3.MICRO AND NANO DRUG DELIVERY SYSTEMS(cont.)
3.4.Dendrimers
Dendrimers are small molecules which have a core and a series of branches symmetrically formed around the core resulting in a monodisperse, symmetrical macromolecule. They can be synthesized either starting from the core molecules and going out to the periphery by connecting the branch groups or by forming the branches first and then collecting all around the core. Functionality of the branching units is generally 2 or 3, which makes the layer of branching units doubles or triples. The interior cavity is very suitable for the entrapment of the drugs and their unique properties such as high degree of branching, multivalency, globular architecture and well-defined molecular weight, make dendrimers promising new carriers for drug delivery. Their nanometer size, ease of preparation and functionalization, and their ability to display multiple copies of surface groups for biological reorganization processes increase their attraction in biomedical applications.Interaction of dendrimer macromolecules with the molecular environment is predominantly controlled by their terminal groups. By modifying their termini, the interior of a dendrimer may be made hydrophilic while its exterior surface is hydrophobic, or vice versa. Drug molecules can be loaded both in the interior of the dendrimers as well as attached to the surface groups. Water-soluble dendrimers are capable of binding and solubilizing small molecules and can be used as coating agents to protect or deliver drugs to specific sites in the body or as time-release vehicles for transporting biologically active agents. In the last decades, research has increased on the design and synthesis of biocompatible dendrimers and their application to many areas of bioscience including drug delivery, immunology and the development of vaccines, antimicrobials and antivirals gained great attantion.A series of lipidic peptide dendrimers based on lysine with 16 surface alkyl (C12 ) chains has been synthesised by Florence et al (2000). A fourth generation dendrimer with a diameter of 2.5 nm was studied for its absorption at different organs after
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