ABSTRACT
The recent completion of the human genome project advanced understanding of genetic diseases.1 It is now theoretically possible to treat diseases of genetic origin by replacing the mutated genes, inhibiting gene expression, or promoting a protective immune response by administering genes encoding specific antigens. Hence DNA and nucleic acid-based drugs have emerged as potential new therapeutic modalities to introduce deficient genes in patients, suppress diseaserelated genes, or act as genetic vaccines. The field of gene therapy has attracted the attention of many scientists all over the world, which is exemplified by the current volume. Although the majority of gene delivery approaches so far have involved adenoviral or retroviral vectors, more recently nonviral vectors are receiving increasing attention as gene delivery vehicles because of several advantages, such as ease of manipulation, low cost, safety, and high flexibility regarding the size of the transgene delivered. One major approach in nonviral gene therapy is based on polyplexes, complexes formed by mixing DNA with polycations. The polyplexes form spontaneously as a result of electrostatic interactions between the positively charged groups of the polycation
and the negatively charged phosphate groups of the DNA. This results in DNA condensation, protection from the nuclease digestion, and more efficient delivery within a cell.
