Nonviral vectors, tissue-specific

Nonviral vectors are also under investigation. Among these are receptor-mediated gene transfers. By its very nature these would be highly tissue specific. Here particular glycoproteins would target specific organs such as the liver (Wu, 1991). Liposomal encapsulation was already mentioned. In vivo injection of DNA can afford a direct transfection into cells. This nonvector method holds particular promise for muscle cells (Wolff etal., 1990). 

Figure 7.1-3. The ideal synthetic (nonviral) gene delivery vector. After dense DNA packaging is accomplished (e.g., by protamine sulfate), the surface of synthetic particles (which is usually positively charged) needs to be shielded (e.g., by poly (ethylene-glycol) [PEG]) so that they do not attach to blood elements or to each other and, therefore, have an extended circulating plasma half-life (1) (passive targeting to leaky vessels ). The surface of the particles will contain specific ligands for active targeting to selected cells/ tissues (2). By engineering viral fusion proteins to the particle coat, cell entry is facilitated...

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