In this thesis the synthesis, characterization and properties of different dendritic structures are described as well as their application in the field of biomedicine.

After the first introductory chapter, where the structural characteristics, synthetic methodologies and applications (especially biomedical) of dendrimers are briefly explained, we report the development of different synthetic routes for the preparation of new multichromophoric dendritic systems with an hybrid structure. Specifically, dendritic architectures whose backbone is constituted by alternated layers of poly(amidoamine) PAMAM and poly(phenylenevinylene) (PPV).

In chapter 2, the preparation of the aforementioned compounds following a convergent methodology is described. It is necessary the previous preparation of dendritic hybrid wedges, which were built through both covalent and electrostatic linkages. Likewise, it has been carried out a preliminary study of the optical properties of this kind of structures by UV-visible absorption and fluorescence spectroscopies.

The third chapter deals with the synthesis of hybrid dendrimers through a divergent methodology, preparing in this way compounds of different generations and number of branches in their structure. After a full characterization, where a preliminary analysis of the aggregation of these compounds by DLS and AFM is also performed, a detailed study about the potential of these molecules as non viral gene transfection agents in neuronal cells is presented.

In the last chapter the work carried out during a predoctoral stay in the University of York (United Kingdom), under the supervision of Prof. David K. Smith, is reported. In this time, the synthesis of the amphiphilic systems that spontaneously self-assemble into spherical micelles, 'pseudo-dendrimers', was accomplished. They act as protein mimetics such as protamine, and uncover their ability to form organized nanostructured assemblies in presence of heparin (an anticoagulant widely used in surgery).