PAMAM dendrimers carboxyl terminated

Fig. 16.10 Reaction scheme for immobilization of DNA onto functionalized Si02 substrates. Plasma treated Si02 substrates are denoted as Si OH, APTMS functionalized substrates are denoted as Si NH2, dendrimer functionalized substrates are denoted as Si G(4.5)COOH, and substrates to which DNA capture probes have been immobilized are denoted as Si DNA. Inset Repeat unit of PAMAM dendrimer possessing terminal carboxylic acid functionality...

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. 

Amine-terminated, G3 (PAMAM) dendrimer, (0.316 g 45.7 moles) was dissolved in anhydrous methyl sulfoxide (5 ml) in a 100 ml round-bottom flask flushed with dry nitrogen. After dendrimer had completely dissolved, succinic anhydride (Aldrich) (0.363 g 3.6 mmol) was added to the reaction mixture with vigorous stirring, and the mixture was allowed to react for 24 h at room temperature. The product solution was diluted with deionized water, transferred to 3500 MWCO dialysis tubing (Spectrum) and dialyzed against deionized water (18 Mil) for 3 d. The retentate solution was clarified by filtration through Whatman No. 1 filter paper, concentrated with a rotary evaporator, and lyophilized to yield a colorless powder (0.435 g, 94%). The product was analyzed by 13C-NMR, FT-IR, SEC and MALDI-MS. The analytical data were consistent with the expected carboxylic acid-terminated product. 

Amine-terminated, full-generation PAMAM and PPI dendrimers, as well as carboxylate-terminated half-generation PAMAM dendrimers, can directly bind metal ions to their surfaces via coordination to the amine or acid functionality. A partial hst of metal ions that have been bound to these dendrimers in this way includes Na+, K+, Cs+, Rb+, Fe +, Fe +, Gd +, Cu+, Cu +, Ag+, Mn +, Pd, Zn, Co, Rh+,Ru +,andPt + [18,19,27,36,54,82-96]. Tuxro et al.have also shown that the metal ion complexes, such as tris(2,2 -bipyridine)ruthenium (Rulbpylj), can be attached to PAMAM dendrimer surfaces by electrostatic attraction [97]. A wide variety of other famihes of dendrimers have also been prepared that bind metal ions to their periphery. These have recently been reviewed [3]. Such surface-bound metal ions can be used to probe dendrimer structure using optical spectroscopy, mass spectrometry, and electron paramagnetic resonance (EPR) [86-88,90,97-99]. 

Poly(3inido amine) (PAMAM) Dendrimers. These dendrimers have a hydro-phihc polyamide interior that is relatively open to solvent, in contrast to a micellar assembly. Yet, the picture of a unimolecular micelle also emerged for a generation 4.5 PAMAM dendrimers having sodium carboxylate terminal groups (Fig. 11.4). 

Starburst PAMAM dendrimers (Fig. 1), a specific class of commercially available dendrimers that have repeating amine/amide branching units, have drawn considerable interest in recent years due to their potential applications in medicine, nanotechnology, and catalysis [3-7]. These dendrimers are readily functionalized to terminate in diverse moieties such as primary amines, carboxylates, hydroxyls, or hydrophobic alkyl chains. Because dendrimer size and end groups can be varied, they are typically named by their generation (Gl, G2, etc.) and exterior functionality (- NH2, - OH). 

Fig. 1. (a) A chemical structure of a 2.5th generation carboxylic acid-terminated poly(amido amine) (PAMAM) dendrimer. (b) Transmission surface enhanced infrared absorption spectra (SEIRAS) of dendrimer adlayers prepared at 30 min adsorption from aqueous solutions (0.01 wt.%) of a dendrimer at different pHs. Numerical values are pHs of the solutions, (c) Adsorption-desorption profiles as a function of time at different pHs and adlayer thicknesses at adsorption and desorption equilibrium as a function of pH for aqueous solutions (0.1 wt.%) of the dendrimer. The symbols, j and J, in the top figure denote start of adsorption and desorption, respectively. In the bottom figure, filled circle and opened square denote adlayer thicknesses at adsorption and desorption equilibrium, respectively. The dark tie denotes the calculated dendrimer size width. A solid curve is drawn to be visual, (d) Schematic illustration of dendrimers adsorbed at different pHs. Reprinted with permission from Ref. [69], 2006, American Scientific Publishers. 

NaPGA) and amine-terminated PAMAM dendrimers [102-105], The flexible NaPGAs are possible to interact not only with protonated primary amines in the periphery of a dendrimer but also with tertiary amines in its interior. Opposite combination of the complex, which is stimulated by the electrostatic interaction, was formed between cationic synthetic polyelectrolyte, poly(dial-lyldimethylammonium chloride), and anionic carboxyl-terminated PAMAM dendrimers [106-109],... 

Wade. D.A. Torres. P.A. Tucker, S.A. Spectrochemical investigations in dendritic media Evaluation of nitrometh-ane as a selective fluorescence quenching agent in aqueous carboxylate-terminated polyamido amine (PAMAM) dendrimers. Anal. Chim. Acta 1999.397, 17-31. 

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