Polycationic dendrimers

Stoddart et al. developed a convergent route to polycationic dendrimers based on mesitylene units [65]. Positively charged dendrons obtained by the Menschut-kin reaction are attached as branching units around the l,3,5-tris(diethylamino-methyl)benzene core unit (3) (Fig. 4.36). (Anion) exchange of bromide with hex-afluorophosphate ions provides better solubility. 

Fig. 4.36 Convergent synthesis of polycationic dendrimers (according to Stoddart et al.)...

Alternatively, Michael reaction of the nonaol with acrylonitrile yields a nonanitrile, which can be reduced to the nonaamine. This nonaamine was allowed to react with chloro-carbonylmetallocenes and other chlorocarbonyl sandwich complexes to yield nonaamido-metallocenes [61-63] and nonaamido-sandwich compounds [63] (Scheme 20). These metallodendrimers also give rise to only one cyclic voltammetry wave, the intensity of which corresponds to approximately nine electrons using the technique indicated above (the solvent was CH2CI2 for the nonaamidoferrocene and MeCN for the polycationic dendrimers). Chemical reversibility was observed at room temperature, although some adsorption was noted. 

Wimmer, N., Marano, R. J., Kearns, P. S., Rakaczy, E. P., and Toth, I. (2002) Syntheses of polycationic dendrimers on lipophilic peptide core for complexation and transport of oligonucleotides. Biorg. Med. Chem. Lett. 12, 2635-2631. 

Preparation and possible applications of polycationic dendrimers (120a -120c) have been patented. ... 

Zhang, Z.Y. Smith, B.D. High-generation polycationic dendrimers are unusually effective at disrupting anionic vesicles membrane bending model. Bioconjug. Chem. 2000, 11, 805-814. 

Fig. 11. Hybrid multilayers made of (a) polycationic dendrimers and polystyrenesulfonic acid (b) polycationic dendrimers and glucose oxidase (c) thickness of the multilayers obtained in (a) depending on the number of layers and measured by ellipsometry...

Polycationic dendrimers and dendrons have also been assembled with DNA in order to generate complexes which have well-defined nanoscale sizes (ca. 50-200 nm) that are capable of transfecting DNA into cells [35]. 

More recently. Oh and coworkers" developed PAMAM dendrimers with both primary amines and quaternary ammonium groups at the dendrimer periphery, in an attempt to facilitate templating of Au precursors within the dendrimer. Upon reduction by NaBH4, gold nanoparticles on the order of 1 to 2 nm were formed for DMNs containing between 55 and 300 Au atoms. Utilizing this polycationic dendrimer precursor results in the formation of gold particles with smaller and more controlled particle diameters than those previously reported. - Just as in the case of Pt, however, more work needs to be performed to elucidate the mechanism of Au nanoparticle formation. 

Dendrimers have also found application as carriers of genetic materials into cells [84,298-300]. In this usage, the dendrimers can be thought of as a histone mimetic. With appropriately charged surface groups the polycationic dendrimers forms a supramacromoleeular complex with the poly-anionie nucleic acid biopolymer. This dendrimerie nanodevice transports the genetic material across... 

Fig. 2. Examples of polycationic dendrimers. top a tetraphosphonium dendrimer bottom a tetraammonium dendrimer...

The utility of polycationic dendrimers for interacting with DNA, in particular as synthetic vectors in transfection experiments, has been recognized very early, most experiments in this field being carried out with Poly(AMidoAMine) dendrimers (PAMAM) [91]. Phosphorus-containing dendrimers are also usable as vehicles to transport DNA or plasmids inside cells. Functional tests, to verify if the... 

Maszewska M, Leclaire J, Cieslak M, Nawrot B, Okmszek A, Caminade AM, Majoral JP (2003) Water-soluble polycationic dendrimers with a phosphraamidothioate backbone preliminary studies of cytotoxicity and oligonucleotide lasmid delivery in human cell culture. Oligonucleotides 13 193-205... 

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