Dendrimers PAMAM

The properties of the various PAMAM dendrimer precursors are shown in Table 9.1. 

Table 9.1 Properties of PAMAM dendrimers containing an ammonia core...

Crystallization of CaCOj with the Anionic PAMAM Dendrimers... 

Fig. 2. Poly(amidoamine) (PAMAM) dendrimers with carboxylate groups at the external surface...

Crystallization of CaCOj is highly dependent on nucleation condition. The precipitation of CaCOj in the absence or the presence of the G4.5 PAMAM dendrimer was carried out by a carbonate diffusion method similar to the method described by Addadi et al. [35]. A solution of the dendrimer with calcium chloride in 200 ml of distilled water was adjusted to pH 8.5 with aqueous NHj, and then placed in a closed desiccator containing crushed ammonium carbonate (Fig. 5). Carbon dioxide was introduced to the solution via vapor diffusion. The critical point of the appearance in the turbidity of the solution was observed at around 5 min. These solutions were kept at 30 °C under N2 for one day. The crys-... 

Table 1. The precipitation of CaCOj in the absence and the presence of the G4.5 PAMAM dendrimer (adapted from [30]...

SEM observations showed that the most crystals obtained in the absence and the low concentration of the G4.5 PAMAM dendrimer were rhombohedral. In the high concentration of the G4.5 PAMAM dendrimer, the vaterite products were spherical. Each shape of CaCOj is a typical morphology for each polymorph. The particle sizes of the spherical vaterite particles obtained in the presence of the PAMAM dendrimer were depended on the concentration of the dendrimer. As the concentration of -COONa increased from 5.3 to 10.6 mmol/1, the particle sizes of the spherical vaterite particles were reduced from 8.7 1.0 to 5.2 3.0 pm. 

The precipitations of CaCOj in the presence of the Cl.5, G3.5, and G4.5 PAMAM dendrimers were carried out with constant -COONa unit and calcium ions of 0.1 mol/1. Although vaterite was predominantly formed by the G4.5 dendrimer, relatively high amount of calcite was observed in the case of the G3.5 and G1.5 dendrimers (Table 2). These results suggest that the G4.5 dendrimer effec-... 

Fig. 6. Potentiometric titrations of the G1.5, G3.5, and G4.5 PAMAM dendrimers in the absence open symbols) and the presence close symbols) of calcium ions in 1.0 mol/1 KCl solution with 0.01 mol/1 HCl solution. The -COONa unit of the PAMAM dendrimers was constant at 3.0x10 mmol (adapted from [30]...

Anionic poly(amidoamine) (PAMAM) dendrimer was selected as a model of the soluble acidic-rich proteins to prepare CaC03 film on a poly(ethylenimine) film [49]. The CaCOj/polylethylenimine) composite film was obtained in the... 

Spherical vaterite crystals were obtained with 4-mercaptobenzoic acid protected gold nanoparticles as the nucleation template by the carbonate diffusion method [51]. The crystallization of calcium carbonate in the absence of the 4-MBA capped gold nanoparticles resulted in calcite crystals. This indicates that the polymorphs of CaCOj were controlled by the acid-terminated gold nanoparticles. This result indicates that the rigid carboxylic acid structures can play a role in initiating the nucleation of vaterite as in the case of the G4.5 PAMAM dendrimer described above. 

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

Structure of PAMAM Dendrimers and Activated PAMAM Dendrimers 230... 

Theory of Gene Transfer with Activated PAMAM Dendrimers.232... 

Newly synthesized PAMAM dendrimers have a defined size and shape and can be used in gene transfer experiments, but the efficiency of transfection can be greatly increased by a process called activation of the dendrimer. In activation, some of the tertiary amines are removed, resulting in a molecule with a higher... 

Fig.1. Non-activated and activated PAMAM-dendrimers. Schematic diagram of a non-acti-vated (left) and activated dendrimer (middle). The right panel shows a magnification of the dendrimer branches...

PAMAM dendrimers are synthesized in a multistep process. Starting from a multifunctional amine (for example ammonia, ethylenediamine, or tris(2-amino-ethyl)amine) repeated Michael addition of methylacrylate and reaction of the product with ethylenediamine leads to dendrimers of different generation numbers [1,9]. Two methylacrylate monomers are added to each bifunctional ethylenediamine generating a branch at each cycle. Unreacted ethylenediamine has to be completely removed at each step to prevent the initiation of additional dendrimers of lower generation number. Excess methylacrylate has also to be removed. Bridging between two branches of the same or of two different dendrimers by ethylenediamine can also be a problem, and has to be avoided by choosing appropriate reaction conditions. 

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