Several recent studies indicate that PAMAM dendrimer can be used as a delivery agent for biomolecules inside mammalian cells.  At physiological pH PAMAM dendrimers are positively charged and can effectively bind negatively charged biomolecules such as DNA and can be used as gene delivery materials.  There are indications that lower toxicity and higher transfection efficiency can be obtained by using complexes between DNA and PAMAM dendrimers.  The charge distribution of DNA within the dendrimer-DNA complex has a direct influence on the stability and activity of such transfection complex. It also affects the DNA conformations within such complex.  However, it is not yet clear how the dendrimer environment and other various factors such as pH, salt concentration affects the DNA conformations. The answers to questions such as, what the mechanism by which dendrimer condensed with DNA and what role the terminal amine group (primary amines) plays in condensation, remain unclear