Research Description:

Chemical Optimization of PEI (polyethleneimine) for Gene Delivery

Gene delivery has many real world applications such as treating diseases that do not have current therapies and potentially curing genetic diseases, such as cystic fibrosis. The major challenge in gene delivery is developing an effective delivery system. Currently there are two viable systems the use of virus and chemical based systems.  Viral delivery has been plagued with a series of health related problems increasing research interest in chemical based systems such as cationic liposomes and polymers.  A driving force allowing cationic macromolecules to interact with plasmid DNA is the electrostatic differences between the two molecules.  The greater the charge density (e.g., how often/distance a charge occurs on the macromolecule) the greater the reaction rate.  Polyethleneimine (PEI) has the highest charge density of any cationic polymer and the charge density of plasmid DNA can not be altered without impacting on the ability of the DNA to transfect.  The high charge density of PEI leads to problems in the formation of polyplexes (plasmid DNA/cationic polymer particles).  The reaction is not a single PEI molecule interacting with a single plasmid but multiple molecules of interacting with each other.  This multiple rapid interaction creates a perplexing problem  we need the interaction to proceed but we also need methods to control the reaction rate.  In non-controlled reactions the polyplexes can interact with each other and aggregate precipitating for the solution. This aggregates can are non effective in gene delivery and worse they can have a toxic effect.  We hypothesize that the rate and extent of the interaction can be controlled by transiently altering (decreasing) the charge density of PEI.  The decrease in charge density will allow for a more controlled interaction between plasmid DNA and PEI resulting in a more homogenous and smaller size of polyplexes.  A second hypothesis is that smaller more uniform polyplexes will result in greater transgene delivery and expression. The overall goal of my research project is to formulate a better, more effective vector for gene delivery.