Synthesis, properties and applications of dendronized chitosan.

MIRIAM STRUMIA

Siegen

Congreso; Polychar 18. Advanced Materials; 2010

The dendronized polymer architecture has gained increasing attention during the latest years thanks to its controllable size, shape, and versatile functionalization possibilities. In addition, their highly branched structure with a presumably high degree of functionality, provide them with unique physical properties, such as low viscosity at high molecular weight. This subclass of comb polymers was first mentioned in a patent by Tomalia et al. in 1987 and then was synthesized by Hawker and Fréchet in 1992. Since then, a large number of dendronized polymers have been developed, and promising applications in nanotechnology for these new materials have been suggested. More recently, our research group has begun to work in the chemical functionalization of polymers through dendronization methodology. Interesting properties were found in these new products, as stimuli responsive behavior in solvent of different polarity1, rheological synergism2 and multivalency effect in Afinity Chromatography3.  At the moment, we are studying the effect of the dendronization of Chitosan. It is a polysaccharide formed primarily of repeating units of b (1-4)-2-amino-2-deoxy-D-glucose, although a small amount of N-acetyl-D-glucosamine is included in the structure. The free amino and hydroxyl groups of chitosan offer great potential for further derivation. Chitosan has shown interesting applications as biomaterial due to its excellent biocompatibility, low toxicity, immunostimulatory activities, antibacterial and antifungal action, and anticoagulant properties. Furthermore, the degradation products of chitosan have been shown to be nontoxic, non-immunogenic and noncancinogenic. It is well known that the effects of dendronization are of two types: one of them is of topological nature, according to the architecture and size of the dendrons, and the other, is of chemical nature, according to the chemical structure of the dendrons. Therefore, our goal is to obtain a new material by modification of chitosan using dendritic molecules of different generation or chemical structure. The challenge of this research is to find in these products new properties maintaining the well known advantages of the Chitosan. Consequently, it allows increasing the functional utility of this polymer to facilitate the use in a variety of applications like supports in drug delivery or affinity chromatography. Therefore, different chitosan-based polymers were functionalized with the first and second generation of dendritic molecules.  The products were chemically characterized showing the covalent incorporation of the dendrons. The studies of their properties are in progress. In a next step, is our interest to evaluate the influence of dendritic effects on the efficiency of dendrons as multivalent ligand. __________________