DENDRIMER-BASED HOST/GUEST SYSTEMS FOR DRUG DELIVERY

Dendrimers are highly branched macromolecules obtained by stepwise controlled, reaction sequences. Starting from a central core it is possible to grow successive generations by the repetitive addition of branch units, either from the core to the outer surface (divergent method) or from the end-groups to the core (convergent method). The ability to be designed for specific uses, through the suitable choice of the core molecule, interior region, and peripheral surface, makes dendrimers versatile systems for the study of molecular organisation at the nano-scale. Due to these properties, dendrimers provide unprecedented components to control the structural organization of matter during the bottom-up synthesis of functional nano-structures. One of the major expected applications of dendrimers in the field of nanotechnology consists in the encapsulated guest molecules in their internal cavities or in the entrapment of dendrimers and their partitioning within bio-membranes. For this kind of application a fundamental information needed regard the determination of dendrimer spatial distribution structure as well as the investigation of the peculiar type of interactions that take place between the guest molecules and the particular end-groups employed. Analysis of recent research achievements outline how the control of specific system parameters can be exploited to enhance specific interactions with bio-materials as well as to preserve the releasing efficiency at the target site. As one of the main challenges in drug delivery is not only the targeting of bioactive to a specific site but also retaining it for an optimum duration to attain the desired task, methods of entrapment/encapsulation of bioactive dendrimers and their partitioning within model lipid membranes are described. For guest dendrimers, segregated in different compartments of lipid nanocarrier, electrostatic interaction and dimensions of involved nanoparticles are the main parameters that influence the membrane stability in water solution. Although possible toxicity problems may be present, they can be resolved by modifying dendrimer structure. In this respect the development of highly-efficient and highly biocompatible carriers will rely strongly on the advances in our understanding of interactions involved in the drug delivery processes