Nanoparticles dendrimer-derived

A variety of secondary structures can be formed from dendrimer or dendron primary units (98). We have prepared dendrisomes (vesicles) from amphipathic dendrons (Fig. 16). Dendriplexes can be formed by interactions between anionic macromolecules and cationic dendrimers or dendrons, for example. Hydrophobic dendrimers whose surface groups are reacted to form an alkyl surface will aggregate and can be formulated as so-called dendrimer-derived nanoparticles some 200 nm in diameter (99). 

Singh B, Florence AT. Hydrophobic dendrimer-derived nanoparticles. Int J Pharm 2005 298 348-353. 

Recently, a combination of fluorous substituents and a sugar-derived structure allowed the preparation of the scC02-soluble copolymer 53 as a novel phase-transfer catalyst (Figure 4.8). ° Dendrimers with fluorous substituents were also prepared for the same use. ° They are soluble in dense carbon dioxide and can solubilize otherwise C02-insoluble compounds such as Pd-nanoparticles (Scheme 92). The resulting dendrimer-encapsulated Pd catalyzes the hydrogenation of styrene and the Heck reaction of phenyl iodide. 

Suzuki-Miyaura reactions of iodoarene and bromoarene derivatives were remarkably catalyzed by this dendrimer-stabilized Pd nanoparticle, with the resulting TONs equal to or larger than 10 . The catalytic activity for Sonogashira coupling was also impressive, and only 0.01% mol Pd was required. 

In a study conducted by Liu et at, a doxorubicin (Dox)-carrier system was developed by electrostatic complexion of G4 PAMAM dendrimer with a pH-sensitive diblock copolymer of poly(methacryloyl sulfadimethoxine) (PSD) and PEG, with lactose (LA) coupled at the distal end of the PEG chain [77]. A higher cumulative Dox release from LA-PEG-b-PSD/PAMAM complexes was observed at pH 6.5 compared to pH 7. In another study, a pH-sensitive dendrimer nanoparticle was prepared, where surface cationic charge of the PAMAM dendrimer was reduced to prevent opsonization in the systemic circulation [78]. Zwitterionic chitosan (ZWC), a chitosan derivative with a unique pH-sensitive charge profile, was used to modify the cationic surface of PAMAM dendrimers. A stable electrostatic complex between ZWC and PAMAM was formed at pH 7.4, where the PAMAM dendrimer surface was covered with ZWC. The results demonstrated that ZWC can mask the surface charge, which minimizes hemolytic and cytotoxic activities of PAMAM dendrimers. However, the complex dissociated due to the charge conversion at low pH, allowing PAMAM dendrimer charge to be exposed and facilitate its entrance into the cells. 

M. Ehara, Carhohydrate-derived hydrogels and microgels, in R. Narain, ed.. Engineered Carbohydrate-Based Materials for Biomedical Applications Polymers, Surfaces, Dendrimers, Nanoparticles, and Ely dr o gels, Wiley, Hoboken, NJ, 2011. 

Crooks group prepared monodisperse (1.7 0.2nm) palladium nanoparh-cles within the interiors of three different generations of hydroxyl-terminated PAMAM dendrimers [41]. This process involved encapsulation of the nonselec-tive catalyst (the Pd nanoparticle) within a selective nanoporous cage (the dendr-imer). These dendrimer-encapsulated palladium nanoparticles were used as catalysts to hydrogenate allyl alcohol and four R-substituted derivatives in a metha-nol/water mixture. The results showed that higher-generation dendrimer encapsulated catalysts (DECs) or larger substrates resulted in lower turnover frequencies. 

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