Know your Dendrimer

The word 'dendrimer' is derived from the Greek word dendra, which refers to a tree. To put it in simpler terms, a dendrimer is polymer that branches. It is an artificially manufactured or synthesized molecule built up from branched units called monomers. It involves working on the nanoscale (a nanoscale refers to 109 or a billionth of a meter or a millionth of a millimeter). Dendrimers are a novel class of three-dimensional nanoscale, core-shell structures that can be precisely synthesized for a wide range of applications. Dendrimers are spherical polymeric molecules with a defined core, internal branching, and terminating groups. The repeat unit in this case is designated as a branch cell.

Depending on the generation, the molecular properties of a particular core dendrimer vary. In the past, they have been used as precise nano-reactors, where organization of small molecules, noble metals, metal oxides or ions can occur followed by their immobilization/stabilization as guest material. The dendrimer can start with 3 to 8 (or more) branches, with 3 and 4 being the most common numbers observed, but this is subject to the dendrimer core. Dendritic polymers are recognized as the fourth major class of polymeric architecture. This important polymer class consists of four sub-classes that may be defined by their degree of structural control.

Dendrimers, with their highly customizable properties, are basic building blocks with the promise of allowing specific nano-structures to be built to meet existing needs and solve evolving problems. The combination of a discrete number of functionalities and their high local densities makes dendrimers attractive as multifunctional platforms for amplified substrate binding. Such enhanced activity arises mainly from cooperative effect. As a result of their unique architecture and construction, dendrimers possess inherently valuable physical, chemical and biological properties. Dendrimer research and development is currently making an impact across a broad range of fields. Dendrimer synthesis is a relatively new field of polymer chemistry defined by regular, highly branched monomers leading to a mono-disperse, tree-like or generational structure. Synthesizing mono-disperse polymers demands a high level of synthetic control. Dendrimers branch out in a highly predictable fashion to form amplified three-dimensional structures with highly ordered architectures. Internal cavities intrinsic to dendrimer structures can be used to carry and store a wide range of metals, organic, or inorganic molecules. The outer shell of each dendrimer can be manipulated to contain a large number of reactive groups. Each of these reactive sites has the potential to interact with a target entity, often resulting in polyvalent interactions.

Building on a central core, dendrimers are formed by the step-wise, sequential addition of concentric shells consisting of branched molecules and connector groups. The majority of dendrimer systems display very low cytotoxicity levels. The basic structure of dendrimers enables for a lot of flexibility, which is leverage in the case of the application of dendrimers. The surface properties of dendrimers may be manipulated by the use of appropriate 'capping' reagents on the outermost generation. Their three-dimensional structure dendrimers have a high resistance to shear forces and solution conditions.

Companies all over the world operating in sectors as diverse as biotechnology, organic chemistry and telecommunications are pumping in millions of dollars to gauge the practical applicability of dendrimers. Branched polymers are critical components of biomolecular nanotechnology i.e. starch and glycogen. Synthetic chemists have found methods to create highly branched synthetic polymers by iterative chemical reactions. Dendrimers have found actual and potential use as molecular weight and size standards, gene transfection agents, as hosts for the transport of biologically important guests, and as anti-cancer agents. Dendrimers might also prove useful in the manufacture of nanoscale batteries and lubricants, catalysts, and herbicides. Much of the interest in dendrimers involves their use as catalytic agents, utilizing their high surface functionality and ease of recovery. Dendrimers' globular shape and molecular topology, interests biological systems aficionados as well.

The practical applicability of dendrimers is growing, but the pace of growth is slow. The key reason for this is that dendrimer research is time-consuming and expensive. Dendrimers are of interest to researchers in medical technology. They contend that the next breakthrough in drug delivery systems will be attributed to dendrimers. Dendrimers could also serve as a replacement for various plasma components.