Gene therapy using nanotechnology
Pilot phase I experiments involving gene therapy in human subjects have already been conducted for diseases like cystic fibrosis and muscular dystrophy. Some of the attractive targets for gene therapy include the following:
(i) epithelial surfaces of the lungs and gastrointestinal tract; (ii) endothelial cells lining the blood vessels, muscle myoblasts and skin fibroblasts, and (iii) tumour cells. In all these cases, the plasmid DNA carrying the gene sequence should reach the nucleus of the target cel1, overcoming an the hurdles (capture by endosome and lysosome) on its way to the nucleus. In the nucleus, it wil1 stay as an episome and express itself.

Three main types of gene-delivery systems have been described: (i) viral vectors; (ii) non-viral vectors (particles and polymers), and (iii) gene guns for direct injection of the genetic material into the target tissue. Since viral vectors pose some serious problems, the non-viral vectors are the gene-delivery system of choice by many. In this non-viral vector system, negatively charged plasmid DNA is condensed into a nonparticulate structure, 50-200 nm in size.