The present provides methods and compositions that enable effective delivery
of nucleic acids to desired cells, including to a solid organ such as a mammalian
heart. The methods and compositions enable effective gene transfer and subsequent
expression to a majority of cells throughout a solid organ such as the heart. Methods
and compositions of the invention preferably provide enhanced vascular permeability
that enables increased gene transfer to targeted cells, but without significant
degradation or injury to endothelial cell layers.