bound porphyrins can be suppressed. 

N. Tomioka, D. Takasu, T. Takahashi, T. Aida, Electrostatic Assembly of Dendrimer Electrolytes Negatively and Positively Charged Dendrimer Porphyrins , Angew. Chem. Int. Ed., 37,1531 (1998)... 

Figure 20. Schematic representations of photochemical events in aryl ether dendrimer porphyrins of spherical (left) and nonspherical (right) morphologies [44].

Zhang GD, Harada A, Nishiyama N, Jiang DL, Koyama H, Aida T, Kataoka K (2003a) Polyiori complex micelles entrapping cadonic dendrimer porphyrin Effecdve photosensidzer for photodynamic dierapy of cancer. J Control Release 93 141—150. 

Jiang, D.-L., Aida, T. (1998). Morphology-dependent photochemical events in aryl ether dendrimer porphyrins Cooperation of dendron subunits for singlet energy transduction, 7. Aot. Chem. Soc., 720 10895. 

Nishiyama N, Stapert HR, Zhang GD, Takasu D, Jiang DL, Nagano T, Aida T, Kataoka K. Light-harvesting ionic dendrimer porphyrins as new photosensitizers for photod3mamic therapy. Bioconj Chem 2003 14 58-66. 

Stapert HR, Nishiyama N, Kataoka K, Jiang DL, Aida T. Polyion complex micelles encapsulating light-harvesting dendrimer porphyrins. Langmuir 2000 16 8182-8188. 

Uyemura, M. Aida. T. Steric control of organic transformation by a dendrimer cage Organocobalt dendrimer porphyrins as novel coenzyme 8,2 mimics. J. Am. Chem. Soc. 2002. 124 (38). 11392-11103. 

Figure 141. Molecular models showing a side view of the binding sites of dendrimer porphyrins. Top riieicr subsliluted fl fT/S. S -C1P)P). Bottom ortho-substituted dendiimer-porphyrin H..[T(2, 6 -C1AP)PJ. Note the open cavity of ss 10 A versus a narrow siil of s 5, respectiveiy in both cases, lop access to the porpisyrin is compieteiy blocked.

Figure 142. Binding of axial ligands to dendrimer porphyrins log(fCq) values for a series of nitrogenous bases with various sha ses.

Dendrimer Porphyrins and Metalloporphyrins Syntheses, Structures and Functions Takuzo Aida... 

In this chapter, we would like to introduce PIC micelles encapsulating ionic dendrimer porphyrins as a photosensitiser (PS) for photodynamic therapy (PDT). PDT is a topical therapeutic modality of malignant tumors, which treats tumor cells with cytotoxic singlet oxygen ( O2) produced by PS through photo-excitation at its characteristic wavelength A successful PDT may be completed by the development of potent PSs their tumor-selective delivery and selective and effective photoirradiation at the... 

Nishiyama, N., Stapert, H. R., Zhang, G.-D., Takasu, D., Jiang, D.-L., Nagano, T., Aida, T., Kataoka, K., Light-harvesting dendrimer porphyrins as new photosensitizers for photodynamic therapy, Bioconj. Chem. In press. 

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