Dendrimer complex

Polynuclear dendrimer complexes of this type can undergo redox reactions at the metal centre and have luminescent properties. They have been proposed as molecular photochemical devices, although no practical examples have yet been produced. 

Fig. 14. Rotaxane dendrimers from crown ether-terminated polypropylimine dendrimer complexation with dibenzylammonium ion...

Self-assembly of aromatic dendron subunits has been tried by the design of coordination to multivalent metal cations (i.e., metal-cored dendrimer complexes). Several metal-cored dendrimer complexes have successfully exhibited luminescence by antenna effects. 

PBE dendrons bearing a focal bipyridine moiety have been demonstrated to coordinate to Ru + cations, exhibiting luminescence from the metal cation core by the excitation of the dendron subunits [28-30]. The terminal peripheral unit was examined (e.g., phenyl, naphthyl, 4-f-butylphenyl) to control the luminescence. The Ru +-cored dendrimer complexes are thought to be photo/redox-active, and photophysical properties, electrochemical behavior, and excited-state electron-transfer reactions are reported. 

Two practical advantages of luminescence species engulfed in antenna dendrimer scaffolds are apparent, namely their miscibility with organic media (solvents or/and resins) and their ability to form thin films. For example the lanthanide-cored dendrimer complexes described in this chapter can be regarded as organic-soluble inorganic luminescers. 

The PBE dendron has a glass transition at about 40 °C and is soluble in various organic solvents (e.g., THF, acetone, toluene). It is therefore a moldable, thermoplastic, film-forming material. This practical feature is maintained for the lanthanide-cored dendrimer complexes. The complexes are partially miscible with poly(methyl methacrylate), affording transparent luminescence compositions by mixing in solvent. 

Vinylphenyl-terminated PBE dendrons were prepared as polymerizable den-drons from 4-vinylbenzyl chloride [37]. The vinylphenyl-terminated PBE dendrons are useful to make the lanthanide-cored dendrimer complexes polymerizable. The Ist-generation Tb +-cored dendrimer complex bearing the vinyl-phenyl terminal on the dendron subunits (Fig. 5) was copolymerized with N-iso-propylacrylamide in the presence of methylene bis-acrylamide (as crosslinker) in DMSO to give a green-luminescence transparent gel. The DMSO gel was con-... 

Fig. 5. A Ist-generation Tb +-cored dendrimer complex bearing polymerizable vinylphenyl groups on the dendron subunits...

The red-luminescence (612 nm) europium complex is an excellent luminescer in commercial use however, the green-luminescence Tb +-cored dendrimer complex enables a simultaneous assay at another wavelength (545 nm). The latex formation was carried out by mini-emulsion radical polymerization of the monomers dissolving the Tb +-cored dendrimer complexes. The polymeriza-... 

Fig.7. A demonstration of fluoroimmunoassay. Green circles (Tb-cored dendrimer complex) and red circles (conventional Eu complex) corresponds to different assays...

Keywords. Polyamidoamine dendrimers. Activation of PAMAM dendrimers. Transfection, Gene transfer, DNA-dendrimer complex... 

PAMAM dendrimers have the following characteristics which are important for their use as transfection reagents. They bind and form complexes with nucleic acids, allow transfer of the DNA-dendrimer complex into the cytoplasm of the... 

Activated PAMAM dendrimers interact with DNA to form a DNA-dendrimer complex with a toroid-like structure (Fig. 2). Such DNA-dendrimer complexes have diameters of 50-100 nm [10],which means that the DNA molecules are highly condensed in these complexes. A 6-kb plasmid alone, for example, has an extended structure several hundred nanometers in diameter. In transfection experiments, typically an 8- to 12-fold excess of positive amino groups over negatively... 

Fig. 8 Nanosystems that may function as simultaneous drug delivery and imaging agents for targeting T cells (a) liposomal systems, (b) solid biodegradable nanoparticulates, and (c) macro-molecular dendrimer complexes. PEG polyethylene glycol, Gd-DTPA gadolininum-diethylene triamine penta acetic acid. (Adapted from [48])...

Such sugar-dendrimer complexes ( sugar balls ) have been used to inhibit the interactions of viruses with cell surfaces. Many viruses bind to particular carbohydrate residues on cell surfaces, which in turn facilitate their entry into cells and the resultant infection process. A virus particle presents a multi-dentate surface consisting of many carbohydrate-binding proteins able to interact with multiple cell-surface carbohydrates. The surface of a dendrimer that is modified with... 

Purify the conjugate by gel filtration to separate protein-dendrimer complexes from excess protein or dendrimer. 

A similar type of biotin-dendritic multimer also was used to boost sensitivity in DNA microarray detection by 100-fold over that obtainable using traditional avidin-biotin reagent systems (Stears, 2000 Striebel et al., 2004). With this system, a polyvalent biotin dendrimer is able to bind many labeled avidin or streptavidin molecules, which may carry enzymes or fluorescent probes for assay detection. In addition, if the biotinylated dendrimer and the streptavidin detection agent is added at the same time, then at the site of a captured analyte, the biotin-dendrimer conjugates can form huge multi-dendrimer complexes wherein avidin or streptavidin detection reagents bridge between more than one dendrimer. Thus, the use of multivalent biotin-dendrimers can become universal enhancers of DNA hybridization assays or immunoassay procedures. 

The broad emission band displayed by these silver/dendrimer constructs actually was found to consist of 5 overlapping fluorescent peaks caused by individual silver/dendrimer complexes. Each of these complexes evidently contained a uniquely sized silver nanocluster, which resulted in an individual emission peak. Therefore, all the silver/dendrimer complexes together in solution presented a combined average of these 5 discrete emission peaks, and thus displayed the broad emission band covering nearly 200 nm in width across the spectrum. 

Kawa, M., and Frechet, J.M.J. (1998) Self-assembled lanthanide-cored dendrimer complexes enhancement of the luminescence properties of lanthanide ions through site-isolation and antenna effects. Chem. Mater. 10, 286-296. 

The Lipari-Szabo approach was used to understand the cause of the pH-dependent relaxivities of PAMAM-type dendrimeric Gdm complexes (74). Three different generations (5,7,9) of PAMAM dendrimers loaded with the [Gd(EPTPA)(H20)]2 chelate via a benzyl-thiourea linkage have been investigated (Scheme 8). The relaxivities show a strong and reversible pH dependency for all three dendrimer complexes,... 

SCHEME 3.81 Solution processible iridium dendrimer complex. 

Table 19.2 Sensitivity determination with analyte-specific primary antibody in the form of a dendrimer complex or a double-antibody immune complex...

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