Dendrimer ionic strength

PAMAM dendrimer in methanol[19], and larger also than the 60 A maximum physical radius of a completely stretched structure, but has been employed consistently. In terms of the model, some of the scatter in Figure 4 can be explained by considering that the radius of gyration of this polyelectrolyte is likely to depend on the ionic strength, pH, and even the concentration of borate diesters (internal cycles) none of these factors were systematically controlled in this study. 

Huang, Q.R. Dubin, P.L. Moorefield, C.N. Newkome, G.R. Counterion binding on charged spheres effect of ph and ionic strength on the mobility of carboxyl-terminated dendrimers. J. Phys. Chem. B 2000, 104, 898-904. 

The SEC partition coefficient [6] (.K sec) was measured on a Superose 6 column for three sets of well-characterized symmetrical solutes the compact, densely branched nonionic polysaccharide, Ficoll the flexible chain nonionic polysaccharide, pullulan and compact, anionic synthetic polymers, carboxylated starburst dendrimers. All three solutes display a congruent dependence of K ec on solute radius, R. In accord with a simple geometric model for SEC, all of these data conform to the same linear plot of i sEc versus R. This plot reveals the behavior of noninteracting spheres on this column. The mobile phase for the first two solutes was 0.2M NaH2P04-Na2HP04, pH 7.0. In order to ensure the suppression of electrostatic repulsive interactions between the dendrimer and the packing, the ionic strength was increased to 0.30M for that solute. 

Cationic polymers, such as poly(L-lysine) (PEL), polyethylenimine (PEI), chitosan, polyamidoamine (PAMAM) dendrimers, poly(2-dimethylamino) ethyl methacrylate, and polyphosphoesters, condense DNA to form compacted polyplexes. ° The size and the stability of polyplexes depend on the ratio of cations vs. anions, temperature, ionic strength, and the solvent. Stability of polyplexes can be enhanced by conjugating PEG to the polycations or by using PEG-containing block or graft polymers that form micelles. Small cationic peptides are also able to condense DNA, however, six-consecutive-cations is the minimal requirement to achieve this effectively. 

Dendrimers have an architecture which is intrinsically accessible, because their branched structure allows the passage of substfates and products. In the case of PICsomes, the use of polyelectrolytes, which self-assemble into intrinsically porous systems, favors accessibility to the inner cavity where the active compounds are located [25]. Their membranes are permeable to small molecules, such as Tokyo-Green- 3-galactoside, while encapsulated active biomacromolecules, such as trypsin, cannot escape from the vesicular assemblies [25]. In the case of LbL capsules, permeabiUzation of the shell is tuned by its polymer composition, thickness, solvent, pH, or ionic strength [88,89]. 

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