ABSTRACT
Gene therapy is a powerful procedure in treating a variety of inherited and acquired diseases. Most of the gene therapy trials rely on viral vectors because viruses achieve a high efciency of gene transfer in vivo. However, the use of viral vectors has several limitations such as immunogenicity, potential infectivity, complicated production, and inammation of human body (Smith 1995). Nonviral vectors are rapidly receiving increased attention as gene delivery systems because of their biosafety, biocompatibility, and a high exibility of size of the delivered nucleic acid (Li and Huang 2000). Among nonviral vectors, lipids and polymers are by far the most widely
28.1 Introduction .......................................................................................................................... 377 28.2 Parameters Affecting Transfection Efciency or Gene Silencing
of Chitosan/Gene Complexes ............................................................................................... 378 28.2.1 Degree of Deacetylation ........................................................................................... 378 28.2.2 Molecular Weight ..................................................................................................... 379 28.2.3 pH ............................................................................................................................. 379 28.2.4 Serum ........................................................................................................................ 379 28.2.5 Charge Ratio ............................................................................................................. 379 28.2.6 Cell Type ................................................................................................................... 379
28.3 Specic Ligand Modication ...............................................................................................380 28.3.1 Galactose Ligand ......................................................................................................380 28.3.2 Mannose Ligand .......................................................................................................380 28.3.3 Folate Ligand ............................................................................................................ 383 28.3.4 Transferrin Ligand .................................................................................................... 383
28.4 pH-Sensitive Modication .................................................................................................... 383 28.4.1 Urocanic Acid ........................................................................................................... 383 28.4.2 PEI ............................................................................................................................384
28.5 siRNA Delivery .................................................................................................................... 385 28.5.1 In Vitro Application .................................................................................................. 385 28.5.2 In Vivo Application ................................................................................................... 386
28.6 Conclusions ........................................................................................................................... 387 Acknowledgments .......................................................................................................................... 387 References ...................................................................................................................................... 387
