Charge dendrimers

The SANS experiments [51] were performed with solutions of G8 PAMAM dendrimer in D20, methyl-d4, ethyl-d6, and n-butyl-d10 alcohol at a temperature of T = 20.0 °C. PAMAM dendrimers do not dissolve in acetone, but they readily dissolve in methyl alcohol/acetone mixtures over a wide range of composition. Solvents of different composition, were prepared and added to a weighed amount of dried G5 or G8 dendrimer. In a separate set of experiments, the NIST NG7 30 m instrument was used to measure the effects of charging on the dendrimer size. PAMAM G8 dendrimers in D20 were charged by addition of HC1 in the presence of various amounts of NaCl to the charged dendrimers to screen the electrostatic interactions. 

Scheme 2 Electrostatic assembly of positively charged dendrimers to form a well-defined photofunctional aggregate...

Fluorescence lifetime measurements on the aggregate have shown that the rate constant of the intermolecular energy transfer from the zinc porphyrin unit to the free-base porphyrin unit has been evaluated to be 3.0 x 109 s-1. This value is reasonable from a model in which dendritic donor 6b and acceptor 5a contact each other directly at their exterior surfaces (Scheme 2). Therefore, electrostatic assembly of positively and negatively charged dendrimers provides a promising supramolecular approach to construct photofunctional materials with nanometric precision. 

Lyulin SV, Darinskii AA, Lyulin AV, Michels MAJ. Computer simulation of the dynamics of neutral and charged dendrimers. Macromolecules 2004 37 4676-4685. 

Terao T. Counterion distribution and many-body interaction in charged dendrimer solutions. Mol Phys 2006 104 2507-2513. 

Zhang H, Dubin PL, Ray J, Manning GS, Moorefield CN, Newkome GR. Interaction of a polycation with small oppositely charged dendrimers. J Phys Chem B 1999 103 2347-2354. 

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)... 

A layer-by-layer alternate electrostatic adsorption of monolayers of a positively-charged dendrimer (G4 poly(amidoamine)) and the negatively-charged protein glucose oxidase allows the preparation of multilayered assemblies for the construction of amperometric glucose sensors. This multilayer... 

Surface-charged dendrimers are those in which chaises are located only at the termini of the elaborated branches, while the core and branch system are uncharged. In general, the species of this category, which have been constructed, have involved anionic sites, specifically carboxylate anions, at the termini of the branches. 

The toxicological profiles of dendrimers and dendritic nanoparticles can be also controlled by their size and surface modifications. Importantly, the charge-based non-specific interaction between positively charged dendrimers and cell membranes are typically associated with toxicity.[84,85] As discussed earlier (Section 2.A non-specific cell interaction), the electrostatic interactions of cationic dendrimers with cell membrane induced membrane disruption, which could be a reason for the apparent toxicity observed in animal studies.[86] Surface modification of terminal amine groups to different groups (charge neutral or... 

Fig. 11 Representation of a DNA biosensor prepared via layer-by-layer deposition of positively and negatively charged dendrimers...

Simulations on such charged dendrimer/linear PEL systems were made by Klos and Sommer [58] based on one dendrimer binding at one charged chain, including counterions, with temperature as the main simulation parameter. The results are shown in Fig. 12. They found that the distribution of tail lengths of the adsorbed chain depends on both temperature and length of the chain. Although for short... 

Klos JS, Sommer JU (2011) Monte Carlo simulations of charged dendrimer-linear polyelectrolyte complexes and explicit counterions. J Chtan Phys 134 204902... 

Figure 5 Scanning small-angle X-ray scattering and diffraction in a hydrodynamic focusing device. A solution of negatively charged double-stranded DNA molecules is hydrodynamically focused by solutions of positively charged dendrimers. Different spatial positions in the outlet channel correspond to different concentration ratios of the reaction partners, which can be seen by the position dependant SAXS 2D-pattern.

Figure 43 Schematic representation of the eiectrostatic interaction between negativeiy and positiveiy charged dendrimer eiectroiytes. D represents a donor and A an acceptor in energy transfer. (Courtesy of Angew. Chem. Int. Ed. 1998, 37(11) 1533. Copyright Wiiey-VCH Veriag GmbH, Weinheim, Germany.)...

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