Imaging gene delivery with fluorescence microscopy

Gene delivery offers the promise of treatment for a range of human diseases. Although carried out initially with modified viruses, the use of synthetic molecules, including polymers, lipids and peptides, has extended the possibilities greatly for rationally designed vectors tailored to individual gene-delivery applications. Underlying the rational design of gene-delivery vectors is the need to understand the individual steps of the gene-delivery pathway. Using new methods in fluorescence microscopy, it is now possible to isolate individual steps along the gene-delivery pathway to characterize the mechanisms of cellular binding, cellular internalization and nuclear entry. This review describes the advances made in the gene-delivery field with the assistance of fluorescence microscopy. The focus of this review is the use of synthetic gene-delivery vectors, especially polyethylenimine, and the live-cell imaging and single-particle tracking techniques that reveal the intracellular dynamics of the gene-delivery process.