Dendrimers physicochemical properties

Formation of a complex between DNA and polycationic compounds appears to be the initial and quite possibly a critical parameter for nonviral gene delivery. Several synthetic vector systems, which are generally cationic in nature, including poly(lysines), cationic liposomes or various types of block copolymers and recently dendrimers, have been shown to self-assemble with plasmid DNA [13-15] [16]. Specific physicochemical properties manifested by these DNA complexes depend on the type of cationic agent used however, interesting patterns for such interactions are beginning to evolve [17, 18]. Under certain conditions, the interaction of DNA with polyvalent cations results in... 

The above-mentioned results and drawbacks made futile any effort to grow larger generations of the dendrimer series 5 and 6 in order to get super high-spin macromolecules. Nevertheless, the outstanding structural characteristics and physicochemical properties of the first generations of both dendrimer series, 5 (G = 1) and 6 (G = 1), make both modest dendrimers worthy of detailed physicochemical studies. 

Synthetic polymer. Among the cationic synthetic polymers used for gene delivery are polyethylenimine (PEI), polyamidoamine dendrimers, and poly(2-dimethylaminoethyl methacrylate).161-164 Depending on the flexibility (or rigidity) of the polymers, they form either a small (<100 nm) DNA polyplex or a large (>1 to 10 pm) DNA polyplex.165 More detailed physicochemical properties and their transfection efficacy are to be discussed. 

In many cases, the constituents of a dendrimer sample are structurally very similar and differ only slightly in their physicochemical properties. A gradientlike alteration of the polarity of the solvent by increasing admixture of a more polar or less polar solvent frequently leads to better separation in such cases (gradient separation). 

In this chapter we introduce structures and physicochemical properties of dendrimers. Then synthesis and characterization of dendrimer-nanoparticles are discussed. 

Sakthivel T, Toth I, Florence AT. Synthesis and physicochemical properties of lipophilic polyamide dendrimers. Pharm Res 1998 15 776-782. 

Polyplexes are formed from many cationic polymers such as histones, PEI, dendrimers (pDMAEM) or carbohydrate-based polymers such as chitosan and cyclodextrin. Polyplexes are smaller in size than lipoplexes, which is a major physicochemical property for gene delivery, especially in vivoJ... 

Therefore, the physicochemical properties of nanoparticles must be uniformly controlled for the biological behaviors of nanoparticles to be predictable as polydispersity within one batch of nanoparticles or between different batches of the same nanomaterials could result in significantly different interactions with cell membranes. Considering their spherical, highly deformable, and close-to-monodispersed properties, dendrimers and dendritic nanoparticles offer a great opportunity to precisely control their cellular interactions, which is advantageous for their use in biomedical applications. 

Possible Mechanisms and Key Characteristics of Nanomaterials. A nanoparticle/nanomaterial is generally defined as a particle/ material having a physicochemical structure greater than typical atomic/molecular dimensions but at least one dimension smaller than lOOnm. It includes particles/ materials engineered or manufactured by humans on the nanoscale with specific physicochemical composition and structure to exploit properties and functions associated with its dimensions. Some of the common nanoparticle types are (1) carbon-based materials (e.g., nanotubes, fullerenes), (2) metal-based materials (e.g., nanogold, nanosilver, quantum dots, metal oxides), and (3) dendrimers (e.g., dendritic forms of ceramics). 

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