The overall objective of this study is to develop a mechanistic understanding of shape control of self-assembled DNA nanoparticles, and to test the hypothesis that nanoparticle shape can influence their cellular uptake, intracellular trafficking and gene delivery efficiency. Several recent studies have raised the prospect that the morphology of virus particles and various types of synthetic nanoparticles is an important determinant for their transport properties and biological functions. We have developed a method for the self-assembly of DNA-containing nanoparticles with several distinct shapes (spherical, rod-like and worm-like) similar to some viral particles for the purpose of gene transfection. Such nanoparticles are ideal systems for understanding the mechanism of DNA-induced self-assembly and the effect of nanoparticle shape on their stability, cell- nanoparticle interactions, transfection efficiency and in vivo transport kinetics. With this Exploratory Grant, we plan (1) to determine the key experimental parameters that effectively control the shape and size of nanoparticles, and to understand the mechanism of shape control in DNA condensation by PEGylated polycations using a combined experimental and computational modeling approach; and (2) to demonstrate nanoparticle shape dependence in cellular uptake, intracellular trafficking and transfection efficiency in vitro and in vivo in a liver-targeted gene delivery model. This study will provide a mechanistic understanding of the major driving forces for the self-assembly of DNA/PEG-polycation nanoparticles and identify key parameters involved in their shape control. It will offer an effective method to control the size and shape of DNA/polymer nanoparticles that can be applicable to a variety of PEGylated gene carriers in synthesizing nanoparticles with high degree of control over their shapes or morphologies.