Dendri-poly

The procedures described are based on improved modifications from original publications [4-8]. They focus on the divergent excess reagent syntheses of dendri-poly(amidoamines) using various alkylenediamine cores. Examples of both divergent in situ branch cell methods, as well as divergent preformed branch cell methods are presented. 

Kubasiak LA, Tomalia DA (2005) Cationic dendiimcas as gene transfection vectors dtaidri-poly(amidoamines) and dendri-poly(propylenimines). In Amiji MM (ed) Polymeric gene delivery-principles and applications. CRC, Boca Raton, pp 133-157... 

Covalent, stoichiometric [dendrimer core fullerene shell] nanocompotmds were readily formed by allowing a [core l,2-diaminoethane] (4 2) dendri-poly (amidoamine)-(NH2)64 (G = 4) PAMAM dendrimer to react with an excess of buckminsterfullerene (Ceo) [177]. In the presence of an excess of C o, only 30 Ceo moieties bonded to the dendrimer surface to produce a well-defined, stoichiometric [dendrimer (core) fuUerene (shell) ] nanocompotmd, i.e., [S-l (H-5)3o] core-shell-type as shown in Fig. 27. These structures were characterized extensively by MALDI-TOF, thermogravimetric analysis (TGA), UV-vis spectroscopy, and Fourier transform infirared (FTIR) spectroscopy. Such nanocompounds exhibited new fullerene-like solubility and photo-properties by readily generating singlet 02 in either aqueous or organic solvents. However, they offered other unique features such as larger size and nanocontainer-type properties that would normally be associated with the dendrimer core interior. 

Dendrons and dendrimers are the most intensely investigated subset of dendritic polymers. In the past decade over 2000 literature references have appeared on this unique class of structure controlled polymers. The term dendrimer was coined by Tomalia, et al. over 15 years ago in the first reports on poly(amidoamine) (PAMAM) dendrimers [75, 76]. It is derived from the Greek words dendri-(branch tree-like) and meros - part of). Poly(amidoamine) dendrimers constitute the first dendrimer family to be commercialized and undoubtedly represent the most extensively characterized and best understood series at this time. In view of the extensive literature information in this area, much of the remaining overview will focus on PAMAM dendrimers and will... 

Figure 6.35. Hydrophobic-functionalized PAMAM (G4-Ci2) and poly(propyleneimine) (PPI) dendri-mers, which serve as templates for Au nanocluster growth. Reproduced with permission from Knecht, M. R. Garcia-Martinez, J. C. Crooks, R. M. Langmuir 2005, 21, 11981. Copyright 2005 American Chemical Society.

Liu, M. Kono, K. Erechet, J.M.J. Water-soluble dendri-mer-poly(ethylene glycol) starlike conjugates as potential drug carriers. J. Polym. Sci. Part A Polym. Chem. 1999, 37, 3492-3503. 

Malenfant, P.R.L., L. Groenendaal, and J.M.J. Frechet. 1998. Well-defined triblock hybrid dendri-mers based on lengthy oligothiophene cores and poly(benzylether dendrons). / Am Chem Soc 120 10990-10991. 

COLCOM (http //www.colcom.eu/uk/index.php and subpages thereof, accessed 8 July 2010) offers polydisperse Dendri-Graft Poly-Lysine, based on the amino acid L-lysine, of generations 1-5 with different surface functionalities. The company also offers diagnostic kits for detection and quantification of the total bacterial flora in water, DENDRIDIAG . 

Photochemical and photophysical properties of a poly(propylene amine) dendri-mer (2) functionalized with -stilbene units have been studied [102]. Z-photoisome-rization and photocyclization of the Z-isomer of the stilbene units were investigated in air-equilibrated acetonitrile solutions. The quantum yields of the E Z photoisomerization reaction and the fluorescence quantum yield of the E were found to be equal to 0.30 and 0.014, respectively. Stilbene dendrimers prepared by coupling 4,4 -dihydroxystilbene with first-, second-, third-, or fourth-generation benzyl ether-type dendrons underwent photoisomerization with the same efficiency as that of 4,4 -dimethoxystilbene [103], The lifetime of the core structure was found to be shorter then 1 ns. According to [104], polyphenylene-based stilbene dendrimers, Gl, G2, and G3, underwent mutual cis-trans isomerization upon direct irradiation with 310 nm light at room temperature. In a solvent glass at 77 K, one-way cis-trans isomerization was observed for G2. 

Very interesting amphiphilic behavior at the air-water interface was observed by van Hest and Meijer [93] for hydrophobe (focal point) modified poly(propyleneimine) (PPI) dendrons [i.e., poly(styrene)-pressure-area isotherms. The lower generations (i.e., G - 1 and 2) all displayed isotherm curves indicating they transitioned directly to solid-state behavior. 

Poly(amidoamine) and poly(propylenimine) dendri-mers (Fig. 28.12) have been shown to effidendy deliver nudeic adds in numerous cell lines. Their ability to transfect cells increases with the generation, unfortunately as does their toxidty, which is directly related to molecular weight. It is therefore necessary to find a compromise situation allowing transfection enhancement without toxic effects. Such a balance was found in the lower-generation 3 poly(propylenimine) dendrimers. 

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