PAMAM dendrimers scaffolds

Figure 1.21 Periodic properties for poly(amidoamine) (PAMAM) dendrimers as a function of generation G = 0-10 (I) flexible scaffolding (G = 0-3) (II) container properties (G = 4-6) and (III) rigid surface scaffolding (G = 7-10) various chemo/ physical dendrimer surfaces amplified according to Z = NCN where Nc = core multiplicity, Nb = branch cell multiplicity, G = generation...

As outlined in other chapters in this volume, Tomalia et al. first reported the successful well-characterized synthesis of dendrimers in the early 1980s [1], These molecules range in size from 10 A to 130 A in diameter for generation 0 (GO) through generation 10 (G10). In the ideal situation, PAMAM dendrimers are monodispersed spherical conformation with a highly branched three-dimensional structure (Figure 18.1) that provides a scaffold for the attachment of... 

Bradley described the first solid-phase synthesis of PAMAM dendrimers in 1997 [220]. To this end, phthaloyl-protected norspermidine was coupled to aminomethyl functionalised polystyrene-polyethylene-glycol resin ((PS-PEG)-NH2) through an acid-labile linker (see Fig. 23). PAMAM dendrons were assembled by treating deprotected scaffold-bound resin 24 first with an excess of methyl acrylate... 

An advantage of the divergent method - which was the first to be developed [1] - is the attainable high-molecular (nano)scaffold architecture as well as the possibility of automation of the repetitive steps. The divergent method is therefore the method of choice for - commercially available - POP AM and PAMAM dendrimers (see Section 4.1). 

The principal focus of interest has hitherto been on the group of flexible dendrimers, which embraces the major part of the dendrimers reported in the literature, also including the commercially available POPAM and PAMAM dendrimers having an aliphatic scaffold. In recent years valuable knowledge about the density profile, the three-dimensional structure, and the interactions of dendrimers in solution has been obtained with the aid of small-angle scattering techniques, as is apparent from the following overview. 

Unimolecular contamer/scaffolding behavior appears to be a periodic property that is specific to each dendrimer family or series. These properties will be determined by the size, shape, and multiplicity of the construction components that are used for the core, interior, and surface of the dendrimer. Higher multiplicity components and those that contribute to tethered congestion will hasten the development of container properties or rigid surface scaffolding as a function of generation. Within the PAMAM dendrimer family, these periodic properties are generally manifested in three phases as shown in Fig. 42.12. 

Given the success of Bertozzi s example, it is perhaps surprising that not more multivalent scaffolds based on glycosyl hydrazide chemistry have been reported. One of the few examples has been described by Liu and coworkers, who have shown that oligosaccharides can readily be displayed on modified poly(amido amine) (PAMAM) dendrimers via a hydrazide linkage. These dendrimers were shown to be readily taken up by hepatocytes in a glycan-dependent fashion [35]. Similarly, dendrimers have been used to increase the density of carbohydrate... 

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