Peptides are very attractive nanomaterials with signi™cant potential for biomedical applications. —e development of peptide nanomaterials is based on the biochemical understanding that the active sites of protein molecules, such as enzymes, receptor ligands, and antibodies, usually involve only 5-20 amino acid residues (Sparrow et al. 1998). With the rapid advances in structural biology and high-throughput genomics and proteomics, the identi™cation of peptide motifs associated with biological functions has

9.1 Introduction ...................................................................................... 9-1 9.2 RNA Interference .............................................................................. 9-2 9.3 siRNA Delivery ................................................................................. 9-3

9.5 Methods for Evaluating Peptide-Based Vectors ........................ 9-13 9.6 Conclusion ....................................................................................... 9-14 References ....................................................................................................9-16

been drastically accelerated (Saito et al. 2007). —us, peptide materials oŸer a highly attractive feature of incorporating various natural or synthetic sequences with biological activities, for example, cell targeting domain and nuclear targeting domain. Peptides are relatively easy to be synthesized in large scale and can be characterized with well-established chemistry and instrumental operation. As biomaterials, peptides are generally less toxic and have low immunogenicity compared to high molecular weight (MW) polymers (Fabre and Collins 2006) and undergo degradation in the body to naturally occurring compounds. DiŸerent nanometric structures can arise from peptide-cargo or interpeptide interactions of electrostatic, hydrophobic, or aromatic nature. A good example is nanometric complex formed by peptides and nucleic acids. In this chapter, published studies using peptides to encapsulate siRNA noncovalently into nanoparticles will be reviewed and discussed in detail. A short summary of commonly used methods to deliver siRNA will also be presented.